• NASA has discovered a “super-Earth”, which is dubbed as TOI-715b, in the habitable zone, only 137 light-years away.
• The exoplanet was spotted by NASA’s Transiting Exoplanet Survey Satellite (TESS).
• Super-Earth is a class of planets unlike any in our solar system. They are more massive than Earth yet lighter than ice giants like Neptune and Uranus, and can be made of gas, rock or a combination of both. They are between twice the size of Earth and up to 10 times its mass.
• Exoplanet TOI-175b is about one and a half times as wide as Earth, and orbits within the “conservative” habitable zone around its parent star.
• The parent star of TOI-715b is a red dwarf, smaller and cooler than our Sun. A number of such stars are known to host small, rocky worlds. At the moment, they are the best bet for finding habitable planets.
• These planets make far closer orbits than those around stars like our Sun, but because red dwarfs are smaller and cooler, the planets can crowd closer and still be safely within the star’s habitable zone.
• Exoplanet TOI-175b joins the list of habitable-zone planets that could be more closely scrutinised by the James Webb Space Telescope, perhaps even for signs of an atmosphere.
• Much will depend on the planet’s other properties, including how massive it is and whether it can be classed as a “water world” – making its atmosphere, if present, more prominent and far less difficult to detect than that of a more massive, denser and drier world, likely to hold its lower-profile atmosphere closer to the surface.
Transiting Exoplanet Survey Satellite (TESS)
• Transiting Exoplanet Survey Satellite (TESS) was launched aboard a SpaceX Falcon 9 rocket on April 18, 2018.
• It is the first space-based, all-sky surveyor to search for exoplanets – planets outside of our own solar system.
• TESS is designed to discover thousands of exoplanets in orbit around the brightest dwarf stars in the sky.
• In its prime mission, a two-year survey of the solar neighborhood, TESS monitored the brightness of stars for periodic drops caused by planet transits.
• The prime mission ended on July 4, 2020 and TESS is now in an extended mission. TESS is finding planets ranging from small, rocky worlds to giant planets, showcasing the diversity of planets in the galaxy.
How TESS finds planets?
• Like the Kepler mission before it, TESS is using the transit method – that is, it will stare intently at the stars in a given section of the sky, watching for the telltale flicker of a passing (transiting) planet.
• Kepler, which launched in 2009, focused on one portion of the sky and sought to find Earth-like planets. TESS, on the other hand, will look for stars 30 to 100 times brighter than those observed by Kepler. It also will scan a far larger area.
• TESS discovered its first Earth-size planet in the habitable zone, which was announced in early 2020. The planet named TOI 700 d orbits a cool M dwarf star approximately 40 per cent the mass and size of the Sun and is just over 100 light years away in the southern constellation of Draco.