Messier-Katalog

The orange filaments are the tattered remains of the star and consist mostly of hydrogen. The rapidly spinning neutron star embedded in the center of the nebula is the dynamo powering the nebula's eerie interior bluish glow. The blue light comes from electrons whirling at nearly the speed of light around magnetic field lines from the neutron star. The neutron star, like a lighthouse, ejects twin beams of radiation that appear to pulse 30 times a second due to the neutron star's rotation. A neutron star is the crushed ultra-dense core of the exploded star.

The Crab Nebula derived its name from its appearance in a drawing made by Irish astronomer Lord Rosse in 1844, using a 36-inch telescope. When viewed by Hubble, as well as by large ground-based telescopes such as the European Southern Observatory's Very Large Telescope, the Crab Nebula takes on a more detailed appearance that yields clues into the spectacular demise of a star, 6,500 light-years away.

Angle of view: 12' x 12' (0.3515625" per pixel), north is up.

KPNO/NOIRLab/NSF/AURA Acknowledgment: PI: M.T. Patterson (New Mexico State University)

Out of this whirl: The Whirlpool Galaxy (M51) and companion galaxy

The graceful, winding arms of the majestic spiral galaxy M51 (NGC 5194) appear like a grand spiral staircase sweeping through space. They are actually long lanes of stars and gas laced with dust.

This sharpest-ever image, taken in January 2005 with the Advanced Camera for Surveys aboard the NASA/ESA Hubble Space Telescope, illustrates a spiral galaxy's grand design, from its curving spiral arms, where young stars reside, to its yellowish central core, a home of older stars. The galaxy is nicknamed the Whirlpool because of its swirling structure.

The Whirlpool's most striking feature is its two curving arms, a hallmark of so-called grand-design spiral galaxies. Many spiral galaxies possess numerous, loosely shaped arms that make their spiral structure less pronounced. These arms serve an important purpose in spiral galaxies. They are star-formation factories, compressing hydrogen gas and creating clusters of new stars. In the Whirlpool, the assembly line begins with the dark clouds of gas on the inner edge, then moves to bright pink star-forming regions, and ends with the brilliant blue star clusters along the outer edge.

Some astronomers believe that the Whirlpool's arms are so prominent because of the effects of a close encounter with NGC 5195, the small, yellowish galaxy at the outermost tip of one of the Whirlpool's arms. At first glance, the compact galaxy appears to be tugging on the arm. Hubble's clear view, however, shows that NGC 5195 is passing behind the Whirlpool. The small galaxy has been gliding past the Whirlpool for hundreds of millions of years.

As NGC 5195 drifts by, its gravitational muscle pumps up waves within the Whirlpool's pancake-shaped disk. The waves are like ripples in a pond generated when a rock is thrown in the water. When the waves pass through orbiting gas clouds within the disk, they squeeze the gaseous material along each arm's inner edge. The dark dusty material looks like gathering storm clouds. These dense clouds collapse, creating a wake of star birth, as seen in the bright pink star-forming regions. The largest stars eventually sweep away the dusty cocoons with a torrent of radiation, hurricane-like stellar winds, and shock waves from supernova blasts. Bright blue star clusters emerge from the mayhem, illuminating the Whirlpool's arms like city streetlights.

The Whirlpool is one of astronomy's galactic darlings. Located 31 million light-years away in the constellation Canes Venatici (the Hunting Dogs), the Whirlpool's beautiful face-on view and closeness to Earth allow astronomers to study a classic spiral galaxy's structure and star-forming processes.

Credit:

NASA, ESA, S. Beckwith (STScI), and The Hubble Heritage Team STScI/AURA)

About the Image

NASA caption
Id:	heic0506a
Type:	Observation
Release date:	25 April 2005, 06:00
Related releases:	heic0506
Size:	11477 x 7965 px

About the Object

Name:	Messier 51, Whirlpool Galaxy
Type:	• Local Universe : Galaxy : Type : Spiral
• Galaxies Images/Videos
Distance:	25 million light years

Colours & filters

Band	Wavelength	Telescope
Optical B 	435 nm 	Hubble Space Telescope ACS
Optical V 	555 nm 	Hubble Space Telescope ACS
Optical H-alpha + Nii 	658 nm 	Hubble Space Telescope ACS
Infrared I 	814 nm 	Hubble Space Telescope ACS

Angle of view: 7.5' x 7.5' (0.3515625" per pixel), north is up.

diverse

Picture Details:

