Scientists have observed a massive planet, about nine times the mass of Jupiter, at a remarkably early stage of formation – describing it as still “in the womb”, in a discovery that challenges current understanding of planetary formation.
The researchers used the Subaru Telescope, located near the summit of an inactive volcano in Hawaii, and the Earth-orbiting Hubble Space Telescope to detect and study the planet, a gas giant that orbits remarkably far from its young host star. Gas giants are planets, like the largest in our solar system, Jupiter and Saturn, composed primarily of hydrogen and helium, with gases that revolve around a smaller solid core.
“We think it’s still very early in its ‘birth’ process,” said astrophysicist Thayne Currie of the Subaru Telescope and the Nasa-Ames Research Center, lead author of the study published Monday in the journal Nature. Astronomy.
“Evidence suggests that this is the first stage of formation of a gas giant ever observed.”
It is embedded in an expansive disk of gas and dust, carrying the material that forms planets, surrounding a star called AB Aurigae located 508 light-years — the distance light travels in a year, 9.46 trillion kilometers — from Earth. Earth. This star had a fleeting moment of fame when her image appeared in a scene from the movie “Don’t Look Up”.
About 5,000 planets beyond our solar system, or exoplanets, have been identified. This one, called AB Aur b, is among the largest. It approaches the maximum size to be classified as a planet rather than a brown dwarf, an intermediate body between planet and star. It is heated by gas and dust that fall into it.
Forming planets — called protoplanets — have been observed around just one other star.
Almost all known exoplanets have orbits around their stars within the distance that separates our Sun and its most distant planet, Neptune. But this planet orbits three times farther than Neptune from the Sun and 93 times the distance from Earth to the Sun.
Its birth appears to follow a different process than the standard model of planetary formation.
“Conventional thinking is that most — if not all — planets form by the slow accretion of solids into a rocky core, and that gas giants go through this phase before the solid core is massive enough to start accumulating gas. “, said astronomer and study co-author Olivier Guyon of the Subaru Telescope and the University of Arizona.
In this scenario, protoplanets embedded in the disk around a young star gradually grow from dust to boulder-sized solid objects, and if that core reaches several times the mass of Earth, then they begin to accumulate gas from the disk.
“This process cannot form giant planets at a large orbital distance, so this discovery challenges our understanding of planet formation,” Guyon said.
Instead, the researchers believe AB Aur b is forming in a scenario where the disk around the star cools and gravity causes it to break up into one or more massive clumps that form into planets.
“There’s more than one way to cook an egg,” Currie said. “And apparently there could be more than one way to form a Jupiter-like planet.”
The star AB Aurigae is about 2.4 times more massive than our Sun and nearly 60 times brighter. It’s about 2 million years old — a child by stellar standards — compared to about 4.5 billion years old for our middle-aged Sun. The Sun early in its life was also surrounded by a disk that gave rise to Earth and the other planets.
“New astronomical observations continually challenge our current theories, improving our understanding of the universe,” Guyon said. “Planet formation is very complex and confusing, with many surprises still ahead.”
Translation by Luiz Roberto M. Goncalves
