Globular Cluster Archives

July 18, 2016July 18, 2016 by Tammy Plotner

Messier 19 (M19) – The NGC 6273 Globular Cluster

Messier Object 19, as imaged with an amateur telescope.Credit: Hewholooks/Wikipedia Commons

Welcome back to Messier Monday! In our ongoing tribute to the great Tammy Plotner, we take a look at the Messier 19 globular star cluster. Enjoy!

In the 18th century, while searching the night sky for comets, French astronomer Charles Messier began noticing a series of “nebulous objects” in the night sky. Hoping to ensure that other astronomers did not make the same mistake, he began compiling a list of these objects,. Known to posterity as the Messier Catalog, this list has come to be one of the most important milestones in the research of Deep Sky objects.

One of these objects is Messier 19, a globular star cluster located in the constellation Ophiuchus. Of all the known globular clusters, M19 appears to be one of the most oblate (i.e. flattest) in the night sky. Discovered by William Herschel, this cluster is relatively difficult to spot with the naked eye, and appears as a fuzzy point of light with the help of magnification.

Description:

Speeding away from us at a rate of 146 kilometers per second, this gravitationally bound ball of stars measuring 140 light years in diameter, is one of the Messier globular clusters that has the distinction of being closest to the center of the Milky Way. At a little more than 5000 light-years from the intense gravitation of our own galactic core, it has played havoc on M19’s round shape.

In essence, Milky Way’s gravity has caused M19 to become one of the most oblate of all globular clusters, with twice as many stars along the major axis as along the minor. And, although it is 28,000 light-years from Earth, it’s actually on the opposite side of the galactic core. For all of its rich, dense mass, four RR Lyrae variable stars have been found in M19.

*The constellation Ophiuchis. Credit: iau.org*

Is Messier 19 unique? It has some stellar branch properties that are difficult to pinpoint. And even its age (though estimated at around 11.9 billion years old) is indeterminate. Says F. Meissner and A. Weiss in their 2006 study, “Global fitting of globular cluster age indicators“:

“The determination of globular cluster (GC) ages rests on the fact that colour-magnitude diagrams (CMDs) of single-age single composition stellar populations exhibit specific time-dependent features. Most importantly, this is the location of the turn-off (TO), which – together with the cluster’s distance – serves as the most straightforward and widely used age indicator. However, there are other parts of the CMD that change their colour or brightness with age, too. Since the sensitivity to time is different for the various parts of the cluster CMD, it is possible to use either the various indicators independently, or the differences in colour and brightness between pairs of them; these latter methods have the advantage of being independent of distance.”

What’s occurring is a horizontal branch gap – an not-quite explainable difference in the way the stars inside M19 are aging. However, science is looking for the answer. As G. Busso et al. explained in their 2008 paper titled “The Peculiar Horizontal Branch Morphology of the Galactic Globular Clusters NGC 6388 and NGC 6441“:

“I show that a possible solution of the puzzle is to assume that a small fraction of the stellar population in the two clusters is strongly helium enriched. The presence of two distinct stellar populations characterized by two different initial He contents can help in explaining the brightness difference between the red portion of the HB and the blue component.”

*The Messier 19 globular cluster, as viewed by the Two Micron All-Sky Survey (2MASS). Credit: 2MASS/ipac.caltech.edu*

Is helium the answer? Quite probably so. M. Salaris Astrophysics Research Institute and an international team of researchers explained in their 2004 study “The initial helium abundance of the Galactic globular cluster system“:

“Based on a recently updated set of stellar evolution models, we performed an accurate statistical analysis in order to assess whether GGCs show a statistically significant spread in their initial He abundances, and whether there is a correlation with the cluster metallicity. As in previous works on the subject, we do not find any significant dependence of the He abundance on the cluster metallicity; this provides an important constraint for models of Galaxy formation and evolution. Apart from GGCs with the bluest Horizontal Branch morphology, the observed spread in the individual helium abundances is statistically compatible with the individual errors. This means that either there is no intrinsic abundance spread among the GGCs, or that this is masked by the errors. In the latter case we have estimated a firm upper limit of 0.019 to the possible intrinsic spread. In case of the GGCs with the bluest Horizontal Branch morphology we detect a significant spread towards higher abundances inconsistent with the individual errors; this can be fully explained by additional effects not accounted for in our theoretical calibrations, which do not affect the abundances estimated for the clusters with redder Horizontal Branch morphology.”

History of Observation:

M19 was one of Charles Messier’s original discoveries, which he first observed on June 5th, 1764. In his notes, he wrote:

“I have discovered a nebula, situated on the parallel of Antares, between Scorpius and the right foot of Ophiuchus: that nebula is round & doesn’t contain any star; I have examined it with a Gregorian telescope which magnified 104 times, it is about 3 minutes of arc in diameter: one sees it very well with an ordinary refractor of 3 feet and a half. I have observed its passage of the Medirian, and compared it with that of the star Antares; I have determined the right ascension of that nebula of 252d 1′ 45″, and its declination of 25d 54′ 46″ south. The known star closest to that nebula is the 28th of the constellation Ophiuchus, after the catalog of Flamsteed, of sixth magnitude.”

Messier 19 and Antares. Credit: Wikisky — *The Messier 19 globular cluster, relative to M4, M80 and Antares. Credit: Wikisky*

While Charles didn’t resolve it, we must give him due credit for discovery, for its size wouldn’t make it a particularly easy object given his optics. Later, in 1784, William Herschel would become the first to open up its true identity:

“When the 19th of the Connoiss. is viewed with a magnifying power of 120, the stars are visible; the cluster is insulated; some of the small stars scattered in the neighborhood are near it; but they are larger than those belonging to the cluster. With 240 it is better resolved, and is much condensed in the centre. With 300 no nucleus or central body can be seen. The diameter with the 10 feet is 3’16”, and the stars in the centre are too accumulated to be separately seen. It will not be necessary to add that the two last mentioned globular clusters, viewed with more powerful instruments, are of equal beauty with the rest; and 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.”

While you may – or may not – resolve Messier 19’s individual stars, even small telescopes can pick up on some of its ellipticity and larger telescopes will make out a definite blue tinge to its coloration. Before you yawn at viewing another globular cluster, remember that you are looking at the other side of our galactic center and think on the words about M19 from Admiral Symth.

“The whole vicinity,” he wrote, “afford a grand conception of the grandeur and richness even of the exterior creation; and indicate the beautious gradation and variety of the heaven of heavens. Truly has it been said, “Stars teach us as well as shine.” This is near the large opening or hole, about 4deg broad, in the Scorpion’s body, which WH [William Herschel] found almost destitute of stars.”

en:Messier 19 globular cluster by en:Hubble Space Telescope; 2.5? view en:NASA, en:STScI, en:WikiSky - en:WikiSky's — *The Messier 19 globular cluster, as imaged by the Hubble Space Telescope. Credit:NASA/STSc /HST/WikiSky*

Locating Messier 19:

Finding M19’s location in binoculars is quite easy – it’s less than a fistwidth (8 degrees) east of Antares (Alpha Scorpi). However, ‘seeing’ M19 in binoculars (especially smaller ones) is a little more problematic. The steadier the binoculars are, the better your chances, since it will appear almost stellar at first glance. A good indicator is to have optical double 26 Ophiuchi in the field at the 2:00 position and look for the star that won’t quite come to focus in the 8:00 position.

