Now that astronomers have discovered planets around other stars, and judged that those planets could have Earth-like conditions, the next step is to find out for sure. While we can’t visit them, astronomers hope to gather clues via telescopes.
The Transiting Exoplanet Survey Satellite (TESS), a new space-based telescope that NASA expects to launch in 2017, will conduct an “all-sky survey,” scrutinizing stars throughout the sun’s neighborhood, to find any yet-undiscovered exoplanets that may orbit them. According to George Ricker, the TESS mission’s principal investigator, the TESS sky scan will cover 400 times as much sky as any previous mission.
The Kepler telescope revealed hundreds of potential exoplanets in its four years in orbit. Unfortunately, most of those planets are in star systems that are a thousand or more light-years away from Earth. Such vast distances will make it impossible for us to study them in any greater depth. The TESS mission, by contrast, will attempt to find more promising study subjects by focusing on stars closer to Earth. They might turn up in orbit around one or more of the many red-dwarf stars and seven sun-like stars that astronomers have all calculated to be within 20 light-years of Earth.
TESS could assess these stars and others in conjunction with the James Webb Space Telescope (JWST), another orbital telescope that NASA plans to deploy in 2018. The JWST will be equipped to view infrared light waves and thereby detect many objects that are out of range of visible light, such as stars or planets that are concealed within nebula.
Should the two telescopes find planets within a few dozen light-years of Earth, the two could coordinate on some chemical inventories. Although they wouldn’t be able to give us clear images of the planets’ surfaces, they could reveal some information about the planets’ atmospheres and provide clues as to whether or not the planets have oceans.
It will be easier if those planets are “super-Earths”—terrestrial planets several times the size of Earth—like the ones that Kepler found in some faraway star systems. Astrobiologists are now formulating models of super-Earths and their potential atmospheres to offer hints as to what chemical indicators might suggest life. They say that the presence of oxygen, ozone, and nitrous oxide are encouraging signs but not hard proof. Even a super-Earth that possessed all of them might still be uninhabitable if other life-inhibiting factors, such as excessive greenhouse effect or no shielding magnetic field, were there. If nothing else, though, perhaps these missions will give us some candidate planets to visit once we develop interstellar space flight.