Giant planet 9 times mass of Jupiter still "in the womb"
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Observers think that AB Aurigae b is at the earliest stage of development ever witnessed for a gas giant, and that it is not developing in the typical way that planets do.
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An illustration shows a newly forming exoplanet, AB Aurigae b. (NASA, Reuters)
In a finding that contradicts existing understanding of planetary formation, scientists have detected a massive planet approximately nine times the mass of Jupiter at a relatively early stage of creation - characterizing it as "still in the womb."
The Subaru telescope, located at the top of an extinct Hawaiian volcano, and the Hubble space telescope in orbit were used to find and examine AB Aurigae b, a gas giant orbiting extremely distant from its youthful host star. Gas giants, like our solar system's biggest planets Jupiter and Saturn, are comprised primarily of hydrogen and helium, with whirling gases around a tiny solid core.
It is buried in a vast disk of gas and dust that contains the material that makes planets and orbits a star known as AB Aurigae. It is about 508 light-years away from Earth. This star's picture appears in a scene in the 2021 film Don't Look Up, giving it a brief moment of fame.
Astrophysicist Thayne Currie of the Subaru Telescope and the NASA-Ames research center, stated that it may still be very early on in its "birthing process." According to the astrophysicist, “Evidence suggests that this is the earliest stage of formation ever observed for a gas giant.”
Exoplanets, or planets outside our solar system, number around 5,000. This is one of the biggest. It is getting close to the maximum size for classification as a planet rather than a brown dwarf, an entity halfway between a planet and a star. It's heated by gas and dust that falls into it.
Only one other star has been seen to contain planets in the process of development, known as protoplanets.
Almost all known exoplanets circle their stars within the space between our solar and its most distant planet, Neptune. However, this planet circles the sun three times as far as Neptune and 93 times as distant as Earth. Its creation appears to be distinct from the usual planetary formation hypothesis.
Astronomer and study co-author Olivier Guyon of the Subaru telescope and the University of Arizona has said that “The conventional thinking is that most – if not all – planets form by slow accretion of solids onto a rocky core, and that gas giants go through this phase before the solid core is massive enough to start accreting gas."
In this scenario, protoplanets contained in the disk encircling a young star progressively evolve from dust- to boulder-sized solid objects, and if this core reaches several times the mass of Earth, it begins to accumulate gas from the disk.
“This process cannot form giant planets at large orbital distance, so this discovery challenges our understanding of planet formation,”according to Guyon.
Researchers speculate that AB Aurigae b is formed under a scenario in which the disk surrounding the star cools and gravity drives it to split into one or more large clumps that create 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 almost 2.4 times the mass of our sun and over 60 times brighter. It is roughly 2 million years old — a baby by stellar standards – compared to our middle-aged sun, which is about 4.5 billion years old. Early in its life, the sun was also encircled by a disk, which gave rise to Earth and the other planets.
“New astronomical observations continuously challenge our current theories, ultimately improving our understanding of the universe,” Guyon said. “Planet formation is very complex and messy, with many surprises still ahead.”
