Ho hum, another boring gorgeous sparkling beehive of stars

By Phil Plait | May 10, 2012 6:45 am

Orbiting our galaxy in the lonely depths of intergalactic space, 160+ globular clusters are among the oldest structures we know. They’re composed of thousands, sometimes hundreds of thousands, of stars, all held together by their mutual gravity. I always think of them as beehives, with the stars buzzing around on orbits all tilted willy-nilly.

The European Southern Observatory just released this picture of the globular cluster M55 using the VISTA telescope., and it’s very pretty:

[Click to englobulenate, or grab the 6Mb 3k x 3k pixel version!]

Honestly, there’s not a lot of science I can add to this that I haven’t written about a bazillion times before (see Related Posts, below). M55 is 17,000 light years away toward the galactic center, which is relatively close as these things go. It’s big, 100 light years across, so from Earth it looks to be roughly 2/3 the size of the Moon. In this unusual picture by VISTA, we’re seeing it in infrared — at 1 micron (colored blue in the picture) and 1.5 microns (colored red), so stars that look red are really much cooler than the Sun.

But other than that, it’s just another run-of-the-mill globular. Which is remarkable enough! And you know what: despite their clunky name, there’s no such thing as an ugly globular cluster. That’s reason enough to share this lovely picture.

Image credit: ESO/J. Emerson/VISTA. Acknowledgment: Cambridge Astronomical Survey Unit


Related Posts:

Desktop Project Part 12: The galactic deep diver M9
Desktop Project Part 3: The massive massiveness of M54
Gorgeous globular hides hundreds of rejuvenated stars
Lonely sentinel of the galaxy

CATEGORIZED UNDER: Astronomy, Pretty pictures

Comments (14)

  1. Even as a child, I always desired that our solar system was smack in the middle of one of these. Imagine the night sky then! Although, I wonder how that would affect things like an Oort cloud or the planetary orbits? That may make for an interesting simulation to run (if I had the software and computing power).

  2. davem

    One thing I’ve never understood about globular clusters: I assume that they’re held together by gravity, right? In which case, why don’t they collapse on themselves, or start rotating, and create mini-galaxies?

  3. Peter Davey

    Poul Anderson wrote a short story, “Starfog”, concerning people who lived on a world in the middle of such a cluster, and who eventually explored to the edge of it, staggered by the vast, empty, universe on the other side.

  4. Messier Tidy Upper

    @ 3. Peter Davey : Cheers – may have to find that tale somewhere. :-)

    Guess everyone already knows about the Isaac Asimov classic Nightfall right?

    See :

    http://en.wikipedia.org/wiki/Nightfall_(Asimov_short_story_and_novel)

    if not.

    Incidentally if you want to see what fate apparently lies in store for Messier 55 and other globulars, well, check out this clip here :

    http://www.youtube.com/watch?v=_mr9y4F6ME4&feature=player_embedded#!

    Whilst this youtube clip :

    http://www.youtube.com/watch?v=8WEUrOCe33U&feature=related

    takes you all the way from our night sky into the core of globular 47 Tucanae, one of – if not *the* very best and brightest in all Earth’s skies. :-)

    Spectacular VISTA indeed – cheers BA & European Southern Observatory. :-)

  5. Chris A.

    @davem:
    In a sense, they are mini-galaxies, of the E0 elliptical type (i.e. with near zero ellipticity). In other words, the stars all orbit their common center of mass–there’s just no organization to their motions like you find in a spiral galaxy, with most of the stars going in more or less the same direction. So, they don’t collapse for the same reason that our solar system doesn’t collapse: angular momentum.

    That being said, some globulars (about 1 in 5) do collapse, in their cores, anyway (called core-collapse globulars, unsurprisingly). What it really means is that the more massive stars tend to “sink” to the inner regions, while the less massive stars migrate outward. Crudely put, it’s a bit like the heavy bits sinking and the light bits floating. In the end, the cluster’s star density peaks sharply toward the center (as opposed to a “normal” globular, whose density plateaus in the inner region).

  6. Chris

    @2 davem

    Why don’t they collapse because of the gravity? Because they are moving around. The gravitational potential wants to collapse things, but the kinetic energy wants to blow them apart. In the cluster, the two are in balance. Unless two stars collide they’ll keep on orbiting the cluster’s center of mass. Now stars will be ejected and when that happens the other star will go closer to the center. That’s why the cluster is denser in the center and diffuse on the edges.

  7. John

    anyone know a good source to purchase prints, framed or unframed, of images like the one linked in this post?

    Thanks!

  8. kat wagner

    wait, is there a black hole in the middle of that cluster too? I read about black holes til two in the morning the other night and I could hardly go to sleep – I was trying to wrap my brain around all that weird bat guano. so anytime you want to chat up black holes, well I’m all over it.

  9. Open clusters are the nurseries of stars. Globulars are the retirement facilities.

  10. BCFD36

    So we know that all the stars in a globular cluster are moving. Over a period of time, have we been able to see the stars actually change position or has there not yet been enough time?

    I have the same question about some of the nebulae… over the time we have been photographing them, have we seen changes, like in the Crab or the Eagle?

    D. Scruggs

  11. þorfinn

    What is the orange stripe on the top+right side of the cluster, on the 3k*3k image Gimp read 2290,1190 as the co-ordinates.
    The objects at (2560,1735) (0708,2790) (1055,2120) & (0520,0950) are all background galaxies to the main image.
    þ

  12. Mike

    Something else about M55 — you can detect the tidal arms of the Sagittarius dwarf in the background.

  13. Jon Hanford

    @7 John,

    ESO has a large number of mounted images on sale, check here for selection: http://www.eso.org/public/products/mountedimages/

  14. @8. kat wagner asked : “wait, is there a black hole in the middle of that cluster too?”

    No Intermediate Mass central Black Hole in Messier 55 from all I’ve been able to find in a quick~ish web search through quite a few pages on it.

    Messier 54 (wiki-link in my name here) apparently does have such an IMBH but Messier *55* does not – or at least not that we’ve found so far and not that I’m aware of yet.

    There could well be stellar mass black holes in Messier 55 too naturally – although there’s also no mention of them that I could find.

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