Star 26 also makes for a great finderscope lead when locating M19 in a telescope as well. Even for aperture sizes as small as 114mm, this globular cluster will show quite easily in a telescope and reveal its oblate nature. When aperture size increase to the 8″ range, it will begin resolution and as it nears 12″ or more, you’ll pick up on blue stars.

And for your convenience, here are the quick facts of M19:

Object Name: Messier 19
Alternative Designations: M19, NGC 6273
Object Type: Class VIII Globular Star Cluster
Constellation: Ophiuchus
Right Ascension: 17 : 02.6 (h:m)
Declination: -26 : 16 (deg:m)
Distance: 28.0 (kly)
Visual Brightness: 6.8 (mag)
Apparent Dimension: 17.0 (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.

June 20, 2016April 17, 2019 by Tammy Plotner

Messier 15 (M15) – The Great Pegasus Cluster

The M15 Globular Cluster (aka. Great Hercules Cluster). Astronomers suspect the existence of one or more intermediate-mass black holes at its heart. Credit: NASA/ESA/HST

Welcome back to Messier Monday! Today, in our ongoing tribute to Tammy Plotner, we take a look at the M15 globular cluster, one of the oldest and best known star clusters in the night sky. Enjoy!

In the 18th century, French astronomer Charles Messier began noticing a series of “nebulous objects” in the night sky while looking for comets. Not wanting other astronomers to make the same mistake, he began compiling a list of these objects into a catalog. In time, this list would include 100 objects, and came to be known by future astronomers as the Messier Catalog.

One of these objects is the globular cluster known as M15. Located in the northern constellation Pegasus, it is one of the brightest clusters in the night sky (with a visual brightness that is roughly 360,000 times that of our Sun). It is also one of the finest globular clusters in the northern section of the sky, the best deep-sky object in the constellation of Pegasus, and one of the oldest and best known globular clusters.

Description:

Messier 15 is probably the most dense globular cluster in our entire Milky Way galaxy – having already undergone a process of contraction. What does that mean to what you’re seeing? This ball of stars measures about 210 light years across, yet more than half of the stars you see are packed into the central area in a space just slightly more than ten light years in size.

By looking for single stars within globular clusters, the Hubble Space Telescope was either looking for a massive black hole or evidence of a “core collapse” – the intense gravity of so many stars so close together. Although it was peeking nearly 37,000 light-years away, the Hubble was able to resolve hundreds of stars converging on M15’s core. Like magnetism, their gravity would either cause them to attract or repel one another – and a black hole may have formed at some point in the cluster’s 12-billion-year life.

*The globular cluster known as Messier 15, located some 35 000 light-years away in the Pegasus constellation. Credit: Mount Lemmon SkyCenter/University of Arizona*

The study which addressed this data – which appeared in the January 1996 issue of the Astronomical Journal, was led by Puragra Guhathakurta of UCO/Lick Observatory, UC Santa Cruz – asked the question of whether or not the speed of the cluster’s stars could tell us if M15’s dense core was caused by a single huge object, or just mutual attraction. As Guhathakurta stated in the study:

“It is very likely that M15’s stars have concentrated because of their mutual gravity. The stars could be under the influence of one giant central object, although a black hole is not necessarily the best explanation for what we see. But if any globular cluster has a black hole at its center, M15 is the most likely candidate.”

John Bahcall and astrophysicist Jeremiah Ostriker of Princeton University were the first to forward the idea that Messier 15 might be hiding a black hole. While it is distinct from many other globular clusters by having such a dense core, it really isn’t that much different than all the rest of the globular clusters we see. Yet, no where else in our galaxy, except at its core, are the stars that dense!

It is estimated that 30,000 distinct stars exist in the inner 22 light-years of the cluster alone. The closer the Hubble telescope looked, the more stars it found. This increase in stellar density continued all the way to within 0.06 light-years of the center – about 100 times the distance between our Sun and Pluto. “Detecting separate stars that close to the core was at the limit of Hubble’s powers,” says Brian Yanny of the Fermi National Accelerator Laboratory.

*The location of M15, within the Pegasus Constellation. Credit: IAU and Sky & Telescope magazine (Roger Sinnott & Rick Fienberg)*

At this point, even the great Hubble could not distinguish individual stars, or locate the exact position of the core. Guhathakurta and is colleagues theorized that the stars crowd even closer inside the radius, so they plotted the distribution of the stars as a function of distance from the core. When the results came back, they had two answers – either a black hole was responsible, or a gravothermal catastrophe called core collapse was the culprit.

“It’s a catastrophe in the sense that once it starts, this process can run away very quickly,” said Guhathakurta. “But other processes could cause the core to bounce back before it collapses all the way.”

At an estimated 13.2 billion years old, it is one of the oldest known globular clusters, but it isn’t done throwing some surprises at us. M15 was the first globular cluster in which a planetary nebula, Pease 1 or K 648 (“K” for “Kuster”), could be identified – and can be seen with larger aperture amateur telescopes. Even stranger is the fact that Messier 15 contains 112 variable stars, and 9 known pulsars – neutron stars which are the leftovers of ancient supernovae. And one of these is a double neutron star system – M15 C.

History of Observation:

M15 was discovered by Jean-Dominique Maraldi on September 7, 1746 while he was looking for a comet. Says he:

“On September 7 I noticed between the stars Epsilon Pegasi and Beta Equulei, a fairly bright nebulous star, which is composed of many stars, of which I have determined the right ascension of 319d 27′ 6″, and its northern declination of 11d 2′ 22”. About 25 years later, Charles Messier would independently rediscover it to add to his own catalog, describing it as: “In the night of June 3 to 4, 1764, I have discovered a nebula between the head of Pegasus and that of Equuleus it is round, its diameter is about 3 minutes of arc, the center is brilliant, I have not distinguished any star; having examined it with a Gregorian telescope which magnifies 104 times, it had little elevated over the horizon, and maybe that observed at a greater elevation one can perceive stars.”

Camera SBIG STX16803 CCD Camera Filters Astrodon Gen II Dates December 2015 Location Mount Lemmon SkyCenter Exposure RGB = 2 : 2 : 2 Hours Acquisition Astronomer Control Panel (ACP), Maxim DL/CCD (Cyanogen), FlatMan XL (Alnitak) Processing CCDStack, Photoshop, PixInsight Credit Line & Copyright Adam Block/Mount Lemmon SkyCenter/University of Arizona — *Deep Broadband (RGB) image of M15, taken from the Mount Lemmon SkyCenter. Credit and Copyright: Adam Block/Mount Lemmon SkyCenter/University of Arizona*

Sir William Herschel would be the first to resolve some of its stars, but not the core. It would be his son John who would later pick up structure. However, like the dutiful and colorful observer that he was, Admiral Smyth will leave us with this lasting impression:

“Although this noble cluster is rated as globular, it is not exactly round, and under the best circumstances is seen as in the diagram, with stragglers branching from a central blaze. Under a moderate magnifying power, there are many telescopic and several brightish stars in the field; but the accumulated mass is completely insulated, and forcibly strikes the senses as being almost infinitely beyond those apparent comets. Indeed, it may be said to appear evidently aggregated by mutual laws, and part of some stupendous and inscrutable scheme of involution; for there is nothing quiescent throughout the immensity of the vast creation.”

