Gigantic Jupiter-like alien planet still seen ‘in the womb’

Scientists have observed a huge 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.

Researchers used the Subaru Telescope located near the top of an inactive Hawaiian volcano and the orbiting Hubble Space Telescope to detect and study the planet, a gas giant orbiting unusually far from its young host star. Gas giants are planets, like the largest in our solar system, Jupiter and Saturn, composed mostly of hydrogen and helium, with swirling gases surrounding a smaller solid core.

“We think it’s still very early in its ‘birth’ process,” said astrophysicist Thayne Currie of the Subaru Telescope and NASA-Ames Research Center, lead author of the study published Monday. in the journal Nature Astronomy. “Evidence suggests this is the earliest stage of formation ever observed for a gas giant.”

It is embedded in a vast disc of gas and dust, carrying the material that forms planets, which surrounds a star called AB Aurigae located 508 light years away – the distance light travels in one year, 9.5 trillion kilometers – from the Earth. This star had a fleeting moment of glory when her image appeared in a scene from the 2021 film 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 most important. It approaches the maximum size to be classified as a planet rather than a brown dwarf, an intermediate body between a planet and a star. It is heated by the gas and dust falling into it.

Planets in the process of formation, called protoplanets, have only been observed around one other star.

Almost all known exoplanets orbit their stars within the distance between our sun and its outermost planet, Neptune. But this planet orbits three times farther than Neptune from the sun and 93 times the distance from Earth to the sun.

Not a “standard” way to form a planet

Its birth seems to follow a different process from the standard model of planetary formation.

“Conventional thinking is that most – if not all – planets form by slow accretion of solids onto a rocky core, and gas giants pass through this phase before the solid core is massive enough to begin accreting gas. said astronomer and study co-author Olivier Guyon of the Subaru Telescope and the University of Arizona.

The researchers were able to directly image the newly formed exoplanet AB Aurigae b over a period of 13 years. In 2007, top right, AB Aurigae b is in a due south position relative to its host star, which is covered by the instrument’s coronagraph. The image captured in 2021 shows that the protoplanet has moved counterclockwise over time. (NASA, ESA, Thayne Currie/Subaru Telescope, Eureka Scientific Inc.)

In this scenario, protoplanets embedded in the disk surrounding a young star gradually grow from solid boulder-sized objects and, if that core reaches several times the mass of Earth, then begin to accumulate gas. from disk.

“This process cannot form giant planets at large orbital distances, so this discovery challenges our understanding of planet formation,” Guyon said.

Instead, the researchers believe AB Aur b forms in a scenario in which the disk around the star cools and gravity causes it to fragment into one or more massive clusters that form planets.

“There’s more than one way to cook an egg,” Currie said. “And apparently there may 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 almost 60 times brighter. It’s about two million years old — a child by stellar standards — compared to about 4.5 billion years old for our middle-aged sun. At the beginning of its life, the sun was also surrounded by a disc which gave rise to the Earth and the other planets.

“New astronomical observations continually challenge our current theories, ultimately improving our understanding of the universe,” Guyon said. “Planet formation is very complex and messy, with many surprises yet to come.”