Charles Messier Archives

August 7, 2017August 7, 2017 by Tammy Plotner

Messier 53 – the NGC 5024 Globular Cluster

Messier 53, as imaged by the Hubble Space Telescope. Credit: ESA/Hubble & NASA

Welcome back to Messier Monday! In our ongoing tribute to the great Tammy Plotner, we take a look at globular cluster known as Messier 53!

During the 18th century, famed French astronomer Charles Messier noted the presence of several “nebulous objects” in the night sky. Having originally mistaken them for comets, he began compiling a list of these objects so others would not make the same mistake he did. In time, this list (known as the Messier Catalog) would come to include 100 of the most fabulous objects in the night sky.

One of these objects is Messier 53, a globular cluster located in the northern Coma Berenices constellation. Located about 58,000 light years from the Solar System, it is almost equidistant from Galactic Center (about 60,000 light years). As Messier Objects go, it is relatively easy to find since it lies in the same area of the sky as Arcturus, the fourth brightest star in the night sky.

Description:

Heading towards us at a speed of 112 kilometers per second, globular cluster M53 is one of the furthest distant globular clusters in our Milky Way halo and lay almost equally distant between our solar system and the galactic center. This 220 light year diameter ball of stars in tightly compacted towards its core – where low metal is the name of the game and RR Lyra type variable stars once ruled. But recent studies have found that there are some new kids on the block. The blue stragglers…

According to G. Beccari (et al) the population of these definitely appears to violate standard theories of stellar evolution. And there not just a few blues… There’s a whole host of them. As Beccari noted in a 2008 study:

“We used a proper combination of high-resolution and wide-field multiwavelength observations collected at three different telescopes (HST, LBT, and CFHT) to probe the blue straggler star (BSS) population in the globular cluster M53. Almost 200 BSSs have been identified over the entire cluster extension. We have also used this database to construct the radial star density profile of the cluster; this is the most extended and accurate radial profile ever published for this cluster, including detailed star counts in the very inner region. A deviation from the model is noted in the most external region of the cluster. This feature needs to be further investigated in order to address the possible presence of a tidal tail in this cluster.”

Is this possible? Then take a closer look into this research. One where a millisecond pulsar was discovered inside. As S.R. Kulkarni (et al) indicated in a 1991 study:

“Millisecond pulsars are conventionally assumed to be spun up through the action of binary companions, although some subsequently lose their companions and appear as isolated pulsars. Such objects should therefore be more numerous in dense stellar systems. We report here the surprising discovery of two pulsars in low-density globular clusters: one is a single 10-ms pulsar (1639+36) in M13 (NGC 6205), the other a 33-ms pulsar (1310+18) in a 256-d binary in M53 (NGC 5024). Their ages, inferred from their luminosities and constraints on their period derivatives, seem to be 10 9 years, significantly greater than previously reported ages ( ! 10 8 years) of cluster pulsars. The implied birth rate is inconsistent with the conventional two-body tidal capture model, suggesting that an alternative mechanism such as tidal capture between primordial binaries and a reservoir of (hundreds of) primordial neutron stars may dominate the production of tidal binaries in such clusters. The period derivative of PSR1639+36 is surprisingly small, and may be corrupted by acceleration due to the mean gravitational potential of the cluster.”

*The Messier 53 globular star cluster. Credit: Ole Nielsen*

History of Observation:

This globular cluster was first discovered on February 3, 1775 by Johann Elert Bode, but independently recovered on February 26, 1777 by Charles Messier who writes:

“Nebula without stars discovered below & near Coma Berenices, a little distant from the star 42 in that constellation, according to Flamsteed. This nebula is round and conspicuous. The Comet of 1779 was compared directly with this nebula, & M. Messier has reported it on the chart of that comet, which will be included in the volume of the Academy for 1779. Observed again April 13, 1781: It resembles the nebula which is below Lepus [M79].”

Sir William Herschel would revisit M53, but he did not publish his findings when studying Messier objects. Very seldom did Herschel wax poetic in his writings, but of this particular object he said: “A cluster of very close stars; one of the most beautiful objects I remember to have seen in the heavens. The cluster appears under the form of a solid ball, consisting of small stars, quite compressed into one blaze of light, with a great number of loose ones surrounding it, and distinctly visible in the general mass.”

He would return again in later years to include in his notes: “From what has been said it is obvious that here the exertion of a clustering power has brought the accumulation and artificial construction of these wonderful celestial objects to the highest degree of mysterious perfection.”

*The Messier 53 globular cluster. Credit: NASA/ESA/Hubble*

Although it did not touch Sir John Herschel quite so much, M53 also engaged Admiral Smyth who wrote:

“A globular cluster, between Berenice’s tresses and the Virgin’s left hand, with a coarse pair of telescopic stars in the sf [south following, SE] quadrant, and a single one in the sp [south preceding, SW]. This is a brilliant mass of minute stars, from the 11th to the 15th magnitude, and from thence to gleams of star-dust, with stragglers to the np [north preceding, NW], and pretty diffused edges. From the blaze at the centre, it is evidently a highly compressed ball of stars, whose law of aggregation into so dense and compact a mass, is utterly hidden from our imperfect senses. It was enrolled by Messier in 1774 as No. 53, and resolved into stars by Sir W. Herschel. The contemplation of so beautiful an object, cannot but set imagination to work, though the mind may be soon lost in astonishment at the stellar dispositions of the great Creator and Maintainer. Thus, in reasoning by analogy, these compressed globes of stars confound conjecture as to the models in which the mutual attractions are prevented from causing the universal destruction of their system. Sir John Herschel thinks, that no pressure can be propagated through a cluster of discrete stars; whence it would follow, that the permanence of its form must be maintained in a way totally different from that which our reasoning suggest. Before quitting this interesting ball of innumerable worlds, I may mention that it was examined by Sir John Herschel, with Mr. Baily, in the 20-foot reflector; and that powerful instrument showed the cluster with curved appendages of stars, like the short claws of a crab running out from the main body. A line through Delta and Epsilon Virginis, northward, meeting another drawn from Arcturus to Eta Bootis, unite upon this wonderful assemblage; or it is also easily found by its being about 1 deg northeast of 42 Comae Berenices, the alignment of which is already given.”

Locating Messier 53:

M53 can be easily found just about a degree northeast of 42 Alpha Comae Berenices, a visual binary star. To located Alpha, draw a mental line from Arcturus via Eta Bootis where you’ll see it about a fist width west. Alternately you can starhop from Gamma Viginis to Delta and on to Epsilon where you can locate M53 approximately 4 fingerwidths to the north/northeast.

To see this small globular cluster in binoculars will require dark skies and it will appear very small, like a large, out of focus star. In small telescopes it will appear almost cometary – and thus why Messier cataloged these objects! However, with telescopes approaching the 6″ range, resolution will begin and larger telescopes will shatter this gorgeous globular cluster. Requires dark skies.

*The location of Messier 53 in the northern Coma Berenices constellation. Credit: IAU and Sky & Telescope magazine (Roger Sinnott & Rick Fienberg)*

A ball of worlds… What a unique description! May you enjoy your observations as well!

And here are the quick facts on this Messier Object to help you get started!

Object Name: Messier 53
Alternative Designations: M53, NGC 5024
Object Type: Class V Globular Cluster
Constellation: Coma Berenices
Right Ascension: 13 : 12.9 (h:m)
Declination: +18 : 10 (deg:m)
Distance: 58.0 (kly)
Visual Brightness: 7.6 (mag)
Apparent Dimension: 13.0 (arc min)

We have written many interesting articles about Messier Objects here at Universe Today. Here’s Tammy Plotner’s Introduction to the Messier Objects, , M1 – The Crab Nebula, M8 – The Lagoon Nebula, and David Dickison’s articles on the 2013 and 2014 Messier Marathons.

Be to sure to check out our complete Messier Catalog. And for more information, check out the SEDS Messier Database.

Sources:

July 31, 2017August 7, 2017 by Tammy Plotner

Messier 52 – the NGC 7654 Open Star Cluster

The location of the Messier 52 open star cluster, located in the direction of the southern constellation Cassiopeia. Credit: Wikisky

Welcome back to Messier Monday! We continue our tribute to our dear friend, Tammy Plotner, by looking at the open star cluster of Messier 52. Enjoy!

In the 18th century, while searching the night sky for comets, French astronomer Charles Messier kept noting the presence of fixed, diffuse objects in the night sky. In time, he would come to compile a list of approximately 100 of these objects, with the purpose of making sure that astronomers did not mistake them for comets. However, this list – known as the Messier Catalog – would go on to serve a more important function.

One of these objects is Messier 52, an open star cluster that can seen in proximity to the northern constellation Cassiopeia. Located about 5000 light years from Earth, this star cluster is easily spotted in the night sky because of its association with Cassiopeia’s familiar W-shape. It can viewed with binocular and telescopes, and will appears as a hazy, nebulous patch of light.

Description:

Located roughly 5000 light years away, this 35 million year old cluster of stars has around 200 members – one of which is a very peculiar Of star. According to A.K. Pandy (et al), M52 is an interesting cluster in which to study star formation history. As they stated in their 2001 study:

“The colour magnitude diagrams show a large age spread in the ages. Star formation was biased towards relatively higher masses during the early phase of star formation whereas most of the low mass stars of the cluster were formed during the later phase. The star formation seems to have been a gradual process that proceeded sequentially in mass and terminated with the formation of most massive stars.”

*The Messier 52 open star cluster. Credit: Wikisky*

Indeed, M52 has been very studied for its star structure, including a search for variables. As S.L. Kim (et al), wrote in a 2000 study:

“We have performed a long-term project of CCD photometry of open clusters. Its primary goal is to search for variable stars, in particular short-period (less than a few days) pulsating stars such as Delta Sct, Gamma Dor, and slowly pulsating B-type stars (SPBs). These pulsating stars are recognized as important objects in studying stellar structure and testing evolution theory of intermediate-mass main sequence stars. Thus these clusters are ideal targets to investigate whether Gamma Dor type variability occurs in old open clusters or not.”

