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It is called TOI 700-d, it was discovered thanks to the NASA space telescope, TESS, but the astrophysicists almost missed it without seeing it because its star had been badly classified. Fortunately, thanks to the report of Alton Spencer, a high school amateur astronomer, the scientists observed it more closely and their discovery is important: it could contain liquid water and, why not, be habitable!
One star for three planets
The planet TOI 700-d revolves around the 700th star observed by the TESS space telescope .
TOI 700 is a small star located only 100 light years south of the solar system, in the constellation Dorade. It measures about 40% of our sun and its surface temperature is half the temperature. Three planets orbit around it: TOI 700-b, c and d, so named according to their respective distance from their star.
This system has been observed often enough during this first year of the TESS mission to obtain certainties as to how it works: of the three planets orbiting the star, TOI-700-d is the one that is just the right distance away to be habitable.
📣Discovery Alert! 📣
Meet three new exoplanets discovered by @NASA_TESS. One of the planets, TOI 700 d, is an Earth-sized🌍 world in its star's habitable zone (where liquid water💧 * could * exist on the surface).
👋TOI 700 b, c & d! We see you.https: //t.co/92PlSDNnVQ pic.twitter.com/DCI5ySj7OY
Discovering exoplanets
The TESS telescope - Transiting Exoplanet Survey Satellite - was designed to discover exoplanets (planets outside our solar system) from space. TESS scans large portions of the sky repeatedly for 27 days straight, allowing it to detect the presence of spinning planets as they pass their star. Indeed, at that time, the brightness of the star temporarily decreases, which is what allowed TESS to detect the mass and the orbit of the planet observed.
For NASA astronomers, TOI-700-d is in synchronous rotation with its star, which means that it always shows the same face (like the moon of our sun).
What is YOU 700-d from?
YOU 700-d is a little bigger than Earth (+ 20%) and revolves around its star in 37 days. Its fixed position relative to the star implies that the temperature is different on the 2 faces, which should generate an atmospheric circulation of winds and clouds very different from that which we know. Its lit face receives 86% of the energy supplied by the Sun to the Earth.
But regarding the composition of its atmosphere, TESS says nothing, so the researchers used predictive climate models. Of the 20 versions generated, at least one is close to Earth, without the oceans, with winds blowing from the hidden side towards the lit side, when another looks more like the planet Mars when it was young.
Observe the future
Because TOI 700 is bright and shows no signs of solar flares, it is quite easy to observe its system from Earth and deduce more precise data. These observations could confirm the hypothesis that the 2 planets, inner (b) and outer (d), are rocky and the central planet (c) is gaseous. As for future NASA missions, including other space telescopes, they could identify the planets of the system with an atmosphere and even determine their composition.
We bet that if YOU 700-d really looks like our planet, this time we will treat it with respect!
NASA's TESS discovered its first Earth-size planet in a star's habitable zone, the range of distances where conditions may be just right to allow the presence of liquid water on the surface. @NASAspitzer followed up and confirmed it. https://t.co/k6XGFSuliy pic.twitter.com/S0r8wLqcp7
NASA Universe (@NASAUniverse) January 7, 2020