NASA's TESS has discovered the second Earth-sized world in the planetary system

 

By JEANETTE KAZMIERCZAK

January 14, 2023

                       Scientists have discovered a planet the size of Earth called TOI 700 e that is orbiting within the habitable zone of its star, or the range of distances where liquid water could exist on a planet's surface. This planet was discovered using data from NASA's Transiting Exoplanet Survey Satellite. It is 95% as big as Earth and probably 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.

The study's lead author, Emily Gilbert, a postdoctoral fellow at NASA's Jet Propulsion Laboratory in Southern California, noted that this is one of the few known systems containing many tiny, livable planets. "As a result, the TOI 700 system presents a promising opportunity for further investigation. The system also demonstrates how further TESS observations help us discover ever-smaller planets because planet e is around 10% smaller than planet d.

At the 241st meeting of the American Astronomical Society in Seattle, Gilbert delivered the findings on behalf of her team. The Astrophysical Journal Letters approved an article on the recently found planet.

A tiny, cold M dwarf star called TOI 700 may be found in the southern constellation Dorado at a distance of around 100 light-years. Gilbert and others reported the finding of three planets in 2020, including the Earth-sized, habitable-zone planet d, which is on a 37-day orbit.

The innermost planet, TOI 700 b, circles the star every ten days and is nearly 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 just once each circle such that one side always faces the star, much as the Moon always faces Earth from one side of its orbit.

TESS observes broad areas of the sky, known as sectors, for around 27 days at a time. These prolonged gazes enable the satellite to monitor variations in stellar brightness brought on by an occurrence known as a transit, in which a planet seems to pass in front of its star from our perspective. Starting in 2018, the expedition followed this plan to investigate the southern sky before moving on to the northern sky. It went back to the southern sky in 2020 to make more measurements. The researchers was able to improve the first planet sizes, which are around 10% lower than earlier estimations, because to the additional year of data.

"If the star was a little closer or the planet a little bigger, we might have been able to spot TOI 700 e in the first year of TESS data," said Ben Hord, a graduate researcher at NASA's Goddard Space Flight Center in Greenbelt, Maryland, and a doctoral candidate at the University of Maryland, College Park. However, the signal was so weak that we need 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 range of distances from a star where liquid surface water may have existed at some time in a planet's history is what scientists refer to as the optimistic habitable zone. To either side of the conservative habitable zone—the region where scientists believe liquid water might 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 planets.

According to Gilbert, more research into the TOI 700 system using both ground- and space-based observatories is continuing and might provide new information about this unusual system.

According to Allison Youngblood, a research astronomer and the TESS deputy project scientist at Goddard, "TESS just finished its second year of northern sky studies. We eagerly anticipate the additional fascinating findings that the mission's vast data set will hold.

TESS is a NASA Astrophysics Explorer project that is administered by NASA's Goddard Space Flight Center and is directed and operated by the Massachusetts Institute of Technology in Cambridge, Massachusetts. The Center for Astrophysics | Harvard & Smithsonian in Cambridge, Massachusetts; MIT's Lincoln Laboratory; Northrop Grumman, situated in Falls Church, Virginia; NASA's Ames Research Center in California's Silicon Valley; and the Space Telescope Science Institute in Baltimore are other collaborators. The mission involves more than a dozen colleges, research centres, and observatories from across the world.