And it’s not just the structure they’re looking at – but the time frame in which they formed. As Anil K. Pandey wrote in her 2001 study:

“The distribution of stars in NGC 7654 indicates that the star formation within the cluster is not coeval and has an age spread -50 Myr. We found that star formation took place sequentially in the sense that low mass stars formed first. The star formation history in NGC 7654 supports the conventional picture of star formation in cluster where ‘low mass stars’ form first and star formation continues over a long period of time. The star formation within the cluster terminates with the formation of most massive stars in the cluster.”

History of Observation:

M52 was an original discovery of Charles Messier, captured on the night of September 7th, 1774. As he wrote in his notes at the time:

“Cluster of very small stars, mingled with nebulosity, which can be seen only with an achromatic telescope. It was when he observed the Comet which appeared in this year that M. Messier saw this cluster, which was close to the comet on the 7th of September 1774; it is below the star d Cassiopeiae: that star was used to determine both the cluster of stars and the comet.”

*Atlas Image mosaic of Messier 52, as part of the Two Micron All Sky Survey (2MASS). Credit: UMass/UPAC/Caltech/NASA/NSF*

Sir William Herschel would also observe M52, but he would keep his notes private. As he wrote on August 29th, 1873:

“All resolved into innumerable small stars without any suspicion of nebulosity. 7 ft., 57. In the sweeper, 30, shews nebulosity, the stars being too obscure to be distinguished with its light tho’ considerable.” and again on December 23, 1805: “Review. Large 10 feet. This is a cluster of pretty condensed stars of different sizes. It is situated in a very rich part of the heavens and can hardly be called insulated, it may only be a very condensed part of the Milky Way which is here much divided and scattered. It is however so far drawn together with some accumulation that it may be called a cluster of the third order.”

Herschel’s son John would also add it to the General Catalog a few years later with less descriptive narrative, but it was Admiral Smyth who described M52’s beauty best when he said:

“An irregular cluster of stars between the head of Cepheus and his daughter’s throne; it lies north-west-by-west of Beta Cassiopeiae, and one third of the way towards Alpha Cephei. This object assumes somewhat of a triangular form, with an orange-tinted 8th-mag star at its vertex, giving it the resemblance of a bird with outspread wings. It is preceded by two stars of 7th and 8th magnitudes, and followed by another of similar brightness; and the field is one of singular beauty under a moderate magnifying power. While these were under examination, one of those bodies called falling stars passed through the outliers. This phenomenon was so unexpected and sudden as to preclude attention to it; but it appeared to be followed by a train of glittering and very minute spangles.”

May it glitter and spangle for you!

*The location of Messier 52 in proximity to the constellation Cassiopeia. Credit: IAU and Sky & Telescope magazine (Roger Sinnott & Rick Fienberg)*

Locating Messier 52:

In the rich star cluster fields of Cassiopeia, M52 is distinctive for its size and brightness. It’s not hard to find! Begin by identifying the W-shape of Cassiopeia and focus on its two brightest stars – Alpha and Beta. Because this constellation is circumpolar, remembering to look at the side that has the brightest stars or the steepest angle, will help you remember how to find this great open cluster. Now, just draw a mental line between Alpha, the lower star, and Beta, the upper.

Extend that line into space about the same distance and aim your binoculars or finderscope there. In binoculars M52 will show clearly as a beginning to resolve star cloud and a hazy patch in a telescope finderscope. Even the smallest of telescopes can expect resolution from this multi-magnitude beauty and the more aperture you apply, the more stars you will see. M52 is well suited to urban or light polluted skies and stands up well to fairly moonlit conditions and hazy skies.

Object Name: Messier 52
Alternative Designations: M52, NGC 7654
Object Type: Open Galactic Star Cluster
Constellation: Cassiopeia
Right Ascension: 23 : 24.2 (h:m)
Declination: +61 : 35 (deg:m)
Distance: 5.0 (kly)
Visual Brightness: 7.3 (mag)
Apparent Dimension: 13.0 (arc min)

We have written many interesting articles about Messier Objects here at Universe Today. Here’s Tammy Plotner’s Introduction to the Messier Objects, M1 – The Crab Nebula, and David Dickison’s articles on the 2013 and 2014 Messier Marathons.

Be to sure to check out our complete Messier Catalog. And for more information, check out the SEDS Messier Database.

Sources:

July 24, 2017August 7, 2017 by Tammy Plotner

Messier 51 – the Whirlpool Galaxy

Visible light (left) and infrared image (right) of the Whirlpool Galaxy, taken by NASA’s Hubble Space Telescope. Credit: NASA/ESA/M. Regan & B. Whitmore (STScI), & R. Chandar (U. Toledo)/S. Beckwith (STScI), & the Hubble Heritage Team (STScI/AURA

Welcome back to Messier Monday! In our ongoing tribute to the great Tammy Plotner, we take a look at that swirling, starry customer, the Whirlpool Galaxy!

During the 18th century, famed French astronomer Charles Messier noted the presence of several “nebulous objects” in the night sky. Having originally mistaken them for comets, he began compiling a list of them so that others would not make the same mistake he did. In time, this list (known as the Messier Catalog) would come to include 100 of the most fabulous objects in the night sky.

One of these is the spiral galaxy located in the constellation Canes Venatici known as the Whirlpool Galaxy (aka. Messier 51). Located between 19 and 27 million light-years from the Milky Way, this deep sky object was the very first to be classified as a spiral galaxy. It is also one of the best known galaxies among amateur astronomers, and is easily observable using binoculars and small telescopes.

Description:

Located some 37 million light years away, M51 is the largest member of a small group of galaxies, which also houses M63 and a number of fainter galaxies. To this time, the exact distance of this group isn’t properly known… Even when a 2005 supernova event should have helped astronomers to correctly calculate! As K. Takats stated in a study:

“The distance to the Whirlpool galaxy (M51, NGC 5194) is estimated using published photometry and spectroscopy of the Type II-P supernova SN 2005cs. Both the expanding photosphere method (EPM) and the standard candle method (SCM), suitable for SNe II-P, were applied. The average distance (7.1 +/- 1.2 Mpc) is in good agreement with earlier surface brightness fluctuation and planetary nebulae luminosity function based distances, but slightly longer than the distance obtained by Baron et al. for SN 1994I via the spectral fitting expanding atmosphere method. Since SN 2005cs exhibited low expansion velocity during the plateau phase, similarly to SN 1999br, the constants of SCM were recalibrated including the data of SN 2005cs as well. The new relation is better constrained in the low-velocity regime, that may result in better distance estimates for such SNe.”

Visible light (left) and infrared image (right) of M51, taken by the Kitt Peak National Observatory and NASA’s Spitzer Space Telescope, respectively. Credit: NASA/JPL-Caltech/R. Kennicutt (Univ. of Arizona)/DSS

Of course, one of the most outstanding features of the Whirlpool Galaxy is its beautiful spiral structure – perhaps result of the close interaction between it and its companion galaxy NGC 5195? As S. Beckwith,

“This sharpest-ever image of the Whirlpool Galaxy, taken in January 2005 with the Advanced Camera for Surveys aboard NASA’s Hubble Space Telescope, illustrates a spiral galaxy’s grand design, from its curving spiral arms, where young stars reside, to its yellowish central core, a home of older stars. At first glance, the compact galaxy appears to be tugging on the arm. Hubble’s clear view, however, shows that NGC 5195 is passing behind the Whirlpool. The small galaxy has been gliding past the Whirlpool for hundreds of millions of years. As NGC 5195 drifts by, its gravitational muscle pumps up waves within the Whirlpool’s pancake-shaped disk. The waves are like ripples in a pond generated when a rock is thrown in the water. When the waves pass through orbiting gas clouds within the disk, they squeeze the gaseous material along each arm’s inner edge. The dark dusty material looks like gathering storm clouds. These dense clouds collapse, creating a wake of star birth, as seen in the bright pink star-forming regions. The largest stars eventually sweep away the dusty cocoons with a torrent of radiation, hurricane-like stellar winds, and shock waves from supernova blasts. Bright blue star clusters emerge from the mayhem, illuminating the Whirlpool’s arms like city streetlights.”

But there were more surprises just waiting to be found – like a black hole, surrounded by a ring of dust. What makes it even more odd is a secondary ring crosses the primary ring on a different axis, a phenomenon that is contrary to expectations and a pair of ionization cones extend from the axis of the main dust ring. As H. Ford,

“This image of the core of the nearby spiral galaxy M51, taken with the Wide Field Planetary camera (in PC mode) on NASA’s Hubble Space Telescope, shows a striking , dark “X” silhouetted across the galaxy’s nucleus. The “X” is due to absorption by dust and marks the exact position of a black hole which may have a mass equivalent to one-million stars like the sun. The darkest bar may be an edge-on dust ring which is 100 light-years in diameter. The edge-on torus not only hides the black hole and accretion disk from being viewed directly from earth, but also determines the axis of a jet of high-speed plasma and confines radiation from the accretion disk to a pair of oppositely directed cones of light, which ionize gas caught in their beam. The second bar of the “X” could be a second disk seen edge on, or possibly rotating gas and dust in MS1 intersecting with the jets and ionization cones.”

History of Observation:

The Whirlpool Galaxy was first discovered by Charles Messier on October 13th, 1773 and re-observed again for his records on January 11th, 1774. As he wrote of his discovery in his notes:

“Very faint nebula, without stars, near the eye of the Northern Greyhound [hunting dog], below the star Eta of 2nd magnitude of the tail of Ursa Major: M. Messier discovered this nebula on October 13, 1773, while he was watching the comet visible at that time. One cannot see this nebula without difficulties with an ordinary telescope of 3.5 foot: Near it is a star of 8th magnitude. M. Messier reported its position on the Chart of the Comet observed in 1773 & 1774. It is double, each has a bright center, which are separated 4’35”. The two “atmospheres” touch each other, the one is even fainter than the other.”

