Artist’s impression of a rogue terrestrial planet. Because the world is so far from any source of heat, the surface is covered with ice. (Image credit: NASA’s Goddard Space Flight Center).
Rogue planets are worlds that do not orbit a host star. NASA’s Nancy Grace Roman Space Telescope could detect about 400 exotic planets with masses comparable to Earth, a study has revealed.
NASA builds the Nazi Grace Roman Space Telescope, a wide-field infrared instrument to conduct surveys to hunt for exoplanets and map the distribution of dark matter. The space agency plans to deploy the telescope by May 2027. Researchers estimate that the Roman telescope could detect about 400 rogue planets, or worlds that do not orbit any of their host stars.
Exoplanets are detected by microlensing because of the slight enhancement and distortion of light from a background object such as a star or galaxy caused by the gravitational lensing of a foreground object, in this case, a rogue exoplanet. A pair of papers describing the study’s findings were selected for publication The Astronomical Journal.
Most of the 5,000+ exoplanets discovered so far are massive because the transit method commonly used to find most of these worlds favors finding large planets in orbit around their host stars. However, rogue exoplanets are expected to be on the smaller side. Lead author of a paper, Takahiro Sumi says, “We found that Earth-sized rogues are more common than more massive ones. The difference in the average mass of star-bound and free-floating planets holds a key to understanding planet formation mechanisms.
It is estimated that there are 20 times more rogue planets than stars in the Milky Way, which means that there could be trillions of worlds floating between stars, in material left over from the birth of new stars, ejected by random processes in the circumstellar disks, which are places for planetary assembly. Microlensing is currently the only practical method known to detect terrestrial planets with masses similar to or less than Earth’s.