# Where can I find a database on the masses of different galaxies?

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I want to get the data for masses of galaxies, more information about them can only be helpful. Can anyone point me to a site where I can get this sort of information?

As a starting point, I would suggest searching on VizieR for catalogues of galaxies. E.g. select "Galaxies" in the "Astronomy" menu (on the right-hand side of the initial form) and put "Masses" in the "Find catalogs" search box (the upper one, the lower one is for searching by position which is less useful here).

In the results section, the elliptical icons on the right-hand side allow you to see roughly what the sky coverage is for the catalogue. Once you select a catalogue, you can take a look at what fields are there.

## Galaxies

Galaxies are large systems of stars and interstellar matter, typically containing several million to some trillion stars, of masses between several million and several trillion times that of our Sun, of an extension of a few thousands to several 100,000s light years, typically separated by millions of light years distance. They come in a variety of flavors: Spiral, lenticular, elliptical and irregular. Besides simple stars, they typically contain various types of star clusters and nebulae.

We live in a giant spiral galaxy, the Milky Way Galaxy, of 100,000 light years diameter and a mass of roughly a trillion solar masses our Sun is one of several 100 billions of stars of the Milky Way. The nearest dwarf galaxies, satellites of the Milky Way, are only a few 100,000 light years distant (and closer in case of some dwarfs which are currently merged with the Milky Way), while the nearest giant neighbor, the Andromeda Galaxy (M31), also a spiral, is about 2-3 million light years distant.

## Where can I find a database on the masses of different galaxies? - Astronomy

We get quite a few requests here at Curious for help in finding stars that have been "purchased" by our readers. If you're still just thinking about buying a star please read Can I Buy a Star? for our opinions on the companies that offer this service and our suggestions for a much more personal approach. Included below are a few example questions and answers, and I'll start with some general tips.

To find a star, the easiest thing would be to figure out which constellation it is in and where it is in relation to brighter stars. Included with your 'bought star' I presume there is a finding chart which shows this information. Hopefully that includes the constellation it is in and nearby easily recognizable stars. Then you can use a service like www.heavens-above.com or a smartophone app like SkyMap on Android or SkyView on iPhone, to figure out when that area of the sky will be visible for you and then locate the constellation and use that to find the star. Most stars which are 'sold' are very dim and hard to find, which is a shame for people who spend money hoping they will be able to find them.

Another option is to use something like Sky View which has a database of pictures of the whole sky. Pick the 'non-Astronomers' interface enter the RA and Dec in the "Sky Co-ordinates or Object" box and select the Optical survey. This will give you a small image of the sky in which "your" star will be at the center.

What follows are some examples of specific answers. Please try the above, and read-on to see if you can figure it out yourself before sending us specific requests to find your particular star.

I bought a star and a telescope for my boyfriend but we still can't figure out where it is the R.A is 273.21034167 (what does that mean?) DEC is -63.68550278 (don't know what that means either!) could you please help me find it. I need to know the basics of finding it on our own telescope or even just by the naked eye.

R.A. and Dec are abbreviations for Right Ascension and Declination, which are basically like latitude and longitude on the sky. They are explained further in our answer to What are RA and DEC?

The RA and Dec in the above question are listed in decimal degrees, Astronomers more typically use RA and DEC in hours and degrees, converted into that format the RA and Dec above are:M
R.A. = 18 hours, 12 minutes and 50 seconds
Dec = -63 degrees, 41 minutes, 8 seconds

From a given location on Earth you can only see stars at a certain range of declinations. The more negative the declination, the further south you need to be (you have to be further north for positive declinations). Stars at Dec=-63 degrees only just make it above the horizon for people south of latitude 27 degrees, and only comfortably if you are considerably south of that. I hope you live pretty far south, or you will never see this star and if that is the case my opinion of companies who sell stars has dropped even further.

I am a complete novice regarding the stars, although I love looking at them and am in awe. In this vain, I bought my daughter a star in the sky for her first Christmas. It is known as Cygnus RA20h11m42.76s D48deg48m5.66s. Other than identifying the seven sisters to the naked eye, I have no idea what I'm looking for in the sky. I understand that stars move and are only visible in certain areas at certain times of the year. We live in Spain in the Costa Blanca if that helps with timings. I would be very grateful if you could tell a layman how to find a certain star please. Is it visible or would it be too faint and we would need a telescope?

