Globular Cluster Photo Series (Part 18): M53

Today's picture (I'm slowly getting through the ones I have lying around) is the globular cluster Messier 53. M53 is a bit large as far as physical size goes, measuring about 220 light-years across, which gives it a visual diameter of 13.0 arcminutes at its estimated distance of a whopping 58,000 light-years from us. M53 is genuinely far out there, as it is also about 60,000 light-years from the galactic center, almost twice as far away from it as we are.

Messier 53 in Coma Berenices.

Like Messier 64 that I showcased yesterday, M53 is located in the constellation Coma Berenices, or Berenice's Hair, a small, faint constellation near Leo. According to legend, Queen Berenice II of Egypt had long, golden hair that she was quite proud of, and which she promised to sacrifice to Aphrodite if her husband King Ptolemy III Euergetes returned safely from his military expedition against the Seleucids. When he did so, she cut her hair and donated it to the temple, only for it to turn up missing the next morning. Thinking quickly, the court astronomer, a guy by the name of Conon of Samos, told the furious royal pair that the gods had apotheosized Berenice's hair into a constellation, indicating a misty patch of stars that have ever after borne that name. Interestingly, Ptolemy (the 2nd-century astronomer, not the king) did not include it in his definitive list of 48 recognized constellations, considering it part of Leo, though he did refer to is as “the lock [of hair]”. (He considered it to be the tuft of hair at the end of Leo's tail, which does make sense given its place in the sky.)

M53 contains a total of 47 RR Lyrae variable stars, a not inconsiderable number. Its stars also happen to be even lower in elements heavier than hydrogen and helium than most other globular clusters, which are already much lower than stars like the Sun. And other than that, I'm afraid there really isn't much more of interest to write about it tonight. A hui hou!

Supernova Hat Trick.

The last year has really been pretty good for astronomers studying supernovae. I glossed over it in my post about them, but there is still much we don't know about supernovae. This is mainly because they're so rare. Basically, the more massive the star, the fewer of them there are. Stars large enough to go supernova make up only a tiny fraction of the stars in a galaxy, much less than 1%. (For comparison, our own Sun, often called a fairly average star, is still larger than 80% of the stars in the universe, and star don't really go supernova until they're nearly ten times more massive than that.) Typically in a spiral galaxy like the Milky Way one supernova will go off on average every fifty to a hundred years. However, there a lot of galaxies out there, so if you watch enough galaxies frequently enough you should catch one going off eventually. This is the basis behind all systematic supernova hunts, which can image tens of thousands of galaxies night after night.

This sounds like good news for supernova hunters, but the hidden catch is that many (most) of these supernovae are very, very far away, simply because the majority of galaxies in the universe are very, very far away. This makes them hard to study and analyze because they're hard to see well so far away. It's not often that we get supernova within a few dozen million light-years or so, but in the space of the last ten months we've had three of them go off within 40 million light-years, all three in bright galaxies on the Messier list. And no, despite the date of this post, I'm not making this up.

In June we had SN2011dh go off in M51, 23\(\pm\)4 million light-years away, then in September SN2011fe went off in M101 at 20.9\(\pm\)1.8 million light-years. Finally, on March 16, supernova SN2012aw was discovered in M95, about 32.6\(\pm\)1.4 million light-years away.

I wasn't able to get a picture of it before due to bad weather, but last Thursday the stars finally aligned for me (or, rather, the clouds finally got out of the way) and I was able get the picture you see below:

Messier 95 (bottom, with SN2012aw) and Messier 96 (top) in Leo. North is to the left.

At the top of the picture you can see Messier 96, a galaxy close to M95. At the bottom you can see M95, with SN2012aw marked. Remember, every other star you see in this picture is part of the Milky Way, and SN2012aw is outshining many of them, despite being over three thousand times farther away. That's how powerful a supernova is (not to mention that it's still putting out an amount of light comparable to the rest of M95, two weeks after it went off).

Also, I just wanted to mention that I think the central detail on M95 is really pretty. That's a pretty nice ring of star formation there around the central bar.

Leonine Galactic Triplets

Monday night I was able to take out the imaging telescope for the first time this year, after spots of bad weather and poor conditions the last few weeks. Fortunately, conditions were pretty good and I was able to get several images, including the following image of the charming collection of galaxies known as the Leo Triplet.

The two galaxies near the top were spotted by Charles Messier in 1780, and bear the Messier numbers 65 (left) and 66 (right) respectively. The bottom galaxy was faint enough to elude his small telescope and was discovered instead by Sir William Herschel (who also discovered the planet Uranus) in 1784. It has the NGC number 3628. These three galaxies form what is believed to be a physical group at a distance of about 35 million light-years.

Each of the three galaxies is roughly the size of our own Milky Way galaxy, and it seems likely that some or all of them have had close gravitational interactions in the past. M66 in particular appears to show signs of gravitational disturbance, visible in the slightly distorted shape of the top spiral arm in this image. It's a bit harder to tell with the other two, lying nearly edge-on to us as they do, although you can kind of make out that the dust lane running across NGC 3628 is bent, tell-tale evidence of past (and ongoing) interaction.

All three galaxies show pretty nice dust lanes, really, whether they're edge-on or more face-on to us.