Earth-like Exosolar Planets

By Allison Jones

People have wondered about other stars hosting planets for centuries.  And speculation about potential extraterrestrial life on those theoretical planets is prevalent.  Part of this is just human curiosity, but we can also learn from the search for and study of discovered planets.

The first time a planet was discovered around another star, Gamina Cephei, was 1988, though it wasn’t confirmed until 2003.  By then other planets had been confirmed around other stars.  As of February 14, 2012, 760 exosolar planets have been confirmed; 609 of them are in planetary systems, and 100 of those are multiple planet systems.  About 39 of those planets were confirmed in the last two months.

This explosion of discovery has occurred because instruments have become more sensitive allowing smaller planets to be found as well as more detection methods used.  Recently earth-like planets have been discovered orbiting in the habitable zone of their parent stars.  Earth-like means that the planet has a similar mass to Earth.  The habitable zone is the area around a star where it is possible for liquid water to exist.  

In the beginning the only planets astronomers could measure the presence of were large gas giants in very close orbit around their parent star.  Now some planets smaller than the Earth have been discovered around distant stars.  While most planets discovered orbit their stars closer than Mercury orbits our sun, some scientists estimate that 1/3 of sun-like stars may have terrestrial planets in the habitable zone.

These discoveries are exciting for many people, but why should we spend resources finding out about places so far removed from us?  Beyond the drive to explore and understand the universe, we learn things that can be applied at home on Earth.  

The more we learn about other places, the better we understand our own planet.  It was discoveries about Venus’ atmosphere that clued scientists into the properties of greenhouse gasses and what effect they can have on climate.  If we find evidence of life originating elsewhere, we will have a better understanding of what conditions life requires and how things work and have developed in our own biosphere.