Cygnus is one of my favourite constellations. It makes the shape of a swan flying along the Milky Way (when it is dark enough to see the Milky Way). It's overhead in summer evenings, so a really pleasant constellation to look at, the star at its tail is one of the three brightest stars in the summer sky which make up the "Summer triangle". You can use a site like www.heavens-above.com to make "whole sky charts" for your location and a given time, and with a bit of effort and practice should be able to match that to the stars in the sky.

As for the star you have "bought", it is likely to be too faint for you to see without a telescope. On the other hand Cygnus is a lovely constellation and there is no-one to stop you from "claiming" it for your daughter - it would certainly be a nice tradition for you to go out together as a family to see it every summer.

I'm an employee here at Cornell in the ILR School. For Christmas this year I had a star named after my dad. I have the location of the Star - but I would really like to be able to look at it and know exactly where in the constellation Ursa Major - that it is located. I know how to locate the "Big Dipper" by just looking in the sky - but I really really want to know exactly where in the constellation that his star is located. The chart that they sent me along with the info - does not give any specifics other than the Astronomical Position Star # USC3263172-83, Astronomical Position is Right Ascension 11H45M8.71S, Declination +29D52M39S, Magnitude 14.62. Would it be possible for you to tell me where in the constellation it is located and/or let me see if through the observatory telescope here on campus? Would it be possible to get a chart or photo that I could give to my father along with the location information?

One option you have is to find it in an online Astronomical database. A nice one is Sky View who have a special non-Astronomers interface. If you enter the co-ordinates of the star as 11 45 8.71 +29 52 39 and search the optical database you get a small optical picture of the star. You can pick the size of the image you want up to a few degrees across which allows you to see the star in relation to nearer brighter ones. SIMBAD is another such service, and lets you make a finder chart for objects within a certain radius of the position. You should check the epoch of the co-ordinates you have. I am assuming it is 2000 which is what I put into the search engines (and should be the default), but it is possible that it is 1950 which makes somewhat of a difference. There is also software you can download to do this. Some free ones is Carte du Ciel (which only works for Windows computers) and Stellarium which works on all major operating systems.

The star this company has 'sold' you is a 14th magnitude star, which means it is so dim that it can only be seen with a telescope. The limiting brightness for stars seen with the naked eye is about magnitude 6.5, with binoculars you can see to magnitudes of about 10 (the bigger the number the fainter the star). A 14th magnitude star can only be seen by a fairly large amateur telescope on a dark site. I actually doubt that it is possible to see it using the refracting telescope on the Cornell campus even on a clear night because of the light pollution from north campus. The Cornell Astronomy Club hosts public observing nights most Fridays if you want to try, although they may not be keen to point at your specific star. The name you have for the star (USCetc) appears to be the companies personal ID for the star and is not recognized by any Astronomical catalogues.

It feels mean to tell you this right before you plan to give the present to your father, but actually the bad guys here are the company that sold you the star and continue to make money out of the general public's ignorance about astronomy. As mentioned in the posted article above, it could be nicer (and is just as official) to pick any star you can actually see and make your own certificate.

That's ok, I appreciate the openness. Yesterday another student emailed me and told me basically the same thing. I will probably ask the company for my money back - and see if I can go about it the way that you have suggested.

• Stars
• Stargazing
• Telescopes
• Hoax
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• Brightness
• Declination
• Constellations
• Right Ascension
• Magnitude
• Money

#### Karen Masters

Karen was a graduate student at Cornell from 2000-2005. She went on to work as a researcher in galaxy redshift surveys at Harvard University, and is now on the Faculty at the University of Portsmouth back in her home country of the UK. Her research lately has focused on using the morphology of galaxies to give clues to their formation and evolution. She is the Project Scientist for the Galaxy Zoo project.

