Question: how do planets float in space? How do you find things out about planets?

Jen Gupta answered on 16 Jun 2011:

Well I want to say that planets don’t float in space. Planets are bound by gravity to the star that they orbit around so they move on fixed paths around the star. HOWEVER, astronomers have found free floating planets that don’t orbit around a star and only last month some astronomers announced that they had found a bunch of them (http://www.universetoday.com/85781/lone-planets-more-common-than-stars/). Technically these aren’t planets because the International Astronomical Union’s definition of a planet says that they have to be orbiting around a star but to all intents and purposes these objects are planets.

The second part of your question depends on whether you mean finding things out about the planets in our solar system or planets orbiting around other stars. The planets in our solar system are relatively easy to find things out about – we just look at them through telescopes and send spacecraft to take a closer look. Planets around other stars are more difficult. We have only managed to directly image a handful of extrasolar planets so we can look at how the light from the star gets dimmer when the planet passes in front of it or how the the planet makes the star wobble slightly. If you want to know more about this then comment but I’m worried this answer is going to get too long!