Considering Smyth’s observations were made nearly two centuries before we really began to understand what was going on inside Messier 15, you’ll have to admit he was a very good observer!

Locating Messier 15:

Surprisingly enough, globular cluster M15 is easy to find. Once you’ve located the “Great Square” of Pegasus, simply choose its brightest and southwesternmost star – Alpha. Now identify the small, kite shape of the constellation of Delphinus. Roughly halfway between these two (and slightly south), you’ll spy a slightly reddish star – Epsilon Peg (Enif).

By placing Enif in your binoculars or image correct finderscope at the 7:00 position, you can’t miss this bright, compact beauty. Even the smallest of optics will reveal the round glow and telescopes starting at 4″ will begin resolution – while large telescopes will simply amaze you. However, don’t expect to open this globular up to the core region. As already noted, its pretty dense in there!

And here are the quick facts for Messier 15, for your convenience:

Object Name: Messier 15
Alternative Designations: M15, NGC 7078
Object Type: Class IV Globular Cluster
Constellation: Pegasus
Right Ascension: 21 : 30.0 (h:m)
Declination: +12 : 10 (deg:m)
Distance: 33.6 (kly)
Visual Brightness: 6.2 (mag)
Apparent Dimension: 18.0 (arc min)

May 16, 2016June 20, 2016 by Tammy Plotner

Messier 14 (M14) – the NGC 6402 Globular Cluster

Messier 14 with amateur telescope. Credit: Wikipedia Commons/Hewholooks

Welcome back to Messier Monday! Today, in our ongoing tribute to Tammy Plotner, we take a look at the M14 globular cluster!

In the 18th century, French astronomer Charles Messier began cataloging all the “nebulous objects” he had come to find while searching the night sky. Having originally mistook these for comets, he compiled a list these objects in the hopes of preventing future astronomers from making the same mistake. In time, the list would include 100 objects, and would come to be known as the Messier Catalog to posterity.

One of these objects was the globular cluster which he would designate as M14. Located in the southern constellation Ophiuchus, this slightly elliptically-shaped stellar swarm contains several hundred thousand stars, a surprising number of which are variables. Despite these stars not being densely concentrated in the central region, this object is not hard to spot for amateur astronomers that are dedicated to their craft!

Description:

Located some 30,000 light years from Earth and measuring 100 light years in diameter, this globular cluster can be found in the southern Ophiuchus constellation, along with several other Messier Objects. Although it began its life some 13.5 billion years ago, it is far from being done changing. It is still shaking intracluster dust from its shoes.

What this means is that M14, like many globular clusters, contains a good deal of matter that it picked up during its many times orbiting the center of our Galaxy. According to studies done by N. Matsunaga (et al):

“Our goal is to search for emission from the cold dust within clusters. We detect diffuse emissions toward NGC 6402 and 2808, but the IRAS 100-micron maps show the presence of strong background radiation. They are likely emitted from the galactic cirrus, while we cannot rule out the possible association of a bump of emission with the cluster in the case of NGC 6402. Such short lifetime indicates some mechanism(s) are at work to remove the intracluster dust… (and) its impact on the chemical evolution of globular clusters.”

Another thing that makes Messier 14 unusual is the presence of CH stars, such as the one that was discovered in 1997. CH stars are a very specific type of Population II carbon stars that can be identified by CH absorption bands in the spectra. Middle aged and metal poor, these underluminous suns are known to be binaries. Patrick Cote, the chief author of the research team that discovered the star, wrote in their research report to the American Astronomical Society:

“We report the discovery of a probable CH star in the core of the Galactic globular cluster M14 (=NGC 6402 = C1735-032), identified from an integrated-light spectrum of the cluster obtained with the MOS spectrograph on the Canada-France-Hawaii telescope. Both the star’s location near the tip of the red giant branch in the cluster color-magnitude diagram and its radial velocity therefore argue for membership in M14. Since the intermediate-resolution MOS spectrum shows not only enhanced CH absorption but also strong Swan bands of C2, M14 joins Centaurus as the only globular clusters known to contain “classical” CH stars. Although evidence for its duplicity must await additional radial velocity measurements, the CH star in M14 is probably, like all field CH stars, a spectroscopic binary with a degenerate (white dwarf) secondary.”

History of Observation:

The first recorded observations of the cluster were made by Charles Messier, who described it as a nebula without stars and catalogued it on June 1st, 1764. As he noted in his catalog:

“In the same night of June 1 to 2, 1764, I have discovered a new nebula in the garb which dresses the right arm of Ophiuchus; on the charts of Flamsteed it is situated on the parallel of the star Zeta Serpentis: that nebula is not considerable, its light is faint, yet it is seen well with an ordinary [non-achromatic] refractor of 3 feet & a half [FL]; it is round, & its diameter can be 2 minutes of arc; above it & very close to it is a small star of the nineth magnitude. I have employed for seeing this nebula nothing but the ordinary refractor of 3 feet & a half with which I have not noticed any star; maybe with a larger instrumentone could perceive one. I have determined the position of that nebula by its passage of the Meridian, comparing it with Gamma Ophiuchi, it has resulted for its right ascension 261d 18? 29?, & for its declination 3d 5? 45? south. I have marked that nebula on the chart of the apparent path of the Comet which I have observed last year [the comet of 1769].”

In 1783, William Herschel observed the cluster and was the first to resolve it into individual stars. As he noted, “With a power of 200, I see it consists of stars. They are better visible with 300. With 600, they are too obscure to be distinguished, though the appearance of stars is still preserved. This seems to be one of the most difficult objects to be resolved. With me, there is not a doubt remaining; but another person, in order to form a judgement, ought previously to go through all the several gradations of nebulae which I have resolved into stars.“

As always, it was Admiral William Henry Smyth who provided the most lengthy and detailed description, which he did in July of 1835:

“A large globular cluster of compressed minute stars, on the Serpent-bearer’s left arm. This fine object is of a lucid white colour, and very nebulous in aspect; which may be partly owing to its being situated in a splendid field of stars, the lustre of which interferes with it. By diminishing the field under high powers, some of the brightest of these attendants are excluded, but the cluster loses its definition. It was discovered by Messier in 1764, and thus described: “A small nebula, no star; light faint; form round; and may be seen with a telescope 3 1/2 feet long.” The mean apparent place is obtained by differentiation from Gamma Ophiuchi, from which it is south-by-west about 6deg 1/2, being nearly midway between Beta Scorpii and the tail of Aquila, and 16deg due south of Rasalhague [Alpha Ophiuchi]. Sir William Herschel resolved this object in 1783, with his 20-foot reflector, and he thus entered it: “Extremely bright, round, easily resolvable; with [magnification] 300 I can see the stars. The heavens are pretty rich in stars of a certain size [magnitude, brightness], but they are larger [brighter] than those in the cluster, and easily to be distinguished from them. This cluster is considerably behind the scattered stars, as some of them are projected upon it.” He afterwards added: “From the observations with the 20-foot telescope, which in 1791 and 1799 had the power of discering stars 75-80 times as far as the eye, the profundity of this cluster must be of the 900th order.” “It resembles the 10th Connoissance des temps [Messier 10], which probably would put on the same appearance as this, were it removed half its distance farther from us.”