The first known galaxies were longly known before their nature as "island universes" came to light - this fact was finally proven only in 1923 by Edwin Powell Hubble, when he found Cepheid variable stars in the Andromeda Galaxy M31. Ancient observers have known the Milky Way and - on the Southern Hemisphere - the Large and the Small Magellanic Cloud since prehistoric times, and there are speculations that also the Andromeda Galaxy M31 may have been observed and recorded as a nebulous patch by anonymous Babylonian observers around 1,300 B.C.. This object was certainly known to medevial Persian astronomers before 905 A.D., and cataloged and described by Persian astronomer Al Sufi in 964 A.D. All other galaxies have been discovered only after the invention of the telescope: The Triangulum Galaxy M33 was first seen by Italian Priest astronomer G.B. Hodierna before 1654. Next, French astronomer Legentil discovered M32, a companion of the Andromeda Galaxy, in 1749, and his compatriot Abbé Lacaille found M83 in 1752, the first galaxy beyond the Local Group to be discovered. These six were all external galaxies to be known, before Charles Messier started to survey the sky for comets and "nebulae." His first original discovery of a galaxy, M49, a giant elliptical member of the Virgo Cluster, occurred in 1771. The Messier Catalog in his modern form contains 40 galaxies, all but the two Magellanic Clouds that have been found up to 1782. Starting in 1783, William Herschel found and cataloged over 2,500 star clusters and "nebulae" up to 1802, 2,143 of them actually galaxies. J.L.E. Dreyer's NGC catalog contains 6,029 (about 75.9%), and his IC catalog another 3,971 galaxies (about 73.7%).

for HTML browser supporting tables (e.g., Netscape, IBM Webexplorer) for HTML browsers not supporting tables (Lynx, Mosaic)

The most massive galaxies are giants which are a million times more massive than the lightest: Their mass range is from at most some million times that of our Sun in case of the smallest dwarfs, to several trillion solar masses in case of giants like M87 or M77. Accordingly, the number of stars in them varies in the same range.

The linear size of galaxies also scatters, ranging from small dwarfs of few thousands of light years diameter (like M32) to respectable several 100,000 light years. Among the biggest Messier galaxies are the Andromeda galaxy M31 and the bright active Seyfert II galaxy M77.

Our Milky Way Galaxy, a spiral galaxy, is among the massive and big galaxies with at least 250 billion solar masses (there are hints that the total mass may even be as large as 750 billion to 1 trillion times that of the Sun) and a disk diameter of 100,000 light years.

, large but quite compact agglomerations of some 100,000 to several million stars. These large clusters have about the same mass as the smallest galaxies, and are among the oldest objects in galaxies. Often, they form conspicuous systems, and occur at galaxies of every type and size. The globular cluster systems vary in a wide range in richness between the individual galaxies.
• As the stars develop, many of them leave nebulous remnants (planetary nebulae or supernova remnants) which then populate the galaxies.
• While the older stars, including the globular clusters, tend to form an ellipsoidal bulge, the interstellar gas and dust tends to accumulate in clouds near an equatorial disk, which is often conspicuous (i.e., in spiral and lenticular galaxies).
• The interstellar clouds are the places of star formation. More acurately, huge diffuse star-forming nebulae are places where crowded (open) clusters and associations of stars are formed.
• A rather dense galactic nucleus, which is somewhat similar to a "superlarge" globular cluster. In many cases, galactic nuclei contain supermassive dark objects, which are often considered as Black Hole candidates. Some of the more massive and conspicuous globulars are suspected to be the remnants of former nuclei of small galaxies which have been disrupted and cannibalized by larger galaxies.

Some galactic nuclei are remarkably distinguished from the average: These so-called Active Galactic Nuclei (AGNs) are intensive sources of light of all wavelengths from radio to X-rays. The activities seen in the AGNs are caused by gaseous matter falling into, and interacting with, the supermassive central objects mentioned above, according to the current consensus of most researchers. Sometimes, the spectra of these nuclei indicate enormous gaseous masses in rapid motion galaxies with such a nucleus are called Seyfert galaxies (for their discoverer, Karl Seyfert). M77 is the brightest Seyfert galaxy in the sky. Few galaxies have even more exotic nuclei, which are extremely compact and extremely bright, outshining their whole parent galaxy these are called quasars (an acronym for QUAsi-StellAR objects). From their properties, quasars resemble extremely active Seyfert galaxy nuclei. However, quasars are so rare and the nearest is so remote that the brightest of them, 3C273, about 2 billion lightyears away in the constellation Virgo, is only of magnitude 13.7, and none of them is in Messier's or even in the NGC or IC catalog.

