And the cottonball galaxies shall inherit the Universe

By Phil Plait | April 25, 2011 9:30 am

Out there in the Universe, tucked in between the magnificent spirals and bloated ellipticals, lie the dwarf galaxies. They almost certainly vastly outnumber their larger brethren, but because they’re small and don’t contain as many stars they’re harder to see at great distances. Almost all the ones we see are very close by, and so these are objects under intense scrutiny… like UGC 9128:

[Click to unendwarfenate, or beam down the brobdingnagian 3800 x 3800 pixel version.]

Isn’t that pretty? In this small version here you’re not getting the whole effect, so I strongly encourage you to grab a bigger one.

UGC 9128 is pretty close as galaxies go, lying about 8 million light years away. Only a handful of galaxies are closer; this is only a little more than twice as far away as the much more famous (and far, far larger) Andromeda Galaxy. But it’s so diminutive it’s very faint. It’s only about a hundred million stars strong — compare that to the 400 billion in the Milky Way! — which is why you’ve never heard of it. From stem to stern it’s perhaps 3300 light years long; again, tiny compared to the 100,000 light year breadth of our galaxy.

But in this Hubble image it’s very lovely. This is a false color image; what you see as blue is actually orange light from stars, and red is near-infrared, just a bit farther out in the spectrum than the human eye can see. These two filters are used because they do a good job of separating out different kinds of stars, allowing astronomers to sample the stellar population of the galaxy.

There’s quite a bit of evidence that these galaxies collide and merge to form bigger galaxies, and we know that big galaxies like our own still sometimes gravitationally gobble down such small galaxies, ingesting them like cosmic cannibals, growing larger in the process. Studying dwarfs like UGC 9128 gives us insight into how this process occurs.

This particular galaxy lies in a part of the sky to our galactic north, where our own galaxy is thinner. That’s why there are fewer foreground stars than you usually see in a Hubble picture, and lots of background galaxies. Those galaxies are much farther away, certainly hundreds of millions of light years, and the smaller ones are probably more like a billion light years distant! That may give you an idea of just how small UGC 9128 is; I picture it like a cotton ball held in front of my face, with those other galaxies being serving platters clear across the room.

But again, these galaxies may dominate the Universe… after all, how many cotton balls do you have in your house compared to the number of serving platters?

ESA/Hubble & NASA

Related posts:

Hubble snaps a cosmic photobomb
A tiny galaxy that hides a big sercet
The Milky Way bridges from here to eternity
Bang! A-boom-a-boomerang

CATEGORIZED UNDER: Astronomy, Pretty pictures, Top Post

Comments (29)

Links to this Post

  1. Stellar Zoo: Meet the Species | August 26, 2012
  1. So like red dwarf stars being the most populous, these galaxies may outnumber the spectacular ones we are used to seeing? Learn something new every day!

  2. Matt B.

    Did you notice the background galaxy in the upper right edge of UGC 9128? It has a bright core, an elliptical(-looking) body, and then a ring of fainter material around it.

  3. Messier Tidy Upper

    Great image – love the background galaxies starring (or should that be ‘galaxying’?) in it too. :-)

    That is a new one for me too. Cheers! :-)

    … how many cotton balls do you have in your house compared to the number of serving platters?

    Well, unless I’ve got some cotton balls in my first aid kit – & I’d have to check & see – I think the answer in my case is neither of either item there. ūüėČ

  4. Why is it taking so long to create a laptop with a 3800×3800 resolution! Gosh! Please be on more podcasts; you’re always fun to listen to.

  5. thetentman

    Do I have cotton balls? Do I look like a teddy bear?

  6. Gary Ansorge

    “Only” 100 million stars, fluffy and disorganized. Sounds like the low rent district.

    Wonder what the Hamptons of galaxies would look like?


    Gary 7

  7. jess tauber

    Anyone have a clue as to whether such dwarf galaxies are structurally stable enough (or big enough to avoid the deleterious effects of supermassive black holes while feeding and supernovae) to have a chance at hosting planets with life? I’ve heard that globular and new open clusters ain’t so great a place to live.

  8. Pete Jackson

    Galaxies like this have been around for a long, long time, and so have lots of very old stars. But star formation and evolution is still going on, but at a slow rate compared with big galaxies like the Milky Way. This has resulted in young stars that have heavy element abundances much lower than for disk stars in the Milky Way galaxy.

    They are very important in the history and evolution of our Universe, but also so very hard to study because of their faintness. It’s good to see this galaxy getting some Hubble time.

  9. Chris A.

    The question that springs to my mind is this: How many galactic mergers occurred to make the Milky Way? Assuming they were all pipsqueaks like this, it would take roughly 4000! (Not taking into account how many of the Milky Way’s 4×10^11 stars were born post-mergers.)