Finder Chart for M14 (also shown M10 and M12). Credit: freestarcharts.com — *Finder Chart for Messier 14 (also showing M10 and M12). Credit: freestarcharts.com*

Locating Messier 14:

Messier 14 can be found by first locating Delta Ophiuchi, which M14 is located at about 21 degrees east and 0.4 degrees north from. It can also be found about one-third of the way from Beta to Eta Ophiuchi. If you know where Messier 10 is, take a look 0.8 degrees north and 10 degrees east of it to find M14. The cluster can also be located along the imaginary line from Cebalrai, an orange giant with an apparent magnitude of 2.76 and the fifth brightest star in Ophiuchus, to Antares, the bright red supergiant located in Scorpius.

With an apparent magnitude of +7.6, M14 can be easily observed with binoculars. For those using small telescopes, the bright center and faint halo can be viewed, whereas 8-inch instruments will reveal the cluster’s elliptical shape. To resolve individual stars, you will need a 12-inch telescope or larger. The best time of year to observe the cluster is in the months of May, June and July.

And here are the quick facts for Messier 15, for your convenience:

Object Name: Messier 14
Alternative Designations: M14, NGC 6402
Object Type: Globular Cluster
Constellation: Ophiuchus
Right Ascension: 17 : 37.6 (h:m)
Declination: -03 : 14 (deg: m)
Distance: 30.3 (kly)
Visual Brightness: 7.6 (mag)
Apparent Dimension: 11.0 (arc minutes)

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

April 4, 2016April 4, 2016 by Tammy Plotner

Messier 10 (M10) – The NGC 6254 Globular Cluster

Messier Object 10. as imaged by the Hubble Space Telescope Credit: NASA/:STScI:WikiSky

Welcome to another installment of Messier Monday! Today, we continue in our tribute to our dear friend, Tammy Plotner, by taking a look at Messier Object 10.

In the 18th century, French astronomer Charles Messier noted the presence of several “nebulous objects” in the night sky while searching for comets. Hoping to ensure that other astronomers did not make the same mistake, he began compiling a list of 1oo of them. This list came to be known as the Messier Catalog, and would have far-reaching consequences.

In addition to being as a major milestone in the history of astronomy and the study of Deep Sky Objects. One of these objects is known as Messier 10 (aka. NGC 6254), a globular cluster that is located in the equatorial constellation of Ophiuchus. Of the many globular clusters that appear in this constellation (seven of which were cataloged by Messier himself) M10 is the brightest, and can be spotted with little more than a pair of binoculars. Continue reading “Messier 10 (M10) – The NGC 6254 Globular Cluster”

February 29, 2016February 29, 2016 by Tammy Plotner

Messier 5 (M5) – The NGC 5904 Globular Cluster

The globular cluster Messier 5, one of the oldest belonging to the Milky Way. Credit: NASA/ESA/HST

In the late 18th century, Charles Messier was busy hunting for comets in the night sky, and noticed several “nebulous” objects. After initially mistaking them for the comets he was seeking, he began to compile a list of these objects so other astronomers would not make the same mistake. Known as the Messier Catalog, this list consists of 100 objects, consisting of distant galaxies, nebulae, and star clusters.

Among the many famous objects in this catalog is the M5 globular star cluster (aka. NGC 5904). Located in the galactic halo within the Serpens Constellation, this cluster of stars is almost as old as the Universe itself (13 billion years)! Though very distant from Earth and hard to spot, it is a favorite amongst amateur astronomers who swear by its beauty.

Continue reading “Messier 5 (M5) – The NGC 5904 Globular Cluster”

December 29, 2014December 23, 2015 by Bob King

Put Yourself in the Way of Beauty

Comet C/2014 Q2 Lovejoy photographed overnight December 28-29, 2014 remotely from Siding Spring, Australia as passed within 1/6 degree of the globular cluster M79. The coma glows green from fluorescing carbon molecules while the narrow ion tail is carbon monoxide gas fluorescing in UV sunlight. Credit: Rolando Ligustri

Oh my, oh my. Rolando Ligustri captured this scene last night as Comet Q2 Lovejoy swished past the globular cluster M79 in Lepus. If you’ve seen the movie Wild or read the book, you’ll be familiar with the phrase “put yourself in the way of beauty”, a maxim for living life adopted by one of its characters. When I opened up my e-mail today and saw Rolando’s photo, I felt like the beauty truck ran right over me.

Another striking image of the comet's juxtaposition with the globular cluster M79. Lovejoy is presently 48 million miles from Earth; the cluster shines from the immense distance of 410,000 light years. Credit: Chris Schur — Another striking image of the comet’s juxtaposition with the globular cluster M79. Lovejoy is presently 48 million miles from Earth; the cluster lies at the immense distance of 41,000 light years. Credit: Chris Schur

More beautiful images arrived later including this one by Chris Schur of Arizona.

Even with the Moon at first quarter phase, the comet was plainly visible in binoculars last night shining at magnitude +5. I used 8x40s and had no problem seeing Lovejoy’s blobby glow. With a coma about 15-20 arc minutes in diameter or more than half the size of a the Full Moon, it really fills up the field of view when seen through a telescope at low to medium magnification.

A tighter view of the top image shows not only the star cluster but also shows 13th magnitude NGC 1886, an edge-on spiral galaxy. Credit: Rolando Ligustri

If you love the aqua blue hues of the Caribbean, Lovejoy will remind you it’s time to book another tropical vacation. In both my 15-inch (37-cm) and 10-inch (25-cm) reflectors, the coma glowed a delicious pale blue-green in contrast to the pearly white cluster. I encourage you to look for the comet in the next few nights before the Moon is full. Starting on January 6-7, the Moon begins its move out of the evening sky, giving observers with dark skies a chance to view Lovejoy with the naked eye. I’m looking forward to seeing its long, faint tail twist among the stars of Eridanus as the comet rapidly moves northward over the next week.

Using Photoshop I made this drawing of the comet and cluster that captures its visual appearance through the telescope. Credit: Bob King — Using Photoshop I made this drawing of the comet and cluster that captures its visual appearance through the telescope last night December 28th. The nuclear region is very intense and bright and about 10 arc seconds across. Credit: Bob King

For a map on how to find the comet, check my recent article on Lovejoy’s many tails. Cheers to finding beauty the next clear night!

Comet Lovejoy was bright enough to nab in a 15-second time exposure with a 200mm telephoto lens last night. Details: f/2.8 at 13 seconds. Credit: Bob King

August 14, 2014December 23, 2015 by Elizabeth Howell

Diamond Pinpricks: Gorgeous Shot Of Star Group That Once Baffled Astronomers

A Hubble Space Telecope picture of globular cluster IC 4499. The new observations showed that it is about 12 billion years old, contrary to previous observations showing a puzzling young age. Credit: European Space Agency and NASA

Is this group of stars belonging to one generation, or more? That’s one of the things that was puzzling astronomers for decades, particularly when they were trying to pin down the age of IC 4499 — the globular cluster you see in this new picture from the Hubble Space Telescope.

While astronomers now know the stars are from a single generation that are about 12 billion years old (see this paper from three years ago), for about 15 years before that at least one paper said IC 4499 was three billion to four billion years younger than that.

“It has long been believed that all the stars within a globular cluster form at the about same time, a property which can be used to determine the cluster’s age,” stated information from the European Space Agency reposted on NASA’s website.

“For more massive globulars however, detailed observations have shown that this is not entirely true — there is evidence that they instead consist of multiple populations of stars born at different times.”