Occasionally, at irregular intervals given by chance, in any type of galaxies, a supernova occurs: This is a star suddenly brightning to a high luminosity which may well outshine the whole galaxy the maximal absolute magnitude of a supernova may well reach -19 to -20 magnitudes. This remarkable phenomenon has attracted the attention of many astronomers (equally both professionals and amateurs), who observe galaxies regularly as they "hunt" supernovae. Supernovae have been observed in several Messier catalog galaxies.

According to our current scientific understanding, at least most galaxies (including our Milky Way and those in Messier's catalog) have formed during a comparatively short period, at about the same time, within the first billion years after the universe started to expand, from an initial hot state. Thus they are all almost as old as the universe itself, currently thought to be about 10-15 billion years. It is thought that galaxy formation started when primordial clouds of gaseous matter (hydrogen and helium), the proto-galaxies, were singled out and started to collapse by their own gravity. According to computer simulations, the variety of galaxy forms results from different initial parameters of the proto-galaxies such as the amount of (initial) angular momentum, as well as their later evolution in their environments, such as interaction with other neighboring galaxies.

## Where can I find a database on the masses of different galaxies? - Astronomy

No one is sure exactly how many galaxies there are in total—many millions for sure! To illustrate how many galaxies there are that are known, a single 2 year survey (the 2dF Galaxy Survey) which finished in 2003 surveyed 250,000 galaxies in order to make a 3D map of the Universe. And that's certainly not all known galaxies! Check out the 2dF website for more on this. As another example, there are 932 million objects in the 15th data release of the Sloan Digital Sky Survey (SDSS), although many of those are stars, and SDSS has specta for about 2.5 milion galaxies. There are about 667 million distinct known galaxies in the NASA Extragalactic Database (NED)! And

2 million sources which still need to be analyzed to determine if they're new objects or just new measurements of known old objects. This is still probably not everything either. When a new telescope comes online that has a significant upgrade in observing power compared to what was available before, Astronomers will generally do a big survey to find new galaxies, and it takes time for these new galaxy catalogs to be merged with big databases like NED. So the exact number of known galaxies is constantly changing!

For the observable Universe, it is estimated that there are as many as 200 billion galaxies, but we aren't able to see all of them as our telescopes are not sensitive enough. In addition, different types of telescopes are better at finding different types of galaxies. For example, many very distant galaxies (galaxies early in cosmic history) are very dusty, and dust blocks the optical starlight. Therefore optical telescopes like Hubble won't see these dusty galaxies. However, that dust gets hot from absorbing the starlight and then emits light in the infrared, which can be detected with infrared telescopes like Herschel. Collating these different galaxy surveys together can be challenging and affects estimates about the number of galaxies in the Universe.

This page was last updated by Catie Ball on January 28, 2019

#### Karen Masters

Karen was a graduate student at Cornell from 2000-2005. She went on to work as a researcher in galaxy redshift surveys at Harvard University, and is now on the Faculty at the University of Portsmouth back in her home country of the UK. Her research lately has focused on using the morphology of galaxies to give clues to their formation and evolution. She is the Project Scientist for the Galaxy Zoo project.

## Hubble Spots Massive Cluster of Galaxies: ACO S 295

This image, taken by the NASA/ESA Hubble Space Telescope, shows the massive galaxy cluster ACO S 295. The image is made up of observations from Hubble’s Wide Field Camera 3 (WFC3) and Advanced Camera for Surveys (ACS) instruments in the infrared and optical parts of the spectrum. Seven filters were used to sample various wavelengths. The color results from assigning different hues to each monochromatic image associated with an individual filter. Image credit: NASA / ESA / Hubble / F. Pacaud / D. Coe.

Galaxy clusters contain thousands of galaxies of all ages, shapes and sizes. Typically, they have a mass of about one million billion times the mass of the Sun.

At one point in time they were believed to be the largest structures in the Universe — until they were usurped in the 1980s by the discovery of superclusters.