  10. Oli

    Since these are so small, would it be possible for inhabitants of a random star in that galaxy to see every other star in it? That’s impossible in the Milky Way because of the bright core and all of the dust, but I don’t see a bright nucleus or much dust in that galaxy…

  11. andy

    Anyone have a clue as to whether such dwarf galaxies are structurally stable enough (or big enough to avoid the deleterious effects of supermassive black holes while feeding and supernovae) to have a chance at hosting planets with life?

    Typically dwarf galaxies have very low abundances of metals (elements heavier than helium) which is not a good sign in terms of the likelihood of planets.

  12. Unless estimates (or math) have changed, 8 million light years away would make it a little more than *three* times as far away as M31.

    I’m also curious as to the potential for life in (presumably) less tempestuous corners of the universe like this. It sounds like some degree of cosmic chaos and destruction is necessary for life to arise though, and these sleepy hamlets may just be too quiet.

  13. jess tauber

    I just found this on the science newsfeeds- might be relevant:

  14. chris j.

    Matt B. @2,

    i love playing the “count the ‘rare’ ring galaxies” game with these high-res pictures, but this one’s too easy.

    but move over ring galaxy, what the heck is that thing to its left? barred ring galaxy? or did hubble capture one of the “close encounters” spaceships in passing?

  15. jess tauber

    And while not directly relevant to tinier galaxies, this might raise eyebrows:

  16. Jamey

    How do you distinguish between a globular cluster and a very dwarf galaxy? I’m thinking we’re in planet/brown dwarf territory here, or planet/dwarf planet territory.

  17. Keith Bowden

    “beam down the brobdingnagian”

    Hahahaha! Love it. :)

  18. Joseph G

    @16 Jamey: Creepy! You seriously took the words right out of my mouth, even down to the brown dwarf/planet and planet/dwarf planet analogies :)

    /Also eagerly awaiting an answer on this.

  19. Joseph G

    @15 kess tauber: I’ve never seen the phrase “Mexican Wave” before.
    Sounds like an oversized house Margarita from Chili’s or something ūüėõ

  20. Gosh I love those platters… They’re so much more detailed then the deep-field collection.. (of course these are much closer) Can’t remember ever seeing a picture with such a fine collection of far away galaxies, anyone?

  21. “But again, these galaxies may dominate the Universe‚Ķ after all, how many cotton balls do you have in your house compared to the number of serving platters?”

    Sounds like astrology logic. (ha!)

  22. Other Paul

    @MessierTidyUpper #3: Maybe it should be ‘galactating’? (Yikes)

  23. T. Ray

    Is there a difference between cottonball galaxies and globular clusters? They seem like the same thing with a more marketable name.

  24. Off Colfax

    @chris j. #14

    That is exactly what I was wondering… It almost looks like a ring galaxy with gravitational lensing effects within the ring. Then again, I Am Not An Astronomer.

    Then again, looking closely at the brobdingnagian version, it appears that there are structural similarities between the galaxy we’re staring at, at the roughly 10 o’clock position, and the one that Matt B. #2 was referencing at the 1 o’clock position. At first, I was thinking that they were gravitational lensing artifacts. Yet the orientation of the bars in comparison to the ring doesn’t line up, so there’s little probability that they’re lensed copies of the same galaxy.

    Phil, inquiring minds want to know.

  25. jennyxyzzy

    Whilst we’re discussing odd galaxies in this photo, what is with the small reddish one at about 9 o’clock from the main dwarf galaxy. It’s got a void in the form of a bar running through it (at least that’s what it looks like on the photo!)

  26. Beautiful picture. But, umm… what’s that evil-looking thing in the top left corner (directly beneath the bright pointy star, and above and slightly to the right of that pretty spiral?)

  27. Donna gaumond

    Please tell me what the bright red disks are with the bright centers. I’ve been doing the milky way in zooniverse and I think they are probably galaxies that are red shifted or are red because they are taken in infrared. The one with spikes, are the spikes an distortion from the lens or is that a foreground star. I need to know. I got some students interested and I can identify the bubbles which I believe are the result of gas from a supernova. The green and yellow knots are protostars? I can identify many galaxies because they look like galaxies. But there are so many of there’d spheres. Someone help!! Are there identifyiNG features for a quasar? I,ve been lookin for answers with some ideas but no confirmation.

  28. @ 7. jess tauber :

    A galaxy can only have stars with rocky (i.e. “Earthlike”) planets if one or more waves of star formation happened after the first stars formed. The first stars will be very poor in heavy elements; only the effluvium from the first Supernovae will create enough heavy elements for later stars to be heavy-element-rich.

    Giant elliptical galaxies are notorious for having all their stellar formation happen at once, and then having no new stars ever form again. Dwarf ellipticals are probably the same, although dwarf irregulars can apparently have 2nd- or 3rd-generation star formation.


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