IC 4499 is somewhere in between these extremes, but only has a single generation of stars — its gravity wasn’t quite enough to pull in neighboring gas and dust to create more. Goes to show you how important it is to re-examine the results in science.

Source: NASA and the European Space Agency

January 11, 2013April 26, 2016 by Jason Major

So. Many. Stars…

Infrared image of globular cluster 47 Tucanae (NGC 104) captured by ESO’s VISTA telescope.

“My god, it’s full of stars!” said Dave Bowman in the movie 2010 as he entered the monolith, and one could imagine that the breathtaking view before him looked something like this.

Except this isn’t science fiction, it’s reality — this is an image of globular cluster 47 Tucanae taken by the European Southern Observatory’s VISTA telescope at the Paranal Observatory in Chile. It reveals in stunning detail a brilliant collection of literally millions of stars, orbiting our Milky Way galaxy at a distance of 15,000 light-years.

The full image can be seen below.

47 Tucanae (also known as NGC 104) is located in the southern constellation Tucana. It’s bright enough to be seen without a telescope and, even though it’s very far away for a naked-eye object, covers an area about the size of the full Moon.

In reality the cluster is 124 light-years across.

Although globular clusters like 47 Tucanae are chock-full of stars — many of them very old, even as stars go — they are noticeably lacking in clouds of gas and dust. It’s thought that all the gaseous material has long since condensed to form stars, or else has been blown away by radiation and outbursts from the cluster’s exotic inhabitants.

At the heart of 47 Tucanae lie many curious objects like powerful x-ray sources, rapidly-spinning pulsars, “vampire” stars that feed on their neighbors, and strange blue stragglers — old stars that somehow manage to stay looking young. (You could say that a globular cluster is the cosmic version of a trashy reality show set in Beverly Hills.)

Red giants can be seen surrounding the central part of the cluster, old bloated stars that are running out of fuel, their outer layers expanding.

The background stars in the image are part of the Small Magellanic Cloud, which was in the distance behind 47 Tucanae when this image was taken.

VISTA is the world’s largest telescope dedicated to mapping the sky in near-infrared wavelengths. Located at ESO’s Paranal Observatory in Chile, VISTA is revealing new views of the southern sky. Read more about the VISTA survey here.

Image credit: ESO/M.-R. Cioni/VISTA Magellanic Cloud survey. Acknowledgment: Cambridge Astronomical Survey Unit

July 15, 2012December 23, 2015 by Tammy Plotner

Weekly SkyWatcher’s Forecast: July 16-22, 2012

Messier 19 - Credit: Doug Williams, REU Program/NOAO/AURA/NSF

Greetings, fellow SkyWatchers! My satellite dish and internet connection has now returned from the land of Oz. While it was great to have a span of days where no electric meant no annoying lights, it also meant creative cooking excursions on the gas grill in 100 degree weather. Ah, well… the things we do for dark skies! This is New Moon week, so get out there and enjoy the Milky Way! Whenever you’re ready, meet me in the back yard…

Monday, July 16 – Today in 1850 at Harvard University, the first photograph of a star (other than the Sun) was made. The honors went to Vega! In 1994, an impact event was about to happen as nearly two dozen fragments of Comet Shoemaker-Levy 9 were speeding their way to the surface of Jupiter. The result was spectacular, and the visible features left behind on the planet’s atmosphere were the finest ever recorded.

Now let’s return again to the oblate and beautiful M19 and drop two fingerwidths south for another misshapen globular – M62 (Right Ascension: 17 : 01.2 – Declination: -30 : 07).

At magnitude 6, this 22,500 light-year distant Class IV cluster can be spotted in binoculars, but comes to wonderful life in the telescope. First discovered by Messier in 1771, Herschel was the first to resolve it and report on its deformation. Because it is so near to the galactic center, tidal forces have “crushed” it – much like M19. You will note when studying in the telescope that its core is very off center. Unlike M19, M62 has at least 89 known variable stars – 85 more than its neighbor – and the dense core may have undergone collapse. A large number of X-ray binaries have also been discovered within its structure, perhaps caused by the close proximity of stellar members. Enjoy it tonight!

Tuesday, July 17 – If you’re up to another challenge tonight, let’s go hunting Herschel I.44, also known as NGC 6401. You’ll find this 9.5 magnitude globular cluster around two fingerwidths northeast of Theta Ophiuchi and a little more than a degree due east of star 51 (Right Ascension: 17 : 38.6 – Declination: -23 : 55).

Discovered by William Herschel in 1784 and often classed as “uncertain,” today’s powerful telescopes have placed this halo object as a Class VIII and given it a rough distance from the galactic center of 8,800 light-years. Although neither William nor John could resolve this globular, and they listed it originally as a bright nebula, studies in 1977 revealed a nearby suspected planetary nebula named Peterson 1. Thirteen years later, further study revealed this to be a symbiotic star.

Symbiotic stars are a true rarity – not a singular star at all, but a binary system. A red giant dumps mass towards a white dwarf in the form of an accretion disc. When this reaches critical mass, it then causes a thermonuclear explosion resulting in a planetary nebula. While no evidence exists that this phenomenon is physically located within metal-rich NGC 6401, just being able to see it in the same field makes this journey both unique and exciting!

Wednesday, July 18 – On this day 27 years ago, India launched its first satellite (Rohini 1), and 31 years ago in the United States Gemini 10 launched carrying John Young and Michael Collins to space.

Now, let’s carry ourselves into space as we take a very unusual and beautiful journey to a bright and very colorful pair of stars known as Omicron 1 Cygni. Easily located about halfway between Alpha (Deneb) and Delta on the western side, this is a pure delight in binoculars or any size telescope. The striking gold color of 3.7 magnitude 31 Cygni (Omicron 1) is easily highlighted against the blue of same field companion, 5th magnitude 30 Cygni. Although this wide pairing is only an optical one, the K-type giant is a double star – an eclipsing variable around 150 times larger than or own Sun – and is surrounded by a gaseous corona more than double the size as the star itself. If you are using a scope, you can easy spot the blue tinted, 7th magnitude B star about one third the distance as between the two giants. Although our true pair are some 1.2 billion miles apart, they are oriented nearly edge-on from our point of view – allowing the smaller star to be totally eclipsed during each revolution. This total eclipse lasts for 63 days and happens about every 10.4 years, but don’t stay up too late… We’ve still got 7 years to wait!

Thursday, July 19 – Today in 1846, Edward Pickering was born. Although his name is not well known, he became a pioneer in the field of spectroscopy. Pickering was the Harvard College Observatory Director from 1876 to 1919, and it was during his time there that photography and astronomy began to merge. Known as the Harvard Plate Collection, these archived beginnings still remain a valuable source of data.

It’s New Moon, so why not have a look at something that would make Edward Pickering proud? He enthusiastically encouraged amateur astronomers, and founded the American Association of Variable Star Observers – so set your sights on RR Scorpius about two fingerwidths northeast of Eta and less than a fingerwidth southwest M62 (RA 16 56 37.84 Dec -30 34 48.2). This very red Mira type can reach as high as magnitude 5 and drop as low as 12 in about 280 days!

