Tammy was a professional astronomy author, President Emeritus of Warren Rupp Observatory and retired Astronomical League Executive Secretary. She’s received a vast number of astronomy achievement and observing awards, including the Great Lakes Astronomy Achievement Award, RG Wright Service Award and the first woman astronomer to achieve Comet Hunter's Gold Status.
(Tammy passed away in early 2015... she will be missed)
Welcome back to Messier Monday! Today, we continue in our tribute to our dear friend, Tammy Plotner, by looking at the globular cluster known as Messier 70.
In the late 18th century, French astronomer Charles Messier spent much of his time looking up at the night sky in search of comets. Over time, he discovered 100 fixed, diffuse objects that resembled comets, but were something else entirely. Messier compiled a list of these objects, hoping to prevent other astronomers from making the same mistake. What resulted was the Messier Catalog, one of the influential catalogs of Deep Sky Objects.
One of the objects he catalogued is Messier 70 (aka. NGC 6681), a globular cluster located 29,300 light years away from Earth and close to the Galactic Center. It’s location within the asterism known as the “Tea Pot” (which is part of the northern Sagittarius constellation). It is also in close proximity to both the M54 and M69 globular clusters. Continue reading “Messier 70 – the NGC 6681 Globular Cluster”
The globular clusters M69 and M70, which lie in the Sagittarius Constellation. Image: Wikisky
Welcome back to Messier Monday! Today, we continue in our tribute to our dear friend, Tammy Plotner, by looking at the globular cluster known as Messier 69.
In the 18th century, while searching the night sky for comets, French astronomer Charles Messier kept noting the presence of fixed, diffuse objects he initially mistook for comets. In time, he would come to compile a list of approximately 100 of these objects, hoping to prevent other astronomers from making the same mistake. This list – known as the Messier Catalog – would go on to become one of the most influential catalogs of Deep Sky Objects.
One of these objects is known as Messier 69 (NGC 6637), a globular cluster located in the constellation Sagittarius. Located about about 29,700 light-years away from Earth, this cluster lies close to Messier 70 (both of which were discovered Charles Messier on August 31st, 1780). Both objects lie close to the galactic center, and M69 is one of the most metal-rich globular clusters known. Continue reading “Messier 69 – the NGC 6637 Globular Cluster”
Messier 68, shown in proximity to the Hydra constellation. Credit: Wikisky
Welcome back to Messier Monday! Today, we continue in our tribute to our dear friend, Tammy Plotner, by looking at the globular cluster known as Messier 68.
In the 18th century, while searching the night sky for comets, French astronomer Charles Messier kept noting the presence of fixed, diffuse objects he initially mistook for comets. In time, he would come to compile a list of approximately 100 of these objects, hoping to prevent other astronomers from making the same mistake. This list – known as the Messier Catalog – would go on to become one of the most influential catalogs of Deep Sky Objects.
One of these objects is the globular cluster known as Messier 68. Located roughly 33,000 light-years away in the Constellation of Hydra, this cluster is orbiting through the Milky. In addition to being one of the most metal-poor globular clusters, it may be undergoing core collapse, and is believed to have been acquired from a satellite galaxy that merged with the Milky Way in the past. Continue reading “Messier 68 – the NGC 4590 Globular Cluster”
The location of the King Cobra open star cluster (aka. Messier 67). Credit: Wikisky
Welcome back to Messier Monday! Today, we continue in our tribute to our dear friend, Tammy Plotner, by looking at the big snake – the King Cobra Cluster (aka. Messier 67).
In the 18th century, while searching the night sky for comets, French astronomer Charles Messier kept noting the presence of fixed, diffuse objects he initially mistook for comets. In time, he would come to compile a list of approximately 100 of these objects, hoping to prevent other astronomers from making the same mistake. This list – known as the Messier Catalog – would go on to become one of the most influential catalogs of Deep Sky Objects.
One of these objects is the open star cluster known as Messier 67, aka. the King Cobra Cluster. Located in the Cancer Constellation, and with age estimates ranging from 3.2 and 5 billion years, this cluster is one of the oldest clusters known. And at a distance of roughly 2610 and 2930 (800 – 900 pc) from Earth, it is the closest of any of the older open star clusters. Continue reading “Messier 67 – the King Cobra Open Star Cluster”
The Leo Triplet, featuring Messier 65, Messier 66 and NGC 3628. Image: Wikisky
Welcome back to Messier Monday! Today, we continue in our tribute to our dear friend, Tammy Plotner, by looking at the intermediate spiral galaxy known as Messier 66.
In the 18th century, while searching the night sky for comets, French astronomer Charles Messier kept noting the presence of fixed, diffuse objects he initially mistook for comets. In time, he would come to compile a list of approximately 100 of these objects, hoping to prevent other astronomers from making the same mistake. This list – known as the Messier Catalog – would go on to become one of the most influential catalogs of Deep Sky Objects.
One of these objects is the intermediate elliptical galaxy known as Messier 66 (NGC 3627). Located about 36 million light-years from Earth in the direction of the Leo constellation, this galaxy measures 95,000 light-years in diameter. It is also the brightest and largest member of the Leo Triplet of galaxies and is well-known for its bright star clusters, dust lanes, and associated supernovae.
Description:
Enjoying life some 35 million light years from the Milky Way, the group known as the “Leo Trio” is home to bright galaxy Messier 66 – the easternmost of the two M objects. In the telescope or binoculars, you’ll find this barred spiral galaxy far more visible and much easier to see details within its knotted arms and bulging core.
Hubble image of the intermediate spiral galaxy Messier 66. Credits: NASA, ESA and the Hubble Heritage (STScI/AURA)-ESA/Hubble Collaboration/Davide De Martin/Robert Gendler
Because of interaction with its neighboring galaxies, M66 shows signs of a extremely high central mass concentration as well as a resolved noncorotating clump of H I material apparently removed from one of the spiral arms. Even one of its spiral arms got it noted in Halton Arp’s collection of Peculiar Galaxies! So exactly what did it collide with?As Xiaolei Zhang (et al) indicated in a 1993 study:
“The combined CO and H I data provide new information, both on the history of the past encounter of NGC 3627 with its companion galaxy NGC 3628 and on the subsequent dynamical evolution of NGC 3627 as a result of this tidal interaction. In particular, the morphological and kinematic information indicates that the gravitational torque experienced by NGC 3627 during the close encounter triggered a sequence of dynamical processes, including the formation of prominent spiral structures, the central concentration of both the stellar and gas mass, the formation of two widely separated and outwardly located inner Lindblad resonances, and the formation of a gaseous bar inside the inner resonance. These processes in coordination allow the continuous and efficient radial mass accretion across the entire galactic disk. The observational result in the current work provides a detailed picture of a nearby interacting galaxy which is very likely in the process of evolving into a nuclear active galaxy. It also suggests one of the possible mechanisms for the formation of successive instabilities in postinteraction galaxies, which could very efficiently channel the interstellar medium into the center of the galaxy to fuel nuclear starburst and Seyfert activities.”
