Hubble pokes at a galactic bulge

By Phil Plait | November 18, 2009 4:01 am

When you poke the Pillsbury dough boy in his bulging tummy, he giggles. When you poke the bulge in NGC 4710, however, you get the history of how galaxies form. Voila!

hst_ngc4710

Awesome. And you really need to embiggen this one to get a sense of the incredible beauty and resolution of the picture. Try the 4000 x 2000 pixel one on for size!

NGC 4710 is an edge-on spiral galaxy located about 60 million light years away in the Virgo Cluster. That puts it in the next town over, cosmically speaking, so it’s a rich target for something like Hubble Space Telescope. This image, newly released (but taken in 2006 before the last servicing mission), reveals spectacular details in the sideways galaxy. Views like this really accentuate the huge sprawling dust complexes littering spiral galaxies.

But it isn’t the dust astronomers are interested in here. Spirals have three main parts: a more-or-less spherical bulge in the center, the disk (which has the spiral arms), and a giant halo of stars surrounding them both. We understand a lot about spirals, but lots of big questions remain, including how and when the bulge forms. A galaxy is born out of a vast, collapsing cloud of gas. It’s possible that the bulge forms straight away, with the infalling gas of the protogalaxy making stars which build up in the galactic center. It’s also possible that the bulge forms later, well after the galaxy itself takes shape, as stars in the inner part of the galactic disk interact gravitationally and fall to the center, building up the bulge.

It turns out there might be a way to distinguish these formation mechanisms, even billions of years after the fact. Globular clusters are small (well, a couple of dozen light years across or so) balls of hundreds of thousands of stars. They orbit bigger galaxies; the Milky Way has well over 100 orbiting it. We know that many globulars formed at the same time as their parent galaxies; the stars in the clusters can be incredibly old. This means that perhaps the formation of the galaxy and its attendant clusters are connected.

In fact, it’s thought that the same process that creates the bulge in the "forms at the same time as the galaxy itself" scenario also creates globular clusters, but the other process (stars from the disk falling inward) does not create globulars.

That’s where NGC 4710 comes in. Being edge-on, we can see the bulge clearly, so it can be studied. But it also presents a good view of its globulars, so scientists can look at pictures like this one and simply count up the number of globular clusters near the galaxy and then figure out if the number is consistent with one of the two formation mechanisms.

In this case, NGC 4710 sports very few globulars, indicating the bulge formed after the galaxy itself. But NGC 4710 is only one of many galaxies being studied this way. Will they all show the same sluggish beginnings to their central bulges?

Time will tell. But I hope that as more of these galaxies are studied more images as lovely as this one become available.

Image credit: NASA & ESA

CATEGORIZED UNDER: Astronomy, Pretty pictures

Comments (44)

  1. DrFlimmer

    Would it be highly unlikely that both mechanisms take place in the universe?

  2. How silly, we all know that the bulge forms after two galaxies come together to have little galaxies. The original pair now spends too much time at work in order to support the proto-galaxies, they stop working out and they acquire a bulge in the middle.

  3. Picture is cool but the ability to just click on and download a picture that big without even giving it a second thought is even cooler

  4. I may not understand the science, but I do love the beauty of these shots!

  5. Prophet Zarquon

    It looks as though there is an X-shaped structure around the central bulge. Is it an image artefact? It looks rather odd.

  6. The dust lanes are spectacular, and almost scary.
    But I really like all the more distant galaxies scattered around the image. Very cool.

  7. Petrolonfire

    When you poke the Pillsbury dough boy in his bulging tummy, he giggles. When you poke the bulge in NGC 4710, however, …

    You need to have a *ve-ery* loooooo-ooong arm! ;-)

    An arm that’s millions of light years long in fact … Not even rubber girl from The Incredibles could do that! ;-)

  8. Flying sardines

    Great image but I wonder …

    NGC 4710 is an edge-on spiral galaxy located about 60 million light years away in the Virgo Cluster.

    How can we tell it is NOT an edge on barred spiral galaxy? Not meaning to be silly, its a genuine question here; what if we’re seeing the bar in a barred spiral as the dark dusty bit there with the milky white extensions from there as arms curving off from that galactic bar?

    That puts it in the next town over, cosmically speaking, so it’s a rich target for something like Hubble Space Telescope. This image, newly released (but taken in 2006 before the last servicing mission), reveals spectacular details in the sideways galaxy.

    Okay, also curious – why take an image back in 2006 then wait until 2009 to release it? What was the hold- up stopping them from releasing it right away?

