Distant exoplanet defies planet formation theory

A recently discovered giant Jupiter-like planet found a huge distance from its star appears to defy most theories of planetary formation. However, the host star's young age could help researchers unravel how not only this planet formed, but others like it throughout the Galaxy.

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An simulated image of the HD 106906 stellar debris disk, showing the ring of material rotating around the star.
Credit: Erika Nesvold/Carnegie Institution for Science

A recently discovered giant Jupiter-like planet found a huge distance from its star appears to defy most theories of planetary formation. However, the host star's young age could help researchers unravel how not only this planet formed, but others like it throughout the Galaxy.

The planet, HD106906b, orbits 650 times the distance between Earth and the Sun from its host star. However, most theories of planetary formation state that planets form in dusty discs of debris found close to the centre of the planetary system.

“Our current planet formation theories do not account for a planet beyond its debris disc,” says Smadar Naoz from the University of California, Los Angeles.

Some planets can form close to their star before being flung out at a later date, but that does not seem to be the case here, which poses questions about how the planet came to be.


Read more about strange exoplanets from BBC Sky at Night Magazine:


The host star is extremely young by celestial standards, no more than 13 million years old compared with the Sun’s 4.5 billion.

“This is such a young star; we have a snapshot of a baby star that just formed its planetary system – a rare peek at the final stage of the planet formation,” says Naoz.

The star also hosts a disc of dusty debris, thought to be similar to our own Solar System’s Kuiper Belt. However, HD106906b has a highly elliptical 1,500-year orbit, and its gravitational pull has pulled the disc into a lopsided shape causing one side of the disc to by much warmer than the other. There are no other known planets in the disc.

“In our Solar system, we’ve had billions of years of evolution,” says Michael Fitzgerald, an associate professor of physics and astronomy at the University of California, Los Angeles. “We’re seeing this young system revealed to us before it has had a chance to dynamically mature.” 


 

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