Ah, yes! Star forming regions… And what better way to look deeper than through the eyes of the Spitzer Space Telescope? As R. Kennicutt (University of Arizona) and the SINGS Team observed:
“M66’s blue core and bar-like structure illustrates a concentration of older stars. While the bar seems devoid of star formation, the bar ends are bright red and actively forming stars. A barred spiral offers an exquisite laboratory for star formation because it contains many different environments with varying levels of star-formation activity, e.g., nucleus, rings, bar, the bar ends and spiral arms. The SINGS image is a four-channel false-color composite, where blue indicates emission at 3.6 microns, green corresponds to 4.5 microns, and red to 5.8 and 8.0 microns. The contribution from starlight (measured at 3.6 microns) in this picture has been subtracted from the 5.8 and 8 micron images to enhance the visibility of the dust features.”
Colour composite image of the spiral galaxy M66 (or NGC 3627) obtained with the FORS1 and FORS2 multi-mode instruments (at VLT MELIPAL and YEPUN, respectively). Credit: ESO
Messier 66 has also been deeply studied for evidence of forming super star clusters, too. As David Meier indicated:
“Super star clusters are thought to be precursors of globular clusters and are some of the most extreme star formation regions in the universe. They tend to occur in actively starbursting galaxies or near the cores of less active galaxies. Radio super star clusters cannot be seen in optical light because of extreme extinction, but they shine brightly in infrared and radio observations. We can be certain that there are many massive O stars in these regions because massive stars are required to provide the UV radiation that ionizes the gas and creates a thermally bright HII regions. Not many natal SSCs are currently known, so detection is an important science goal in its own right. In particular, very few SSCs are known in galactic disks. We need more detections to be able to make statistical statements about SSCs and fill in the mass range of forming star clusters. With more detections, we will be able to investigate the effects of other environments (e.g. bars, bubbles, and galactic interaction) on SSCs, which could potentially be followed up in the far future with the Square Kilometer Array to discover their effects on individual forming massive stars.”
But there’s still more. Try magnetic properties in M66’s spiral patterns. As M. Soida (et al) indicated in their 2001 study:
“By observing the interacting galaxy NGC 3627 in radio polarization we try to answer the question; to which degree does the magnetic field follow the galactic gas flow. We obtained total power and polarized intensity maps at 8.46 GHz and 4.85 GHz using the VLA in its compact D-configuration. In order to overcome the zero-spacing problems, the interferometric data were combined with single-dish measurements obtained with the Effelsberg 100-m radio telescope. The observed magnetic field structure in NGC 3627 suggests that two field components are superposed. One component smoothly fills the interarm space and shows up also in the outermost disk regions, the other component follows a symmetric S-shaped structure. In the western disk the latter component is well aligned with an optical dust lane, following a bend which is possibly caused by external interactions. However, in the SE disk the magnetic field crosses a heavy dust lane segment, apparently being insensitive to strong density-wave effects. We suggest that the magnetic field is decoupled from the gas by high turbulent diffusion, in agreement with the large Hi line width in this region. We discuss in detail the possible influence of compression effects and non-axisymmetric gas flows on the general magnetic field asymmetries in NGC 3627. On the basis of the Faraday rotation distribution we also suggest the existence of a large ionized halo around this galaxy.”
History of Observation:
Both M65 and M66 were discovered on the same night – March 1, 1780 – by Charles Messier, who described M66 as, “Nebula discovered in Leo; its light is very faint and it is very close to the preceding: They both appear in the same field in the refractor. The comet of 1773 and 1774 has passed between these two nebulae on November 1 to 2, 1773. M. Messier didn’t see them at that time, no doubt, because of the light of the comet.”
Both galaxies would be observed and cataloged by the Herschel family and further expounded upon by Admiral Smyth:
“A large elongated nebula, with a bright nucleus, on the Lion’s haunch, trending np [north preceding, NW] and sf [south following, SE]; this beautiful specimen of perspective lies just 3deg south-east of Theta Leonis. It is preceded at about 73s by another of a similar shape, which is Messier’s No. 65, and both are in the field at the same time, under a moderate power, together with several stars. They were pointed out by Mechain to Messier in 1780, and they appeared faint and hazy to him. The above is their appearance in my instrument.
“These inconceivably vast creations are followed, exactly on the same parallel, ar Delta AR=174s, by another elliptical nebula of even a more stupendous character as to apparent dimensions. It was discovered by H. [John Herschel], in sweeping, and is No. 875 in his Catalogue of 1830 [actually, probably an erroneous position for re-observed M66]. The two preceding of these singular objects were examined by Sir William Herschel, and his son [JH] also; and the latter says, “The general form of elongated nebulae is elliptic, and their condensation towards the centre is almost invariably such as would arise from the superposition of luminous elliptic strata, increasing in density towards the centre. In many cases the increase of density is obviously attended with a diminution of ellipticity, or a nearer approach to the globular form in the central than in the exterior strata.” He then supposes the general constitution of those nebulae to be that of oblate spheroidal masses of every degree of flatness from the sphere to the disk, and of every variety in respect of the law of their density, and ellipticity towards the centre. This must appear startling and paradoxical to those who imagine that the forms of these systems are maintained by forces identical with those which determine the form of a fluid mass in rotation; because, if the nebulae be only clusters of discrete stars, as in the greater number of cases there is every reason to believe them to be, no pressure can propagate through them. Consequently, since no general rotation of such a system as one mass can be supposed, Sir John suggests a scheme which he shows is not, under certain conditions, inconsistent with the law of gravitation. “It must rather be conceived,” he tells us, ” as a quiescent form, comprising within its limits an indefinite magnitude of individual constituents, which, for aught we can tell, may be moving one among the other, each animated by its own inherent projectile force, and deflected into an orbit more or less complicated, by the influence of that law of internal gravitation which may result from the compounded attractions of all its parts.”
Messier 66 location. Credit: IAU and Sky & Telescope magazine (Roger Sinnott & Rick Fienberg)
Locating Messier 66:
Even though you might think by its apparent visual magnitude that M66 wouldn’t be visible in small binoculars, you’d be wrong. Surprisingly enough, thanks to its large size and high surface brightness, this particular galaxy is very easy to spot directly between Iota and Theta Leonis. In even 5X30 binoculars under good conditions you’ll easy see both it and M65 as two distinct gray ovals.
A small telescope will begin to bring out structure in both of these bright and wonderful galaxies, but to get a hint at the “Trio” you’ll need at least 6″ in aperture and a good dark night. If you don’t spot them right away in binoculars, don’t be disappointed – this means you probably don’t have good sky conditions and try again on a more transparent night. The pair is well suited to modestly moonlit nights with larger telescopes.
May you equally be attracted to this galactic pair!
And here are the quick facts on M66 to help you get started:
Object Name: Messier 66 Alternative Designations: M66, NGC 3627, (a member of the) Leo Trio, Leo Triplet Object Type: Type Sb Spiral Galaxy Constellation: Leo Right Ascension: 11 : 20.2 (h:m) Declination: +12 : 59 (deg:m) Distance: 35000 (kly) Visual Brightness: 8.9 (mag) Apparent Dimension: 8×2.5 (arc min)
Hubble image of the intermediate spiral galaxy known as Messier 65, which is located in the Leo constellation. Credit: ESA/Hubble & NASA
Welcome back to Messier Monday! Today, we continue in our tribute to our dear friend, Tammy Plotner, by looking at the intermediate spiral galaxy known as Messier 65.