   Optics            32-inch Schulman RC Optical Systems Telescope
   Camera            SBIG STX 16803 CCD Camera
   Filters           AstroDon Gen II
   Dates             May 2016
   Location          Mount Lemmon SkyCenter
   Exposure          RGB = 5 : 5 : 5 Hours
   Acquisition       Maxim DL/CCD (Cyanogen), AStronomer Control Panel (DC3- Dreams)
   Processing        CCDStack (CCDWare), Photoshop CC, PixInsight
   Credit Line and Copyright        Adam Block/Mount Lemmon SkyCenter/University of Arizona 

This image of Messier 64 (M64) was taken with Hubble's Wide Field Planetary Camera 2 (WFPC2). The color image is a composite prepared by the Hubble Heritage Team from pictures taken through four different color filters. These filters isolate blue and near-infrared light, along with red light emitted by hydrogen atoms and green light from Strömgren y.

M64 has a spectacular dark band of absorbing dust in front of the galaxy's bright nucleus, giving rise to its nicknames of the Black Eye or Evil Eye galaxy.

At first glance, M64 appears to be a fairly normal pinwheel-shaped spiral galaxy. As in the majority of galaxies, all of the stars in M64 are rotating in the same direction, clockwise as seen in the Hubble image. However, detailed studies in the 1990's led to the remarkable discovery that the interstellar gas in the outer regions of M64 rotates in the opposite direction from the gas and stars in the inner regions.

Active formation of new stars is occurring in the shear region where the oppositely rotating gases collide, are compressed, and contract. Particularly noticeable in the image are hot, blue young stars that have just formed, along with pink clouds of glowing hydrogen gas that fluoresce when exposed to ultraviolet light from newly formed stars.

Messier had no idea of the significance of his discovery at the time, and it wasn’t until over two centuries later, in 1994, that astronomers found Messier 54 to be part of the miniature galaxy and not our own. Current estimates indicate that the Sagittarius dwarf, and hence the cluster, is situated almost 90 000 light-years away — more than three times as far from the centre of our galaxy than the Solar System.

Ironically, even though this globular cluster is now understood to lie outside the Milky Way, it will actually become part of it in the future. The strong gravitational pull of our galaxy is slowly engulfing the Sagittarius dwarf, which will eventually merge with the Milky Way creating one much larger galaxy.

Angle of view: 12' x 12' (0.3515625" per pixel), north is up.

This is a unique view of the disk galaxy NGC 5866 tilted nearly edge-on to our line-of-sight. Hubble's sharp vision reveals a crisp dust lane dividing the galaxy into two halves. The image highlights the galaxy's structure: a subtle, reddish bulge surrounding a bright nucleus, a blue disk of stars running parallel to the dust lane, and a transparent outer halo. NGC 5866 is a disk galaxy of type "S0" (pronounced s-zero). Viewed face on, it would look like a smooth, flat disk with little spiral structure. It remains in the spiral category because of the flatness of the main disk of stars as opposed to the more spherically rotund (or ellipsoidal) class of galaxies called ellipticals. Such S0 galaxies, with disks like spirals and large bulges like ellipticals, are called lenticular galaxies. NGC 5866 lies in the Northern constellation Draco, at a distance of 44 million light-years. It has a diameter of roughly 60,000 light-years only two-thirds the diameter of the Milky Way, although its mass is similar to our galaxy. This Hubble image of NGC 5866 is a combination of blue, green and red observations taken with the Advanced Camera for Surveys in February 2006.

And from the image's page:

This is a unique NASA Hubble Space Telescope view of the disk galaxy NGC 5866 tilted nearly edge-on to our line-of-sight.

Hubble's sharp vision reveals a crisp dust lane dividing the galaxy into two halves. The image highlights the galaxy's structure: a subtle, reddish bulge surrounding a bright nucleus, a blue disk of stars running parallel to the dust lane, and a transparent outer halo.

Some faint, wispy trails of dust can be seen meandering away from the disk of the galaxy out into the bulge and inner halo of the galaxy. The outer halo is dotted with numerous gravitationally bound clusters of nearly a million stars each, known as globular clusters. Background galaxies that are millions to billions of light-years farther away than NGC 5866 are also seen through the halo.

NGC 5866 is a disk galaxy of type "S0" (pronounced s-zero). Viewed face on, it would look like a smooth, flat disk with little spiral structure. It remains in the spiral category because of the flatness of the main disk of stars as opposed to the more spherically rotund (or ellipsoidal) class of galaxies called "ellipticals." Such S0 galaxies, with disks like spirals and large bulges like ellipticals, are called 'lenticular' galaxies.