However, clusters do have one thing to cling on to superclusters are not held together by gravity, so galaxy clusters still retain the title of the biggest structures in the Universe bound by gravity.

Albert Einstein predicted in his theory of general relativity that massive objects will deform the fabric of space itself.

When light passes one of these objects, such as a massive galaxy cluster, its path is changed slightly.

Known as gravitational lensing, this effect is only visible in rare cases and only the best telescopes can observe the related phenomena.

“The ACO S 295 cluster dominates the center of the new image, both visually and physically,” Hubble astronomers said.

“The huge mass of the galaxy cluster has gravitationally lensed the background galaxies, distorting and smearing their shapes.”

“As well as providing astronomers with a natural magnifying glass with which to study distant galaxies, gravitational lensing has subtly framed the center of this image, producing a visually striking scene.”

“Galaxies of all shapes and sizes populate this image, ranging from stately spirals to fuzzy ellipticals,” the researchers added.

“As well as a range of sizes, this galactic menagerie boasts a range of orientations, with spiral galaxies such as the one at the center of this image appearing almost face on, and some edge-on spiral galaxies visible only as thin slivers of light.”

## Size Matters: Astronomers Discover Rare, 'Super Spiral' Galaxies

A team of astronomers has recently discovered a total of 53 ‘super spiral’ galaxies which are enormous in size, three of which are shown in the image above. The galaxies shown at the left and center images also exhibit a double nucleus, which could be the result of a past galactic merger. Image Credit: Sloan Digital Sky Survey

One of the essential aspects of astronomy is that of classification. Whatever their type, celestial objects are mainly categorised according to their basic properties like their size, mass, and brightness. For instance, on the realm of planetary bodies there are objects as small as Ceres and Pluto in our own Solar System as well as exoplanets with two times the size of Jupiter that have been found in orbit around other stars. The latter also exhibit a wide range of masses and sizes from 1/10 to more than a thousand times that of the Sun. When it comes to the specimens of the galactic zoo, these fall under three different categories: spiral, elliptical and irregular galaxies which similarly exhibit a wide range of sizes, with the biggest ones that had been found to date spanning more than 200,000 light-years across—twice that of our own galaxy, the Milky Way. Recently, astronomers were able to shatter this long-held record by announcing the unexpected discovery of a new population of galactic beasts, consisting of gigantic spiral galaxies that are up to four times larger than the Milky Way. In addition to their ‘wow’ factor, these ‘super spirals’ represent a challenge for astronomers in their efforts to determine how, contrary to theoretical models, these monstrous stellar cities can grow to such enormous sizes.

One of the major open questions in cosmology and astrophysics today, is the formation and evolution of galaxies. Despite the great strides that have taken place in the study of galaxies and galactic clusters during the last couple of decades with the help of ground and space-based observatories, the exact physical processes with which the first structures in the primordial Universe formed and later evolved in order to create the large diversity of galaxies that is observable today, remains an actively debated topic among astronomers. According to the standard model of cosmology, minuscule, random density fluctuations in the otherwise uniform distribution of matter in the early Universe were the seeds that gave rise to the great variety of structure that exists on a cosmic scale today. Yet, the specific mechanisms that have driven this process are currently unknown. One hypothesis, known as the ‘top-down scenario’, posits that the hydrogen gas that dominated the early Universe had coalesced to form gigantic gas clouds which eventually collapsed and fragmented under their own gravity into smaller clumps of matter – the protogalaxies. With the passage of cosmic time these primordial, baby galaxies grew bigger, eventually giving rise to the large, fully grown galaxies of all shapes and sizes that we see today. On the other hand, a competing hypothesis which has gained much traction in recent years, known as the ‘bottom-up scenario’, postulates that the first galaxies formed directly from the primordial density fluctuations and through the process of colliding and merging with one another they led to the development of the large-scale structures that characterise the Universe today.