    @ 4. Prophet Zarquon Says:

    It looks as though there is an X-shaped structure around the central bulge. Is it an image artefact? It looks rather odd.

    Looks to me a bit like the “filaments” punched through a starburst galaxy like Messier 82 (the “cigar galaxy”) and like there’s quite a warp in the disk /bar /arm /structure there.

    Gravitational interaction from a nearby neighbour maybe? Is there another satellite or larger galaxy near it?

    Looks like stuff streaming away from it too with some of those dust lanes.

    Finally, about those other galaxies – are they part of the Virgo supercluster & at approx. the same distance too or are they further away & in the distant background? Anyone care to enlighten us?

  9. Flying sardines

    D’oh! This paragraph was meant to be in italics as a quote from the BA :

    That puts it in the next town over, cosmically speaking, so it’s a rich target for something like Hubble Space Telescope. This image, newly released (but taken in 2006 before the last servicing mission), reveals spectacular details in the sideways galaxy.

    Not that it makes much difference but sorry if that caused any confusion.

    BTW off topic & all but question to the BA if that’s alright :

    Have you had any luck spotting any Leonids this year?

    Link to :

    http://blogs.discovermagazine.com/badastronomy/2009/11/16/watch-the-leonids/

  10. Jar Jar Binks Killer

    2. Thomas Says:

    How silly, we all know that the bulge forms after two galaxies come together to have little galaxies.

    I know you prob’ly weren’t being serious there but actually its the little galaxies coming together that makes the big ones! ;-)

    How do galactic mergers (which is how galaxies are formed & grow right?) affect the bulge formation question here?

  11. Jason Nyberg

    Re: the “X” structure: You’re probably seeing a conical distribution of stars; It looks like an X because you see a greater density of stars at the portions of the cone viewed tangentially vs. through the center. I’d say the large number of stars in this fairly well-defined distribution of off-axis orbits are the remnants of a small galaxy that collided with this one and was incorporated.

  12. Halo Halo Halo

    Quote: ” Spirals have three main parts: a more-or-less spherical bulge in the center, the disk (which has the spiral arms), and a giant halo of stars surrounding them both. ” Unquote

    I can see the bulge and disk but I’m not sure I can see the giant halo of stars. :-(

    Is it that glow around that galaxy or that just its light?

    If the giant halo is “full of of stars” how come it seems so dim and why isn’t it more prominent than the disk and bulge of this galaxy and also the band of our own Milky Way? If the halo has the most stars shouldn’t our Galaxy be a sphere or donut sort of thing or am I getting mixed up? Is the halo just the disk the arms are embedded in?

  13. johan

    They should have named the galaxy Ciconia ciconia instead.

  14. Prophet Zarquon

    @Flying sardines and Jason: Thanks! The explanation that this is the result of a merger sounds very likely.

  15. Gary Ansorge

    Is that a galactic bulge or are you just really happy to see me?

    I have a galactic bulge: but then again, I’m fraking OLD,,,

    I’d love to see that image in some other wavelengths. So much detail being hidden by all that light.

    GAry 7

  16. DM

    Ben Browder had the best galactic bulge ever as Crichton on Farscape.

  17. Derek

    I hope someone can answer this for I know not where to properly ask.

    What’s with all the noise on these images? I even downloaded the TIFF and the background is still all spotty. How can they tell galaxies from noise? And I even wondered this in the ultra-deep field where it was noted “every smudge” is a galaxy. Smudge? noise? I can’t tell the difference, can you tell the difference?

    In this particular image, there is a long straight line in the upper right quadrant. Noise? artifact? real?

    What are these images so dirty and how are they correctly interpreted?

  18. How do bulges form? Eating too many milkyways? :P

  19. Gary Ansorge

    13. Timechick

    NAw. It’s what you get when a Milky Way eats too many Clusters. My favorites are the ones with nuts in them. Which explains my presence here,,,

    GAry 7

  20. Dave L

    “Globular clusters are small (well, a couple of dozen light years across or so) balls of hundreds of thousands of stars. ”

    Really, they’re THAT small?

    I honestly don’t know, but that actually seems like a very small space for hundreds of thousands of stars.

  21. Knowing that this image is actually of a three-dimentional object, the “X” shape (which can be seen in the image — great) is likely two hyperbolic cones placed small end to small end at the center of the galaxy. This would provide a “X” appearance from any “edge” on view 360 degrees around the galaxy (or could it be referred to as an “hourglass”).