It would be his faithful friend and assistant, Pierre Mechain who would discover NGC 5195 on March 21st, 1781. Even though it would be many, many years before it was proven that galaxies were indeed independent systems, historic astronomers were much, much sharper than we gave them credit for. Sir William Herschel would observe M51 many times, but it would be his son John who would be the very first to comment on M51’s scheme:

“This very singular object is thus described by Messier: – “Nebuleuse sans etoiles.” “On ne peut la voir que difficilement avec une lunette ordinaire de 3 1/2 pieds.” “Elle est double, ayant chacune un centre brillant eloigne l’un de l’autre de 4′ 35″. Les deux atmospheres se touchent.” By this description it is evident that the peculiar phenomena of the nebulous ring which encircles the central nucleus had escaped his observation, as might have been expected from the inferior light of his telescopes. My Father describes it in his observations of Messier’s nebulae as a bright round nebula, surrounded by a halo or glory at a distance from it, and accompanied by a companion; but I do not find that the partial subdivision of the ring into two branches throughout its south following limb was noticed by him. This is, however, one of its most remarkable and interesting features. Supposing it to consist of stars, the appearance it would present to a spectator placed on a planet attendant on one of them eccentrically situated towards the north preceding quarter of the central mass, would be exactly similar to that of our Milky Way, traversing in a manner precisely analogous the firmament of large stars, into which the central cluster would be seen projected, and (owing to its distance) appearing, like it, to consist of stars much smaller than those in other parts of the heavens. Can it, then, be that we have here a brother-system bearing a real physical resemblance and strong analogy of structure to our own? Were it not for the subdivision of the ring, the most obvious analogy would be that of the system of Saturn, and the idea of Laplace respecting the formation of that system would be powerfully recalled by this object. But it is evident that all idea of symmetry caused by rotation on an axis must be relinquished, when we consider that the elliptic form of the inner subdivided portion indicates with extreme probability an elevation of that portion above the plane of the rest, so that the real form must be that of a ring split through half its circumference, and having the split portions set asunder at an angle of about 45 deg each to the plane of the other.”

*Sketch of M51 by William Parsons, 3rd Earl of Rosse (Lord Rosse) in 1845. Credit: Public Domain*

As with other Messier Objects, Admiral Smyth also had some insightful and poetic observations to add. As he wrote of this galaxy in September of 1836:

“We have then an object presenting an amazing display of the uncontrollable energies of the Omnipotence, the contemplation of which compels reason and admiration to yield to awe. On the outermost verge of telescopic reach we perceive a stellar universe similar to that to which we belong, whose vast amplitudes no doubt are peopled with countless numbers of percipient beings; for those beautiful orbs cannot be considered as mere masses of inert matter.

And it is interesting to know that, if there be intelligent existence, an astronomer gazing at our distant universe, will see it, with a good telescope, precisely under the lateral aspect which theirs presents to us. But after all what do we see? Both that wonderful universe, our own, and all which optical assistance has revealed to us, may be only the outliers of a cluster immensely more numerous.

The millions of suns we perceive cannot comprise the Creator’s Universe. There are no bounds to infinitude; and the boldest views of the elder Herschel only placed us as commanding a ken whose radius is some 35,000 times longer than the distance of Sirius from us. Well might the dying Laplace explain: “That which we know is little; that which we know not is immense.”

Lord Rosse would continue on in 1844 with his 6-feet (72-inch) aperture, 53-ft FL “Leviathan” telescope, but he was a man of fewer words.

“The greater part of the observations were made when the eye was affected by lamp-light, which made it difficult to estimate correctly the centre of the nucleus; it was of importance that no time should be unnecessarily spent, and after the lamp had been used a new measure was taken, as it was judged that the object was sufficiently seen. With the brighter stars this would frequently happen before the nucleus was well defined, as all impediments to vision seem to affect nebulae much more than stars the light of which would be estimated as of the same intensity. In the foregoing list the greatest discrepancies are in the measures of bright objects, and this is probably the proper account of it. No stars have been inserted in the sketch which are not in the table of the measurements. The general appearance of the object would have been better given if the minute stars had been put in from the eye-sketch, but it would have created confusion.”

May the stars from this distant island universe fill your eyes!

*The Whirlpool Galaxy (Spiral Galaxy M51, NGC 5194), a classic spiral galaxy located in the Canes Venatici constellation, and its companion NGC 5195. Credit: NASA/ESA*

Locating Messier 51:

Locating M51 isn’t too hard if you have dark skies, but this particular galaxy is very difficult where light pollution of moonlight is present. To find it, start with Eta UM, the star at the handle of the Big Dipper. In the finderscope or binoculars, you’ll clearly see 24 UM to the southwest. Now, center your optics there and move slowly southwest towards Cor Caroli (Alpha CVn) and you’ll find it!

In locations where skies are clear and dark, it is easy to see spiral structure in even small telescopes, or to make out the galaxy in binoculars – but even a change in sky conditions can hide it from a good location. Rich field telescopes with fast focal lengths to an outstanding job on this galaxy and companion and you may be able to make out the nucleus of both galaxies on a good night from even a bad location.

Object Name: Messier 51
Alternative Designations: M51, NGC 5194, The Whirlpool Galaxy
Object Type: Type Sc Galaxy
Constellation: Canes Venatici
Right Ascension: 13 : 29.9 (h:m)
Declination: +47 : 12 (deg:m)
Distance: 37000 (kly)
Visual Brightness: 8.4 (mag)
Apparent Dimension: 11×7 (arc min)

Be to sure to check out our complete Messier Catalog. And for more information, check out the SEDS Messier Database.

Sources:

July 10, 2017July 10, 2017 by Tammy Plotner

Messier 50 – the NGC 2323 Open Star Cluster

The Messier 50 open star cluster, shown in proximity to the Seagull Nebula (IC 2177). Credit: Wikisky

Welcome back to Messier Monday! We continue our tribute to our dear friend, Tammy Plotner, by looking at the open star cluster of Messier 50. Enjoy!

One of these objects is the open star cluster known as Messier 50 (aka. NGC 2323). Located at a distance of about 3,200 light-years from Earth, this object sits near the border between the Monoceros and Canis Major constellations. It is described as a ‘heart-shaped’ figure, occupies an area about half the size of the full Moon, and is easy to find because of its proximity to Sirius (the brightest star in the night sky).

Description:

Located about 3,200 light years from our solar system, this stellar gathering could be perhaps as much as 20 light years across, but the central concentration is believed to only span across roughly 10 light years. While that doesn’t seem that large, it’s lit by the candlepower of what could be 200 stars! And picking such a group of stars out of a well-known OB1 association isn’t easy. It requires photometry. As J.J. Claria (et al) remarked in a 1997 study:

“UBV and DDO photoelectric photometry in the field of the open cluster NGC 2323 is presented. The analysis yields 109 probable members; one of them being a red giant, and 3 possible members. The basic cluster parameters are derived. NGC 2323 appears not to be physically connected to the CMa OB1 association.”

*Close up of the Messier 50 open star cluster. Credit: Wikisky*

In this region of the sky are vast molecular clouds compressing into star forming regions known as OB1 associations. The stars spawned by these vast clouds form into open clusters containing dozens to thousands of members and, over time, disassociate with not only the molecular cloud, but their sibling star clusters as well. Sure, it took 100-120 million years for it to happen, but as the group of stars cut away from the field, each member also aged differently.

By studying open clusters like M50 and its relative M35, we can learn more about the dynamics of star clusters which formed roughly at the same time in the same area. As Jasonjot Kalirai (et al) indicated in their 2003 study:

“The color-magnitude diagrams for the clusters exhibit clear main sequences stretching over 14 mag in the (V, B-V)-plane. Comparing these long main sequences with those of earlier clusters in the survey, as well as with the Hyades, has allowed for accurate distances to be established for each cluster. Analysis of the luminosity and mass functions suggests that, despite their young ages, both clusters are somewhat dynamically relaxed, exhibiting signs of mass segregation. This is especially interesting in the case of NGC 2323, which has an age of only 1.3 times the dynamical relaxation time. The present photometry is also deep enough to detect all of the white dwarfs in both clusters. We discuss some interesting candidates that may be the remnants of quite massive (M>=5Msolar) progenitor stars. The white dwarf cooling age of NGC 2168 is found to be in good agreement with the main-sequence turnoff age. These objects are potentially very important for setting constraints on the white dwarf initial-final mass relationship and the upper mass limit for white dwarf production.”

So, did age or movement produce the colorful display of stars we can observe in M50 – or was it simply the chemical ingredients responsible? According to a 2005 study conducted by Bragaglia and Monica:

“We describe a long-term project aimed at deriving information on the chemical evolution of the Galactic disk from a large sample of open clusters. The main property of this project is that all clusters are analyzed in a homogeneous way to guarantee the robustness of the ranking in age, distance, and metallicity. Special emphasis is devoted to the evolution of the earliest phases of the Galactic disk evolution, for which clusters have superior reliability with respect to other types of evolution indicators. The project is twofold: on one hand we derive the age, distance, and reddening (and indicative metallicity) by interpreting deep and accurate photometric data with stellar evolution models, and on the other hand, we derive the chemical abundances from high-resolution spectroscopy. The importance of quantifying the theoretical uncertainties by deriving the cluster parameters with various sets of stellar models is emphasized. Stellar evolution models assuming overshooting from convective regions appear to better reproduce the photometric properties of the cluster stars. The examined clusters show a clear metallicity dependence on the galactocentric distance and no dependence on age. The tight relation between cluster age and magnitude difference between the main-sequence turnoff and the red clump is confirmed.”

*The M50 open cluster. Credit: Ole Nielsen*

History of Observation:

While M50 was possibly discovered by G.D. Cassini 1711, it was independently recovered by Charles Messier on the night of April 5th, 1772. In his notes, he wrote of his discovery:

“Cluster of small stars, more or less brilliant, above the right loins of the Unicorn, above the star Theta of the ear of Canis Major, & near a star of 7th magnitude. It was while observing the Comet of 1772 that M. Messier observed this cluster. He has reported it on the chart of that comet, on which its trace has been drawn.”

It would later be observed by William Hershel, but not until his son John cataloged it before anyone began to notice colors in the stars. However, Admiral Smyth did!

“This is an irregularly round and very rich mass, occupying with its numerous outliers more than the field, and composed of stars from the 8th to the 16th magnitudes; and there are certain spots of splendour which indicate minute masses beyond the power of my telescope. The most decided points are, a red star towards the southern verge, and a pretty little equilateral triangle of 10th sizers, just below, or north of it. The double star here noted was carefully estimated under a full knowledge of the vertical and parallel lines of the field of view: this was made triple by H. [John Herschel], whose 2357 of the Fifth Series it is; but he must be mistaken in calling it Struve 748, which is Theta Orionis. It is sufficiently conspicuous as a double star, and though I perceive an infinitesimal point exactly om the vertical of A, I cannot ascertain whether it is H.’s C. This superb object was discovered by Messier in 1771 [actually 1772], and registered “a mass of small stars more or less brilliant.” It is 9 deg north-north-east of Sirius, and rather more than one-third of the distance between that star and Procyon.”

