A tiny hot planet as dense as iron slides around a red dwarf star


This illustration shows a recently discovered exoplanet called GJ 367b, located about 31 light years from Earth and orbiting its star in just about 8 hours, with a density greater than that of our planet and an internal structure similar to that of Mercury. SPP 1992 / Patricia Klein / Document via REUTERS

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WASHINGTON, Dec. 2 (Reuters) – Scientists have spotted one of the smallest planets ever discovered outside of our solar system, a scorching world a little larger than Mars and about as dense as pure iron zooming around its original star every eight hours.

Researchers said on Thursday they had successfully detected the planet, located 31 light years relatively close to Earth, and discerned some of its important features, illustrating improvements in recent years in the ability to characterize smaller planets. size beyond our solar system.

Scientists are eager to find exoplanets, as these alien worlds are known, that could harbor life. The newly discovered one, called GJ 367b, certainly couldn’t, as it has fierce surface temperatures and possibly a surface of molten lava on the side facing its star, they said. But other small exoplanets discovered and studied using the same methods could emerge as good candidates for nurturing alien life.

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A quarter of a century after the first discoveries of exoplanets, scientists turned to their more precise characterization to better understand their variety, from large Jupiter-like gas giants to smaller, rocky Earth-like planets where life could thrive.

“Gas giants like Jupiter, as we know them, are uninhabitable because they have more extreme temperatures, weather conditions, pressures and a lack of building blocks essential to support life,” said the astronomer Kristine Lam of the Planetary Research Institute of Germany. Aerospace Center (DLR), lead author of the study published in the journal Science.

“Unlike gas giants, small terrestrial worlds like Earth are more temperate and consist of important ingredients, such as liquid water and oxygen, to house life forms. Although not all terrestrial exoplanets are not habitable, look for smaller worlds and identify the type of planets they can help us understand how planets were formed, what makes a planet habitable and whether our solar system is unique, ”Lam added.

GJ 367b is the smallest exoplanet to be characterized with such precision. It is about 5,600 miles (9,000 km) in diameter – compared to 7,900 miles (12,700 km) from Earth and 4,200 miles (6,800 km) from Mars. Its mass is 55% that of the Earth and it is denser – close to that of pure iron.

Researchers have calculated that 86% of GJ 367b is made up of iron, with an interior structure resembling Mercury, the planet closest to our sun. They wonder if the planet has lost an outer mantle that once enveloped its core.

“Perhaps like Mercury, GJ 367b might have experienced a giant impact episode that ripped off the mantle, leaving behind a large iron core. Or maybe the exoplanet is a remnant of a gaseous planet from the size of Neptune or super-Earth, where the planet’s atmosphere has completely washed away as the planet is blown away by a large amount of radiation from the star, ”Lam said.

It orbits very close to a red dwarf star that’s smaller, cooler, and less luminous than our sun – more than 99% closer than Earth’s distance from the sun, according to the astronomer and co-author of the study Szilard Csizmadia, also from the Institute of the DLR Planetary Research.

GJ 367b orbits its star once every 7.7 hours, placing it in a category of “ultra-short-lived” exoplanets that roam their home stars in less than 24 hours. One side of GJ 367b is likely facing its star at all times, with surface temperatures of up to about 2,700 degrees Fahrenheit (1,500 degrees Celsius).

“This temperature is high enough to evaporate any atmosphere GJ 367b may have had in the past, as well as to melt all the silicate rocks and metallic iron on the planet,” Lam said.

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Reporting by Will Dunham, editing by Rosalba O’Brien

Our standards: Thomson Reuters Trust Principles.


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