In the 18th century, while searching the night sky for comets, French astronomer Charles Messier kept noting the presence of fixed, diffuse objects he initially mistook for comets. In time, he would come to compile a list of approximately 100 of these objects, hoping to prevent other astronomers from making the same mistake. This list – known as the Messier Catalog – would go on to become one of the most influential catalogs of Deep Sky Objects.
One of these objects is the intermediate spiral galaxy known as Messier 65 (aka. NGC 3623), which is located about 35 million light-years from Earth in the Leo constellation. Along with with Messier 66 and NGC 3628, it is part of a small group of galaxies known as the Leo Triplet, which makes it one of the most popular targets among amateur astronomers.
Description:
Enjoying life some 35 million light years from the Milky Way, the group known as the “Leo Trio” is home to bright galaxy Messier 65 – the westernmost of the two M objects. To the casual observer, it looks like a very normal spiral galaxy and thus its classification as Sa – but M65 is a galaxy which walks on the borderline. Why? Because of close gravitational interaction with its nearby neighbors. Who can withstand the draw of gravity?!
The Messier 65 intermediate spiral galaxy. Credit: ESO/INAF-VST/OmegaCAM/Astro-WISE/Kapteyn Institute
Chances are very good that Messier 65 is even quite a bit larger than we see optically as well. As E. Burbidge (et al) said in a 1961 study:
“A fragmentary rotation-curve for NGC 3623 was obtained from measures of the absorption features Ca ii X 3968 and Na I X 5893 and the emission lines [N ii] X 6583 and Ha. The measures from two outer regions are discordant if only circular velocities are assumed, and it is concluded that the measured velocity of one of these regions-the only prominent H ii region in the galaxy-has a large non-circular component. The approximate mass derived from the velocity in the outer arm relative to the center is 1.4 X 1011 M0. It is concluded that the total mass is larger than this, perhaps between 2 and 3 X 1011 M0. This would suggest that the mass-to-light ratio in solar units (photographic) for this galaxy, which is intermediate in type between Sa and Sb, lies between 10 and 20.”
But just how much interaction has been going on between the three galaxies which coexist so closely? Sometimes it takes things like studying in multicolor photometry data to understand. As Zhiyu Duan of the Chinese Academy of Sciences Astronomical Observatory indicated in a 2006 study:
“By comparing the observed SEDs of each part of the galaxies with the theoretical ones generated by instantaneous burst evolutionary synthesis models with different metallicities (Z = 0.0001, 0.008, 0.02, and 0.05), two-dimensional relative age distribution maps of the three galaxies were obtained. NGC 3623 exhibits a very weak age gradient from the bulge to the disk. This gradient is absent in NGC 3627. The ages of the dominant stellar populations of NGC 3627 and NGC 3628 are consistent, and this consistency is model independent (0.5-0.6 Gyr, Z = 0.02), but the ages of NGC 3623 are systematically older (0.7-0.9 Gyr, Z = 0.02). The results indicate that NGC 3627 and NGC 3628 have undergone synchronous evolution and that the interaction has likely triggered starbursts in both galaxies. The results indicate that NGC 3627 and NGC 3628 have undergone synchronous evolution and that the interaction has likely triggered starbursts in both galaxies. For NGC 3623, however, the weak age gradient may indicate recent star formation in its bulge, which has caused its color to turn blue. Evidence is found for a potential bar existing in the bulge of NGC 3623, and my results support the view that NGC 3623 does interact with NGC 3627 and NGC 3628.”
Messier 65, as imaged by the Hubble Space Telescope. Credit: NASA,/ESA/Hubble Space Telescope
So, let’s try looking at things in a slightly different color – integral-field spectroscopy. As V.L. Afanasiev (et al) said in a 2004 study:
“The mean ages of their circumnuclear stellar populations are quite different, and the magnesium overabundance of the nucleus in NGC 3627 is evidence for a very brief last star formation event 1 Gyr ago whereas the evolution of the central part of NGC 3623 looks more quiescent. In the center of NGC 3627 we observe noticeable gas radial motions, and the stars and the ionized gas in the center of NGC 3623 demonstrate more or less stable rotation. However, NGC 3623 has a chemically distinct core – a relic of a past star formation burst – which is shaped as a compact, dynamically cold stellar disk with a radius of ?250-350 pc which has been formed not later than 5 Gyr ago.”
Now, let’s take a look at that gas – and the properties for the gases that exist and co-exist in the galactic trio. As David Hogg (et al) explained in a 2001 study:
“We have studied the distribution of cool, warm, and hot interstellar matter in three of the nearest bright Sa galaxies. New X-ray data for NGC 1291, the object with the most prominent bulge, confirm earlier results that the ISM in the bulge is dominated by hot gas. NGC 3623 has a lesser amount of hot gas in the bulge but has both molecular gas and ionized hydrogen in the central regions. NGC 2775 has the least prominent bulge; its X-ray emission is consistent with an origin in X-ray binary stars, and there is a strict upper limit on the amount of molecular present in the bulge. All three galaxies have a ring of neutral hydrogen in the disk. NGC 3623 and NGC 2775 each have in addition a molecular ring coincident with the hydrogen ring. We conclude that even within the morphological class Sa there can be significant differences in the gas content of the bulge, with the more massive bulges being likely to contain hot, X-ray–emitting gas. We discuss the possibility that the X-ray gas is part of a cooling flow in which cool gas is produced in the nucleus.”
The Leo Triplet, with M65 at the upper right, M66 at the lower right, and NGC 3628 at the upper left. Credit: Scott Anttila. Credit: Wikipedia Commons/Anttler
Even more studies have been done to take a look a disc properties associated with M65. According to M. Bureau (et al);
“NGC 3623 (M 65) is another highly-inclined galaxy in the Leo group, but it is of much later type than NGC 3377, SABa(rs). It is part of the Leo triplet with NGC 3627 and NGC 3628 but does not appear to be interacting. NGC 3623’s kinematics an has barely been studied and observations provide a glimpse of its dynamics. The large-scale velocity reveals minor-axis rotation, in agreement with the presence of a bar. In addition, a quasi edge-on disk is present in the center, where the iso velocity contours flatten out abruptly.”
History of Observation:
Both M65 and M66 were discovered on the same night – March 1, 1780 – by Charles Messier, who described M65 as “Nebula discovered in Leo: It is very faint and contains no star.” Sir William Herschel would later observe M65 as well, describing it as “A very brilliant nebula extended in the meridian, about 12′ long. It has a bright nucleus, the light of which suddenly diminishes on its border, and two opposite very faint branches.”
However, it would be Lord Rosse who would be the first to see structure: “March 31, 1848. – A curious nebula with a bright nucleus; resolvable; a spiral or annular arrangement about it; no other portion of the nebula resolved. Observed April 1, 1848 and April 3, with the same results.”
Locating Messier 65:
Even though you might think by its apparent visual magnitude that M65 wouldn’t be visible in small binoculars, you’d be wrong. Surprisingly enough, thanks to its large size and high surface brightness, this particular galaxy is very easy to spot directly between Iota and Theta Leonis. In even 5X30 binoculars under good conditions you’ll easy see both it and M66 as two distinct gray ovals.
Messier 65 location. Credit: IAU and Sky & Telescope magazine (Roger Sinnott & Rick Fienberg)
A small telescope will begin to bring out structure in both of these bright and wonderful galaxies, but to get a hint at the “Trio” you’ll need at least 6″ in aperture and a good dark night. If you don’t spot them right away in binoculars, don’t be disappointed – this means you probably don’t have good sky conditions and try again on a more transparent night. The pair is well suited to modestly moonlit nights with larger telescopes.
Capture one of the Trio tonight! And here are the quick facts on this Messier Object:
Object Name: Messier 65 Alternative Designations: M65, NGC 3623, (a member of the) Leo Trio, Leo Triplet Object Type: Type Sa Spiral Galaxy Constellation: Leo Right Ascension: 11 : 18.9 (h:m) Declination: +13 : 05 (deg:m) Distance: 35000 (kly) Visual Brightness: 9.3 (mag) Apparent Dimension: 8×1.5 (arc min)
Image of the Black Eye Galaxy (Messier 64), taken with Hubble's Wide Field Planetary Camera 2 (WFPC2). Credit: NASA and The Hubble Heritage Team (AURA/STScI)
Welcome back to Messier Monday! Today, we continue in our tribute to our dear friend, Tammy Plotner, by looking at that “evil” customer known as Messier 64 – aka. the “Black Eye Galaxy”!
In the 18th century, while searching the night sky for comets, French astronomer Charles Messier kept noting the presence of fixed, diffuse objects he initially mistook for comets. In time, he would come to compile a list of approximately 100 of these objects, hoping to prevent other astronomers from making the same mistake. This list – known as the Messier Catalog – would go on to become one of the most influential catalogs of Deep Sky Objects.
One of these objects is known as Messier 64, which is also known as the “Black Eye” or “Evil Eye Galaxy”. Located in the Coma Berenices constellation, roughly 24 million light-years from Earth, this spiral galaxy is famous for the dark band of absorbing dust that lies in front of the galaxy’s bright nucleus (relative to Earth). Messier 64 is well known among amateur astronomers because it is discernible with small telescopes.
Description:
Residing about 19 million light years from our home galaxy, the “Sleeping Beauty” extends across space covering an area nearly 40,000 light years across, spinning around at a speed of 300 kilometers per second. Toward its core is a counter-rotating disc approximate 4,000 light years wide and the friction between these two may very well be the contributing factor to the huge amounts of starburst activity and distinctive dark dust lane.
Infrared image taken by the Hubble Space Telescope, which penetrated the dust clouds swirling around the centers of the M64 galaxy. Credits: Torsten Boeker, Space Telescope Science Institute and NASA/ESA
Stars themselves appear to be forming in two waves, first evolving outside following the density gradient where abundant interstellar matter was waiting, and then evolving slowly. As the material from the mature stars began beig pushed back by their stellar winds, supernovae, and planetary nebulae, increased amounts of interstellar matter once again compressed, beginning the process of star formation again. This “second wave” may very well be represented by the dark, obscuring dust lane we see.
But, M64 isn’t without it share of turmoil. Its dual rotation may have started as a collision when two galaxies merged some billion years ago – or so theory would suggest. But did it? As Robert Braun and Rene Walterbos explained in their 1995 study:
“This galaxy is known to contain two nested, counter rotating, gas disks of a few 108 solar mass each, with the inner disk extending to approximately 1 kpc and the outer disk extending beyond. The stellar kinematics along the major axis, extending across the transition region between the two gas disks, show no hint of velocity reversal or increased velocity dispersion. The stars always rotate in the same sense as the inner gas disk, and thus it is the outer disk which ‘counterrotates’. The projected circular velocities inferred from the stellar kinematics and from the H I disks agree to within approximately 10 km/s, supporting other evidence that the stellar and gaseous disks are coplanar to approximately 7 deg. This upper limit is comparable to the mass of detected counter rotating gas. This low mass of counter rotating material, combined with the low-velocity dispersion in the stellar disk, implies that NGC 4826 cannot be the product of a retrograde merger of galaxies, unless they differed by at least an order of magnitude in mass. The velocities of the ionized gas along the major axis are in agreement with that of the stars for R less than 0.75 kpc. The subsequent transition toward apparent counter rotation of the ionized gas is spatially well resolved, extending over approximately 0.6 kpc in radius. The kinematics of this region are not symmetric with respect to the galaxy center. On the southeast side there is a significant region in which vproj (H II) much less than vcirc approximately 150 km/s, but sigma (H II) approximately 65 km/s. The kinematic asymmetries cannot be explained with any stationary dynamical model, even is gas inflow or warps were invoked. The gas in this transition region shows a diffuse spatial structure, strong (N II) and (S II) emission, as well as the high-velocity dispersion. These data present us with the conundrum of explaining a galaxy in which a stellar disk, and two counter rotating H I disks, at smaller and much larger radii, appear in equilibrium and nearly coplanar, yet in which the transition region between the gas disks is not in steady state.”
So is all what it really appears to be? Are new stars being born in the darkness? As A. Majeed (et al) indicated in their 1999 study:
“The Evil Eye galaxy (NGC 4826; M64) is distinguished by an asymmetrically placed, strongly absorbing dust lane across its prominent bulge. We obtained a long-slit spectrum of NGC 4826, with the slit across the galaxy’s nucleus, covering equal parts of the obscured and the unobscured portions of the bulge. By comparing the spectral energy distributions at corresponding positions on the bulge, symmetrically placed with respect to the nucleus, we were able to study the wavelength dependent effects of absorption, scattering, and emission by the dust, as well as the presence of ongoing star formation in the dust lane. We report the detection of strong extended red emission (ERE) from the dust lane within about 15 arcsec distance from the nucleus of NGC 4826. The ERE band extends from 5400 A to 9400 A, with a peak near 8800 A. The integrated ERE intensity is about 75 % of that of the estimated scattered light from the dust lane. The ERE shifts toward longer wavelengths and diminishes in intensity as a region of star formation, located beyond 15 arcsec distance, is approached. We interpret the ERE as originating in photoluminescence by nanometer-sized clusters, illuminated by the galaxy’s radiation field, in addition to the illumination by the star-forming complex within the dust lane. When examined within the context of ERE observations in the diffuse ISM of our Galaxy and in a variety of other dusty environments such as nebulae, we conclude that the ERE photon conversion efficiency in NGC 4826 is as high as found elsewhere, but that the size of the nanoparticles in NGC 4826 is about twice as large as those thought to exist in the diffuse ISM of our Galaxy.”
Messier 64 (“Black Eye Galaxy”) imaged using amateur telescope. Credit: Jeff Johnson.
But the debate is still on. As R.A. Walterbos (et al) expressed in their 1993 study:
“The close to coplanar orientation of the gas disks is one aspect which is in good agreement with what is expected on the basis of a merger model for the counter-rotating gas. The rotation direction of the inner gas disk with respect to the stars, however, is not. In addition, the existence of a well defined exponential disk probably implies that if a merger did occur it must have been between a gas-rich dwarf and a spiral, not between two equal mass spirals. The stellar spiral arms of NGC 4826 are trailing over part of the disk and leading in the outer disk. Recent numerical calculations by Byrd et al. for NGC 4622 suggest that long lasting leading arms could be formed by a close retrograde passage of a small companion. In this scenario, the outer counter-rotating gas disk in NGC 4826 might be the tidally stripped gas from the dwarf. However, in NGC 4826 the outer arms are leading, while it appears that in NGC 4622 the inner arms are leading. A realistic N-body/hydro simulation of a dwarf-spiral encounter is clearly needed. It may also be possible that the counter-rotating outer gas disk is due to gradual infall of gas from the halo, rather than from a discrete merger event.”
History of Observation:
M64 was discovered by Edward Pigott on March 23, 1779, just 12 days before Johann Elert Bode found it independently on April 4, 1779. Roughly a year later, Charles Messier independently rediscovered it on March 1, 1780 and cataloged it as M64. Said Pigot:
“.. on the 23rd of March [1779], I discovered a nebula in the constellation of Coma Berenices, hitherto, I presume, unnoticed; at least not mentioned in M. de la Lande’s Astronomy, nor in M. Messier’s ample Catalogue of nebulous Stars [of 1771]. I have observed it in an acromatic instrument, three feet long, and deduced its mean R.A. by comparing it to the following stars Mean R.A. of the nebula for April 20, 1779, of 191d 28′ 38″. Its light being exceedingly weak, I could not see it in the two-feet telescope of our quadrant, so was obliged to determine its declination likewise by the transit instrument. The determination, however, I believe, may be depended upon to two minutes: hence, the declination north is 22d 53″1/4. The diameter of this nebula I judged to be about two minutes of a degree.”
However, Pigott’s discovery got published only when read before the Royal Society in London on January 11, 1781, while Bode’s was published during 1779 and Messier’s in late summer, 1780. Pigott’s discovery was more or less ignored and recovered only by Bryn Jones in April 2002! (May the good Mr. Pigot know that he was remembered here and his reports placed first!!)
Messier 64, the Black Eye Galaxy. Credit: Miodrag Sekulic
So how did it get the name “Black Eye Galaxy”? We have Sir William Herschel to thank for that: “A very remarkable object, much elongated, about 12′ long, 4′ or 5′ broad, contains one lucid spot like a star with a small black arch under it, so that it gives one the idea of what is called a black eye, arising from fighting.” Of course, John Herschel perpetuated it when he wrote in his own notes:
“The dark semi-elliptic vacancy (indicated by an unshaded or bright portion in the figure,) which partially surrounds the condensed and bright nucleus of this nebula, is of course unnoticed by Messier. It was however seen by my Father, and shown by him to the late Sir Charles Blagden, who likened it to the appearance of a black eye, an odd, but not inapt comparison. The nucleus is somewhat elongated, and I have a strong suspicion that it may be a close double star, or extremely condensed double nebula.”
Locating Messier 64:
Locating M64 isn’t particularly easy. Begin by identifying bright orange Arcturus and the Coma Berenices star cluster (Melotte 111) about a hand span to the general west. As you relax and let your eyes dark adapt, you will see the three stars that comprise the constellation of Coma Berenices, but if you live under light polluted skies, you may need binoculars to find its faint stars. Once you have confirmed Alpha Comae, star hop approximately 4 degrees north/northwest to 35 Comae. You will find M64 around a degree to the northeast of star 35.
While Messier 64 is binocular possible, it will require very dark skies for average binoculars and will only show as a very small, oval contrast change. However, in telescopes as small as 102mm, its distinctive markings can be seen on dark nights with good clarity. Don’t fight over it… There’s plenty of dark dustlane in this Sleeping Beauty to go around!
The location of Messier 64 in the Coma Berenices constellation. Credit: IAU/Sky & Telescope magazine (Roger Sinnott & Rick Fienberg)
And here are the quick facts on this Messier Object to help you get started:
Object Name: Messier 64 Alternative Designations: M64, NGC 4826, The Black Eye Galaxy, Sleeping Beauty Galaxy, Evil Eye Galaxy Object Type: Type Sb Spiral Galaxy Constellation: Coma Berenices Right Ascension: 12 : 56.7 (h:m) Declination: +21 : 41 (deg:m) Distance: 19000 (kly) Visual Brightness: 8.5 (mag) Apparent Dimension: 9.3×5.4 (arc min)
The Sunflower Galaxy, a spiral galaxy located in the northern constellation Canes Venatici, as imaged by the NASA/ESA Hubble Space Telescope. Credits: ESA/Hubble & NASA
Welcome back to Messier Monday! Today, we continue in our tribute to our dear friend, Tammy Plotner, by looking at the “Sunflower Galaxy”, otherwise known as Messier 63.
In the 18th century, while searching the night sky for comets, French astronomer Charles Messier kept noting the presence of fixed, diffuse objects he initially mistook for comets. In time, he would come to compile a list of approximately 100 of these objects, hoping to prevent other astronomers from making the same mistake. This list – known as the Messier Catalog – would go on to become one of the most influential catalogs of Deep Sky Objects.
One of these objects is the spiral galaxy known as Messier 63 – aka. the Sunflower Galaxy. Located in the Canes Venatici constellation, this galaxy is located roughly 37 million light-years from Earth and has an active nucleus. Messier 63 is part of the M51 Group, a group of galaxies that also includes Messier 51 (the ‘Whirlpool Galaxy’), and can be easily spotted using binoculars and small telescopes.
Description:
Messier 63 is what is known as a a flocculent spiral galaxy, consisting of a central disc surrounded by many short spiral arm segments – one not connected by a central bar structure. Drifting along in space some 37,000 light years from our own galaxy, we known it interacts gravitationally with M51 (the Whirlpool Galaxy) and we also know that its outer regions are rotating so quickly that if it weren’t for dark matter – it would rip itself apart.
Infrared image of the Sunflower Galaxy (Messier 63) taken by the Spitzer Space Telescope. Credit: NASA/JPL-Caltech/SINGS Team
As Michele D. Thornley and Lee G. Mundy, of the Maryland University Department of Astronomy, indicated in a 1997 study:
“The morphology and inematics described by VLA observations of H I emission and FCRAO and Berkeley-Illinois-Maryland Association (BIMA) Array observations of CO emission provide evidence for the presence of low-amplitude density waves in NGC 5055. The distribution of CO and H I emission suggests enhanced gas surface densities along the NIR spiral arms, and structures similar to the giant molecular associations found in the grand design spirals M51 and M100 are detected. An analysis of H I and H? velocity fields shows the kinematic signature of streaming motions similar in magnitude to those of M100 in both tracers. The lesser degree of organization along the spiral arms of NGC 5055 may be due to the lower overall gas surface density, which in the arms of NGC 5055 is a factor of 2 lower than in M100 and a factor of 6 lower than in M51; an analysis of gravitational instability shows the gas in the arms is only marginally unstable and the interarm gas is marginally stable. The limited extent of the spiral arm pattern is consistent with an isolated density wave with a relatively high pattern speed.”
There very well could be a massive object hidden within. As Sebastien Blais-Ouellette of the Universite de Montreal said in a 1998 study:
“In a global kinematical study of NGC 5055 using high resolution Fabry-Perot, intriguing spectral line profiles have been observed in the center of the galaxy. These profiles seem to indicate a rapidly rotating disk with a radius near 365 pc and tilted 50 deg with respect to the major axis of the galaxy. In the hypothesis of a massive dark object, a naive keplerian estimate gives a mass around 10^7.2 to 10^7.5 M.”
Infrared image of the M63 galaxy made by Médéric Boquien, using data retrieved on the SINGS project public archives of the Spitzer Space Telescope. Credit: NASA/JPL-Caltech
But that’s not all they’ve found either… How about a lopsided, chemically unbalanced nucleus! As V.L. Afanasiev (et al) pointed out in their 2002 study:
“We have found a resolved chemically distinct core in NGC 5055, with the magnesium-enhanced region shifted by 2″.5 (100 pc) to the south-west from a photometric center, toward a kinematically identified circumnuclear stellar disk. Mean ages of stellar populations in the true nucleus, defined as the photometric center, and in the magnesium-enhanced substructure are coincident and equal to 3-4 Gyr being younger by several Gyr with respect to the bulge stellar population.”
Yep. It might be beautiful, but it’s warped. As G. Battaglia of the Kapteyn Astronomical Institute indicated in a 2005 study:
“NGC 5055 shows remarkable overall regularity and symmetry. A mild lopsidedness is noticeable, however, both in the distribution and kinematics of the gas. The tilted ring analysis of the velocity field led us to adopt different values for the kinematical centre and for the systemic velocity for the inner and the outer parts of the system. This has produced a remarkable result: the kinematical and geometrical asymmetries disappear, both at the same time. These results point at two different dynamical regimes: an inner region dominated by the stellar disk and an outer one, dominated by a dark matter halo offset with respect to the disk.”
Sunflower Galaxy (Messier 63). Credit: Adam Block/Mount Lemmon SkyCenter/University of Arizona
History of Observation:
Messier Object 63 was the very first discovery by Charles Messier’s friend and assistant Pierre Mechain, who turned it up on June 14, 1779. While Mechain himself did not write the notes, Messier did:
“Nebula discovered by M. Mechain in Canes Venatici. M. Messier searched for it; it is faint, it has nearly the same light as the nebula reported under no. 59: it contains no star, and the slightest illumination of the micrometer wires makes it disappear: it is close to a star of 8th magnitude, which precedes the nebula on the hour wire. M. Messier has reported its position on the Chart of the path of the Comet of 1779.”
Messier 63 would go on to be observed and resolved by Sir William Herschel and cataloged by his son John. It would be descriptively narrated by Admiral Symth and exclaimed over by many astronomers – one of the best of which was Lord Rosse: “Spiral? Darkness south flowing nucleus.” Of all the descriptions, perhaps the best belongs to Curtis, who first photographed it with the Crossley Reflector at Lick Observatory: “Has an almost stellar nucleus. The whorls are narrow, very compactly arranged, and show numerous almost stellar condensations.”
Locating Messier 63:
The beautiful Sunflower Galaxy is among one of the easiest of the Messier objects to find. It’s located almost precisely between Cor Caroli (Alpha Canes Venetici) and Eta Ursa Majoris. With the slightest of optical aid, stars 19, 20 and 23 CnV will show easily in finderscope or binoculars and M63 will be positioned right around two degrees away towards Eta UM.
The location of Messier 63 in the Canes Venatici constellation. Credit: IAU/Sky & Telescope magazine (Roger Sinnott & Rick Fienberg)
While this spiral galaxy has a nice overall brightness, it’s going to be very faint for binoculars, only showing as the tiniest contrast change in smaller models. However, even a modest telescope will easily see a faint oval shape with a concentrated nucleus. The more aperture you apply, the more details you will see. As size approaches 8″ and larger, expect to see spiral structure!
Power up… And look for the spiral in the Sunflower!
Object Name: Messier 63 Alternative Designations: M63, NGC 5055, Sunflower Galaxy Object Type: Type Sb Spiral Galaxy Constellation: Canes Venatici Right Ascension: 13 : 15.8 (h:m) Declination: +42 : 02 (deg:m) Distance: 37000 (kly) Visual Brightness: 8.6 (mag) Apparent Dimension: 10×6 (arc min)
The location of the southern Dorado constellation. Credit and Copyright: Torsten Bronger
Welcome to another edition of Constellation Friday! Today, in honor of the late and great Tammy Plotner, we take a look at that fishiest of asterisms – the Dorado constellation. Enjoy!
In the 2nd century CE, Greek-Egyptian astronomer Claudius Ptolemaeus (aka. Ptolemy) compiled a list of all the then-known 48 constellations. This treatise, known as the Almagest, would be used by medieval European and Islamic scholars for over a thousand years to come, effectively becoming astrological and astronomical canon until the early Modern Age.
Since that time, many additional constellations have been discovered, such as Dorado. This southern constellation, which was discovered in the 16th century by Dutch navigators, is now one of the 88 constellations recognized by the International Astronomical Union (IAU). It is bordered by the constellations of Caelum, Horologium, Hydrus, Mensa, Pictor, Reticulum, and Volans.
Name and Meaning:
Because of its southerly position, Dorado was unknown to the ancient Greeks and Romans so no classical mythological connection exists. However, there are some very nice tales and history associated with this constellation. The name Dorado is Spanish for mahi-mahi, or the dolphin-fish. The mahi-mahi has a opalescent skin that turns blue and gold as the fish dies.
Image of the night sky taken at the European Southern Observatory’s Very Large Telescope in Chile. The Large and Small Magellanic Clouds are visible in the night sky. Credit: ESO, Y. Beletsky
This may very well be the reason Dorado is sometimes called the goldfish is certain stories and legends. Because the early Dutch explorers observed the mahi-mahi chasing swordfish, Dorado was added to their new sky charts following the constellation of the flying fish, Volans. Some very old star atlases refer to Dorado as Xiphias, another form of swordfish, but clearly its “fishy” nature stands!
History of Observation:
Dorado was one of twelve constellations named by Dutch astronomer Petrus Plancius, based on the observations of Dutch sailors that explored the southern hemisphere during the 16th century. It first appeared on a celestial globe published circa 1597-8 in Amsterdam. Dorado was taken a bit more seriously when it was included by Johann Bayer in 1603 in his star atlas, Uranometria, where it appeared under its current name.
It has endured to become one of the 88 modern constellations adopted and approved by the International Astronomical Union.
Notable Objects:
Covering 179 square degrees of sky, it consists of three main stars and contains 14 Bayer/Flamsteed designated stellar members. Dorado has several bright stars and contains no Messier objects. The brightest star in the constellation is Alpha Doradus, a binary star that is approximately 169 light years distant. This binary system is one of the brightest known, and is composed of a blue-white giant (classification A0III) and a blue-white subgiant (B9IV).
The Tarantula Nebula (NGC 2070) located in the southern Dorado constelaltion. Credit: ESO
Beta Doradus, the second brightest star in the constellation, is a Cepheid variable star located approximately 1,050 light years from Earth. Its spectral type varies from white (F-type) to yellow (G-type), like our Sun. Gamma Doradus is another variable, which serves as a prototype for stars known as Gamma Doradus variables, and is approximately 66.2 light years distant.
Another interesting character is HE 0437-5439, an unbound hypervelocity star in Dorado discovered in 2005. This star appears to be receding at the speed of 723 km/s (449 mi/s), and is therefore no longer gravitationally bound to the Milky Way. It is approximately 200,000 light years distant and is a main sequence star belonging to the spectral type BV (a white-blue subdwarf).
Most notable is the Large Magellanic Cloud (LMC), an irregular galaxy located in the constellations Dorado and Mensa. This satellite galaxy to the Milky Way is roughly 1/100 times as massive as our galaxy, with an estimated ten billion times the mass of the Sun. Located about 157,000 light years away, the LMC is home to several impressive objects – like the Tarantula Nebula and the Ghost Head Nebula.
There are no meteor showers associated with the constellation.
The Ghost Head Nebula (NGC 2080), . Credit: ESA/NASA/Mohammad Heydari-Malayeri
Finding Dorado:
The South Ecliptic Pole lies within Dorado and it is bordered by the constellations of Caelum, Horologium, Reticulum, Hydrus, Mensa, Volans and Pictor. It is visible at latitudes between +20° and -90° and is best seen at culmination during the month of January. Let’s begin our explorations with binoculars and Alpha Doradus – the “a” symbol on our map. One of the reasons this star shines so brightly is because it’s not one – but two.
Don’t get your telescope out just yet, because Alpha is separated by only only a couple tenths of a second of arc and both members are about a magnitude apart. Located about 175 light years away from our solar system, this tight pair averages a distance between each other that’s equal to about the same distance as Saturn from our Sun. That’s not particularly unusual for a binary star, but what is unusual is the primary star. Alpha Dor A’s spectrum is “peculiar” – very rich in silicon. It seems to be concentrated in a stellar magnetic spot!
Let’s have a look at Cephid variable star Beta Doradus – the “B” symbol on our map. Beta is an evolved super giant star and every 9.942 days it reaches a maximum brightness of magnitude 3.46 then drops to magnitude 4.08. While these types of changes are so slight they would be difficult to follow with just the eye, that doesn’t mean what happens isn’t important. By studying Cephids we understand “period-luminosity” relation. The pulsation period of a Cepheid gives us absolute brightness, and comparing it with apparent brightness gives us distance. That way, when we find a Cepheid variable star in another galaxy, we can tell just how far away that galaxy is!
Now, let’s go from one end of the constellation to the other with binoculars as we start with Delta Doradus – the “8” shape on our map. If you were on the Moon, this particular star would be the south “pole star” – just like Polaris is to the north on Earth! Sweep along the body of the fish and end at Gamma Doradus – the “Y” shape on our map. Guess what? Another variable star! But this one isn’t a Cepheid. Gamma Doradus variables are variable stars which display variations in luminosity due to non-radial pulsations of their surface.
The stars are typically young, early F or late A type main sequence stars, and typical brightness fluctuations are 0.1 magnitudes with periods on the order of one day. This is a relatively new class of variable stars, having been first characterised in the second half of the 1990s, and details on the underlying physical cause of the variations remains under investigation. We call these mysterious strangers Oscillating Blue Stragglers.
Don’t put away your binoculars yet. We have to look at R Doradus! Here we have a red giant Mira variable star that’s about 200 to 225 light years away from Earth. The visible magnitude of R Doradus varies between 4.8 and 6.6, which makes the variable changes easy to follow with binoculars, but when viewed in the infrared it is one of the brightest stars in the sky. However, this isn’t what the most interesting part is.
With the exception of our own Sun, R Doradus is currently believed to be the star with the largest apparent size as viewed from Earth. The stellar diameter of R Doradus could be as much as 585 million kilometers. That’s upwards to 400 times larger than Sol – yet it has about the same mass! If placed at the center of the Solar System, the orbit of Mars would be entirely contained within the star. Too cool…
Dorado contains a huge amount of deep sky objects very well suited for binoculars, small and large telescopes. So many, in fact, our small star chart would be so cluttered that it would be impossible to read designations. One of the most notable of all is the Large Magellanic Cloud, one of our Milky Way Galaxy’s neighbors and members of our local galaxy group. In itself, it is an irregular dwarf galaxy, distorted by tidal interaction with the Milky Way and may have once been barred spiral galaxies.
The Magellanic Clouds’ radial velocity and proper velocity were recently accurately measured by a team from the Harvard-Smithsonian Center for Astrophysics to produce a 3-D velocity measurement that clocked their passage through the Milky Way galaxy in excess of 480km/s (300 miles per second) using input from Hubble Telescope. This unusually high velocity seems to imply that they are in fact not bound to the Milky Way, and many of the presumed effects of the Magellanic Clouds have to be revised. Be sure to explore the LMC for its own host of nebula and star forming regions. It was host to a supernova (SN 1987A), the brightest observed in over three centuries!
For the telescope, there are many objects in Dorado that you don’t want to miss. (This article would be 10 pages long if I listed them all, so let’s just highlight a few.) For galaxy group fans, why not choose NGC 1566 (RA 04h 20m 00s Dec -56 56.3′) NGC 1566 is a spiral galaxy that dominates the Dorado Group and it is also a Seyfert galaxy as well. At the center of the cluster, look for interacting galaxies NGC 1549 and NGC 1553.
These two bright members are lenticular galaxy NGC 1553 (RA 04h 16m 10.5s Dec -55 46′ 49″), and elliptical galaxy NGC 1549 (RA 04h 15m 45.1s Dec -55 35′ 32″). Their interaction appears to be in the early stage and can be seen in optical wavelengths by faint but distinct irregular shells of emission and a curious jet on the northwest side. Chandra X-ray imaging of NGC 1553 show diffuse hot gas making up 70% of the emissions, dotted with many point-like sources (low-mass X-ray binaries) making up the rest.
Similar to Messier 60, these bright spots are binary star systems of black holes and neutron stars most of which are located in globular clusters and reflect this old galaxy’s very active past. In these systems, material pulled off a regular star is heated and gives off X-rays as it falls toward the accompanying black hole or neutron star.
The location of the southern Constellation Dorado. Credit: IAU/Sky&Telescope magazine
Turn your telescope towards NGC 2164 (RA 05h 58m 53s Dec -68 30.9′). Here we are resolving an open star cluster / globular cluster that’s in another galaxy, folks! Also nearby you’ll find faint open cluster NGC 2172 (RA 5 : 59.9 Dec -68 : 38) and galactic star cluster NGC 2159 (05 57.8, -68 38). What a treat to study in another galaxy!
Would you like to study another complex? Then let’s take a look at NGC 2032 (RA 05h 35m 21s Dec -67 34.1′). Better known as the “Seagull Nebula” this complex that contains four separate NGC designations: NGC 2029, NGC 2032, NGC 2035 and NGC 2040. Spanning across an open star cluster, there are many nebula types here including emission nebula, reflection nebula and HII regions. It is also bissected by a dark nebula, too!
Of course, no telescope trip through Dorado would be complete without stopping by NGC 2070 (RA 05h 38m 37s Dec -69 05.7′) – the “Tarantula Nebula”. Located about 180,000 light years from our solar system and first recorded by Nicolas Louis de Lacaille in 1751, this huge HII region is an extremely luminous object. Its luminosity is so bright that if it were as close to Earth as the Orion Nebula, the Tarantula Nebula would cast shadows. In fact, it is the most active starburst region known in our Local Group of galaxies! At its core lies the extremely compact cluster of stars that provides the energy to make the nebula visible. And we’re glad it does!
Messier 62, shown in proximity to Messier 19 and Antares. Credit: Wikisky
Welcome back to Messier Monday! Today, we continue in our tribute to our dear friend, Tammy Plotner, by looking at the globular cluster known as Messier 62.
In the 18th century, while searching the night sky for comets, French astronomer Charles Messier kept noting the presence of fixed, diffuse objects he initially mistook for comets. In time, he would come to compile a list of approximately 100 of these objects, hoping to prevent other astronomers from making the same mistake. This list – known as the Messier Catalog – would go on to become one of the most influential catalogs of Deep Sky Objects.
One of these objects is the globular cluster known as Messier 62, which spans about 100 light-years in diameter and is approximately 22,200 light years from Earth. Located in the southern constellation of Ophiuchus, this cluster is easy to find because of its proximity to Antares – the brightest star in Scorpius constellation – and is easily viewed suing binoculars and small telescopes.
Description:
Positioned about 22,500 light years away from Earth, this glorious gravitationally bound ball of stars could span as much as 100 light years of space. Captured within its confines are 89 known variable stars – most of them RR Lyrae types. M62 has a very dense core… One which may have experienced core collapse during its long history. An ordinary globular cluster? Not hardly. It’s one that holds some optical surprises.
The globular cluster Messier 62 in the constellation Ophiuchus. Credit: Wikipedia Commons/Hewholooks
As G. Cocozza (et al) indicated in their 2008 study:
“We report on the optical identification of the companion to the eclipsing millisecond pulsar PSR J1701-3006B in the globular cluster NGC 6266. A relatively bright star with an anomalous red color and an optical variability (~0.2 mag) that nicely correlates with the orbital period of the pulsar (~0.144 days) has been found nearly coincident with the pulsar nominal position. This star is also found to lie within the error box position of an X-ray source detected by Chandra observations, thus supporting the hypothesis that some interaction is occurring between the pulsar wind and the gas streaming off the companion. Although the shape of the optical light curve is suggestive of a tidally deformed star which has nearly completely filled its Roche lobe, the luminosity (~1.9 Lsolar) and the surface temperature (~6000 K) of the star, deduced from the observed magnitude and colors, would imply a stellar radius significantly larger than the Roche lobe radius.”
Is it possible that this is the smoking gun for intermediate mass black holes in globular clusters? Julio Chaname seems to think so. As he explained in his 2009 study:
“The existence of intermediate-mass black holes [IMBHs] in star clusters has been predicted by a variety of theoretical arguments and, more recently, by several large, realistic sets of collisional N-body simulations. Establishing their presence or absence at the centers of globular clusters would profoundly impact our understanding of problems ranging from the formation and long-term dynamical evolution of stellar systems, to the nature of the seeds and the growth mechanisms of the supermassive black holes {BHs} that inhabit the centers of most large, luminous galaxies. Observationally, the unambiguous signature of a massive central BH would be the discovery of central, unresolved X-ray or radio emission that is not consistent with more common stellar-mass accreting objects or pulsars. Yet, due to the largely uncertain details of accretion modeling, a precise mass determination of a central BH must necessarily come from stellar dynamics. This goal has not been achieved to date at the centers of Galactic globular clusters because of lack of adequate data as well as the use of too simplified methods of analysis. This situation can be overcome today through the combination of HST proper-motion measurements and state-of-the-art dynamical models specifically designed to take full advantage of this type of dataset. In this project, we will use two HST orbits to obtain another epoch of observations of NGC 6266. This cluster has photometric and structural properties that are consistent with current theoretical expectations for a cluster harboring an IMBH. Even more importantly, it is the only Galactic globular cluster for which there exists a detection of radio emission coincident with the cluster’s core, and with a flux density that appears to rule out a stellar or binary origin. The goal of our project is to obtain proper motion measurements to either confirm an IMBH in this cluster and measure its mass, or to set limits to its mass and existence.”
The Messier 62 globular cluster, as imaged by the Hubble Space Telescope. Credit: NASA, ESA
History of Observation:
While Charles Messier first discovered this globular cluster on June 7, 1771 – he didn’t accurately record its position until June 4, 1779.
“”Very beautiful nebula, discovered in Scorpio, it resembles a little Comet, the center is brilliant and surrounded by a faint glow. Its position determined, by comparing it with the star Tau of Scorpius. M. Messier had already seen this nebula on June 7, 1771, without having determined the position where it is close to. Seen again on March 22, 1781.”
Sir William Herschel would resolve it two years after Messier cataloged it, but it was Admiral Smyth who gave it a little more historic significance when he writes in his notes:
“A fine large resolvable nebula, at the root of the creature’s [Scorpion’s] tail, and in the preceding part of the Galaxy [Milky Way band]. It is an aggregated mass of small stars running up to a blaze in the centre, which renders the differentiating comparatively easy and satisfactory; and in this instance it was referred to its neighbor, 26 Ophiuchi, which is 5deg distant to the north: and it lies only about 7deg from Antares, on the south-east. This was registered in 1779, and Messier described it as “a very pretty nebula, resembling a little comet, the centre bright, and surrounded by a faint light.” Sir William Herschel, who first resolved it, pronounced it a miniature of Messier’s No. 3, and adds, “By the 20-foot telescope, which at the time of these observations was of the Newtonian construction, the profundity of this cluster is of the 734th order.” To my annoyance, it was started as a comet a few years ago, by a gentleman who ought to have known better.”
Locating Messier 62:
M62 is easily located about 5 degrees (3 finger widths) southeast of Antares – but because it is small, it can easily be overlooked in binoculars. Take your time, because it is only just a little more than an average binocular field away from an easy marker star and bright enough to be seen even with smaller instruments under not so good skies.
The locations of Messier 62 in the Ophiuchus constellation. Credit: IAU/Sky & Telescope magazine (Roger Sinnott & Rick Fienberg)
In the finderscope of a telescope, begin with Antares in the center and shift southwest. At 5X magnification, it will show as a faint haze. In a small telescope, you may get some resolution – but expect this globular cluster to appear more comet-like. Larger telescopes can expect a wonderful explosion of stars!
Enjoy your observations! And as always, here are the quick facts on this Messier Object to help you get started:
Object Name: Messier 62 Alternative Designations: M62, NGC 6266 Object Type: Class IV Globular Cluster Constellation: Ophiuchus Right Ascension: 17 : 01.2 (h:m) Declination: -30 : 07 (deg:m) Distance: 22.5 (kly) Visual Brightness: 6.5 (mag) Apparent Dimension: 15.0 (arc min)