Locating Messier 50:

Because M50 is such a big and bright open star cluster, it’s relatively easy to find with complicated starhop instructions. Actually, the constellation of Monoceros is more difficult! Begin by identifying the brightest star in northern hemisphere skies – Alpha Canis Major – Sirius. Roughly a handspan to the northeast you’ll see another prominent bright star – Alpha Canis Minor – Procyon.

*The location of Messier 50 in the Monoceros constellation. Credit: IAU/Sky & Telescope magazine (Roger Sinnott & Rick Fienberg)*

Between these two lay the faint and indistinguishable constellation of Monoceros, and slightly southwest of the center point is Messier 50. In small binoculars and a telescope finderscope, you’ll quickly spot a compression in the starfield, and may even be able to see it as a slight contrast change with the unaided eye. In larger binoculars and small telescopes, it blooms into a cloud of stars, well resolved against the grainy backdrop of fainter stars.

In large aperture telescopes, even more stars resolve and colors begin to appear. Because of magnitude and the nature of star clusters, Messier 50 makes an outstanding target for high light pollution areas, moonlit nights and even less than perfect sky conditions.

Enjoy your own “colorful” observations of this rich and beautiful star cluster!

And as always, here are the quick facts on this Messier Object to help you get started:

Object Name: Messier 50
Alternative Designations: M50, NGC 2323
Object Type: Open Galactic Star Cluster
Constellation: Monoceros
Right Ascension: 07 : 03.2 (h:m)
Declination: -08 : 20 (deg:m)
Distance: 3.2 (kly)
Visual Brightness: 5.9 (mag)
Apparent Dimension: 16.0 (arc min)

Be to sure to check out our complete Messier Catalog. And for more information, check out the SEDS Messier Database.

Sources:

July 3, 2017July 3, 2017 by Tammy Plotner

Messier 49 – the NGC 4472 Elliptical Galaxy

The location of M49, in proximity to other Messier Objects and major stars. Credit: Wikisky

Welcome back to Messier Monday! In our ongoing tribute to the great Tammy Plotner, we take a look at Orion’s Nebula’s “little brother”, the De Marian’s Nebula!

During the 18th century, famed French astronomer Charles Messier noted the presence of several “nebulous objects” in the night sky. Having originally mistaken them for comets, he began compiling a list of them so that others would not make the same mistake he did. In time, this list (known as the Messier Catalog) would come to include 100 of the most fabulous objects in the night sky.

One of these objects is the elliptical galaxy known as Messier 49 (aka. NGC 4472). Located in the southern skies in the constellation of Virgo, this galaxy is one several members of the Virgo Cluster of galaxies and is located 55.9 million light years from Earth. On a clear night, and allowing for good light conditions, it can be seen with binoculars or a small telescope, and will appear as a hazy patch in the sky.

Description:

Messier 49 is the brightest of the Virgo Cluster member galaxies, which is pretty accurate considering it’s only about 60 million light years away and may span an area as large as 160,000 light years. It is a huge system of globular clusters, much less concentrated than Virgo cluster member M87 – but a giant none the less. As Stephen E. Zep (et al) wrote in a 2000 study:

“We present new radial velocities for 87 globular clusters around the elliptical galaxy NGC 4472 and combine these with our previously published data to create a data set of velocities for 144 globular clusters around NGC 4472. We utilize this data set to analyze the kinematics of the NGC 4472 globular cluster system. The new data confirm our previous discovery that the metal-poor clusters have significantly higher velocity dispersion than the metal-rich clusters in NGC 4472. The very small angular momentum in the metal-rich population requires efficient angular momentum transport during the formation of this population, which is spatially concentrated and chemically enriched. Such angular momentum transfer can be provided by galaxy mergers, but it has not been achieved in other extant models of elliptical galaxy formation that include dark matter halos. We also calculate the velocity dispersion as a function of radius and show that it is consistent with roughly isotropic orbits for the clusters and the mass distribution of NGC 4472 inferred from X-ray observations of the hot gas around the galaxy.”

*This ground-based image shows the Small Magellanic Cloud. The area of the SMIDGE survey is highlighted, as well as the position of NGC 248. Credit: NASA/ESA/Hubble/Digitized Sky Survey 2*

However, there was something going on in the mass structure of M49 that astronomers were curious about… Something they couldn’t quite explain. Was it dark matter? As M. Lowenstein wrote in a 1992 study:

“An attempt to constrain the total mass distribution of the well-observed giant elliptical galaxy NGC 4472 is realized by constructing simultaneous equilibrium models for the gas and stars using all available relevant optical and X-ray data. The value of <?>, the emission-weighted average value of kT, derived from the Ginga spectrum, <?> = 1.9 ± 0.2 keV, can be reproduced only in hydrostatic models where nonluminous matter comprises at least 90% of the total mass. However, in general, these mass models are not consistent with observed projected stellar and globular cluster velocity dispersions at moderate radii.”

The next thing you know, nuclear outburst were discovered – the product of interaction with a neighboring galaxy. As B. Biller (et al) indicated in a 2004 study:

“We present the analysis of the Chandra ACIS observations of the giant elliptical galaxy NGC 4472. The Chandra Observatory’s arcsec resolution reveals a number of new features. Specifically: 1) an ~8 arc min streamer or arm (this corresponds to a linear size of 36 kpc) extending southwest of the galaxy and an assymetrical, somewhat truncated streamer to the northeast. Smaller, morphologically similar structures are observed in NGC 4636 and are explained as shocks from a nuclear outburst in the recent past. The larger size of the NGC 4472 streamers requires a correspondingly higher energy input compared to the NGC 4636 case. The asymmetry of the streamers may be due to the interaction of NGC 4472 with the ambient Virgo cluster gas. 2) A string of small, extended sources south of the nucleus. These sources may stem from an interaction of NGC 4472 with the galaxy UGC 7637. 3) X-ray cavities corresponding to radio lobes, where expanding radio plasma has evacuated the X-ray emitting gas. We also present a luminosity function for the X-ray point sources detected within NGC 4472 which we compare to that for other early type galaxies.”

Chandra images showing 4 of the 9 galaxies discovered (left), and an artist’s impression on showing how gas falls towards a black hole and becomes a rapidly spinning disk of matter near the center (right). Credit: NASA/Chandra

But the very best was yet to come… the discovery of a black hole! According to NASA, the results from NASA’s Chandra X-ray Observatory, combined with new theoretical calculations, provide one of the best pieces of evidence yet that many supermassive black holes are spinning extremely rapidly. The images on the left show 4 out of the 9 large galaxies included in the Chandra study, each containing a supermassive black hole in its center.

The Chandra images show pairs of huge bubbles, or cavities, in the hot gaseous atmospheres of the galaxies, created in each case by jets produced by a central supermassive black hole. Studying these cavities allows the power output of the jets to be calculated. This sets constraints on the spin of the black holes when combined with theoretical models. The Chandra images were also used to estimate how much fuel is available for each supermassive black hole, using a simple model for the way matter falls towards such an object.

The artist’s impression on the right side of the main graphic shows gas within a “sphere of influence” falling straight inwards towards a black hole before joining a rapidly spinning disk of matter near the center. Most of the material in this disk is swallowed by the black hole, but some of it is swept outwards in jets (colored blue) by quickly spinning magnetic fields close to the black hole.

Previous work with these Chandra data showed that the higher the rate at which matter falls towards these supermassive black holes, the higher their power output is in jets. However, without detailed theory the implications of this result for black hole behavior were unclear. The new study uses these Chandra results combined with leading theoretical models for the production of jets, plus general relativity, to show that the supermassive black holes in these galaxies must be spinning at close to the maximum rate. If black holes are spinning at this limit, material can be dragged around them at close to the speed of light, the speed limit from Einstein’s theory of relativity.

*Atlas Image obtained of Messier 49, taken by the Two Micron All Sky Survey (2MASS). Credit: NASA/UofMass/IPAC/Caltech/NASA/NSF/2MASS*

History of Observation:

According to SEDS, M49 was the first member of the Virgo cluster of galaxies to be discovered, by Charles Messier, who cataloged it on February 19th, 1771. As he recorded in his notes at the time:

“Nebula discovered near the star Rho Virginis. One cannot see it without difficulty with an ordinary telescope of 3.5-feet [FL]. The Comet of 1779 was compared by M. Messier with this nebula on April 22 and 23: The comet and the nebula had the same light. M. Messier has reported this nebula on the chart of the route of the comet, which appeared in the volume of the Academy of the same year 1779. Seen again on April 10, 1781.” Eight years later, on April 22, 1779, on the occasion of following the comet of that year, and on the hunt for finding more nebulous objects in competition to other observers, Barnabas Oriani independently rediscovered this ‘nebula’: “Very pale and looking exactly like the comet [1779 Bode, C/1779 A1].”

In his Bedford Catalogue of 1844, Admiral William H. Smyth confused this finding with Messier’s discovery:

“A bright, round, and well-defined nebula, on the Virgin’s left shoulder; exactly on the line between Delta Virginis and Beta Leonis, 8deg, or less than half-way, from the former star. With an eyepiece magnifying 93 times, there are only two telescopic stars in the field, one of which is in the sp and the other in the sf quadrant; and the nebula has a very pearly aspect. This object was discovered by Oriani in 1771 [this is wrong: it was Messier who discovered it that year; Oriani found it only in 1779], and registered by Messier as a “faint nebula, not seen without difficulty,” with a telescope of 3 1/2 feet in length. It is a pity that this active and very assiduous astronomer could not have been furnished with one of the giant telescopes of the present days. Had he possessed efficient means, there can be no doubt of the augmentation of his useful and, in its day, unique Catalogue: a collection of objects for which sidereal astronomy must ever remain indebted to him.” This error was repeated by John Herschel in his General Catalogue of 1864 (GC), who also erroneously assigned this object to “1771 Oriani,” and also found its way into J.L.E. Dreyer’s NGC.

Let’s hope you don’t mistake it with the many other galaxies nearby!

