Search patterns in observational studies

[stargazer3]

Hello Physics Forums!

I've just read about the discovery of GJ 667Cc, and it made me ponder on how do astonomers develop the sequence of stars to be examined in search for exoplanets? I know that some telescopes, like Kepler mission, are just collecting raw data from a certain area of space, but what about more flexible observatories? In other words, why, discovering so many distant exoplanets, we know so little about the closest to Sun hundred or so stars (we are trying to find the closest habitable planet, aren't we)?

 

[Drakkith]

It depends on the detection method. For example, if you wanted to do direct imaging to detect planets, your telescopes intrinsic resolution limit would set the upper boundary for the distance the star could be at, so you would image stars that were close by. And even then, if you were using Infrared imaging to detect the heat from young star systems and their planets, you would have to observe stars that were still young enough for their planets to be very hot and emit infrared radiation.

Beyond that, the type of star itself is also a major feature that you must consider. Huge, bright, supergiant stars are usually poor candidates for most detection methods,(I think) as their masses are so high that any planets in orbit would barely cause the star to shift around, making it much more difficult to detect planets using the radial velocity method. These stars would also have a much smaller amount of surface area become blocked by a transiting planet, reducing the chances of using that method as well. Plus, most people are more interested in "sun like" stars, as the star system would be much more similar to Earth's.

In other words, why, discovering so many distant exoplanets, we know so little about the closest to Sun hundred or so stars (we are trying to find the closest habitable planet, aren't we)?

Who says we don't know much?

 

[Radrook]

Drakkith is right, astronomers do know quite a lot about our nearest stars.
Here is an article I found interesting about the Altha Centauri system. Has nice charts displaying what the orbital distances of such planets might be.

Alpha Centauri
A Candidate for Terrestrial Planets And Intelligent Life
http://aether.lbl.gov/www/classes/p139/speed/Alpha-Centauri.html

The following article is also relevant to your question.

Extasolar Planet-finding Methods
http://www.novacelestia.com/space_art_extrasolar_planets/mission_extrasolar_planets.html

 

[stargazer3]

Thanks a lot for both responses, they cover everything I wanted to know to large extend.