    This raises interesting possibilities…

  22. Prophet Zarquon

    @ Anaconda: I think that makes sense, but how do such structures form? I do know of planetary nebulae with a kind of X-shape, so maybe a similar mechanism is working here. Or it could be that we are seeing what is left behind after a stage of explosive star formation, such as in M 82, as Flying sardines said. That last theory might also fit with the observation that bulges form after the galaxy does…
    I love scientific mysteries, especially if they come with pretty pictures such as this one.

  23. Torbjörn Larsson, OM

    Over at Universe Today Atkinson claims the X is the image of the vertical motions of stars in the galaxy’s bar. I assume that we see the bar edge on.

    If so, it’s a more astounding dynamical feature than I assumed. (And the hyperbole spouted by EU religionists then, as per usual, a very improbable outcome.)

    @ IVAN3MAN:

    Thanks, now I understand why people found Loren [so fascinating]. A likewise astounding dynamical feature!

    I once saw another old photo tentatively contributed to Raquel Welch, also with a similar hour glass. (Or so I like to remember it.) Is that a “classic” figure? Young minds wants to know…

  24. @ Ivan3Man:

    Your comment is humorous!

  25. Prophet Zarquon asks: “Anaconda: I think that makes sense, but how do such structures form?”

    Could it be related to the observation by astronomers that galaxies “line up like beads on a string, with their spin axes aligned with the filaments that outline voids”?

    http://www.astronomy.com/asy/default.aspx?c=a&id=4215

    Of course, this also suggests the possibility that the filaments in some way connect the galaxies.

  26. IVAN3MAN AT LARGE

    @ Torbjörn Larsson, OM,

    Yeah, Raquel Welch also had that “classic” figure (remember the movie “One Million
    Years B.C.”? :P ), as well as Ursula Andress in the James Bond movie Dr. No. These so-called “modern women” today are too anorexic!

    @ Anaconda,

    I’m glad that you like it!

  27. IVAN3MAN

    Deleted by author.

  28. astroquoter

    27. IVAN3MAN Says:
    November 18th, 2009 at 5:05 pm
    Deleted by author.

    Why? Just curious.

    ****

    “Yet here we are with our eyes and our minds and our curiosity, six billion passengers aboard a tiny blue boat, bobbing and wheeling our way around one vast Catherine wheel among many.”
    - P.246, Ferris, ‘Seeing in the Dark’, Simon & Schuster, 2002.

  29. IVAN3MAN AT LARGE

    @ astroquoter,

    The reason for that was in order to edit my previous post, which initially I was not able to do because the time had gone past 00:00 UTC, here in the U.K., and due to some sort of ‘cookie’ issue with the system, it was not responding. So, I had to submit a ‘blank’ comment to acquire a new ‘cookie’ to get around that problem, after which I then wrote “Deleted by author” for the redundant comment.

  30. Why do I suspect plasma physics will be rearing its ugly charged head right about….

  31. StevoR

    Cool image! :-)

    @ 31. kuhnigget Says:

    Why do I suspect plasma physics will be rearing its ugly charged head right about….

    Too late – Anaconda’s already beaten you here! Been pretty civilised so far mind .. ;-)

    @ 12. Halo Halo Halo Says:

    I can see the bulge and disk but I’m not sure I can see the giant halo of stars.

    Is it that glow around that galaxy or that just its light?

    If you’re meaning what I think you’re meaning by that ‘glow’ – yeah that’s probably the halo of NGC 4710.

    If the giant halo is “full of of stars” how come it seems so dim and why isn’t it more prominent than the disk and bulge of this galaxy and also the band of our own Milky Way? If the halo has the most stars shouldn’t our Galaxy be a sphere or donut sort of thing or am I getting mixed up? Is the halo just the disk the arms are embedded in?

    As I understand it – & anyone else who knows better please correct me if I’m wrong – the halo is a gigantic sphere of stars and gas and globular clusters in which the entire rest of the galaxy is embedded. So its lot more than just the disk that’s embedded in the halo its the whole shebang. (To pinch one of Tim Ferris’es book titles! ;-) )

    As for why the stars in the halo don’t swamp the rest of the galaxy, I think (again please correct me if I’m mistaken folks) its because they are relatively far apart compared with the space around them and also these are mostly faint and old stars.

    Not sure what percentage of stars are in the halo vs the galactic bulge, disk, arms etc .. anyone else care to elucidate further?

    @ 8. Flying sardines Says:

    … How can we tell it is NOT an edge on barred spiral galaxy? Not meaning to be silly, its a genuine question here; what if we’re seeing the bar in a barred spiral as the dark dusty bit there with the milky white extensions from there as arms curving off from that galactic bar?