*The location of Messier 49 within the Virgo constellation. Credit: IAU and Sky & Telescope magazine (Roger Sinnott & Rick Fienberg)*

Locating Messier 49:

Galaxy hopping isn’t an easy chore and it takes some practice. Starting looking for M49 about halfway between Epsilon and Beta Virginis. Use Gamma to help triangulate your position. At near magnitude 8, Messier 49 is quite binocular possible and would show under dark sky conditions as a faint, very small egg shaped fog. However, it will not show in a finderscope of a telescope – but the nearby stars will.

Use their patterns to help guide you there. Because galaxies require dark skies, M49 cannot be found under urban conditions or during moonlit nights. In telescopes as small as 70mm, it will appear as a nebulous egg shape and become brighter – but no more resolved to larger instruments. To assist in location, begin with lowest magnification and increase magnification once found to darken background field.

And here are the quick facts to help you get started!

Object Name: Messier 49
Alternative Designations: M49, NGC 4472
Object Type: Elliptical Galaxy
Constellation: Virgo
Right Ascension: 12 : 29.8 (h:m)
Declination: +08 : 00 (deg:m)
Distance: 60000 (kly)
Visual Brightness: 8.4 (mag)
Apparent Dimension: 9×7.5 (arc min)

Be to sure to check out our complete Messier Catalog. And for more information, check out the SEDS Messier Database.

Sources:

June 19, 2017June 19, 2017 by Tammy Plotner

Messier 47 – the NGC 2422 Open Star Cluster

The open star clusters of Messier 46 and Messier 47, located in the southern skies in the Puppis constellation. Credit: Wikisky

Welcome back to Messier Monday! In our ongoing tribute to the great Tammy Plotner, we take a look at Orion’s Nebula’s “little brother”, the De Marian’s Nebula!

During the 18th century, famed French astronomer Charles Messier noted the presence of several “nebulous objects” in the night sky. Having originally mistaken them for comets, he began compiling a list of them so that others would not make the same mistake he did. In time, this list (known as the Messier Catalog) would come to include 100 of the most fabulous objects in the night sky.

One of these objects is the open star cluster known as Messier 47 (NGC 2422), which is located in the constellation of Puppis roughly 1,600 light-years from Earth. Located in proximity to Messier 46, this star cluster is estimated to be 78 million years in age. It is also particularly bright, containing about 50 stars and occupying a region that is about the same size as that of the full Moon.

Description:

Spanning across about 12 light years of space, this clump of around 50 stars began their life around 78 million years ago. Now cruising through space some 1600 light years away from Earth, the group continues to distance itself from our solar system at a speed of 9 kilometers per second. For the most part, Messier 47 is a whole lot like the Pleiades star cluster – its brightest member shining just around magnitude 6 and holding a spectral class B2.

But, here you will also find two orange K giants with luminosity of about 200 times that of the Sun. At M47’s center you’ll find binary star, Sigma 1121, with components of magnitude 7.9 both and separated by 7.4 arc seconds. How do we know that M47 is a lot like the Pleiades? Let’s try X-ray sources and the advances of looking at open clusters far more differently than in optical wavelengths. As M. Barbera (et al) said in a 2002 study:

“We present the results of a ROSAT study of NGC 2422, a southern open cluster at a distance of about 470 pc, with an age close to the Pleiades. Source detection was performed on two observations, a 10-ks PSPC and a 40-ks HRI pointing, with a detection algorithm based on wavelet transforms, particularly suited to detecting faint sources in crowded fields. We have detected 78 sources, 13 of which were detected only with the HRI, and 37 detected only with the PSPC. For each source, we have computed the 0.2-2.0 keV X-ray flux. Using optical data from the literature and our own low-dispersion spectroscopic observations, we find candidate optical counterparts for 62 X-ray sources, with more than 80% of these counterparts being late type stars. The number of sources (38 of 62) with high membership probability counterparts is consistent with that expected for Galactic plane observations at our sensitivity. We have computed maximum likelihood X-ray luminosity functions (XLF) for F and early-G type stars with high membership probability. Heavy data censoring due to our limited sensitivity permits determination of only the high-luminosity tails of the XLFs; the distributions are indistinguishable from those of the nearly coeval Pleiades cluster.”

What else might be hiding inside Messier 47? Try new debris disk candidates. As Nadya Gorlova (et al) indicated in a 2004 study:

“Sixty-three members of the 100 Myr old open cluster M47 (NGC 2422) have been detected with the Spitzer Space Telescope. The Be star V 378 Pup shows an excess both in the near-infrared, probably due to free-free emission from the gaseous envelope. Seven other early-type stars show smaller excesses. Among late-type stars, two show large excesses. P1121 is the first known main-sequence star showing an excess comparable to that of Beta Pic, which may indicate the presence of an exceptionally massive debris disk. It is possible that a major planetesimal collision has occurred in this system, consistent with the few hundred Myr timescales estimated for the clearing of the solar system.”

*Iof the star cluster Messier 47 taken by the Wide Field Imager camera on the 2.2-metre telescope at ESO’s La Silla Observatory in Chile. Credit: ESO*

History of Observation:

Messier 47 was originally discovered before 1654 by Hodierna who described it as:

“[A] Nebulosa between the two dogs”… but it was an observation that wasn’t known about until long after Charles Messier independently recovered it on February 19, 1771. “Cluster of stars, little distant from the preceding; the stars are greater; the middle of the cluster was compared with the same star, 2 Navis. The cluster contains no nebulosity.”

However, it was one of those very rare circumstances when Messier actually made a mistake in his position calculations. Despite this error, the cluster was observed by Caroline Herschel and identified as M47 at least twice in early 1783.

As a consequence of Messier’s position mistake, Sir William Herschel also independently rediscovered it on February 4, 1785, and gave it the number H VIII.38. “A cluster of pretty compressed large [bright] and small [faint] stars. Round. Above [more than] 15′ diameter.” It would be John Herschel, on December 16, 1827, who would be the first to resolve Sigma 1121: “The chief star of a large, pretty rich, straggling cluster. It [the star] is double.”

*Atlas Image mosaic obtained of Messier 47 as part of the Two Micron All Sky Survey (2MASS). Credit: UMass/IPAC/Caltech/NASA/NSF*

The “Messy” mistake would haunt star catalogs – including both Herschel’s and Dreyer’s for years, until the whole clerical error was cleared up by Owen Gingerich in 1960:

“More explicit reasons for this identification [of M47 with NGC 2422] were given independently in 1959 by T.F. Morris, a member of the Messier Club of the Royal Astronomical Society of Canada’s Montreal Centre. Dr. Morris suggested that an error in signs in the difference between M47 and the comparison star could account for the position. Messier determined the declination of a nebula or cluster by measuring the difference between the object and a comparison star of known declination. The right ascension could be found by recording the times at which the object and the star drifted across a central wire in his telescope’s field; the time interval gives the difference in right ascension. The differences between Messier’s 1770 [actually 1771] position for M47 and his stated comparison star, 2 Navis (now 2 Puppis), if applied with opposite signs, leads to NGC 2422. Clearly, Messier made a mistake in computation!”

May you have Caroline Herschel’s luck finding it!

Locating Messier 47:

There is no simple way of finding Messier 47 in the finderscope of a telescope, but it’s not too hard with binoculars. Begin your hunt a little more than a fist width east/northeast of bright Sirius (Alpha Canis Majoris)… or about 5 degrees (3 finger widths) south of Alpha Monoceros. (It can sometimes by seen with the unaided eye under good conditions as a dim nebulosity.) There you will find two open clusters that will usually appear in the same average binocular field of view.

*Messier 47 location. Image: IAU and Sky & Telescope magazine (Roger Sinnott & Rick Fienberg)*

M47 is the westernmost of the pair. It will appear slightly brighter and the stars will be more fewer and more clearly visible. In the finderscope it will appear as if it is resolving, while neighboring eastern M46 will just look like a foggy patch. Because M47’s stars are brighter, it is better suited to less than perfect sky conditions, showing as a compression that begins to resolve in binoculars and will resolves almost fully even a small telescope.

And here are the quick facts on this Messier Object to help you get started:

Object Name: Messier 47
Alternative Designations: M47, NGC 2422
Object Type: Open Galactic Star Cluster
Constellation: Puppis
Right Ascension: 07 : 36.6 (h:m)
Declination: -14 : 30 (deg:m)
Distance: 1.6 (kly)
Visual Brightness: 5.2 (mag)
Apparent Dimension: 30.0 (arc min)

Be to sure to check out our complete Messier Catalog. And for more information, check out the SEDS Messier Database.

Sources:

June 12, 2017June 12, 2017 by Tammy Plotner

Messier 46 – the NGC 2437 Open Star Cluster

Welcome back to Messier Monday! In our ongoing tribute to the great Tammy Plotner, we take a look at Orion’s Nebula’s “little brother”, the De Marian’s Nebula!

During the 18th century, famed French astronomer Charles Messier noted the presence of several “nebulous objects” in the night sky. Having originally mistaken them for comets, he began compiling a list of them so that others would not make the same mistake he did. In time, this list (known as the Messier Catalog) would come to include 100 of the most fabulous objects in the night sky.

One of these objects is the open star cluster known as Messier 46, which is located about 5,500 light years away in the southern Puppis constellation. Located in close proximity to another open cluster (Messier 47), this bright, rich cluster is about 300 million years old and is home to many stars – an estimated 500 – and some impressive nebulae too.

Description:

Crammed into about 30 light years of space, around 150 resolvable stars and up to 500 possible stellar members all took off together on a journey through space some 300 million years ago. At this point in time, they are about 5,400 light years away from our solar system, but they aren’t standing still. They’re pulling away from us at a speed of 41.4 kilometers per second.

*The Messier 46 open star cluster. Credit: Jose Luis Martinez*

If you notice something just a bit different about one of the stars along the northern edge – then you’ve caught on to one of the most famous features of Messier 46 – its resident planetary nebula. While radial velocities show it probably isn’t a true member of the cluster, it’s still a cool feature!

