Saturday, January 24, 2009

Cooking with the Astronomers

Spicy and swirly galaxy
Preparation: 10 000 years or so
Cooking times: roughly 13.2 Billion years
Feeds: unknown un species as ever eaten a whole one

Between 10 to the 8 power and 10 to the 10 power hot stars of various ages and metallicity
Between 10 to the 10 power and 10 to the 13 power cold stars of various ages and metallicity
Neutral hydrogen gas, to taste
Ionized hydrogen gas to taste
1 super massive black hole (between 10 to the 6 and 10 to the 9 times the mass of a typical G stars)
10 to the 13 power cold dark matter as can be found in any good universal store
an hint of dark energy.

Cooking step
1. Put dark matter in a large empty area of the universe along with cold hydrogen gas
2. Add the cold stars of the lowest metallicity
3. Stir for a few millions years
4. Add a second helping of cold stars with an high mettalicity
5. Put the super massive black hole in the middle of the dark matter
6. Add the rest of the cold stars
7. Add the young hot stars all over the galaxy
8. Add the ionized gas
9. Stir for the reaming cooking time
10. For extra spice add more ionized gas around the super massive black hole

Here you go a perfect, spiral galaxy with just an hint of nuclear activity. And aside from the fact that the neutral gas is actually the sources of all the stars you will find in the galaxy that a pretty good interpretation of how galaxies are made. And that actually part of what I do for my PhD, of course since I can’t mix the dark matter and cold hydrogen gas my work is a little more complex.

You see, what I do is kinda like trying to figure out how the cake was made simply by looking at the cake (nope not tasting it) and in what proportion everything is present. Let me tell you I’ve made cake and it quite easier to make them from the recipe that to figure out the recipe from the cake. Now luckily I can look using special tools otherwise well the information I could get would be much more limited. You see light contain an amazing volume of information about what emitted it and what stood between you and the source. You can actually measure temperatures of the gas, quantities of elements, velocity of the stars and gas relative to the line of sight and of course what happen around those pesky black hole.

You see, every elements emit in very specifics AND unique way so you can differentiate between the elements simply by seeing what light you are receiving. Also, movement cause the light to either become bluer (if the object is moving toward you) or redder (if it moving away from you), then the intensity of the emission depends on the temperature, pressures and other condition in the medium. The dependence is not unique but every light depend more strongly on one or the other of these condition so you can compute them from the ratios of many lines. So you can tell quite a lot from just the star, but you need to understand quite a lot of thing to make senses of all the information. It’s fascinating to say the least.

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