Comet McNaught is fast fading from Northern Hemisphere skies (and my last good opportunity to see it is tonight right after sunset, if it isn’t cloudy here). We’ll give it a try, but I fear that the chances are slim, due to the immense cloud cover we have right now over Massachusetts. It never fails that when some cool astro-phenomenon is available for viewing, the skies obligingly summon forth the clouds and we see no more. Happens when there are aurora predictions, too.

What does this have to do with hobbits? Well, not much really. But, I was sitting here going through all the press releases I got at the AAS meeting (yes, I’m back in the office again after a day of reasonably good flying yesterday), and I was reading again about the dwarf galaxies that the Sloan Digital Sky Survey has discovered in their survey of the sky. I blogged briefly about the most recent one earlier in the week. But, the press release reminded me of something that happened during the press conference, a little “behind the scenes” look at what us press types experience during these conferences.

So, the astronomers who studied these galaxies described these little guys as “more like than hobbits than dwarf galaxies” (because they’re smaller and fainter than some dwarf galaxies). It’s a cute analogy, and being a Tolkien fan, I find the idea of some undersized galaxies being like little, hairy-footed people to be rather charming.

What struck me right away about the image of the dwarf galaxy Leo T that was the subject of their announcement was how much it looked like an ordinary star cluster as seen through a good backyard telescope. So, I decided to ask (during the Q&A afterwards) about how this sparsely populated galaxy differed from a cluster.

As luck would have it, Rob Naeye of Sky & Telescope Magazine asked the question first, so I got to follow up with some questions about how the dark matter clumps might be constraining the growth of clusters and dwarfs.

The answer to the question Rob asked, however, turns out to be fairly simple for the galaxy we see here: its size is larger than a cluster. But, more importantly, Leo T has experienced at least two periods of star formation its history. Most star clusters have one episode of star formation and we see stars that are all about the same age. Some of Leo T’s stars are now older than five billion years. But others are much younger (less than a billion years old). And, Leo T still has clouds of hydrogen gas—the main ingredient you need if you’re a galaxy that wants to make more stars.

What I thought was rather interesting was that several of us in the press pool saw that picture and immediately thought “cluster!” I looked around the room and saw Martin Ratcliffe (representing Astronomy Magazine), Govert Schilling (a Dutch science writer and long-time skygazer), and Jim Manning (of the Space Telescope Science Institute, himself an amateur astronomer as well as being head of Public Outreach at STScI) all nodding our heads when Rob asked the question that must have occurred to all of us simultaneously.

I should also say that the press types who come to the AAS meetings are all very experienced science writers, with more than a few graduate degrees amongst us. There are usually 3-4 press conferences per day, and when we’re not in PR events, we’re out at the paper sessions and visiting the exhibit hall (which is alive with spacecraft, mission, book seller, and astronomy product sellers as well as poster papers relating to astronomy. In this meeting we also had poster papers from astronomy educators attending the American Association of Physics Teachers meeting held jointly with AAS.

I’ll probably be posting a few more stories from the AAS in the next weeks. I have a few dozen press releases to mine for cool stories!