But, is there more to this cluster than that? You bet. Messier 46 has also been highly studied for its core properties. As Saurabh Sharma (et al) indicated in a 2006 study:

“The study of Galactic open clusters is of great interest in several astrophysical aspects. Young open clusters provide information about current star formation processes and are key objects for clarifying questions of Galactic structure, while observations of old and intermediate-age open clusters play an important role in studying the theories of stellar and Galactic evolution. A detailed analysis of the structure of coronae of open clusters is needed to understand the effects of external environments, like the Galactic tidal field and impulsive encounters with interstellar clouds, etc., on dynamical evolution of open clusters. Extensive studies of the coronal regions of clusters have not been carried out so far mainly because of unavailability of photometry in a large field around open star clusters. The ability to obtain improved photometry of thousands of stars means that large-scale studies of open clusters can be conducted to study the spatial structure and stability of Galactic open clusters. With the addition of photometry of a nearby field region it is possible to construct luminosity functions (LFs) and MFs, which are useful for understanding cluster-formation processes and the theory of star formation in open clusters.”

History of Observation:

Messier 46 is an original discovery of Charles Messier, caught on February 19, 1771, just after he released his first catalog of entries. In his journal, he wrote:

“A cluster of very small stars, between the head of the Great Dog and the two hind feet of the Unicorn, [its position] determined by comparing this cluster with the star 2 Navis, of 6th-magnitude, according to Flamsteed; one cannot see these stars but with a good refractor; the cluster contains a bit of nebulosity.”

At the time of its discovery, Messier had not published his findings quite as immediately as we do today, so another astronomer also independently discovered this cluster as well… Caroline Herschel. “March 4th, [17]83. 1 deg S following the nebula near the 2nd Navis… a Nebula the figure is done by memory. My Brother observed it with 227 and found it to be, an astonishing number of stars. it is not in Mess. catalogue.”

It would be John Herschel in 1833 who would discover the planetary nebula while cataloging it: “The brightest part of a very fine rich cluster; stars of 10th magnitude; which fills the field. Within the cluster at its northern edge is a fine planetary nebula.”

But, as always, Admiral Symth has a way with words and observations. As he wrote of the object:

“A very delicate double star in a fine cluster, outlying the Galaxy, over Argo’s poop. A 8 1/2 [mag], and B 11, both pale white.A noble though rather loose assemblage of stars from the 8th to the 13th magnitude, more than filling the field, especially in length, with power 93; the most compressed part trending sf [south following, SE] and np [north preceding, NW]. Among the larger [brighter] stars on the northern verge is an extremely faint planetary nebula, which is 39 H. IV. [NGC 2438], and 464 of his son’s Catalogue. This was discovered by Messier in 1769, who considered it as being “rather enveloped in nebulous matter;” this opinion, however, must have arisen from the splendid glow of mass, for judging from his own remark, it is not likely that he perceived the planetary nebula on the north. WH [William Herschel], who observed it in 1786, expressly says, “no connexion with the cluster, which is free from nebulosity.” Such is my own view of attentively gazing; but the impression left on the senses, is that of awful vastness and bewildering distance, – yet including the opinion, that those bodies bespangled the vastness of space, may differ in magnitude and other attributes.”

Pretty amazing considering these gentlemen did all of their observations visually and knew nothing about today’s parallaxes, radial velocities or any other type of thing. May your own observations be as talented…

Locating Messier 46:

There is no simple way of finding Messier 46 in the finderscope of a telescope, but it’s not too hard with binoculars. Begin your hunt a little more than a fistwidth east/northeast of bright Sirius (Alpha Canis Majoris)… or about 5 degrees (3 finger widths) south of Alpha Monoceros. There you will find two open clusters that will usually appear in the same average binocular field of view. M46 is the easternmost of the pair.

*Messier 46 location. Credit: IAU/Sky & Telescope magazine (Roger Sinnott & Rick Fienberg)*

It will appear slightly dimmer and the stars will be more concentrated. In the finderscope it will appear as a slightly foggy patch, while neighboring western M47 will try to begin resolution. Because M46’s stars are fainter, it is better suited to darker sky conditions, showing as a compression in binoculars and will resolve fairly well with even a small telescope. However, you will need at least a 6″ telescope to perceive the planetary nebula.

And here are the quick facts on this Messier Object to help you get started:

Object Name: Messier 46
Alternative Designations: M46, NGC 2437
Object Type: Open Galactic Star Cluster
Constellation: Puppis
Right Ascension: 07 : 41.8 (h:m)
Declination: -14 : 49 (deg:m)
Distance: 5.4 (kly)
Visual Brightness: 6.0 (mag)
Apparent Dimension: 27.0 (arc min)

Be to sure to check out our complete Messier Catalog. And for more information, check out the SEDS Messier Database.

Sources:

June 5, 2017June 5, 2017 by Tammy Plotner

Messier 45 – The Pleiades Cluster

Pleiades stars. Image: NASA, ESA, AURA/Caltech, Palomar Observatory. Credit: D. Soderblom and E. Nelan (STScI), F. Benedict and B. Arthur (U. Texas), and B. Jones (Lick Obs.)

Welcome back to Messier Monday! In our ongoing tribute to the great Tammy Plotner, we take a look at the universally-renowned cluster known for its seven major points of light – The Pleiades Cluster!

During the 18th century, famed French astronomer Charles Messier noted the presence of several “nebulous objects” in the night sky. Having originally mistaken them for comets, he began compiling a list of them so that others would not make the same mistake he did. In time, this list (known as the Messier Catalog) would come to include 100 of the most fabulous objects in the night sky.

One of these is the famous Pleiades Cluster, also known as the Seven Sisters (and countless other names). An open star cluster located approximately 390 to 456 light years from Earth in the constellation of Taurus, this cluster is dominated by very bright, hot blue stars. Being both bright and of one of the nearest star clusters to Earth, this cluster is easily visible to the naked eye in the night sky.

Description:

The nine brightest stars of the Pleiades are named for the Seven Sisters of Greek mythology: Sterope, Merope, Electra, Maia, Taygete, Celaeno, and Alcyone, along with their parents Atlas and Pleione. To the X-ray telescopes on board the orbiting ROSAT observatory, the cluster also presents an impressive, but slightly altered, appearance.

*An optical image of the Pleiades. Credit: NOAO/AURA/NSF*

This false color image was produced from ROSAT observations by translating different X-ray energy bands to visual colors – the lowest energies are shown in red, medium in green, and highest energies in blue. (The green boxes mark the position of the seven brightest visual stars.)

The Pleiades stars seen in X-rays have extremely hot, tenuous outer atmospheres called coronas and the range of colors corresponds to different coronal temperatures. This helps to determine mass and the presence of brown dwarf stars within Messier 45. As Greg Ushomirsky (et al) said in a 1998 study:

“We present an analytic calculation of the thermonuclear depletion of the light elements lithium, beryllium, and boron in fully convective, low-mass stars. Under the presumption that the pre-main-sequence star is always fully mixed during contraction, we find that the burning of these rare light elements can be computed analytically, even when the star is degenerate. Using the effective temperature as a free parameter, we constrain the properties of low-mass stars from observational data, independently of the uncertainties associated with modeling their atmospheres and convection. Our analytic solution explains the dependence of the age at a given level of elemental depletion on the stellar effective temperature, nuclear cross sections, and chemical composition. These results are also useful as benchmarks to those constructing full stellar models. Most importantly, our results allow observers to translate lithium nondetections in young cluster members into a model-independent minimum age for that cluster. Using this procedure, we have found lower limits to the ages of the Pleiades (100 Myr) and Alpha Persei (60 Myr) clusters. Dating an open cluster using low-mass stars is also independent of techniques that fit upper main-sequence evolution. Comparison of these methods provides crucial information on the amount of convective overshooting (or rotationally induced mixing) that occurs during core hydrogen burning in the 5-10 Mo stars typically at the main-sequence turnoff for these clusters.”

As one of the closest of star clusters to our solar system, M45 is dominated by hot blue stars that have only formed within the last 100 million years. Alongside Maia is a reflection nebula discovered by Tempel faint nebula which accompanies Merope was discovered by master observer E.E. Barnard. These were first believed to be left over from the formation of the cluster.

However, it didn’t take many years of observation of proper motion for astronomers to realize the Pleiades were actually moving through a cloud of interstellar dust. While this pleasing blue group is still only 440 light years away, it only has about another 250 million years left before tidal interactions will tear it apart. By then, its relative motion will have carried it from the constellation of Taurus to the southern portion of Orion!

Of course, many observers aren’t quite sure if they are seeing the nebulosity in M45 or not. Chances are, if you’re seeing what appears to be a “fog” around the bright stars – you’re on it. Only large aperture or photography reveals the full extent of the reflection nebula… and there’s a whole lot of scientific reasons for it. Said Steven Gibson (et al) in a 2003 study:

“The scattering geometry analysis is complicated by the blending of light from many stars and the likely presence of more than one scattering layer. Despite these complications, we conclude that most of the scattered light comes from dust in front of the stars in at least two scattering layers, one far in front and extensive, the other nearer the stars and confined to areas of heavy nebulosity. The first layer can be approximated as an optically thin, foreground slab whose line-of-sight separation from the stars averages ~0.7 pc. The second layer is also optically thin in most locations and may lie at less than half the separation of the first layer, perhaps with some material among or behind the stars. The association of nebulosity peripheral to the main condensation around the brightest stars is not clear. Models with standard grain properties cannot account for the faintness of the scattered UV light relative to the optical. Some combination of significant changes in grain model albedo and phase function asymmetry values is required. Our best-performing model has a UV albedo of 0.22+/-0.07 and a scattering asymmetry of 0.74+/-0.06. Hypothetical optically thick dust clumps missed by interstellar sight line measurements have little effect on the nebular colors but might shift the interpretation of our derived scattering properties from individual grains to the bulk medium.”

Since the Pleaides really is close to our solar system, have astronomers been able to detect anything within its boundaries that has surprised them? The answer is yes. according to a 1998 study by E.L. Martin:

“We present the discovery of an object in the Pleiades open cluster, named Teide 2, with optical and infrared photometry that places it on the cluster sequence slightly below the expected substellar mass limit. We have obtained low- and high-resolution spectra that allow us to determine its spectral type (M6), radial velocity, and rotational broadening and to detect H? in emission and Li I in absorption. All the observed properties strongly support the membership of Teide 2 in the Pleiades. This object has an important role in defining the reappearance of lithium below the substellar limit in the Pleiades.”

