The successor of the Kepler space telescope continues its cosmic exoplanet hunt.
According to reports, TESS has just discovered its third exoplanet in an observation period o only three months.
The new planet, dubbed HD 21749b, orbits around a bright dwarf star about 53 light-years away in the Reticulum constellation, and appears to have the longest orbital period of the three planets identified so far by TESS (the Transiting Exoplanet Survey Satellite).
The discovery of the new alien world was presented at the annual meeting of the American Astronomical Society held in Seattle, reports the Massachusetts Institute of Technology (MIT), which leads the mission.
HD 21749b orbits its star in a relatively quiet 36-day period, compared to the other two planets discovered so far: Pi Mensae b, a ” super-Earth” with a 6.3-day orbit, and LHS 3844b, a Rocky world that orbits its star in just 11 hours.
The three planets were discovered by TESS in the first three months of observations.
According to scientists, the surface of the newly-found planet is probably around 148 degrees Celsius, which is relatively cool, given its proximity to its star, which is almost as bright as the Sun.
“It’s the coolest small planet that we know of around a star this bright,” says Diana Dragomir, a postdoc in MIT’s Kavli Institute for Astrophysics and Space Research, who led the new discovery.
“We know a lot about atmospheres of hot planets, but because it’s very hard to find small planets that orbit farther from their stars, and are therefore cooler, we haven’t been able to learn much about these smaller, cooler planets. But here we were lucky, and caught this one, and can now study it in more detail.”
As noted by experts, HD 21749b is about three times the size of Earth, which puts it in the category of a “sub-Neptune.”
But it also happens to be 23 times as massive as the Earth.
However, scientists say that it is unlikely that the planet is rocky and habitable. They believe its made of kind of gas that is much denser than the atmospheres of Neptune or Uranus.
“We think this planet wouldn’t be as gaseous as Neptune or Uranus, which are mostly hydrogen and really puffy,” Dragomir says. “The planet likely has a density of water or a thick atmosphere.”