Our galaxy features a wide variety of them

Feb 15, 2010 09:07 GMT  ·  By

Up until now, astronomers using various techniques have been able to identify more than 420 exoplanets in orbit around various stars, pulsars, or simply free-floating around in space. There are several main sizes and types of planets, according to experts, who are now attempting to classify their discoveries in a way that will allow them to conduct surveys more easily. As they analyze more and more planets, astronomers are becoming convinced that finding one just suitable for life may not be far off, Space reports.

Experts believe that we are fairly close to discovering a new category of exoplanets, one that would allow for us to definitely say that life is sustainable at that location. It may be that the particular exoplanet that will lead to this conclusion will already be inhabited by basic life forms, or even more developed ones. Astronomers say that finding such a place is no longer a matter of “if,” but a matter of “when.” At this point, the most common type of exoplanet found is the one called a “Hot Jupiter.” These bodies are gas giants of enormous sizes that orbit around their parent stars closer than Mercury moves around the Sun.

Another type of planet is the one spinning around pulsars, fast-spinning neutron stars that shed impressive amounts of radiations in highly focused jets. A small number of exoplanets have been discovered around such stellar remnants, and neither of them can possibly support life, due to the massive amount of radiation they are subjected to. The situation is different for super-Earths, a class that features members that are up to ten times the mass of our planet. If they spin in the correct orbit around their Sun, they could be more likely than other types to eventually become able to support life.

One of the most peculiar classes of planets are water worlds, which can basically be divided into two distinct groups. You can have an Earth-like planet covered in a large ocean, or you can have a hot, Neptune-like planet, ten to 20 times the mass of the Earth, spinning very close around the parent star. As these giants are made up of ice, the proximity could allow for liquid water to exist on the surface, but the ocean would be thousands of kilometers deep. The atmosphere of these water worlds would most likely be drenched in hydrogen and water vapors.

Chthonian and free-floating planets are some of the weirdest out there. The former type is also called an evaporated remnant core, and it represents all that remains from an exoplanet after the proximity to its parent star riped it apart and stole all of its gas. If the body is tidally locked to the star, then it may be covered fully in lava. The latter type is very peculiar because astronomers don't know exactly where free-floating planets come from. They are not attached to star systems, and may have even not formed close to a star.