# Extrasolar planets

1. Oct 11, 2009

### kmoukiss

Hi everyone !

I am doing a report of some papers on extrasolar planets and I would like to clarify some points!
1) What is the difference between oberving in the IR at 4microns or 24microns ? what do you get in difference in observation ?

2)how can a measure of flux decrement can affect our understanding of the atmosphere of the planet ?

and finally 3) if water and CO are being revealed, how does this affect the survival prospects of extrasolar planets ?

I hope you will be able to help me!
Thanks to all !

2. Oct 16, 2009

### ideasrule

2) Well, if you measure the flux decrement in infrared when the planet passes behind its star, it's possible to deduce how much infrared is coming from the planet itself. From this, you can calculate the planet's temperature and determine what can or cannot exist in the atmosphere.
3) I think this is fairly obvious. CO is toxic; water is vital for just about all life on Earth.

3. Mar 25, 2010

### rasha astro

Hi
I wonder if you can help me, I want the formula or the mathematical equation that calculate the temperature of Extrasolar plantes.

thanks

4. Apr 1, 2010

### amarante

The difference between observing in 4 or 24 microns is what elements are you detecting. Or what you can infer about the composition of the atmosphere. You build a synthetic spectra varying the composition of the possible atmosphere and than you compare with the observed spectra. Actually it is easier to use photometry instead of spectroscopy, but anyway, it is basically this. And also maybe your equipment has a better resolution in one of these IR regions.

It is important to note that water alone does not imply that the planet is habitated.

I think it is not as simple as it could be. But one way to have an idea about the temperature of a STAR is using the Wien's law. But you can do this, because roughly you can consider a star as a blackbody.
$${\nu}_{max} \approx 5.879 \times 10^{10} (Hz/T).T$$

For a planet I am afraid it is completely incorrect to use this formula. You must have a model about the atmosphere of the planet, also you must consider the distance from the star, and the star's flux of energy. There is not a specific formula where you can calculate the temperature of the planet. You must consider it's composition.
You can take a look in this paper http://arxiv.org/abs/0910.1347