During the 1920’s astronomer Edwin Hubble devised the now infamous galaxy classification scheme, also known as the Hubble Tuning Fork, which categorised galaxies according to their shape into spirals, ellipticals and irregulars. The exact mechanisms with which galaxies have evolved into these distinct shapes remain a mystery to this day. Image Credit: Galaxy Zoo

Whatever the exact path was that the Universe chose for the evolution of its constituent stars and galaxies, theoretical predictions have shown that galaxies could only grow to a certain extent, before eventually depleting their gas and dust through star formation. More specifically spiral galaxies, which are named for the spiral arms that extend outward from their center and are rich in young, newly formed blue-white stars as well as huge reservoirs of cold gas and dust, are the places in the Universe where active star formation takes place. Depending on the amount of gas and dust that is available in their spiral arms, spiral galaxies have star-formation rates which range from 1-3 solar masses per year in the case of the Milky Way, to 10 times higher in the case of the so-called ‘starburst’ galaxies like M82. Yet, spiral galaxies can’t hold these rates forever. Eventually their gas and dust runs out, at which point it has been generally hypothesised that their spiral arms slowly fade and star formation comes to a stop. It is thought that this shutting-off of star-formation in spiral galaxies also marks the point where the latter transition towards ellipticals, which are characterised by the presence of aging red stars and are devoid of any gas and dust.

Star formation inside a galaxy can be halted by a host of other processes as well if their reservoirs of cold gas and dust for instance gets expelled from the spiral arms as a result of galaxy collisions, or if it is abruptly heated and compressed by supernovae explosions or from ram-pressure stripping, which results from the galaxy’s movement through the intergalactic medium inside galaxy clusters. These gas-stripping mechanisms are also responsible for limiting the growth of spiral galaxies, leaving galaxy mergers as the dominant process of galaxy evolution with the passage of cosmic time.

Four out of the 53 newly found super spiral galaxies exhibit a double nucleus, which could signify different stages of galactic merger events. (a) Possible collision in progress of two spirals. (b) Possible collision or merger of two spirals, also a brightest cluster galaxy. (c) High-surface brightness disk with possible double AGN, with faint outer arms. The nucleus at the center is classi ed as an SDSS QSO. (d) Possible late-stage major merger with two stellar bulges, with a striking grand spiral design surrounding both nuclei. Image Credit: Sloan Digital Sky Survey

Wanting to shed more light to the processes that drive galactic evolution, a research team led by Patrick Ogle, a professor of astrophysics at the California Institute of Technology, went through the archival data of the NASA/IPAC Extragalactic Database , or NED for short, with the goal of identifying the most massive and luminous galaxies that are located more than 1 billion light-years away. Funded and operated by NASA and Caltech’s Infrared Processing and Analysis Center, or IPAC, respectively, NED is a large online database which consists of multi-wavelength data for more than 200 million extragalactic objects that have been gathered by a series of different projects and space missions, like NASA’s IRAS and GALEX satellites as well as the Sloan Digital Sky Survey and the 2-Micron All-Sky Survey among others.

By far, some of the most massive and luminous galaxies known to date are ellipticals. Even though they are composed of old red stars and have long stopped forming new ones, elliptical galaxies can nevertheless grow to supergiant status, like the famous M87 in the constellation Virgo which has a diameter of approximately one million light-years—10 times greater than that of the Milky Way. Ogle and colleagues expected to only find similar supergiants like M87 in a sample of nearly 800,000 galaxies that they extracted from the NED database for their research. Yet, to their surprise, their search revealed a total of 53 spiral galaxies with sizes and luminosities that by far exceeded that of spirals like our own. Dubbed ‘super spirals’ by the researchers, these newly found behemoths which lie between 1.2 and 3.5 billion light-years away, were found to be eight and fourteen times brighter than the Milky Way while also exhibiting a star formation rate that was up to 30 times higher. Most impressively, the diameter of the biggest one among them is a whopping 440,000 light-years across, making it by far the biggest known spiral galaxy to date. “We have found a previously unrecognized class of spiral galaxies that are as luminous and massive as the biggest, brightest [elliptical] galaxies we know of,” says Ogle. “It’s as if we have just discovered a new land animal stomping around that is the size of an elephant but had shockingly gone unnoticed by zoologists.”

