NASA scientists identified TOI 700 e, a planet the size of Earth that orbits within its star’s habitable zone, or the range of distances where liquid water might exist on a planet’s surface. The planet was discovered using Transiting Exoplanet Survey Satellite data (TESS). It is 95% the size of Earth and is most likely formed of rocks.
TESS is a NASA Astrophysics Explorer project overseen and run by the Massachusetts Institute of Technology in Cambridge, Massachusetts, and is managed by NASA’s Goddard Space Flight Center. Other collaborators include the Center for Astrophysics | Harvard & Smithsonian in Cambridge, Massachusetts; MIT’s Lincoln Laboratory; Northrop Grumman in Falls Church, Virginia; NASA’s Ames Research Center in California’s Silicon Valley; and the Space Telescope Science Institute in Baltimore. More than a dozen institutions, research centres, and observatories from across the world are participating in the endeavour.
Astronomers discovered the TOI 700 b, c, and d planets as the first three in this system. Planet d also spins in the habitable zone. However, it took another year of TESS observations for astronomers to discover TOI 700 e.
Emily Gilbert, a postdoctoral scholar at NASA‘s Jet Propulsion Laboratory in Southern California, who led the study, observed that this is one of the few known systems with multiple small, inhabited planets. As a result, the TOI 700 system offers a viable avenue for further research. Because planet e is around 10% smaller than planet d, the system also highlights how more TESS observations might help us identify ever-smaller planets.
Gilbert presented the findings on behalf of her team at the American Astronomical Society’s 241st conference in Seattle. An essay on the freshly discovered planet has been accepted for publication in the Astrophysical Journal Letters.
A small, cool M dwarf star named TOI 700 may be discovered at a distance of roughly 100 light-years in the southern constellation Dorado. Gilbert and colleagues discovered three planets in 2020, including the Earth-sized, habitable-zone planet d, which orbits the Sun every 37 days.
The innermost planet, TOI 700 b, circles its star every ten days and is around 90 percent the size of Earth. The orbit of TOI 700 c, which is greater than 2.5 times that of Earth, lasts 16 days. Most likely, the planets are tidally locked, which means they spin just once each orbit, such that one side of their orbit always faces the star, similar to how one side of the Moon’s orbit constantly faces Earth.
TESS monitors large sections of the sky, known as sectors, for around 27 days at a time. These extended observations allow the satellite to track changes in stellar brightness caused by a transit, which occurs when a planet seems to pass in front of its star from our perspective. This plan was followed by the expedition beginning in 2018 to examine the southern sky before moving on to the northern sky. In 2020, it returned to the southern sky to take further observations. Because of the additional year of data, the researchers were able to enhance the initial planet sizes, which are roughly 10% smaller than previous estimates.
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, said that if the star had been a little closer or the planet a little bigger, we might have found TOI 700 e in the first year of TESS data. The signal, on the other hand, was so weak that we had to look for it for an extra year.
Planet e is located on TOI 700 e in the so-called optimistic habitable zone between planets c and d, which may also be tidally locked.
The optimistic habitable zone is the range of distances from a star where liquid surface water may have existed at some point in a planet’s history. This area is located on either side of the conservative habitable zone—the region where scientists assume liquid water will stay for the bulk of the planet’s lifespan.
Planetary scientists can learn more about our solar system’s past by identifying other systems in this region with Earth-sized planets.
According to Gilbert, additional study into the TOI 700 system is being conducted utilising both ground- and space-based observatories, which may reveal fresh information about this peculiar system.
Allison Youngblood, a research astronomer and TESS deputy project scientist at Goddard, says TESS has just completed its second year of northern sky investigation. We anxiously await the mission’s large data set’s more exciting discoveries.