Enthusing about astro-ph

[fivemack]

I've been keen on astronomy since I was six; I think small children go for stars or dinosaurs, I was born the month before Voyager 2 launched and was never that keen on animals. It was clear at school and undergraduate level that I was to be a Mathematician, at the moment I'm on the edge of chemistry, I never quite persuaded myself that astronomer was a practical goal, and after doing the Wrong Doctorate I think it now isn't one. I'm happy, and astronomy is something you can do in spare time.

Anyway, while waiting for compiles, or for processing on five DVDs full of images to complete, I often have a look through the astrophysics preprints. When I mentioned this to papersky years ago she said I should write about them; I procrastinated, but now seems as good a time as any. Particularly since I've just told james_nicoll that current astronomy doesn't tend to throw up exciting places to use as story settings.

This week, there are 173 papers. I suppose a paper is about six month's work, so that suggests there are about four thousand active astronomers, and indicates that I'm not going to get to keep up with the field, and might as well start at the top until I find something interesting.

This one is a nice theoretical paper on star formation. In the really early universe (in this case, red-shifts of 10 to 50, so the first couple of billion years) there was nothing heavier than hydrogen around. The way we think stars form involves cooling by radiation emitted by atoms heavier than hydrogen, so there's a question about how these really early stars (called Population III for historical reasons; Baade in 1943 discovered that the stars in the core of the Andromeda galaxy had less metal content than average stars around here, and called them Population II as opposed to average stars being Population I; it was worked out later that Population II was older than Population I, and obviously a set of even-older stars would be Population III) actually formed. Since all the observational constraints on Population III stars are of the form 'we looked for Population III stars in the following way and didn't find any', they are a rich field for speculation.

The authors here say that dark matter is the answer. It seems that the conventional wisdom about dark matter is now that, whilst by definition it interacts very little with normal matter, if you have a dense enough conglobulation of dark matter pairs of its particles start annihilating to produce neutrinos, gamma rays, and energetic electrons. If you have a big cloud of hydrogen mixed with dark matter - say the size of Saturn's orbit - collapsing under its own gravity, it eventually gets to the point where it's dense enough that the dark-matter at the middle is annihilating away, and the cloud is thick enough to stop the annihilation products and be warmed by it. You end up with a huge, incredibly sparse star; they claim it might last to the present day, if dark matter has the right properties. It would be of the scale of an ancient supergiant, but be made purely of hydrogen, and be at best lukewarm by human standards (but I think rather suffused with high-energy radiation) in the middle.

So there's a setting.

Other news this week included a few new transiting extra-solar planets, but the people at Systemic blog about that infinitely more eruditely than I can hope to; their current trick is to simulate the weather on these objects. It's quite exciting; Saturn-sized supersonic hurricanes of rock vapour at blast-furnace temperatures seems to be the normal forecast. The implied lab experiments to work out the albedo of clouds of granite vapour to refine the parameters for the model should be quite entertaining to read about.

Comments

[ellarien]

Doing the Wrong Doctorate isn't necessarily an impediment; I did mine in an obscure corner of condensed matter physics and then, with no formal astronomy education at all, wandered over to solar physics for my first postdoc and never left, and one of my collaborators and former bosses was -- and still is -- a mathematician by training and inclination.

[del-c.livejournal.com]

Or!? I didn't think I was that unusual a small child.

[hilarityallen.livejournal.com]

I liked stars *and* dinosaurs. But if you'd asked me at around age 10 what I wanted to be when I grew up, I'd have said 'a Professor of Astrophysics at Cambridge'. Although apparently when I was four, I told a cousin that I wanted to be a palaentologist when I grew up.

[tau-iota-mu-c.livejournal.com]

I only looked at Astro-ph yesterday for the first time in... a long time (months). Don't like the reorganisation. Why do website reorganisations always result in that website becoming more cumbersome to navigate?

I only went because a coauthor alerted me to http://au.arxiv.org/abs/0705.0357 which made no effort to cite http://au.arxiv.org/abs/astro-ph/0509314, rargh, despite the second author knowing what I was working on, and their research leading to largely the same results.

Damn, I'm developing one of those "you must cite me" egos.