The dust lane is slightly warped compared to the disk of starlight. This warp indicates that NGC 5866 may have undergone a gravitational tidal disturbance in the distant past, by a close encounter with another galaxy. This is plausible because it is the largest member of a small cluster known as the NGC 5866 group of galaxies. The starlight disk in NGC 5866 extends well beyond the dust disk. This means that dust and gas still in the galaxy and potentially available to form stars does not stretch nearly as far out in the disk as it did when most of these stars in the disk were formed.

The Hubble image shows that NGC 5866 shares another property with the more gas-rich spiral galaxies. Numerous filaments that reach out perpendicular to the disk punctuate the edges of the dust lane. These are short-lived on an astronomical scale, since clouds of dust and gas will lose energy to collisions among themselves and collapse to a thin, flat disk.

For spiral galaxies, the incidence of these fingers of dust correlates well with indicators of how many stars have been formed recently, as the input of energy from young massive stars moves gas and dust around to create these structures. The thinness of dust lanes in S0s has been discussed in ground-based galaxy atlases, but it took the resolution of Hubble to show that they can have their own smaller fingers and chimneys of dust.

NGC 5866 lies in the Northern constellation Draco, at a distance of 44 million light-years (13.5 Megaparsecs). It has a diameter of roughly 60,000 light-years (18,400 parsecs) only two-thirds the diameter of the Milky Way, although its mass is similar to our galaxy. This Hubble image of NGC 5866 is a combination of blue, green and red observations taken with the Advanced Camera for Surveys in November 2005.

using the 0.8m Schulman Telescope at the Mount Lemmon SkyCenter

   Optics            32-inch Schulman Telescope (RC Optical Systems), Acquired remotely
   Camera            SBIG STX 16803 CCD Camera
   Filters           AstroDon Gen II
   Dates             January 2012
   Location          Mount Lemmon SkyCenter
   Exposure          LRGB = 240:70:70:70 minutes
   Acquisition       ACP Observatory Control Software (DC-3 Dreams),TheSky (Software Bisque), Maxim DL/CCD (Cyanogen)
   Processing        CCDStack (CCDWare), Photoshop CS5 (Adobe), PixInsight

Messier 105

M105 (aka NGC 3379) - Hubble peered into the core of M105 (also known as NGC 3379) and measured the motions of stars swirling around its center. These observations proved that a supermassive black hole resides at the galaxy’s heart. According to recent estimates, this black hole could be up to 200 million times as massive as our Sun. Credits: NASA, ESA, Karl Gebhardt (University of Michigan) and Tod Lauer (NOAO)

​M105 is an elliptical galaxy 32 billion light-years away in the constellation Leo. It is the largest elliptical in the Messier catalog that is not a member of the Virgo cluster of galaxies. M105 does, however, belong to the M96 (or Leo I) Group, which includes neighbors M95 and M96 as well as several other fainter galaxies. Charles Messier’s colleague Pierre Méchain discovered M105 in 1781 just a few days after locating M95 and M96. Yet M105 was not originally included in Messier’s catalog. It was added in 1947 after astronomer Helen S. Hogg found a letter written by Méchain describing the galaxy.

This Hubble image of M105 was taken in near-infrared and visible light. Like most elliptical galaxies it appears rather featureless and inactive. However, Hubble observations surprised astronomers by revealing young stars and star clusters in M105, indicating that star formation is still taking place in what was thought to be a “dead” galaxy no longer capable of giving birth to new stars. Other Hubble observations measured the speeds of stars moving around the center of the galaxy, which demonstrated that a supermassive black hole resides at M105’s core.

Best observed in April, M105 has an apparent magnitude of 10.2 and can be spotted with a small telescope. Large telescopes will uncover two fainter galaxies (NGC 3384 and NGC 3389) close to the bright elliptical.

For more information about Hubble’s observations of M105, see:

Angle of view: 12' x 12' (0.3515625" per pixel), north is up.

This brilliant image of Messier 30 (M 30) was taken by Hubble's Advanced Camera for Surveys (ACS). Messier 30 formed 13 billion years ago and was discovered in 1764 by Charles Messier. Located about 28000 light-years away from Earth, this globular cluster — a dense swarm of several hundred thousand stars — is about 90 light-years across.

An image of M98. Credit: Astrofotografía http://astroguia.org/astroalbum/displayimage.php?pos=-309

Bucking the trend

This luminous orb is the galaxy NGC 4621, better known as Messier 59. As this latter moniker indicates, the galaxy was listed in the famous catalogue of deep-sky objects compiled by French comet-hunter Charles Messier in 1779. However, German astronomer Johann Gottfried Koehler is credited with discovering the galaxy just days before Messier added it to his collection.