The giant elliptical galaxy M87 as seen from the Hubble Space Telescope. With a diameter of approximately 1 million light-years, M87 is 10 times bigger than our own galaxy. The discovery of ‘super spirals’ shows that spiral galaxies can also grow to enormous sizes. Image Credit: NASA, ESA, and the Hubble Heritage Team (STScI/AURA)

One of the things that stands out regarding these newly found super spiral galaxies, is the strange fact that four of them appear to have two galactic nuclei, making them look like two egg yolks in a frying pan, similar to what has also been observed in recent years in a handful of much smaller spirals. Could this be evidence of an ongoing galaxy merger? If so, that would run counter to the view galactic mergers as cosmic train wrecks where participating galaxies are generally severely deformed, often resulting to spiral galaxies being stripped off their spiral arms and settling into their new life as ellipticals. Nevertheless, according to Ogle’s team, this new population of super spirals may be the missing link between the massive members of both galaxy types. “Super spirals display a range of morphologies, from flocculent to grand-design spiral patterns”, write the researchers in their study which was published at The Astrophysical Journal. “At least 9 super spirals have prominent stellar bars visible in the SDSS images. There are morphological peculiarities in several cases, including one-arm spirals, multi-arm spirals, rings, and asymmetric spiral structure. These types of features may indicate past or ongoing galaxy mergers or collisions … We suggest that super spirals may be the progenitors of red and dead lenticular galaxies of similar mass”.

Whatever the case may be, the finding of just 53 such galaxies out of a total of 800,000 suggests that super spirals are extremely rare specimens in the wider population of the galactic zoo. Nevertheless, theoretical models of galactic evolution will need to be revised in order to account for the presence of even such a small sample, since it was thought that spiral galaxies in general could not grow to such sizes. Furthermore, the discovery of spiral galaxies with two apparently distinct cores could shed more light to the dynamics of galactic mergers, which remains a dominant process in the Universe today. “Super spirals could fundamentally change our understanding of the formation and evolution of the most massive galaxies,” says Ogle. “We have much to learn from these newly identified, galactic leviathans.”

In this regard, the discovery by Ogle’s team is just the start. With more than 200 million extragalactic objects listed in its database, NED is a treasure trove of data for astronomers to analyse further, that could be full of more such fascinating surprises in the future. “Remarkably, the finding of super spiral galaxies came out of purely analyzing the contents of the NASA/IPAC Extragalactic Database, thus reaping the benefits of the careful, systematic merging of data from many sources on the same galaxies,” says George Helou, Executive Director for IPAC and member of Ogle’s team. “NED is surely holding many more such nuggets of information, and it is up to us scientists to ask the right questions to bring them out.”

If such exciting discoveries are the product of past astronomical surveys and space missions, one can’t help but be excited for what the future may bring, when the next-generation of ground- and space-based observatories will come online within the next five years.

## Where can I find a database on the masses of different galaxies? - Astronomy

We present deep 3.6-8 μm imaging of the Hubble Deep Field-South with the Infrared Array Camera (IRAC) on the Spitzer Space Telescope. We study distant red galaxies (DRGs) at z>2 selected by J s -K s >2.3 and compare them with a sample of Lyman break galaxies (LBGs) at z=2-3. The observed UV-to-8 μm spectral energy distributions are fitted with stellar population models to constrain star formation histories and derive stellar masses. We find that 70% of the DRGs are best described by dust-reddened star-forming models and 30% are very well fitted with old and dead'' models. Using only the I-K s and K s -4.5 μm colors, we can effectively separate the two groups. The dead systems are among the most massive at z

2.5 (mean stellar mass <M * >= 0.8×10 11 M solar ) and likely formed most of their stellar mass at z>5. To a limit of 0.5×10 11 M solar , their number density is

10 times lower than that of local early-type galaxies. Furthermore, we use the IRAC photometry to derive rest-frame near-infrared J, H, and K fluxes. The DRGs and LBGs together show a large variation (a factor of 6) in the rest-frame K-band mass-to-light ratios (M/L K ), implying that even a Spitzer 8 μm-selected sample would be very different from a mass-selected sample. The average M/L K of the DRGs is about 3 times higher than that of the LBGs, and DRGs dominate the high-mass end. The M/L K values and ages of the two samples appear to correlate with derived stellar mass, with the most massive galaxies being the oldest and having the highest mass-to-light ratios, similar to what is found in the low-redshift universe.

