Nasa’s Hubble finds Jupiter-like planet forming

This discovery supports a long-debated theory for how planets like Jupiter form.

Nasa’s Hubble Space Telescope has found evidence of a Jupiter-like protoplanet forming through what researchers describe as an ‘intense and violent process’.

This discovery supports a long-debated theory for how planets like Jupiter form, called ‘disk instability’.

The new world under construction is embedded in a protoplanetary disk of dust and gas with distinct spiral structure swirling around, surrounding a young star that’s estimated to be around 2 million years old.

That’s about the age of our solar system when planet formation was underway. Our solar system’s is currently 4.6 billion years old.

‘Nature is clever; it can produce planets in a range of different ways,’ said Thayne Currie, lead researcher on the study.

The dominant theory for planet formation is called ‘core accretion’, where planets embedded in the disk grow from small objects — with sizes ranging from dust grains to boulders — colliding and sticking together as they orbit a star.

This core then slowly accumulates gas from the disk. In contrast, the disk instability approach is a top-down model where as a massive disk around a star cools and gravity causes the disk to rapidly break up into one or more planets.

The newly forming planet, called AB Aurigae b, is probably about nine times more massive than Jupiter and orbits its host star at a whopping distance of 13.8 billion kilometers — over two times farther than Pluto is from our Sun.

At that distance it would take a very long time, if ever, for a Jupiter-sized planet to form by core accretion. This lead researchers to conclude that the disk instability has enabled this planet to form at such a great distance.

Hubble was able to capture a clean image as the vast disk of dust and gas swirling around the star AB Aurigae is tilted nearly face-on to our view from Earth.

Currie emphasised that Hubble’s longevity played a particular role in helping researchers measure the protoplanet’s orbit. He was originally very skeptical that AB Aurigae b was a planet.

‘We could not detect this motion on the order of a year or two years,’ Currie said.

Hubble provided a time baseline of 13 years, which was sufficient to be able to detect orbital motion. The team’s results are published in the April 4 issue of Nature Astronomy.

‘This new discovery is strong evidence that some gas giant planets can form by the disk instability mechanism,’ said Alan Boss of the Carnegie Institution of Science in Washington DC.

‘In the end, gravity is all that counts, as the leftovers of the star-formation process will end up being pulled together by gravity to form planets, one way or the other,’ he said.

Understanding the early days of the formation of Jupiter-like planets provides astronomers with more context into the history of our own solar system. This discovery paves the way for future studies of the chemical make-up of protoplanetary disks like AB Aurigae, including with Nasa’s James Webb Space Telescope.

Astronomers have long searched for clear evidence of this process as a viable candidate in forming large, Jupiter-like planets, and Hubble’s resolution and longevity proved to be a key missing puzzle piece.

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