Modern observations show that Messier 59 is an elliptical galaxy, one of the three main kinds of galaxies along with spirals and irregulars. Ellipticals tend to be the most evolved of the trio, full of old, red stars and exhibiting little or no new star formation. Messier 59, however, bucks this trend somewhat; the galaxy does show signs of star formation, with some newborn stars residing within a disc near the core.

Located in the 2000-strong Virgo Cluster of galaxies within the constellation of Virgo (The Virgin), Messier 59 lies approximately 50 million light-years away from us. This image was taken by the NASA/ESA Hubble Space Telescope’s Advanced Camera for Surveys.

Credit:

ESA/Hubble & NASA, P. Cote

Coordinates
Position (RA): 	12 42 2.17
Position (Dec):	11° 38' 47.46"
Field of view: 	3.13 x 2.50 arcminutes
Orientation:   	North is 105.8° right of vertical

Colours & filters
Band   	Wavelength	Telescope
Optical g	475 nm  	Hubble Space Telescope ACS
Optical V	555 nm  	Hubble Space Telescope ACS
Optical i	702 nm  	Hubble Space Telescope WFPC2
Optical z	850 nm  	Hubble Space Telescope ACS
Optical i	702 nm  	Hubble Space Telescope WFPC2
Optical z	850 nm  	Hubble Space Telescope ACS

Angle of view: 12' x 12' (0.3515625" per pixel), north is up.

Picture Details:

   Optics            24-inch RC Optical Systems Telescope
   Camera            SBIG STL11000 CCD Camera
   Filters           Custom Scientific
   Dates             October 25th- October 26th 2008
   Location          Mount Lemmon SkyCenter
   Exposure          LRGB = 290:60:60:60 minutes
   Acquisition       TheSky (Software Bisque), Maxim DL/CCD (Cyanogen)
   Processing        CCDStack (CCDWare), Mira (MiraMetrics), Maxim DL (Cyanogen), Photoshop CS3 (Adobe)
   Visiting Astronomers: Jimmy and Cathy Dean

Messier 96 lies in the constellation of Leo (The Lion). It is the largest galaxy in the Leo I group of galaxies; including its outermost spiral arms, it spans some 100 000 light-years in diameter — about the size of our Milky Way. Its graceful imperfections likely result from the gravitational pull of other members in the group, or are perhaps due to past galactic encounters.

A multitude of background galaxies peers through the dusty spiral. Perhaps the most striking of these objects is an edge-on galaxy that — because of a chance alignment — appears to interrupt the outermost spiral arm to the upper left of Messier 96's core.

This image was processed by ESO using the observational data found by Oleg Maliy from Ukraine, who participated in ESO's Hidden Treasures 2010 astrophotography competition [1], organised in October–November 2010, for everyone who enjoys making beautiful images of the night sky using astronomical data obtained with professional telescopes. The image was made with data taken at visible and infrared wavelengths through B, V, and I filters.

Notes

Credit:

This excellent image of the Dumbbell Nebula (M27, NGC6853), a planetary nebula in the constellation of Vulpecula, was taken at the 3.5-meter WIYN telescope using the mini-mosaic imager (described in an NOAO newsletter article). The nebula was formed when an evolved, red giant star ejected its outer envelope near the end of its lifetime. The expanding cloud of gas becomes visible once the hot core of the star, visible near the center, is exposed and the high-energy, ultraviolet light from the core ionizes the cloud. This makes the nebula emit mostly a strong emission-line spectrum. This color image was obtained by combining three separate pictures, each one taken through a narrow filter centered at the emission wavelengths of Hydrogen (H alpha, red, 656 nm), doubly ionized Oxygen (OIII, green, 501 nm), and neutral Oxygen (OI, blue, 630 nm). It is physically very interesting that neutral gas can survive in a region right next to highly ionized gas, and this image shows how, as the blue component is concentrated in very dense clumps which act to protect the neutral oxygen from the intense ultraviolet radiation which has ionized the other gas components. We can compare this to a picture combining three images all of ionized gases, (also from the WIYN telecope), and to the more usual color image from the Mayall 4-meter telescope, or the nice deep image from the 2.1-meter telescope. The Dumbbell nebula is about 850 light-years away from Earth and about 1.5 light-years in diameter (although both distance and size are very poorly constrained).

Credit:

George Jacoby, WIYN/NSF

Coordinates
Position (RA):  	19 59 36.22
Position (Dec): 	22° 43' 14.39"
Field of view:  	8.70 x 8.70 arcminutes
Orientation:     	North is 0.2° right of vertical

Colors & filters Band	Wavelength	Telescope
Optical Ol          	630 nm    	WIYN 3.5-meter Telescope Mini Mosaic
Optical Olll         	501 nm    	WIYN 3.5-meter Telescope Mini Mosaic
Optical Ha           	656 nm    	WIYN 3.5-meter Telescope Mini Mosaic

Angle of view: 36' x 36' (0.52734375" per pixel), north is up.