    It looks like you may be right judging by what # 23. Torbjörn Larsson, OM Says:

    “Over at Universe Today Atkinson claims the X is the image of the vertical motions of stars in the galaxy’s bar. I assume that we see the bar edge on.

    But I’m not sure myself – is this a barred spiral or just a spiral spiral? Can anyone tell us definitively? Please?

    Is there a link to that other Universe Todfay discusionof this or is it on the BAUT forum somewhere?

    @ 26. IVAN3MAN AT LARGE Says:

    Yeah, Raquel Welch also had that “classic” figure (remember the movie “One Million
    Years B.C.”? ), as well as Ursula Andress in the James Bond movie Dr. No. These so-called “modern women” today are too anorexic!

    I agree! :-D

    I think the terms are Rubenesque (after the famous painter with some stunning renaissance nudes) & voluptuous – That’s how I like my women too. You don’t want to be counting her ribs as you romance the lady, methinks. No, you want a woman with curves and a nice .. um .. shape, well I do at any rate. (Blushing) :-)

  32. astroquoter

    @ 30. IVAN3MAN AT LARGE

    Thanks for that explanation. :-)

    *****

    “Quasars are so luminous that if one was in action in a local group galaxy, its brilliance would rival that of the Sun.”
    - P.284, Ferris, ‘Seeing in the Dark’, Simon & Schuster, 2002.

    “Around us is a vast galaxy arrayed on scales so gigantic that galactic structure becomes discernible only once the solar system has dwindled to a dot the size of the period of this sentence.”
    - P.211, Ferris, ‘Seeing in the Dark’, Simon & Schuster, 2002.

    “Cosmology also tells us that there are perhaps 100 billion galaxies in the universe and that each contains roughly 100 billion stars. By a curious co-incidence, 100 billion is also the approximate number of cells in a human brain.”
    - Page 237, ‘StarGazer’, Dr Fred Watson, Allen & Unwin, 2004.

  33. IVAN3MAN AT LARGE

    @ StevoR,

    The link to the Universe Today article that Torbjörn Larsson, OM, was referring to is:
    http://www.universetoday.com/2009/11/18/x-marks-puzzling-galactic-bulge/

  34. nick

    if galaxy s are so dusty, why can we see through our dust?

  35. NGC3314

    “But it isn’t the dust astronomers are interested in here.” Speak for yourself! There’s even a connection from the dust in NGC 4710 to some recent Chandra data. One could just sort of fall into an image like this and get lost.

  36. Jan de Wit

    @Dave L (20): I was amazed at the small size too! Wikipedia has the star density at the core in the range of 1000 per cubic parsec. If you space those stars regularly, the nearest star is only 0.3 ly away. Makes interstellar travel a lot easier, too: just wait for a star to get close to your home planet and away you go!

  37. Gary Ansorge

    Anaconda:

    Filaments may be evidence for super strings,,,

    GAry 7

  38. IVAN3MAN AT LARGE

    @ Gary Ansorge,

    Anaconda, like a bloody creationist, and in common with all other EU/PC cranks, only hears what he wants to hear!

  39. StevoR

    @ 34. IVAN3MAN AT LARGE :

    Thanks! :-)

    It sounds like they think NGC 4710 is a barred spiral rather than a plain one but still not 100% sure.

    BTW. This reminds me, did the edge on spiral in the Hubble “vote – for- an-object- to-be-photo’d” competition ever get imaged by the HST?

    I know it didn’t win but I hope they photographed it anyway afterwards..

  40. Plutonium being from Pluto

    See : http://youdecide.hubblesite.org/

    The edge on spiral there was NCG 4289. The winner was colliding galaxies Arp 274 & that was announced March 1st (I presume this year but may have been 2008 0r older even. The BA posted on it at the time but I can’t seem to find the link despite much searching. Archive system here is .. frustrating. )

    - StevoR aka PbfP

  41. StevoR

    Finally!

    See : http://blogs.discovermagazine.com/badastronomy/2009/01/28/you-can-help-point-hubble/

    Thankyou Google and another webpage :

    http://blogs.discovery.com/space_disco/2009/01/vote-hubble-telescope-next-photo.html

    that quoted this! :-D

    Plutonium being from Pluto a.k.a. StevoR

    PS. BA / Discover folks you *really* need to look at making it easier to find old blog posts here IMHON.

  42. Nes

    Flying Sardines @ #8:

    If I remember correctly, scientists who take pictures with the Hubble are given a few years to have the pictures all to themselves so no one else can steal their research, or something like that. Some decide to release the pictures sooner, which is why not all pictures have that delay.

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