*The M45 cluster. Credit: Wikipedia Commons/Did23*

And what star is that? One cataloged as known as HD 23514, which has a mass and luminosity a bit greater than our Sun. But it’s a star surrounded by an extraordinary number of hot dust particles. “Unusually massive amounts of dust, as seen at the Pleiades and Aries stars, cannot be primordial but rather must be the second-generation debris generated by collisions of large objects,” said Song, “”Collisions between comets or asteroids wouldn’t produce anywhere near the amount of dust we are seeing.”

The astronomers analyzed emissions from countless microscopic dust particles and concluded that the most likely explanation is that the particles are debris from the violent collision of planets or planetary embryos. Song calls the dust particles the “building blocks of planets,” which can accumulate into comets and small asteroid-size bodies and then clump together to form planetary embryos, eventually becoming full-fledged planets.

“In the process of creating rocky, terrestrial planets, some objects collide and grow into planets, while others shatter into dust,” Song said. “We are seeing that dust.”

History of Observation:

The recognition of the Pleiades dates back to antiquity, and its stars are known by many names in many cultures. The Greeks and Romans referred to them as the “Starry Seven,” the “Net of Stars,” “The Seven Virgins,” “The Daughters of Pleione,” and even “The Children of Atlas.” The Egyptians referred to them as “The Stars of Athyr;” the Germans as “Siebengestiren” (the Seven Stars); the Russians as “Baba” after Baba Yaga – the witch who flew through the skies on her fiery broom.

*The Pleiades by Elihu Vedder (1885). Credit: Metropolitan Museum of Art, New York City.*

The Japanese call them “Subaru;” Norsemen saw them as packs of dogs; and the Tongans as “Matarii” (the Little Eyes). American Indians viewed the Pleiades as seven maidens placed high upon a tower to protect them from the claws of giant bears, and even Tolkien immortalized the star group in The Hobbit as “Remmirath.” The Pleiades were even mentioned in the Bible! So, you see, no matter where we look in our “starry” history, this cluster of seven bright stars has been part of it.

Charles Messier would log it on March 4, 1769 where his only comment would be: “Cluster of stars known by the name Pleiades: the position reported is that of the star Alcyone.” Even though historic astronomers did little more than comment on M45’s presence, we’re still glad the Charles logged it – for it never received another “official” catalog designation!

Locating Messier 45:

Most normally the Pleiades are easily found with the unaided eye as a very visible cluster of stars about a hand span northwest of Orion. However, if sky conditions are bright, M45 might be a little more difficult to spot. If so, look for bright, red star Aldebaran and set your sights about 10 degrees (an average fist width) northwest.

It will show very easily in any size optics and under virtually any conditions – except for clouds and daylight! Messier 45’s large size makes it an ideal candidate for binoculars, where it will cover about half the average field of view. When using a telescope, chose the least amount of magnification possible to see the entire cluster and use higher magnification to study individual stars.

*The location of the Centaurus constellation in the southern sky. Credit: IAU/Sky & Telescope magazine/Roger Sinnott & Rick Fienberg*

And as always, here are the quick facts on this Messier Object to help you get started:

Object Name: Messier 45
Alternative Designations: M45, the Pleiades, Seven Sisters, Subaru
Object Type: Open Galactic Star Cluster, Reflection Nebula
Constellation: Taurus
Right Ascension: 03 : 47.0 (h:m)
Declination: +24 : 07 (deg:m)
Distance: 0.44 (kly)
Visual Brightness: 1.6 (mag)
Apparent Dimension: 110.0 (arc min)

Be to sure to check out our complete Messier Catalog. And for more information, check out the SEDS Messier Database.

Sources:

May 29, 2017May 29, 2017 by Tammy Plotner

Messier 44 – The Beehive Cluster (Praesepe)

Welcome back to Messier Monday! In our ongoing tribute to the great Tammy Plotner, we take a look at that buzzing nest of stars – the Beehive Cluster!

During the 18th century, famed French astronomer Charles Messier noted the presence of several “nebulous objects” in the night sky. Having originally mistaken them for comets, he began compiling a list of them so that others would not make the same mistake he did. In time, this list (known as the Messier Catalog) would come to include 100 of the most fabulous objects in the night sky.

One of these is the Beehive Cluster (aka. Messier 44, or Praesepe), an open star cluster located in the the Cancer constellation. In addition to containing a larger population of stars than most clusters in its vicinity, it is also one of the nearest open clusters to the Solar System – at a distance of 577 light years (177 parsecs). As such, astronomers have been aware of it since Classical Antiquity.

Description:

According to ancient lore, this group of stars (often called the Praesepe) foretold a coming storm if it was not visible in otherwise clear skies. Of course, this came from a time when combating light pollution meant asking your neighbors to dim their candles. But, once you learn where it’s at, it can be spotted unaided even from suburban settings. Hipparchus called it the “Little Cloud,” but not until the early 1600s was its stellar nature revealed.

*Close up of the Praesepe (Messier 44) open star cluster. Credit: Wikisky*

Believed to be about 550 light-years away, this awesome cluster consists of hundreds of members – with at least four orange giants and five white dwarfs. M44’s age is similar to that of the Pleiades, and it is believed that both clusters have a common origin. Although you won’t see any nebulosity in the Beehive, even the very smallest of binoculars will reveal a swarm of bright stars and large telescopes can resolve down to 350 faint stars.

Messier 44 is the nearest open cluster of its type to our Solar System, and it contains a larger star population than most other nearby clusters. Under dark skies the Beehive Cluster looks like a nebulous object to the unaided eye; thus it has been known since ancient times. The classical astronomer Ptolemy called it “the nebulous mass in the heart of Cancer,” and it was among the first objects that Galileo studied with his telescope.

The cluster’s age and proper motion coincide with those of the Hyades stellar association, suggesting that both share a similar origin. Both clusters also contain red giants and white dwarfs, which represent later stages of stellar evolution, along with main sequence stars of spectral classes A, F, G, K, and M. So far, eleven white dwarfs have been identified, representing the final evolutionary phase of the cluster’s most massive stars, which originally belonged to spectral type B. Brown dwarfs, however, are extremely rare in this cluster, probably because they have been lost by tidal stripping from the halo.

Messier 44 is home to 5 red giant stars and a handful of white dwarf stars. But, M44 also contains one peculiar blue star. Among its members, there is the eclipsing binary TX Cancri, the metal line star Epsilon Cancri, and several Delta Scuti variables of magnitudes 7-8, in an early post-main-sequence state. And in all those stars, there’s a lot of other peculiarities to be found!

*Atlas Image of the Beehive Cluster obtained as part of the Two Micron All Sky Survey (2MASS). Credit: UMass/IPAC (Caltech)/NASA/NSF*

As Sergei M. Andrievsky indicated in a 1998 study:

“We present the results of a spectroscopic study of four blue stragglers from old galactic open cluster NGC 2632 (Praesepe). The LTE analysis based on Kurucz’s atmosphere models and synthetic spectra technique has shown that three stars, including the hottest star of the cluster HD73666, possess an uniform chemical composition: they show a solar-like abundance (or slight overabundance) of iron and an apparent deficiency of oxygen and silicon. Two stars exhibit a remarkable barium overabundance. The chemical composition of their atmospheres is typical for Am stars. One star of our sample does not share such uniform elemental distribution, being generally deficient in metals.”

But is there more hiding in there? Perhaps the kind of stuff that could eventually make planets? According to a 2009 study done by A. Gaspar (et al), this was certainly thought to the be the case:

“Mid-IR excesses indicating debris disks are found for one early-type and for three solar-type stars. The incidence of excesses is in agreement with the decay trend of debris disks as a function of age observed for other cluster and field stars. We show that solar-type stars lose their debris disk 24 um excesses on a shorter timescale than early-type stars. Simplistic Monte Carlo models suggest that, during the first Gyr of their evolution, up to 15%-30% of solar-type stars might undergo an orbital realignment of giant planets such as the one thought to have led to the Late Heavy Bombardment, if the length of the bombardment episode is similar to the one thought to have happened in our solar system.”

In September of 2012, two planets were confirmed to be orbiting around two separate stars in the Beehive Cluster. The finding was significant since the stars were similar to Earth’s Sun, and this was the first instance where exoplanets were found orbiting a Sun-like star within a stellar cluster. These planets were designated as Pr0201b and Pr0211b, both of which are “Hot Jupiters” (i.e. gas giants that orbit close to their stars). In 2016, additional observations showed that the Pr0211 system actually has two planets, the second one being Pr0211-c.

History of Observation:

This beautiful, nearby star cluster has been known since ancient times and played wonderful roles in mythology. Aratos mentioned this object as “Little Mist” as far back as 260 BC, and Hipparchus included this object in his star catalog and called it “Little Cloud” or “Cloudy Star” in 130 BC. Ptolemy mentions it as one of seven “nebulae” he noted in his Almagest, and describes it as “The Nebulous Mass in the Breast (of Cancer)”.

According to Burnham, it appeared on Johann Bayer’s chart (about 1600 AD) as “Nubilum” (“Cloudy” Object). It was even resolved by Galileo in 1609 who said: “The nebula called Praesepe contains not one star only but a mass of more than 40 small stars. We have noted 36 besides the Aselli (Gamma and Delta Cancri).”

Messier 44 was partly resolved by Orion nebula’s discoverer, Peiresc, in 1611, who said, “Nebula was seen in the vicinity of Jupiter to the east. in which more than 15 stars have been counted.” and added to Hevelius’ catalog as number 291. De Cheseaux charted it as his number 11 and Bode as his number 20. Small wonder Messier felt the need to add his own numbers to it as well when he recorded:

“At simple view [with the naked eye], one sees in Cancer a considerable nebulosity: this is nothing but a cluster of many stars which one distinguishes very well with the help of telescopes, and these stars are mixed up at simple view [to the unaided eye] because of their great proximity. The position in right ascension of one of the stars, which Flamsteed has designated with the letter c, reduced to March 4, 1769, should be 126d 50′ 30″, for its right ascension, and 20d 31′ 38″ for its northern declination. This position is deduced from that which Flamsteed has given in his catalog.”

*Image of M44 Beehive cluster taken by the author, Miguel Garcia. Credit: Intihuatana (Miguel Garcia)*

While Sir William Herschel would ignore it and Caroline Herschel would only write that she “observed it”, John Herschel would go on to give it an NGC designation and Admiral Smyth would sing its poetic praises. Is it possible that watching this star cluster could help fortell the weather? If you believe the words of Aratos, it just might.