Angle of view: 27' × 27' (0.792" per pixel), north is up.

Angle of view: 24' x 24' (0.3515625" per pixel), north is up.

Another, perhaps even more striking, feature of Messier 95 is its blazing golden core. It contains a nuclear star-forming ring, almost 2000 light-years across, where a large proportion of the galaxy’s star formation takes place. This phenomenon occurs mostly in barred spiral galaxies such as Messier 95 and our home, the Milky Way.

Angle of view: 12' x 12' (0.3515625" per pixel), north is up.

Angle of view: 14' x 14' (0.42" per pixel), north is up.

In this image, the NASA/ESA Hubble Space Telescope has captured the brilliance of the compact centre of Messier 70, a globular cluster. Quarters are always tight in globular clusters, where the mutual hold of gravity binds together hundreds of thousands of stars in a small region of space. Having this many shining stars piled on top of one another from our perspective makes globular clusters a popular target for amateur skywatchers and scientists alike. Messier 70 offers a special case because it has undergone what is known as a core collapse. In these clusters, even more stars squeeze into the object's core than on average, such that the brightness of the cluster increases steadily towards its centre.

The legions of stars in a globular cluster orbit about a shared centre of gravity. Some stars maintain relatively circular orbits, while others loop out into the cluster's fringes. As the stars interact with each other over time, lighter stars tend to pick up speed and migrate out toward the cluster's edges, while the heavier stars slow and congregate in orbits toward the centre. This huddling effect produces the denser, brighter centres characteristic of core-collapsed clusters. About a fifth of the more than 150 globular clusters in the Milky Way have undergone a core collapse.

Although many globular clusters call the galaxy's edges home, Messier 70 orbits close to the Milky Way's centre, around 30 000 light-years away from the Solar System. It is remarkable that Messier 70 has held together so well, given the strong gravitational pull of the Milky Way's hub.

Messier 70 is only about 68 light-years in diameter and can be seen, albeit very faintly, with binoculars in dark skies in the constellation of Sagittarius (The Archer). French astronomer Charles Messier documented the object in 1780 as the seventieth entry in his famous astronomical catalogue.

This picture was obtained with the Wide Field Camera of Hubble’s Advanced Camera for Surveys. The field of view is around 3.3 by 3.3 arcminutes.

Colours & filters
Band       Wavelength     Telescope
Infrared I 814 nm         Hubble Space Telescope ACS
Optical Pseudogreen (V+I) Hubble Space Telescope ACS
Optical V  606 nm         Hubble Space Telescope ACS

To celebrate the Hubble Space Telescope's 16 years of success, the two space agencies involved in the project, NASA and the European Space Agency (ESA), are releasing this image of the magnificent starburst galaxy, Messier 82 (M82). This mosaic image is the sharpest wide-angle view ever obtained of M82. The galaxy is remarkable for its bright blue disk, webs of shredded clouds, and fiery-looking plumes of glowing hydrogen blasting out of its central regions.

Throughout the galaxy's center, young stars are being born 10 times faster than they are inside our entire Milky Way Galaxy. The resulting huge concentration of young stars carved into the gas and dust at the galaxy's center. The fierce galactic superwind generated from these stars compresses enough gas to make millions of more stars.

In M82, young stars are crammed into tiny but massive star clusters. These, in turn, congregate by the dozens to make the bright patches, or "starburst clumps," in the central parts of M82. The clusters in the clumps can only be distinguished in the sharp Hubble images. Most of the pale, white objects sprinkled around the body of M82 that look like fuzzy stars are actually individual star clusters about 20 light-years across and contain up to a million stars.

The rapid rate of star formation in this galaxy eventually will be self-limiting. When star formation becomes too vigorous, it will consume or destroy the material needed to make more stars. The starburst then will subside, probably in a few tens of millions of years.

Located 12 million light-years away, M82 appears high in the northern spring sky in the direction of the constellation Ursa Major, the Great Bear. It is also called the "Cigar Galaxy" because of the elliptical shape produced by the oblique tilt of its starry disk relative to our line of sight.

ID: phot-33c-03-fullres

Size: 2300x2294

The largest of its kind

Star clusters are commonly featured in cosmic photoshoots, and are also well-loved by the keen eye of the NASA/ESA Hubble Space Telescope. These large gatherings of celestial gems are striking sights — and the subject of this Picture of the Week, Messier 2, is certainly no exception.

