Astronomers have discovered a new multiplanetary system just 33 light-years from our own planet.
The system, now the closest known to Earth, has two terrestrial planets orbiting a cool M-dwarf star called HD 260655.
The inner planet HD 260655b orbits the star every 2.8 days and is about 1.2 times larger than Earth, but is slightly denser, while the outer planet HD 260655c orbits every 5.7 days and is 1.5 times larger than the Earth, but less dense.
These planets, unfortunately, are not habitable; the planets orbit their star at too close a range, exposing them to too high temperatures to maintain liquid water on their surface. Based on their short orbits, it is estimated that the surface of the inner planet is 436 degrees Celsius, while the outer planet is about 286 degrees Celsius.
“We think this range outside the habitable zone is too hot for liquid water to exist on the surface,” said Michelle Kunimoto, a postdoc at the Cavley Institute of Astrophysics and Space Research at the Massachusetts Institute of Technology and one of the discovery’s leading scientists.
But there may be more planets that need to be discovered, as many multiplanetary systems have five or six planets, and this is especially common around small stars. It is possible that a person is in the habitable zone, although MIT scientist Avi Sporer said such a possibility is “optimistic thinking”.
Until then, the proximity and brightness of HD 260655 means that scientists can closely study the properties of the planets and study their atmospheres.
“Both planets in this system are considered one of the best targets for studying the atmosphere because of the brightness of their star,” said Michelle Kunimoto, a postdoc at the Cavley Institute of Astrophysics and Space Research at the Massachusetts Institute of Technology and one of the leading scientists. the discovery.
“Is there an atmosphere around these planets rich in volatiles? And are there any signs of aquatic or carbon species? These planets are fantastic test beds for this research. “
The system was first spotted by NASA’s Transit Exoplanet (TESS) satellite, which detects periodic dips in HD 260655 light – indicative of a planet passing in front of the star.
HD 260655 was also under study of stars taken from the Echelle High Resolution Spectrometer (HIRES), an instrument that operates as part of the Keck Observatory in Hawaii.
HIRES has been observing the star since 1998, so researchers had access to publicly available data from the study, which shortened the time needed to validate the system.
Scientists have used data from other studies to measure the radial velocity of the star – the motion it experiences by gravity when another planet is close to it. “Every planet orbiting a star will have a small gravitational pull on its star,” said Michelle Kunimoto.
“What we’re looking for is some slight movement of this star, which could mean that an object with a planetary mass is pulling it.”
Scientists have now discovered more than 5,000 exoplanets orbiting distant suns. “It’s not just a number,” said Jesse Christiansen, a research fellow at the Exoplanet Archive and a scientist at NASA’s Caltech Institute for Exoplanets.
“Each of them is a new world, a brand new planet. I’m excited about each one because we don’t know anything about them. “
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