[Liberal Classic]

I realize I'm not authoritative, but the planets we've detected through the wobble are all gas giants. Jupiter, for example, has a mass over 300 times that of the earth. The extrasolar planets we've been able to measure are usually compared to Jupiter.

JPL has a nice site on extra-solar plants, and a cool Shockwave atlas.

[Virginia-American]

I wasn't clear. I meant if I had RA's equipment on a planet circling Alpha Centauri, could I detect Earth's radio waves? On a planet around Vega? or whatever star.

Or if there were a duplicate of Earth around a particular star, could it be detected with our equipment?

Actually imaging Earth-like planets may someday be done with massive interferometers in orbit. I'd consider O₂ in the atmosphere a sign of life.

We can't forget that Earth is 4.5 billion years old, over half that time there were no eukaryotes, big animals date from the half a billion ya, and we've only been broadcasting radio for 100-odd years.

[Ophiucus]

I realize I'm not authoritative, but the planets we've detected through the wobble are all gas giants.

As detection became more sensitive and was combined with spectrographic analysis, reflections from small, rocky planets have been detected.

Cut and paste links for the latest:
http://www.universetoday.com/am/publish/large_rocky_planet.html
http://www.cnn.com/2004/TECH/space/08/26/new.planet/
http://www.nsf.gov/news/news_summ.jsp?cntn_id=104243&org=NSF&from=news
http://www.spaceref.com/news/viewnews.html?id=1031