Tonight let’s just enjoy a little stargazing and revel in the beauty of our own galaxy’s spiral arm – the Milky Way. For those living in the city, you owe it to yourself to get away to a dark location to enjoy this veritable “river of stars” which spans out of the galactic center south and runs overhead. Almost directly behind you from the galactic anti-center stretches the Perseus arm, and the sight is a beautiful one. If skies are fine, you can easily see the dark dust rift where the arm separates and the billows of light of unresolved stars. It’s the most glorious sight of summer! While we have many days yet before the Aquarid meteor shower officially reaches its peak, you will be pleasantly surprised at this year’s high activity. They’ve been flying out of the night sky for almost two weeks now, and it would not surprise me if you saw ten or more per hour of these quick, bright visitors.

Friday, July 20 – Today was a busy day in astronomy history! In 1969, the world held its breath as the Apollo 11 lander touched down and Neil Armstrong and Edwin Aldrin became the first humans to touch the lunar surface. We celebrate our very humanity because even Armstrong was so moved that he messed up his lines! The famous words were meant to be “A small step for a man. A giant leap for mankind.” That’s nothing more than one small error for a man, and mankind’s success continued on July 20, 1976 when Viking 1 landed on Mars – sending back the first images ever taken from that planet’s surface.

If you’re out at sunset, be sure to look for the slimmest crescent Moon you can imagine… It will point your way to nearby Mercury! For lucky viewers “down under” this is an occultation event and will only be observable after sunset from southernmost regions of central Australia. Be sure to check the resources for websites like IOTA for specific times and locations.

The first assignment of the evening is a pair of interacting galaxies. 40 degrees northwest of Beta Canum Venaticorum is NGC 4490 (Right Ascension: 12 : 30.6 – Declination: +41 : 38) and smaller, fainter companion NGC 4485 (Right Ascension: 12 : 30.5 – Declination: +41 : 42). This pair, also known as Arp 269, are quite unusual in appearance to the larger scope. NGC 4490 is around magnitude 10 and shows a bright, irregular core region and a rather strange profile. Known as the “Cocoon” galaxy, it appears to almost reach toward its companion 3 degrees to the north. Progressively larger scopes under ideal conditions will be able to make out some faint mottling in the NGC 4490’s structure.

Now let’s honor southern skies by exploring the fantastic, NGC 3372 (Right Ascension: 10 : 43.8 – Declination: -59 : 52) – the Eta Carinae Nebula. As a giant, diffuse nebula with a visual brightness of magnitude 1, (wow!) it contains the most massive and luminous star in our Milky Way galaxy, Eta Carinae. It’s also home to a small cluster, Collinder 228, which is only one of 8 cataloged open clusters within the area of this huge star-forming region; the others are Bochum (Bo) 10, Trumpler (Tr) 14 (also cataloged as Cr 230), Tr 15 (= Cr 231), Cr 232, Tr 16 (= Cr 233), Cr 234, and Bo 11. Star Eta Carinae is involved in open cluster Trumpler 16. This fantastic nebula contains details which northerners can only dream about, such as the dark “Keyhole” and the “Homunkulus” around the giant star itself. A fantastic region for exploration with both telescopes and binoculars!

Saturday, July 21 – Today in 1961, Mercury 4 was launched, sending Gus Grissom into suborbital space on the second manned flight, and he returned safely in Liberty Bell 7.

Since the moonlight will now begin to interfere with our early evening globular cluster studies, let’s waive them for a while as we take a look at some of the region’s most beautiful stars. Tonight your goal is to locate Omicron Ophiuchi, about a fingerwidth northeast of Theta. At a distance of 360 light-years, this system is easily split by even small telescopes. The primary star is slightly dimmer than magnitude 5 and appears yellow to the eye. The secondary is near 7th magnitude and tends to be more orange in color. This wonderful star is part of many double star observing lists, so be sure to note it!

Tonight would be an ideal time to look at a brilliant open cluster about a fist width east of Epsilon Scorpii – M6 (Right Ascension: 17 : 40.1 – Declination: -32 : 13). On a moonless night, the 50 or so members of this 2000 light year distant, 100 million year old cluster can usually be seen unaided as a small fuzzy patch just above the Scorpion’s tail. Tonight we visit because the brighter skies will aid you in seeing the primary stars distinctive asterism. Using binoculars or telescope at lowest power, the outline of stars does truly resemble its namesake – the “Butterfly Cluster”. The M6 is much more than “just a pretty face” and we’ll be back to study under darker skies.

Sunday, July 22 – Tonight instead of lunar exploration, we will note the work of Friedrich Bessel, who was born on this day in 1784. Bessel was a German astronomer and mathematician whose functions, used in many areas of mathematical physics, still carry his name. But, you may put away your calculator, because Bessel was also the very first person to measure a star’s parallax. In 1837, he chose 61 Cygni and the result was no more than a third of an arc second. His work ended a debate that had stretched back two millennia to Aristotle’s time and the Greek’s theories about the distances to the stars.

Although you’ll need to use your finderscope with tonight’s brighter skies, you’ll easily locate 61 between Deneb (Alpha) and Zeta on the eastern side. Look for a small trio of stars and choose the westernmost. Not only is it famous because of Bessel’s work, but it is one of the most noteworthy of double stars for a small telescope. 61 Cygni is the fourth nearest star to Earth, with only Alpha Centauri, Sirius, and Epsilon Eridani closer. Just how close is it? Try right around 11 light-years.

Visually, the two components have a slightly orange tint, are less than a magnitude apart in brightness and have a nice separation of around 30 degrees to the south-southeast. Back in 1792, Piazzi first noticed 61’s abnormally large proper motion and dubbed it “The Flying Star.” At that time, it was only separated by around 10 degrees and the B star was to the northeast. It takes nearly 7 centuries for the pair to orbit each other, but there is another curiosity here. Orbiting the A star around every 4.8 years is an unseen body that is believed to be about 8 times larger than Jupiter. A star – or a planet? With a mass considerably smaller than any known star, chances are good that when you view 61 Cygni, you’re looking toward a distant world!

Until next week, dreams really do come true when you keep on reaching for the stars!

June 3, 2012December 23, 2015 by Tammy Plotner

Weekly SkyWatcher’s Forecast: June 4-10, 2012

Graphic Courtesy of Dave Reneke. — Graphic Courtesy of Dave Reneke

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Greeting, fellow SkyWatchers! It’s gonna’ be a great week! We start off with a partial lunar eclipse of the Strawberry Moon, head into the historic Venus Transit, study some Herschel objects, catch both the Scorpid and Arietid Meteor Showers, practice some binocular astronomy and even take on some challenge objects! How awesome is that? Whenever you’re ready, just follow me into the back yard…

Monday, June 4 – Tonight the Moon is full. Often referred to as the Full Strawberry Moon, this name was a constant to every Algonquin tribe in North America. But, our friends in Europe referred to it as the Rose Moon. The North American version came about because the short season for harvesting strawberries comes each year during the month of June – so the full Moon that occurs during that month was named for this tasty red fruit!

This evening as the Sun sets and the Moon rises opposite of it, take advantage of some quiet time and really stop to look at the eastern horizon. If you are lucky enough to have clear skies, you will see the Earth’s shadow rising – like a dark, sometimes blue band – that stretches around 180 degrees of horizon. Look just above it for a Rayleigh scattering effect known as the “Belt of Venus”. This beautiful pinkish glow is caused by the backscattering of sunlight and is often referred to as the anti-twilight arch. As the Sun continues to set, this boundary between our shadow and the arch rises higher in the sky and gently blends with the coming night. What you are seeing is the shadow of the Earth’s translucent atmosphere, casting a shadow back upon itself. This happens every night! Pretty cool, huh?