Based on observations made with the Spitzer Space Telescope, which is operated by the Jet Propulsion Laboratory, California Institute of Technology, under NASA contract 1407. Support for this work was provided by NASA through contract 125790 issued by JPL/Caltech. Based on service-mode observations collected at the European Southern Observatory, Paranal, Chile (program 164.O-0612). Based on observations with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555

## Where can I find a database on the masses of different galaxies? - Astronomy

Galaxies are gravitationally-bound systems of stars, gas, dust and dark matter. A typical large spiral galaxy such as our home galaxy, the Milky Way, consists of hundreds of billions of stars, enough gas and dust to make billions more stars, and at least ten times as much dark matter as all the stars and gas put together.

In the 1920s, Edwin Hubble used the 100-inch optical telescope on Mount Wilson, in California, to find other galactic systems. NASA's Hubble Space Telescope, named in Hubble's honor, has observed billions of galaxies of different sizes and shapes. There are irregular small dwarf galaxies, majestic spiral galaxies, and elliptical galaxies ranging in size from dwarfs to supergiants ten times larger than the Milky Way galaxy.

The X-ray images of elliptical galaxies reveal that they are filled with multimillion degree gas, heated presumably by supernova explosions. Most of the gas in spiral galaxies is in the form of cool, dusty clouds. In both elliptical and spiral galaxies, X-ray images give us portraits of the end phases of stellar evolution - regions where supernovas have heated gas to millions of degrees, and objects where gravity has tightened its grip to form neutron stars and black holes.

The most extreme examples of gravity's force are found deep in the centers of most galaxies where supermassive black holes lurk. These gravitational monsters can contain masses ranging from a few million to a few billion Suns. In normal galaxies, the supermassive black hole mainly makes its presence known through its gravitational force on the motions of stars, and by X-rays produced when gas is heated as it falls toward the black hole. But when supermassive black holes are surrounded by large supplies of dust and gas, the acceleration and heating of this gas as it is pulled into the black hole can produce stupendous amounts of energy at X-ray and other wavelengths and transform the appearance of the entire galaxy. Such galaxies are called active galaxies or quasars.

## Hubble Observes Massive Galaxy Cluster: Abell 3827

This Hubble image shows the giant galaxy cluster Abell 3827. Image credit: NASA / ESA / Hubble / R. Massey.

Galaxy clusters are fundamental building blocks of the Universe, like stars and galaxies.

Typically, they contain thousands of galaxies of all ages, shapes and sizes.

They have a mass of about one million billion times the mass of the Sun and form over billions of years as smaller groups of galaxies slowly come together.

At one point in time galaxy clusters were believed to be the largest structures in the Universe — until they were usurped in the 1980s by the discovery of superclusters, which typically contain dozens of galaxy clusters and groups and span hundreds of millions of light-years.

However, clusters do have one thing to cling on to superclusters are not held together by gravity, so galaxy clusters still retain the title of the biggest structures in the Universe bound by gravity.

“Looking at this cluster of hundreds of galaxies, it is amazing to recall that until less than 100 years ago, many astronomers believed that the Milky Way was the only galaxy in the Universe,” Hubble astronomers said.

“The possibility of other galaxies had been debated previously, but the matter was not truly settled until Edwin Hubble confirmed that the Great Andromeda Nebula was in fact far too distant to be part of the Milky Way.”

“The Great Andromeda Nebula became the Andromeda Galaxy, and astronomers recognized that our Universe was much, much bigger than humanity had imagined.”

“We can only imagine how Edwin Hubble — after whom the NASA/ESA Hubble Space Telescope was named — would have felt if he’d seen this spectacular image of Abell 3827,” they said.

Abell 3827 was observed by the Hubble telescope in order to study dark matter, which is one of the greatest puzzles cosmologists face today.

The color image of the galaxy cluster was made from separate exposures taken in the visible and infrared regions of the spectrum with Hubble’s Advanced Camera for Surveys (ACS) and Wide Field Camera 3 (WFC3) instruments.

Four filters were used to sample various wavelengths. The color results from assigning different hues to each monochromatic image associated with an individual filter.