TOI 700 d- the newest Earth-size exoplanet

However, the TOI 700 star system is unlike the solar system in that all three planets detected so far are thought to be tidally locked to their star.

Astronomers using NASA’s Transiting Exoplanet Survey Satellite (TESS) has discovered its first Earth-size planet in its star’s habitable zone earlier this year. That’s crucial because it may mean the planet, called TOI 700 d, has liquid water on its surface. It also appears to have one side of the planet in eternal sunshine and the other in a never-ending night. Let’s read why the discovery of new planet is important in space research.

TOI 700 d is orbiting a star called TOI 700, a cool “M dwarf” star about 100 light-years away in the southern constellation of Dorado, the dolphinfish. About 40% of the Sun’s mass and size, and about half its surface temperature, TOI 700 is bright, nearby, and shows no sign of harmful “stellar flares.” That means that any planets in orbit don’t get frequent blasts of deadly radiation that would almost certainly make life impossible.

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However, the TOI 700 star system is unlike the solar system in that all three planets detected so far are thought to be tidally locked to their star. That means they show only one face to the star—as the moon does to Earth—but it therefore means that only one side ever gets daylight. TESS’s first Earth-size planet in its star’s habitable zone is nevertheless destined to be a very weird world indeed.

Role of TESS

TESS, the Transiting Exoplanet Survey Satellite, was launched in 2018 with the goal of discovering small planets around the Sun’s nearest neighbors, stars bright enough to allow for follow-up characterizations of their planets’ masses and atmospheres. TESS has so far discovered seventeen small planets around eleven nearby stars that are M dwarfs — stars that are smaller than the Sun (less than about 60% of the Sun’s mass) and cooler (surface temperatures less than about 3900 kelvin).

How was TOI 700 d discovered?

It’s a red dwarf, the smallest sort of star and the most common type of star in the Milky Way galaxy. However, they’re too small to see with the naked eye. Scientists were able to study TOI 700 a lot during the TESS mission’s first year, detecting a total of three planets crossing TOI 700 from the satellite’s point of view (called a transit).

A team of scientists led by Joseph Rodriguez, an astronomer at the Center for Astrophysics, Harvard & Smithsonian in Cambridge, Massachusetts confirmed the find using NASA’s Spitzer Space Telescope.

Appearance of the planet

What would life be like on a planet that has two halves—one constantly bathed in daylight and one that is always on the night-side. It’s too early to say whether there are moons around TOI 700 d that might bring some kind of reflected light to the night-side.

Since TOI 700 d is tidally locked to its star and has a never-ending day and night, there is likely a stark temperature difference between the two sides. So the planet’s cloud formations and wind patterns may be strikingly different from Earth’s.

How many exoplanets are potentially habitable?

TOI 700 d is one of only a handful Earth-size planets discovered in a star’s habitable zone so far. Others include several planets in the TRAPPIST-1 system and other worlds discovered by NASA’s incredibly successful Kepler Space Telescope. However, all astronomers can say for now is that an exoplanet resides it that star’s habitable zone.

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