“Watch, too, the Manger. Like a faint mist in the North it plays the guide beneath Cancer. Around it are borne two faintly gleaming stars, not far apart nor very near but distant to the view a cubit.s length, one on the North, while the other looks towards the South. They are called the Asses [in the constellation Cancer], and between them is the Manger. On a sudden, when all the sky is clear, the Manger wholly disappears, while the stars that go on either side seem nearer drawn to one another: not slight then is the storm with which the fields are deluged. If the Manger darken and both stars remain unaltered, they herald rain. But if the Ass to the North of the Manger shine feebly through a faint mist, while the Southern Ass is gleaming bright, expect wind from the South: but if in turn the Southern Ass is cloudy and the Northern bright, watch for the North wind.”

And watch for a swarm of incredible starlight!

Locating Messier 44:

Messier 44 is so bright that it easily shows to the unaided eye as a nebulous patch just above the conjunction of the faint, upside down “Y” asterism of the Cancer constellation. However, not everyone lives where dark skies are a rule – so try using both Pollux and Procyon to form the base of an imaginary triangle. Now aim your binoculars or finderscope near the point of the apex to discover M44 – the Beehive.

*The location of Messier 44 in the Cancer constellation. Credit: IAU and Sky & Telescope magazine (Roger Sinnott & Rick Fienberg)*

Since Messier 44 is about a degree and a half in diameter, it will require that you use your lowest magnification eyepiece in a telescope, and it is very well suited to binoculars of all sizes. Because its major stars are also quite bright, it stands up to urban sky and moonlight conditions, but many more stars are revealed with higher magnification and darker skies. Because M44 is very near the ecliptic plane, you’ll often find a planet or the Moon mixing it up with the stars!

Object Name: Messier 44
Alternative Designations: M44, NGC 2632, Beehive Cluster, The Praesepe, The Manger
Object Type: Open Galactic Star Cluster
Constellation: Cancer
Right Ascension: 08 : 40.1 (h:m)
Declination: +19 : 59 (deg:m)
Distance: .577 (kly)
Visual Brightness: 3.7 (mag)
Apparent Dimension: 95.0 (arc min)

Be to sure to check out our complete Messier Catalog. And for more information, check out the SEDS Messier Database.

Sources:

May 22, 2017May 22, 2017 by Tammy Plotner

Messier 43 – the De Marian’s Nebula

The De Mairan's Nebula (aka. Messier 43) and the Orion Nebula. Credit: Wikisky

Welcome back to Messier Monday! In our ongoing tribute to the great Tammy Plotner, we take a look at Orion’s Nebula’s “little brother”, the De Marian’s Nebula!

During the 18th century, famed French astronomer Charles Messier noted the presence of several “nebulous objects” in the night sky. Having originally mistaken them for comets, he began compiling a list of them so that others would not make the same mistake he did. In time, this list (known as the Messier Catalog) would come to include 100 of the most fabulous objects in the night sky.

One of these if the diffuse nebula known as the De Marian’s Nebula (aka. Messier 43). Located in the direction of the Orion constellation (in close proximity to the Orion Nebula), this nebula lies at a distance of 1,600 light years from Earth. Together with the Orion Nebula, it is part of one of the most active star-forming regions visible in the night sky.

Description:

The diffuse nebula M43 surrounds the variable star N U Orionis (HD 37061) – a rather cool, young star cooking in a rich HII region. But is the light that’s reaching us actually coming through a tunnel in this dusty cloud? As Karl Wurm and Mario Perinotto explained in a 1970 study:

“Most of the areas with identical monochromatic features show a high deficiency of cluster stars correlated with a low surface brightnesss and a reduced gas density. This is explained by an opaqueness of the emission strata in the direction in the line of sight and a position of the same nearer to the observer than the extension of the cluster. There appear surface structures at large distances from the Trapezium which show a correlation between the intensity of scattered star light and the intensity of the emission of the higher ions ([Oiii], [Neiii]). This observation is considered as a proof that canals through the nebular cloud complex allow in some directions the exciting radiation to reach large distances from the star without having suffered an appreciable absorption or scattering.”

De Mairan’s Nebula, M43, NGC 1982. Image: NASA, ESA, M. Robberto (Space Telescope Science Institute/ESA) and the Hubble Space Telescope Orion Treasury Project Team — *De Mairan’s Nebula, M43, NGC 1982. Credit: NASA/ESA/M. Robberto (Space Telescope Science Institute/ESA)/Hubble Space Telescope Orion Treasury Project Team*

However, N U is far from being alone…. The whole complex is littered with stars being born! As Bo Reipurth (et al), stated in a 1999 study:

“The OMC-2/3 molecular clouds contain one of the highest concentrations of protostars known in nearby molecular clouds. We have observed an area of about 6 × 15 (0.8 pc × 2 pc) covering the OMC-2/3 region with the Very Large Array in the D configuration at 3.6 cm, matching well the area of a recent 1300 m survey. We detected 14 sources, of which it is highly probable that 11 sources are either protostars or very young stars. This testifies to the star-forming activity and extreme youth of the OMC-2/3 region. The 3.6 cm flux is free-free emission probably due to shocks in outflowing material. Three of the sources are extended even with the relatively low resolution of the present observations, and two of these may be collimated radio jets. The large fraction of submillimeter continuum sources that have a radio continuum counterpart is evidence that outflow is already common at the very earliest evolutionary stages. No relation is found between the radio continuum flux and the 1300 m flux of the associated submillimeter dust clumps.”

History of Observation:

In 1731, Jean-Jacques Dortous de Mairan was the first to notice this independent portion of the Orion nebula, stating:

“Finally I will add that close to the luminous space in Orion [M42], one sees the star d of Huygens [NU Orionis] currently (1731) surrounded by a brilliance very similar to that which produces, as I believe, the atmosphere of our Sun, if it were dense enough and extensive enough to be visible in Telescopes at a similar distance. See it in the form and the situation [given by] D, according to what was determined with the Reticule.”

On March 4, 1771, Charles Messier would also come to the same conclusion as he states in his observing notes:

“The star which is above, and has little distance from that nebula, and of which is spoken in the Traite de l’Aurore boreale [Treat of the Northern Light] by M. de Mairan is surrounded, and equally by a very thin light; the star doesn’t have the same brilliance as the four of the great nebula: its light is pale, and it appears covered by fog. I determined its position; its right ascension was 81d 3′ 0″, and its declination 5d 26′ 37″ south.”

*Close-up view of the Orion Nebula’s little brother, Messier 43, taken by NASA/ESA Hubble Space Telescope. Credit: ESA/Hubble & NASA*

While Sir William Herschel was very careful not to assign his own catalog numbers to Messier Objects, he, too, was fascinated by the M43 region. In his personal notes he writes:

“In the year 1774, the 4th of March, I observed the nebulous star, which is the 43d of the Connoissance des Temps and is not many minutes north of the great nebula; but at the same time I also took notice of two similar, but much smaller nebulous stars; one on each side of the large one, and at nearly equal distance from it. Fig. 37 is a copy of the drawing which was made at the time of observation.

“In 1783, I reexamined the nebulous star, and found it to be faintly surrounded with a circular glory of whitish nebulosity, faintly joined to the great nebula. About the latter end of the same year I remarked that it was not equally surrounded, but most nebulous toward the south.

“In 1784, I began to entertain an opinion that the star was not connected with the nebulosity of the great nebula in Orion, but was one of those which are scattered over that part of the heavens.

“In 1801, 1806, and 1810 this opinion was fully confirmed, by the gradual change which happened in the great nebula, to which the nebulosity surrounding this star belongs. For the intensity of the light about the nebulous star had by this time been considerably reduced, by attenuation or dissipation of nebulous matter; and it seemed now to be pretty evident that the star is far behind the nebulous matter, and that consequently its light in passing through it is scattered and deflected, so as to produce the appearance of a nebulous star. A similar phenomenon may be seen whenever a planet or a star of the 1st or 2nd magnitude happens to be involved in haziness; for a diffused circular light will then be seen, to which, but in a much inferior degree, that which surrounds this nebulous star bears a great resemblance.

“When I reviewed this interesting object in December 1810, I directed my attention particularly to the two small nebulous stars, by sides of the large one, and found that they were perfectly free from every nebulous appearance; which confirmed not only my former surmise of the great attenuation of the nebulosity, but also proved that their former nebulous appearance had been entirely the effect of the passage of their feeble light through the nebulous matter spread out before them.

The 19th of January 1811, I had another critical examination of the same object in a very clear view through the 40-feet telescope; but notwithstanding the superior light of this instrument, I could not perceive any remains of nebulosity about the two small stars, which were perfectly clear, and in the same situation, where about thirty-seven years before I had seen them involved in nebulosity.”

May this wonderful region entertain your brain for as many years as it did Bill Herschel!

*The location of Messier 43 in the constellation of Orion. Credit: IAU/Sky & Telescope magazine (Roger Sinnott & Rick Fienberg)*

Locating Messier 43:

Locating M43 is as easy as locating… well… M42! This small star cluster accompanied by an emission/reflection nebula just to the north of the Orion Nebula’s “Trapezium” region is often mistake for part of the great nebula itself. However, if you look closely, you’ll see the two are separated by a dark dust lane.

Begin by locating the asterism of three stars known as Orion’s Belt. If you cover it with your fist held at arm’s length in a “thumb’s down” gesture with your left hand, the tip of your thumb will just about mark the correct spot in the sky. From a dark location when no Moon is present, you can easily see the haze of the Orion nebula surrounding the stars in the “sword” asterism. While it is easily seen in binoculars on a dark night, it will fade significantly under light pollution or moonlight.

And here are the quick facts on Messier 43 to help you get started:

Object Name: Messier 43
Alternative Designations: M43, NGC 1982, De Mairan’s Nebula, Companion of the Orion Nebula
Object Type: Emission/Reflection Nebula and Open Cluster
Constellation: Orion
Right Ascension: 05 : 35.6 (h:m)
Declination: -05 : 16 (deg:m)
Distance: 1.3 (kly)
Visual Brightness: 9.0 (mag)
Apparent Dimension: 20×15 (arc min)

Be to sure to check out our complete Messier Catalog. And for more information, check out the SEDS Messier Database.

Sources: