WASHINGTON (Reuters) – Scientists express their surprise after discovering a solar system 30 light-years from Earth that defies any understanding of the planet's formation, with a large planet resembling Jupiter orbiting around a star tiny called red dwarf.
An artistic impression of the giant gas planet GJ 3512b orbiting its red dwarf host star, released September 26, 2019. Guillem Anglada-Escude / Handout via REUTERS THIS IMAGE HAS BEEN PROVIDED BY A THIRD PARTY. NO RESALE. NOT ARCHIVES
Stars are usually much larger than even the largest planets that orbit them. But in this case, the star and the planet are not very different in size, announced researchers Thursday.
The star, called GJ 3512, represents about 12% of the size of our sun, while the surrounding planet has a mass of at least half of Jupiter, the largest planet in our solar system.
"Yes, an absolute surprise," said astrophysicist Juan Carlos Morales of the Institute of Space Studies of Catalonia's Institute of Space Science in Spain, who led the published research in the journal Science.
"The discovery was surprising because theoretical training models suggest that low-mass stars typically host small Earth-like planets or small Neptunes. In this case, we found a giant gas planet similar to Jupiter around a very small star, "added Morales.
The planet, which like Jupiter is composed mainly of gas, was discovered with the help of a telescope at the Calar Alto Observatory in Spain. He travels around his star in a very elliptical 204-day orbit.
Red dwarfs are small, with relatively low surface temperatures. GJ 3512 is not only much smaller than our sun, it is about the size of a very large planet and is only 35% larger than Jupiter.
"They emit less energy, so they are fainter than the sun and their surface temperature is rather cool, below 3,800 degrees Kelvin (6,380 degrees Fahrenheit / 3,527 degrees Celsius). That's why they have a reddish color, "said Morales.
There is evidence of a second planet orbiting the star, while a third planet could have been ejected from the star system in the past, explaining the planet's elliptical orbit. like Jupiter, explained Morales.
The planets are born from the same disk of gas and interstellar dust that produces the star around which they gravitate. According to the flagship model of planetary formation, called the "core" model, an object is initially formed from solid particles in the disk and the gravitational tug of this embryonic planet allows an atmosphere to exit the surrounding gas.
A competing model, called a gravitational instability model, may explain this unusual system.
"In this case, the protoplanetary disk around the young star may be slightly thicker than expected and cold," said Morales. "This makes the disc unstable and thus allows the appearance of dense regions. These tufts can grow until they collapse, forming a planet. "
Report by Will Dunham; Edited by Sandra Maler