Messier 2 is located in the constellation of Aquarius (The Water-Bearer), about 55 000 light-years away. It is a globular cluster, a spherical group of stars all tightly bound together by gravity. With a diameter of roughly 175 light-years, a population of 150 000 stars, and an age of 13 billion years, Messier 2 is one of the largest clusters of its kind and one of the oldest associated with the Milky Way.

This Hubble image of Messier 2’s core was created using visible and infrared light. Most of the cluster’s mass is concentrated at its centre, with shimmering streams of stars extending outwards into space. It is bright enough that it can even be seen with the naked eye when observing conditions are extremely good.

Credit:

ESA/Hubble & NASA, G. Piotto et al.

Coordinates
Position (RA): 	21 33 27.20
Position (Dec):	0° 49' 21.79"
Field of view: 	2.43 x 2.44 arcminutes
Orientation:   	North is 12.8° right of vertical

Colours & filters Band	Wavelength	Telescope
Ultraviolet UV	275 nm	Hubble Space Telescope WFC3
Optical u	336 nm	Hubble Space Telescope WFC3
Optical B	438 nm	Hubble Space Telescope WFC3

Angle of view: 12' x 12' (0.3515625" per pixel), north is up.

This is the galactic core shown as a composite image of visible and infrared observations in order to resolve the blue jet.

Angle of view: 45' × 33' (1.8" per pixel), north is not up.

Picture Details:

   Optics            24-inch RC Optical Systems Telescope
   Camera            SBIG STL11000 CCD Camera
   Filters           Custom Scientific
   Dates             February 20th 2009
   Location          Mount Lemmon SkyCenter
   Exposure          LRGB = 90:30:30:30 minutes
   Acquisition       ACP Observatory Control Software (DC-3 Dreams),TheSky (Software Bisque), Maxim DL/CCD (Cyanogen)
   Processing        CCDStack (CCDWare), Mira (MiraMetrics), Maxim DL (Cyanogen), Photoshop CS3 (Adobe)
   Guest Astronomers:                   September 2009 Image Processing Workshop Participants

However, this was not known when Charles Messier first observed it in January 1779. He described Messier 56 as “a nebula without stars”, like most globular clusters that he discovered — his telescope was not powerful enough to individually resolve any of the stars visible here, making it look like a fuzzy ball through his telescope’s eyepiece. We clearly see from Hubble’s image how the development of technology over the years has helped our understanding of astronomical objects.

Astronomers typically infer important properties of globular clusters by looking at the light of their constituent stars. But they have to be very careful when they observe objects like Messier 56, which is located close to the Galactic plane. This region is crowded by “field-stars”, in other words, stars in the Milky Way that happen to lie in the same direction but do not belong to the cluster. These objects can contaminate the light, and hence undermine the conclusions reached by astronomers.

A tool often used by scientists for studying stellar clusters is the colour-magnitude (or Hertzsprung-Russell) diagram. This chart compares the brightness and colour of stars – which in turn, tells scientists what the surface temperature of a star is.

By comparing high quality observations taken with the Hubble Space Telescope with results from the standard theory of stellar evolution, astronomers can characterise the properties of a cluster. In the case of Messier 56, this includes its age, which at 13 billion years is approximately three times the age of the Sun. Furthermore, they have also been able to study the chemical composition of Messier 56. The cluster has relatively few elements heavier than hydrogen and helium, typically a sign of stars that were born early in the Universe’s history, before many of the elements in existence today were formed in significant quantities.

Astronomers have found that the majority of clusters with this type of chemical makeup lie along a plane in the Milky Way’s halo. This suggests that such clusters were captured from a satellite galaxy, rather than being the oldest members of the Milky Way's globular cluster system as had been previously thought.

This image consists of visible and near-infrared exposures from Hubble’s Advanced Camera for Surveys. The field of view is approximately 3.3 by 3.3 arcminutes.

Angle of view: 12' x 6,3' (0.3515625" per pixel), north is up.

This dramatic image of the galaxy Messier 83 was captured by the Wide Field Imager at ESO's La Silla Observatory, located high in the dry desert mountains of the Chilean Atacama Desert. Messier 83 lies roughly 15 million light-years away towards the huge southern constellation of Hydra (the sea serpent). It stretches over 40 000 light-years, making it roughly 2.5 times smaller than our own Milky Way. However, in some respects, Messier 83 is quite similar to our own galaxy. Both the Milky Way and Messier 83 possess a bar across their galactic nucleus, the dense spherical conglomeration of stars seen at the centre of the galaxies.