For some of us, it’s eclipse time! According to NASA’s Fred Espenak, most of the Americas will experience moonset before the partial lunar eclipse ends while eastern Asia will miss the beginning of the eclipse because it occurs before moonrise. The Moon’s contact times with Earth’s shadows are: Penumbral Eclipse Begins: 08:48:09 UT, Partial Eclipse Begins: 09:59:53 UT, Greatest Eclipse: 11:03:13 UT, Partial Eclipse Ends: 12:06:30 UT, Penumbral Eclipse Ends: 13:18:17. At the instant of greatest eclipse the umbral eclipse magnitude will reach 0.3705. At that time the Moon will be at the zenith for observers in the South Pacific. In spite of the fact that just a third of the Moon enters the umbral shadow (the Moon’s southern limb dips 12.3 arc-minutes into the umbra) the partial phase still lasts over 2 hours. Be sure to visit the resource pages for a visibility map and links to precise times and locations!

Tuesday, June 5 – Heads up for all observers! Today’s universal date marks an historic event – Venus will transit the Sun! This event will cross international date lines, so be sure to know ahead of time when and where to watch. North America will be able to see the start of the transit, while South Asia, the Middle East, and most of Europe will catch the end of it. For some great information on when, where and how to watch, visit www.transitofvenus.org. If you’re clouded out, there’s plenty of resources on-line to view this rare event. One that promises to have plenty of extra bandwidth to serve visitors is Astronomy Live. Be there!!

For all you Stargazers, keep watch for the Scorpid meteor shower. Its radiant will be near the constellation of Ophiuchus, and the average fall rate will be about 20 per hour with some fireballs.

While you’re out, take the time to check out Alpha Herculis -Ras Algethi. You will find it not only to be an interesting variable, but a colorful double as well. The primary star is one of the largest known red giants and at about 430 light years away, it is also one of the coolest. Its 5.4 magnitude greenish companion star is easily separated in even small scopes – but even it is a binary! This entire star system is enclosed in an expanding gaseous shell that originates from the evolving red giant. Enjoy it tonight.

Wednesday, June 6 – So far we’ve studied many Herschel objects in disguise as Messier catalog items – but we haven’t really focused on some mighty fine galaxies that are within the power of the intermediate to large telescope. Tonight let’s take a serious skywalk as we head to 6 Comae and drop two degrees south.

At magnitude 10.9, Herschel catalog object H I.35 is also known by its New General Catalog number of 4216 (Right Ascension: 12 : 15.9 – Declination: +13 : 09). This splendid edge-on galaxy has a bright nucleus and will walk right out in larger telescopes with no aversion required. But, the most fascinating part about studying anything in the Virgo cluster is about to be revealed.

While studying structure in NGC 4216, averted vision picks up magnitude 12 NGC 4206 (Right Ascension:12 : 15.3 – Declination: +13 : 02) to the south. This is also a Herschel object – H II.135. While it is smaller and fainter, the nucleus will be the first thing to catch your attention – and then you’ll notice it is also an edge-on galaxy! As if this weren’t distracting enough, while re-centering NGC 4216, sometimes the movement is just enough to allow the viewer to catch yet another edge-on galaxy to the north – NGC 4222 (Right Ascension: 12 : 16.4 – Declination: +13 : 19). At magnitude 14, you can only expect to be able to see it in larger scopes, but what a treat this trio is!

Is there a connection between certain types of galaxy structures within the Virgo cluster? Science certainly seems to think so. While low metallicity studies involving these galaxies are going on, research into evolution of galaxy clusters themselves continue to make new strides forward in our understanding of the universe. Capture them tonight!

Thursday, June 7 – If you’re up before dawn the next two days or out just after sunset, enjoy the peak of the June Arietid meteors – the year’s strongest daylight shower – with up to 30 visible per hour.

If you’d like to try your ear at radio astronomy with the offspring of sungrazing asteroid Icarus, tune an FM radio to the lowest frequency not receiving a clear signal. An outdoor antenna pointed at the zenith increases your chances, but even a car radio can pick up strong bursts! Simply turn up the static and listen. Those hums, whistles, beeps, bongs, and occasional snatches of signals are our own radio signals being reflected off the meteor’s ion trail!

Tonight let’s study a radio-source galaxy so bright it can be seen in binoculars – 8.6 magnitude M87 (Right Ascension: 12 : 30.8 – Declination: +12 : 24), about two fingerwidths northwest of Rho Virginis. This giant elliptical was discovered by Charles Messier in 1781 and cataloged as M87. Spanning 120,000 light-years, it’s an incredibly luminous galaxy containing far more mass and stars than the Milky Way – gravitationally distorting its four dwarf satellites galaxies. M87 is known to contain in excess of several thousand globular clusters – up to 150,000 – and far more than our own 200.

In 1918, H. D. Curtis of Lick Observatory discovered something else – M87 has a jet of gaseous material extending from its core and pushing out several thousand light-years into space. This highly perturbed jet exhibits the same polarization as synchrotron radiation – a property of neutron stars. Containing a series of small knots and clouds as observed by Halton Arp at Palomar in 1977, he also discovered a second jet in 1966 erupting in the opposite direction. Thanks to these two properties, M87 made Arp’s “Catalog of Peculiar Galaxies” as number 152.

In 1954 Walter Baade and R. Minkowski identified M87 with radio source Virgo A, discovering a weaker halo in 1956. Its position over an x-ray cloud extending through the Virgo cluster make M87 a source of an incredible amount of x-rays. Because of its many strange properties, M87 remains a target of scientific investigation. The Hubble has shown a violent nucleus surrounded by a fast rotating accretion disc, whose gaseous make-up may be part of a huge system of interstellar matter. As of today, only one supernova event has been recorded – yet M87 remains one of the most active and highly prized study galaxies of all. Capture it tonight!

Friday, June 8 – Born on this date in 1625 was Giovanni Cassini – the most notable observer following Galileo. As head of the Paris Observatory for many years, he was the first to observe seasonal changes on Mars and measure its parallax (and so, its distance). This set the scale of the solar system for the first time. Cassini was the first to describe Jovian features, and studied the Galilean moons’ orbits. He also discovered four moons of Saturn, but he is best remembered for being the first to see the namesake division between the A and B rings.

Why not honor Cassini’s work by visiting Saturn tonight? In case you hadn’t noticed, the beautiful yellowish “star” has been on the move and is now around a degree away to the southeast from a previous study star – Porrima! Not only is this a lovely visual, but an easy way to find Saturn if you’re new to the game. Seeing the Cassini Division in Saturn’s ring structure and some of the smaller moons will require at least a 114mm telescope and steady seeing. Use as much magnification as conditions will allow and look for unusual things – like seeing the planet edge through the gap!

Tonight we’ll use Rho Virginis as a stepping stone to more galaxies. Get on your mark and move one and a half degrees north for M59 (Right Ascension:12 : 42.0 – Declination: +11 : 39)…

First discovered in 1779 by J. G. Koehler while studying a comet, this 11th magnitude elliptical galaxy was observed and labeled by Messier who was just a bit behind him. Much denser than our own galaxy, M59 is only about one-fourth the size of the Milky Way. In a smaller telescope, it will appear as a faint oval, while larger telescopes will make out a more concentrated core region.

