NASA researchers have found a planet the size of Earth in the habitable region, which may or may not have liquid water on its surface. By utilising NASA’s Transiting Exoplanet Survey Satellite, the researchers have discovered a planet the size of Earth, designated TOI 700 e. The planet is 95% the size of Earth and most likely made of rocks.
The TOI 700 b, c, and d planets were the first three planets in this system to be found by astronomers. The habitable zone is where planet d also revolves. However, it took researchers another year of TESS observations to find TOI 700 e, according to an ANI report.
The study’s lead author, Emily Gilbert, a postdoctoral fellow at NASA’s Jet Propulsion Laboratory in Southern California, said that this is one of the few known systems with several small, habitable planets. “The TOI 700 system is thus a fascinating possibility for further investigation. The system also demonstrates how additional TESS observations help us discover ever-smaller worlds because planet e is about 10% smaller than planet d.”
Gilbert gave the team’s findings a presentation at the 241st American Astronomical Association meeting in Seattle. The Astrophysical Journal Letters accepted a paper on the recently discovered planet.
A small, cool M dwarf star called TOI 700 can be found in the southern constellation Dorado at a distance of about 100 light-years. Gilbert and others announced the discovery of three planets in 2020, including the Earth-sized, habitable-zone planet d, which is in a 37-day orbit.
The innermost planet, TOI 700 b, orbits the star every ten days and is about 90% the size of Earth. The orbit of TOI 700 c, which is more than 2.5 times larger than Earth, lasts 16 days. The planets are likely tidally locked, meaning they rotate only once per orbit so that one side always faces the star, just as the Moon always faces Earth from one side of its orbit.
TESS observes broad areas of the sky, known as sectors, for about 27 days at a time. These prolonged gazes enable the satellite to monitor variations in stellar brightness brought on by an event known as a transit, in which a planet appears to pass in front of its star from our perspective. Starting in 2018, the mission followed this plan to observe the southern sky before moving on to the northern sky. It went back to the southern sky in 2020 to make more observations. The team was able to improve the original planet sizes, which are now about 10% smaller than the initial calculations thanks to the additional year of data.
Ben Hord, a graduate researcher at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, and a doctoral student at the University of Maryland, College Park, said that if the star or planet were a little bit closer or larger, we might have been able to detect TOI 700 e in the first year of TESS data. However, the signal was so weak that we required an extra year of transit observations to locate it.
Planet e is situated in the so-called optimistic habitable zone between planets c and d on TOI 700 e, which may also be tidally locked.
The optimistic habitable zone, according to scientists, is the range of distances from a star where liquid surface water might have existed at some point in a planet’s past. To either side of the conservative habitable zone—the region where scientists believe liquid water could last for the majority of the planet’s lifetime—lies this region. This area is where TOI 700 d orbits.
Planetary scientists can learn more about the past of our own solar system by discovering other systems in this region that have Earth-sized worlds.
According to Gilbert, further research into the TOI 700 system using both ground- and space-based observatories is ongoing and could provide new information about this unusual system.
According to research astrophysicist Allison Youngblood, who serves as the TESS deputy project scientist at Goddard, “TESS just finished its second year of northern sky observations. We eagerly anticipate the additional fascinating findings that the mission’s vast data set will hold.