160,000 light years away sits the Large Magellanic Cloud, an irregular dwarf galaxy that orbits our own Milky Way galaxy. It’s a fascinating object, actually, filled with stars, gas, dust, and all the usual trinkets a galaxy has.

It also has an assortment of globular clusters — roughly spherical collections of a few hundred thousand stars bound by their own gravity orbiting the cluster center like bees buzzing around a hive. NGC 1846 is one such globular cluster, and it looks like most of the others, if a bit sparse and loosely distributed. But it has something that does make it rather special. You can see it if you peruse this lovely Hubble Space Telescope picture that was just released:

[Click to embiggen, or get a much larger version.]

Isn’t that pretty? As much as I like it, the most interesting thing in it, though is actually rather difficult to see here. Look at the center of the cluster, then let your eye go straight down, nearly to the bottom of the frame. See the green spark there? It’s the only green thing in the entire picture. It’s not a star — there are no green stars — but it used to be…
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I will never, ever get tired of insanely gorgeous images of globular clusters.

Holy. Haleakala. [Click to embiggen, or get the ridiculously huge 3900 x 4000 pixel version.]

That is Hubble’s view of M 53, a cluster of several hundred thousand stars crammed into ball about 60,000 light years away — well outside the Milky Way itself, but bound to it, orbiting our galaxy. It’s probably 12 billion years old, but it looks like some of the stars in it have opted for a little cosmetic surgery…

In our galaxy, stars are so far apart that collisions between two of them almost never happen. But in globular clusters stars are so closely packed that many of them have apparently literally collided with each other, merging into objects called blue stragglers. Globulars are old, so having blue, massive stars is weird; they have short lifespans, and should’ve all blown up as supernovae or at least turned into red giants billions of years ago.

When these objects were first discovered in globulars they were really surprising, and while we still don’t understand everything about them, it’s a fair bet they result from two stars having a very, very close encounter. If two older, low mass red stars pass close to each other at low speed, their gravity can cause them to become bound to each other (it helps if a third star is involved; it can steal away energy from the other two, making it easier for them to become stuck together). Over time, they can spiral together and merge, forming a single, more massive, hotter object: a blue straggler. They’re seen in many globular clusters, and tend to be more common where stars are thickest, as you’d expect.

Over 200 of them have been found in M 53 alone, and at first glance, if you didn’t know better, you’d think they were far younger than the ancient stars around them. In a way, I suppose, they are.

But don’t judge. If you were a 12 billion year old star, you might want a facelift, too.

Image credit: ESA/Hubble & NASA

When I first saw this picture of NGC 2100, I thought it was a globular cluster. But I was wrong. That happens sometimes. Still, it’s worth it to see such a magnificent photo:

Yegads! What a shot! [Click to enstellarnate.]

Globular clusters are tightly packed collections of thousands of stars in a roughly spherical shape (hence their name), and are generally very old. But upon second glance, the stars of NGC 2100 in this image didn’t look quite right to me. There didn’t appear to be enough, for one thing, and though they’re highly concentrated in the center, the distribution around the core seemed off somehow.

Turns out that’s correct. (more…)

[Update: I originally had called this the Very Large Survey Telescope, but have learned it's actually the VLT (for Very Large Telescope) Survey Telescope. I've corrected this in the title and below. I like my less-redundant name for it better, but it's best to be accurate.]

The European Southern Observatory is an agency that governs some of the best telescopes on the planet, and they just added a new eye on the sky: the VLTe Survey Telescope (VST), a 2.6 meter ‘scope in Chile. There are lots of telescopes of similar size dotting our planet, but what makes this one special is its huge field of view — a solid one degree across, twice the diameter of the Moon on the sky – and the resolution of the camera: a terrifying 268 megapixels!

When you put that together, you get some dazzling pictures, like this one of the globular cluster Omega Centauri:

[Click to englobulenate to a 4000 x 4000 pixel 13 MB image, or grab yourself the internet-choking 14,540 x 14,540 pixel 280 MB version.]

Omega Cen is one of the largest globular clusters of the 150 or so orbiting the Milky Way galaxy, a collection of hundreds of thousands or even millions of stars all orbiting the cluster center willy-nilly like bees swarming around a hive. Telescopes like the VST will allow astronomers to survey these clusters quickly and deeply, which is important because it’s sometimes difficult to know what stars are in the cluster and which happen to be in the background or foreground. You have to get a good census of cluster membership before moving on to studying how old the stars are, what they’re made of, and how they behave. Since globulars are among the oldest objects in the Universe and are tied with galaxy formation, understanding them leads to understanding a great deal more.

VST also took this spectacular picture of the star-forming region M17, also known as the Omega nebula:

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Globular clusters are among the most spectacular of objects in the entire night sky. Compact balls of hundreds of thousands of stars, well over a hundred orbit our galaxy at various distances. When viewed by Hubble, the result is nothing less than jaw-dropping:

[Click to embiggen, and please do; I had to crop the image to get it to fit and the full-size version is even more spectacular!]

This view of Terzan 5, as it’s called, is gorgeous! The thing is… Terzan 5 may not really be a globular cluster. Sure, it’s a cluster, and it’s globular, but it may not be what we usually think of as a globular cluster.

When I read the press release for the picture, the name Terzan 5 looked familiar. So I searched my blog, and found I’ve written about this object before. That post was about a ground-based Very Large Telescope picture of the cluster, seen here. The picture looks odd because Terzan 5 lies in a very crowded region of the Milky Way, lousy with dust. That interstellar junk tends to scatter away blue light, making objects look redder. The dust blankets across Terzan 5, but is thicker in one half than the other, making that side redder than the other.

Terzan 5 itself is also unusually dense, with stars packed in it more tightly than is usual for a globular cluster. Not only that, but studies have shown the stars in the cluster appear to fall into two different age groups; one significantly older than the other. That’s weird. (more…)

When I was a young Bad Astronomer, one of my favorite night-sky targets for my telescope was the globular cluster M5, an easy-to-spot fuzzy jewel in the southern sky. Over the years I must have taken a look at it a hundred times, my telescope barely resolving a few of the brighter stars in it.

Of course, with Hubble, the view is significantly better:

Holy scintillating jewelbox! [Click to englobenate, or grab the 3150 x 3150 pixel version.]

M5 is a collection of at least 100,000 stars, all orbiting each other like bees around a beehive, held together by their mutual gravity. It’s located about 25,000 light years away, and is something like 150 light years across. It’s one of more than 150 such clusters of stars orbiting our Milky Way galaxy.

And it’s old: it’s probably been around for 12 billion years. Yikes. I hope I look as good when I’m that relatively scaled age.

I don’t have much to add here; I’ve written about globulars many times (see Related Posts below), so instead I’ll simply let you soak in its beauty… and note that despite my best efforts, I couldn’t seem to work in an Ultimate Computer reference in this post’s title. You may pull out the plug, Mr. Spock!

Image credit: ESA/Hubble & NASA