Now shift one half degree east for brighter and larger M60. Also caught first by Koehler on the same night as M59, it was “discovered” a day later by yet another astronomer who had missed M59! It took Charles Messier another four days until this 10th magnitude galaxy interfered with his comet studies and was cataloged. At around 60 million light-years away, M59 is one of the largest ellipticals known and has five times more mass than our galaxy. As a study object of the Hubble Telescope, this giant has shown a concentrated core with over 2 billion solar masses. Photographed and studied by large terrestrial telescopes, M59 may contain as many as 5100 globular clusters in its halo.

While our backyard equipment is essentially revealing M59?s core, there is a curiosity here. It shares “space” with spiral galaxy NGC 4647 (Right Ascension: 12 : 43.5 – Declination: +11 : 35). Telescopes of even modest aperture will pick up the nucleus and faint structure of this small face-on galaxy. Harlow Shapely found the pair odd because – while they are relatively close in astronomical terms – they are very different in age and development. Halton Arp also studied this combination of an elliptical galaxy affecting a spiral and cataloged it as “Peculiar Galaxy 116.” Be sure to mark your notes!

Saturday, June 9 – Today is the birthday of Johann Gottfried Galle. Born in Germany in 1812, Galle was the first observer to locate Neptune. He is also known for being Encke’s assistant – and he’s one of the few astronomers ever to have observed Halley’s Comet twice. Unfortunately, he died two months after the comet passed perihelion in 1910, but at a ripe old age of 98! I wonder if he knew Mark Twain?

Tonight while we’re out, let’s have a look at a Virgo galaxy bright enough for smaller instruments and detailed enough to delight larger scopes. Starting at Delta Virginis, move about a fistwidth to the west where you will see two fainter stars, 16 (south) and 17 (north) Virginis. You’ll find M61 (Right Ascension:12 : 21.9 – Declination: +04 : 28) located about one-half degree south of the yellow double star 17.

Its discovery was credited to Barnabus Oriani during that fateful year of 1779 when Messier was so avid about chasing a comet that he mistook it for one. While Charles had seen it on the same night, it took him two days to figure out it wasn’t moving and four more before he cataloged it. Fortunately, 7 years later Mr. Herschel assigned it his own number of H I.139, even though he wasn’t fond of assigning his own number to Messier catalog objects.

At near 10th magnitude, this spiral galaxy will show a slightly elongated form and brighter core area to small telescopes, and really come to life in larger ones. Close to our own Milky Way galaxy in size, this larger member of the Virgo cluster has great spiral arm structure that displays both knots and dark dustlanes – as well as a beautifully developed nucleus region. M61 has also been host to four supernova events between 1926 and 1999 – all of which have been well within range of amateur telescopes.

For an added Herschel treat tonight for larger scopes, hop back to star 17 and head about one half degree due west for near galactic pair NGC 4281 (H II.573) and NGC 4273 (H II.569). Here is a study of two galaxies similar in magnitude (12) and size – but of different structure. Northeastern NGC 4281 (Right Ascension: 12 : 20.4 – Declination: +05 : 23) is an elliptical, and by virtue of its central concentration will appear slightly larger and brighter – while southwestern NGC 4273 (Right Ascension: 12 : 19.9 – Declination: +05 : 21) is an irregular spiral which will appear brighter in the middle but more elongated and faded along its frontiers. Sharp-eyed observers may also note fainter (13th magnitude) NGC 4270 (Right Ascension: 12 : 19.8 – Declination: +05 : 28) north of this pairing.

Now, go back to Rho once again and about a fingerwidth northwest for yet another bright galaxy – M58 – a spiral galaxy actually discovered by Messier in 1779! As one of the brightest galaxies in the Virgo cluster, M58 (Right Ascension: 12 : 37.7 – Declination: +11 : 49) is one of only four that have barred structure. It was cataloged by Lord Rosse as a spiral in 1850. In binoculars, it will look much like our previously studied ellipticals, but a small telescope under good conditions will pick up the bright nucleus and a faint halo of structure – while larger ones will see the central concentration of the bar across the core. Chalk up another Messier study for both binoculars and telescopes and let’s get on to something really cool!

Around a half degree southwest are NGC 4567 (Right Ascension: 12 : 36.5 – Declination: +11 : 15) and NGC 4569 (Right Ascension: 12 : 36.8 – Declination: +13 : 10). L. S. Copeland dubbed them the “Siamese Twins,” but this galaxy pair is also considered part of the Virgo cluster. While seen from our viewpoint as touching galaxies, no evidence exists of tidal filaments or distortions in structure, making them a line of sight phenomenon and not interacting members. While that might take little of the excitement away from the “Twins,” a supernova event has been spotted in NGC 4569 as recently as 2004. While the duo is visible in smaller scopes as two, with soft twin nuclei, intermediate and larger scopes will see an almost V-shaped or heart-shaped pattern where the structures overlap. If you’re doing double galaxy studies, this is a fine, bright one! If you see a faint galaxy in the field as well, be sure to add NGC 4564 (Right Ascension: 12 : 36.4 – Declination: +11 : 26) to your notes.

Sunday, June 10 – While I’m sure that unaided eye viewers and binocular users are tired of the galaxy hunt, be sure to take the time to look at many old favorites that are now in view. To the eye, one of the most splendid signs of the changing seasons is the Ursa Major Moving Group which sits above Polaris for northern hemisphere observers. For the southern hemisphere, the return of Crux serves the same purpose.

Old favorites have now begun to appear again, such as Hercules, Cygnus and Scorpius… and with them a wealth of starry clusters and nebulae that will soon come into view as the night deepens and the hour grows late. Before we leave Virgo for the year, there is one last object that is seldom explored and such a worthy target that we must visit it before we go. Its name is NGC 5634 and you’ll find it halfway between Iota and Mu Virginis (RA 14 29.37 Dec -05 58.35)…First discovered by Sir William Herschel on March 5, 1785 and cataloged as H I.70, this magnitude 9.5 small globular cluster isn’t for everyone, but thanks to an 11th magnitude line-of-sight star on its eastern edge, it sure is interesting. At class IV, it’s more concentrated than many globular clusters, although its 19th magnitude members make it near impossible to resolve with backyard equipment.

Located a bit more than 82,000 light-years from our solar system and about 69,000 light-years from the galactic center, you’ll truly enjoy this globular for the randomly scattered stellar field which accompanies it. In the finderscope, an 8th magnitude star will lead the way – not truly a member of the cluster, but one that lies between us. Capturable in scopes as small as 4.5?, look for a concentrated central area surrounded by a haze of stellar members – a huge number of which are recently discovered variables. While you look at this globular, keep this in mind… Based on observations with the Italian Telescopio Nazionale Galileo, it is now surmised that the NGC 5634 globular cluster has the same position and radial velocity as does the Sagittarius dwarf spheroidal galaxy. Because of the dwarf galaxy’s metal-poor population of stars, it is believed that NGC 5634 may have once been part of the dwarf galaxy – and been pulled away by our own tidal field to become part of the Sagittarius stream!

Until next week? Wishing you clear skies for the Partial Lunar Eclipse, Venus Transit and the meteor showers!