Credit:

ESO

Coordinates
Position (RA):	13 37 0.91
Position (Dec):	-29° 51' 56.57"
Field of view:	17.59 x 17.59 arcminutes
Orientation:	North is 0.0° left of vertical

Colours & filters Band	Telescope
Optical B       	MPG/ESO 2.2-metre telescope WFI
Optical V       	MPG/ESO 2.2-metre telescope WFI
Optical R       	MPG/ESO 2.2-metre telescope WFI

Angle of view: 24' x 24' (0.3515625" per pixel), north is up.

The Wide Field Imager on the MPG/ESO 2.2-metre telescope at ESO’s La Silla Observatory in Chile has taken this beautiful image, dappled with blue stars, of one of the most star-rich open clusters currently known — Messier 11, also known as NGC 6705 or the Wild Duck Cluster.

Messier 11 is an open cluster, sometimes referred to as a galactic cluster, located around 6000 light-years away in the constellation of Scutum (The Shield). It was first discovered by German astronomer Gottfried Kirch in 1681 at the Berlin Observatory, appearing as nothing more than a fuzzy blob through the telescope. It wasn’t until 1733 that the blob was first resolved into separate stars by the Reverend William Derham in England, and Charles Messier added it to his famous catalogue in 1764.

Messier was a comet hunter and the catalogue came into being as he was frustrated by constantly observing fixed, diffuse objects that looked like comets (for example, objects that we now know to be clusters, galaxies and nebulae). He wanted a record in order to avoid accidentally observing them again and confusing them with possible new comets. This particular stellar cluster was noted down as the eleventh such object — hence the name of Messier 11.

Open clusters are typically found lying in the arms of spiral galaxies or in the denser regions of irregular galaxies, where star formation is still common. Messier 11 is one of the most star-rich and compact of the open clusters, being almost 20 light-years across and home to close to 3000 stars. Open clusters are different to globular clusters, which tend to be very dense, tightly bound by gravity, and contain hundreds of thousands of very old stars — some of which are nearly as old as the Universe itself.

Studying open clusters is great way to test theories of stellar evolution, as the stars form from the same initial cloud of gas and dust and are therefore very similar to one another — they all have roughly the same age, chemical composition, and are all the same distance away from Earth. However, each star in the cluster has a different mass, with the more massive stars evolving much faster than their lower mass counterparts as they use up all of their hydrogen much sooner.

In this way, direct comparisons between the different evolutionary stages can be made within the same cluster: for example, does a 10 million year old star with the same mass as the Sun evolve in a different way to another star that is the same age, but half as massive? In this sense, open clusters are the closest thing astronomers have to “laboratory conditions”.

Because the stars within open clusters are very loosely bound to one another, individuals are very susceptible to being ejected from the main group due to the effect of gravity from neighbouring celestial objects. NGC 6705 is already at least 250 million years old, so in a few more million years it is likely that this Wild Duck formation will disperse, and the cluster will break up and merge into its surroundings [1].

This image was taken by the Wide Field Imager on the MPG/ESO 2.2-metre telescope at ESO’s La Silla Observatory in northern Chile. Notes

[1] The alternative and evocative name for NGC 6705, the Wild Duck Cluster, came about in the 19th century. When the cluster was seen through a small telescope it was noticed that the brightest stars formed an open triangle pattern on the sky that resembled ducks flying in formation.

About the Object Name: M 11, Wild Duck Cluster Type: • Milky Way : Star : Grouping : Cluster : Open

       • X - Star Clusters

Distance: 6000 light years Constellation: Scutum

Coordinates Position (RA): 18 51 3.49 Position (Dec): -6° 15' 33.12" Field of view: 35.59 x 25.70 arcminutes Orientation: North is 0.0° left of vertical

Colours & filters Band Telescope Optical B MPG/ESO 2.2-metre telescope WFI Optical V MPG/ESO 2.2-metre telescope WFI

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

• MessierStarChart.svg: w:user:Jim Cornmell, Zeimusu
• derivative work: CWitte

Nuzzled in the chest of the constellation Virgo (the Virgin) lies a beautiful cosmic gem — the galaxy Messier 61. This glittering spiral galaxy is aligned face-on towards Earth, thus presenting us with a breathtaking view of its structure. The gas and dust of the intricate spiral arms are studded with billions of stars. This galaxy is a bustling hub of activity with a rapid rate of star formation, and both a massive nuclear star cluster and a supermassive black hole buried at its heart.

Messier 61 is one of the largest members of the Virgo Cluster, which is made up of more than a thousand galaxies, and is itself at the centre of the Virgo Supercluster — to which our Milky Way also belongs. This dazzling beauty was first discovered in 1779, and it has been capturing astronomers’ interest ever since. Set against a dark sky littered with galaxies, this image shows the awe-inspiring M61 in its full glory — even at its distance of over 50 million light-years.

