A particularly special world was discovered by the NASA TESS satellite, which looks for exoplanets (planets in other solar systems).
This time, it is a planet of a size similar to Earth and is in the habitable zone of its star, that is, where the conditions for life can occur.
The planet, named TOI 700 d, is part of a system of three planets that orbit its star, 100 light years from us.
This ‘twin’ of the Earth is located in the third position with respect to its star, as well as our precious world with respect to the Sun.
This is a key finding for the TESS, since “it was designed and launched specifically to find Earth-sized planets that orbit nearby stars,” said Paul Hertz, director of NASA’s astrophysics division in Washington.
It is the first time that the TESS finds a planet like ours.
This promising exoplanet acquired its name due to its star, TOI 700, which is small and cold, of the dwarf type M.
It has 40% of the mass and size of the Sun, and has half its surface temperature.
NASA scientists using TESS noted that there were three planets that made their shadow notice when they passed between the star and the satellite.
Initially, the TESS database cataloged the star as similar to the Sun, which meant that the planets seemed larger and hotter than they really are. Then they identified the error.
“When we corrected the parameters of the star, the sizes of its planets fell, and we realized that the outermost was about the size of the Earth and in the habitable zone,” said Emily Gilbert of the University of Chicago, a of the scientists who presented the findings in three documents at the 235th meeting of the American Astronomy Society in Hawaii.
The researchers also noticed that the star does not present an activity that could harm its planets. In 11 months, it did not produce flashes, “which improves the chances that TOI 700 d is habitable and makes it easier to model its atmospheric and surface conditions,” explains Gilbert.
The second fits the characteristics of a planet dominated by gases. But a third was the one that astonished the scientists the most.
TOI 700 d is the only planet in the habitable zone of its system.
It is rocky, barely 20% larger than Earth, orbits its star every 37 days and receives 86% of the energy that our planet receives from the Sun.
The scientists noted that the planet and its two neighbors rotate on its axis once for each orbit (they complete a ‘day’ every ‘year’) due to the gravity that the star exerts on them for being so close. This causes one side of the planet to receive light constantly, while the other goes through perpetual darkness.
On the other hand, scientists from NASA’s Goddard Space Flight Center simulated potential environments for TOI 700 d by computer, in order to find out if life was possible.
One of the models showed the planet covered by an ocean with a dense atmosphere composed of abundant carbon dioxide, similar to what Mars was thought to be at the beginning. It also had a thick layer of clouds on the illuminated side.
Another model turned out to be even more interesting.
TOI 700 d appeared as the Earth currently looks but without clouds, where winds flow from the dark side of the planet and converge on the side that ‘looks’ at the star.
These models were carried out simulating the light of the star that enters the atmosphere of the planet and interacts with elements such as carbon dioxide or nitrogen to produce different signals, known as spectral lines.
“Someday, when we have real spectra of TOI 700 d, we can turn back, join them to the nearest simulated spectrum and then match that with a model,” explains Gabrielle Engelmann-Suissa, who led the team in charge of the simulations.
“It’s exciting because no matter what we discover about the planet, it will look completely different from what we have here on Earth,” he says.
With new exploration missions such as the James Webb Space Telescope in 2021, scientists hope to obtain the first data of the planet’s atmosphere, and thus determine how habitable it can be.
TESS also discovered a planet that orbits around two stars, just as it happens in Star Wars with Tatooine.
The planet was found by Wolf Cukier, a high school student, who was doing an internship for NASA’s Goddard Space Flight Center.
It is the only one in the system with two suns, one of them is 10% larger than ours and the other is smaller and colder.
The Transit Exoplanets Survey Satellite (TESS) was launched in April 2018 to search for exoplanets using the transit method.
Before the TESS, NASA’s Kepler Space Telescope was in charge of searching for exoplanets.
It is estimated that he found about 3500 worlds around different stars of the Milky Way.