Astronomers have spotted two potentially habitable worlds orbiting a red dwarf star in our cosmic backyard. The extrasolar planets or “exoplanets” are only 16 light-years away and have similar masses to our planet.
They are in their star GJ 1002’s “habitable zone,” defined as the envelope around a star that is neither too hot nor too cold to contain liquid water, a vital ingredient.
“Nature seems keen to show us that Earth-like planets are very common,” study author Alejandro Suárez Mascareño of the Instituto de Astrofisica de Canarias (IAC) said in a statement (opens in new tab). “With those two, we now know seven in planetary systems near the Sun.”
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Because liquid water is essential for life to exist, planets in habitable zones are at the center of our quest for life elsewhere in the universe, although mere presence in a habitable zone is no guarantee that life is possible. For example, in the solar system, both Venus and Mars are in the Sun’s habitable zone, but neither could currently support life.
Because GJ 1002 is a relatively cool red dwarf, its habitable zone — and these two new exoplanets — are much closer to it than Earth is to the Sun. The innermost planet, designated GJ 1002b, takes only about 10 days to orbit the star, while the outer planet, GJ 1002c, completes one orbit in 21 days.
“GJ 1002 is a red dwarf star barely one-eighth the mass of the Sun,” study co-author and IAC researcher Vera María Passegger said in the statement. “It’s a fairly cool, faint star. That means its habitable zone is very close to the star.”
Both planets’ proximity to Earth means they could be excellent targets for astronomers wanting to study the atmospheres of Earth-like worlds outside the solar system.
The exoplanets were discovered as a result of a collaboration between the European Southern Observatory’s (ESO) instrument ESPRESSO (Echelle SPectrograph for Rocky Exoplanets and Stable Spectroscopic Observations), installed on the Very Large Telescope (VLT) in the Atacama desert region of northern Chile, and CARMENES (Calar Alto high-Resolution search for M dwarfs with Exoearths with Near-infrared and optical Échelle Spectrographs) at the Calar Alto Observatory in Andalusia, southern Spain.
The two instruments observed the planet’s parent star in two separate periods, CARMENES studied GJ 1002 between 2017 and 2019, while ESPRESSO collected data from the red dwarf between 2019 and 2021.
CARMENES’s sensitivity over a wide range of near-infrared wavelengths makes it well suited to detecting fluctuations in the velocities of stars, which may indicate orbiting planets.
‘Because of its low temperature, the visible light from GJ 1002 is too faint to measure its velocity changes with most spectrographs,’ explained a researcher at the Institute for Space Sciences (ICE-CSIC), Ignasi Ribas.
While ESPRESSO and the light-gathering power of the VLT allowed astronomers to make observations of the system that would not have been possible with any other ground-based telescope, it was the combination of these two powerful instruments that produced results that, on their own, would have struggled to reach these exoplanets and lead to the discovery of these exoplanets.
“Each of the two groups would have faced many difficulties if they had undertaken this work independently,” concluded Suárez Mascareño. “Together we have come much further than we would have done alone.”
The astronomers now hope to be able to use the ANDES spectrograph on the Extremely Large Telescope under construction in the atmosphere of GJ 1002c.
The team’s research is published in the journal Astronomy & Astrophysics. (opens in new tab)
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