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By Will Dunham
WASHINGTON (Reuters) – Scientists have spotted a planet orbiting a star relatively close to our solar system, which could provide a great opportunity to study the atmosphere of a rocky Earth-like alien world – the type of research that might help in the hunt for extraterrestrial life.
Researchers said Thursday that the planet, called Gliese 486b and classified as “super-Earth,” is not itself a promising candidate as a refuge for life. It is believed to be inhospitable – hot and dry like Venus, with possible rivers of lava flowing over its surface.
But its proximity to Earth and its physical characteristics make it well suited for a study of its atmosphere with the next generation of space and ground telescopes, starting with the James Webb Space Telescope that NASA has slated for launch in October. These could give scientists data allowing them to decipher the atmospheres of other exoplanets – planets beyond our solar system – including those that can harbor life.
“We are saying that Gliese 486b will instantly become the Rosetta Stone of exoplanetology – at least for Earth-like planets,” said astrophysicist and study co-author José Caballero from Centro de Astrobiología in Spain , referring to the ancient stone slab that helped experts decipher Egyptian hieroglyphics.
Scientists have discovered more than 4,300 exoplanets. Some were large gas planets similar to Jupiter. Others were smaller, rocky Earth-like worlds, the kind considered candidates to harbor life, but currently available scientific instruments tell us little about their atmosphere.
“The exoplanet must have the right physical and orbital configuration to be suitable for atmospheric research,” said planetologist Trifon Trifonov of the Max Planck Institute for Astronomy in Germany, lead author of the research published in the journal Science.
A “super-Earth” is an exoplanet whose mass is greater than that of our planet but considerably less than that of the ice giants of our solar system, Uranus and Neptune. The mass of Gliese 486 b is 2.8 times that of the Earth.
It is located in our Heavenly Quarter about 26.3 light years – the distance light travels in a year, 9.5 trillion kilometers (5.9 trillion miles) – from Earth, making it one of the closest exoplanets. It revolves around a “red dwarf” star that is smaller, cooler and less luminous than our sun, with about a third of its mass.
The planet orbits very close to its original star, leaving it heavily irradiated. Like Earth, it is a rocky planet and is believed to have a metallic core. Its surface temperature is around 800 degrees Fahrenheit (430 degrees Celsius) and its surface gravity can be 70% stronger than that of Earth.
“Gliese 486b cannot be habitable, at least not as we know it here on Earth,” Trifonov said. “The planet may only have a thin atmosphere, if at all. Our models are consistent with both scenarios because stellar irradiation tends to evaporate the atmospheres, while, at the same time, planetary gravity is strong enough to hold her back. “
Still, Gliese 486b could prove ideal for studying the atmosphere of an Earth-like planet using instruments from the James Webb Space Telescope and the future Extremely Large Telescope, an astronomical observatory currently under construction in Chile. .
The chemical makeup of an atmosphere can say a lot about a planet and its habitability. Scientists are interested in the combination of gases in the atmospheres of Earth-like exoplanets, with a mixture of oxygen, carbon dioxide and methane like that of our own planet, a potential indication of life.
“Everything we learn with the atmosphere of Gliese 486 b and other Earth-like planets will be applied, within a few decades, to the detection of biomarkers or biosignatures: spectral characteristics on the atmospheres of exoplanets which can only be attributed to extraterrestrial life. Added Caballero.
(Report by Will Dunham, edited by Rosalba O’Brien)
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