Astronomers have discovered two potentially habitable worlds orbiting a red dwarf star in our cosmic backyard. Extra-solar planets or “exoplanets” are located only 16 light years away and have masses similar to our planet.
They are located in the “habitable zone” of their star, GJ 1002, defined as the shell around a star that is neither too hot nor too cold to support liquid water, a vital ingredient for life.
“Nature seems determined 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 a new tab). “With these two, we now know of seven in planetary systems fairly close to the sun.”
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Because liquid water is essential for the existence of life, planets in habitable zones are central to our search for life elsewhere in the universe, although simply being in a habitable zone does not guarantee no power to sustain life. For example, in the solar system, Venus and Mars are in the habitable zone of the sun, but neither can 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 about 10 days to orbit the star while the outer planet, GJ 1002c, completes an 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 cold and faint star. That means its habitable zone is very close to the star.”
The two planets’ proximity to Earth means they could make excellent targets for astronomers wishing to study the atmospheres of Earth-like worlds outside the solar system.
The exoplanets were discovered thanks to a collaboration between the ESPRESSO instrument (Echelle SPectrograph for Rocky Exoplanets and Stable Spectroscopic Observations) of the European Southern Observatory (ESO) installed at the Very Large Telescope (VLT) in the desert region of Atacama in northern Chile, and CARMENES (Calar Alto High-Resolution Search for M Dwarfs with Exo-Earths with Optical and Near-Infrared Scale Spectrographs) at the Calar Alto Observatory in Andalusia, southern Spain.
The two instruments observed the parent star of the planets during two separate periods, CARMENES studied GJ 1002 between 2017 and 2019, while ESPRESSO collected the red dwarf data between 2019 and 2021.
CARMENES’ sensitivity over a wide range of near-infrared wavelengths makes it well suited for detecting variations in star velocity that may indicate orbiting planets.
“Due to its low temperature, the visible light of GJ 1002 is too weak to measure its speed variations with the majority of spectrographs”, explained a researcher from the Institute of Space Sciences (ICE-CSIC), Ignasi Ribas.
While ESPRESSO and the light-gathering power of the VLT have enabled astronomers to make observations of the system that would not have been possible with any other ground-based telescope, it is the combination of these two powerful instruments that provided results that, in isolation, would have struggled to achieve and lead to the discovery of these exoplanets.
“Either of the two groups would have had a lot of difficulties if they had approached this work independently,” concluded Suárez Mascareño. “Together we were able to go much further than we could have done by acting independently.”
Astronomers now hope 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 and astrophysics. (opens in a new tab)
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