This image was taken as part of ESO’s Cosmic Gems Programme, an outreach initiative to produce images of interesting, intriguing or visually attractive objects using ESO telescopes, for the purposes of education and public outreach. The programme makes use of telescope time that cannot be used for science observations. In case the data collected could be useful for future scientific purposes, these observations are saved and made available to astronomers through ESO’s Science Archive.

Credit:

ESO

Coordinates
Position (RA):	12 21 57.51
Position (Dec):	4° 28' 25.12"
Field of view:	6.11 x 6.24 arcminutes
Orientation:	North is -0.0° left of vertical

Colours & filters Band	Wavelength	Telescope
Optical b      	440 nm	Very Large Telescope FORS2
Optical v      	557 nm	Very Large Telescope FORS2
Infrared R     	655 nm	Very Large Telescope FORS2
Optical H-alpha	656 nm	Very Large Telescope FORS2

Angle of view: 12' x 12' (0.3515625" per pixel), north is up.

Picture Details:

   Optics            24-inch RC Optical Systems Telescope
   Camera            SBIG STL11000 CCD Camera
   Filters           Custom Scientific
   Dates             April 28th and 29th 2009
   Location          Mount Lemmon SkyCenter
   Exposure          LRGB = 150:50:50:50 minutes
   Acquisition       ACP Observatory Control Software (DC-3 Dreams),TheSky (Software Bisque), Maxim DL/CCD (Cyanogen)
   Processing        CCDStack (CCDWare), Mira (MiraMetrics), Maxim DL (Cyanogen), Photoshop CS3 (Adobe)

(October 26, 1999) Hubble Space Telescope's exquisite resolution has allowed astronomers to resolve, for the first time, hot blue stars deep inside an elliptical galaxy. The swarm of nearly 8,000 blue stars resembles a blizzard of snowflakes near the core (lower right) of the neighboring galaxy M32, located 2.5 million light-years away in the constellation Andromeda. Hubble confirms that the ultraviolet light comes from a population of extremely hot helium-burning stars at a late stage in their lives. Unlike the Sun, which burns hydrogen into helium, these old stars exhausted their central hydrogen long ago, and now burn helium into heavier elements. The observations, taken in October 1998, were made with the camera mode of the Space Telescope Imaging Spectrograph (STIS) in ultraviolet light. The STIS field of view is only a small portion of the entire galaxy, which is 20 times wider on the sky. For reference, the full moon is 70 times wider than the STIS field-of-view. Thirty years ago, the first ultraviolet observations of elliptical galaxies showed that they were surprisingly bright when viewed in ultraviolet light. Before those pioneering UV observations, old groups of stars were assumed to be relatively cool and thus extremely faint in the ultraviolet. Over the years since the initial discovery of this unexpected ultraviolet light, indirect evidence has accumulated that it originates in a population of old, but hot, helium-burning stars. Now Hubble provides the first direct visual evidence.

   Optics            32-inch Schulman Telescope (RC Optical Systems)
   Camera            SBIG STX 16803 CCD Camera
   Filters           AstroDon Gen II
   Dates             January-March 2014
   Location          Mount Lemmon SkyCenter
   Exposure          LRGB = 7:3:3:3 Hours
   Acquisition       ACP Observatory Control Software (DC-3 Dreams), Maxim DL/CCD (Cyanogen), FlatMan XL (Alnitak)
   Processing        CCDStack (CCDWare), Photoshop CC (Adobe), PixInsight
   Credit Line and Copyright        Adam Block/Mount Lemmon SkyCenter/University of Arizona 

Angle of view: 13,5' x 9,5' (0.396" per pixel, SDSS native resolution), north is up.

Astronomers can measure the ages of globular clusters by looking at the light of their constituent stars. The chemical elements leave signatures in this light, and the starlight reveals that globular clusters' stars typically contain fewer heavy elements, such as carbon, oxygen and iron, than stars like the Sun. Since successive generations of stars gradually create these elements through nuclear fusion, stars having fewer of them are relics of earlier epochs in the Universe. Indeed, the stars in globular clusters rank among the oldest on record, dating back more than 10 billion years.

More than 150 of these objects surround our Milky Way galaxy. On a galactic scale, globular clusters are indeed not all that big. In Messier 68's case, its constituent stars span a volume of space with a diameter of little more than a hundred light-years. The disc of the Milky Way, on the other hand, extends over some 100 000 light-years or more.

Messier 68 is located about 33 000 light-years from Earth in the constellation Hydra (The Female Water Snake). French astronomer Charles Messier notched the object as the sixty-eighth entry in his famous catalogue in 1780.