Planetary system with two Suns discovered

Last Updated 03 May 2018, 04:20 IST

The new giant gas planet, found by an international team of astronomers, orbits the primary star identified as HR 7162, which is part of a binary star system 49 light-years away, in the constellation Lyra.

The researchers found the planet using a method called astrometry, which precisely tracks the position of stars over time, LiveScience reported.

"The techniques we're developing could help us better locate Earth-like planets in our local neighbourhood in the galaxy," said study leader Matthew Muterspaugh of Tennessee State University.

The new gas giant isn't the only known planet with more than one sun. Researchers have discovered dozens of them, meaning double sunsets like those seen on Luke Skywalker's home planet of Tatooine in the "Star Wars" movie may not be so rare.
To find the planet using astrometry, Muterspaugh and his team studied the periodic variations in the star HR 7162's location, which indicated something big was tugging on it with its gravity, betraying the presence of the new extrasolar planet.

In principle, the astrometry method is similar to the radial velocity technique, which has been extremely successful at detecting planets' gravitational pull by analysing the speed at which stars are moving toward or away from Earth.

The researchers, who detailed their findings in The Astronomical Journal, found that the companion star near HR 7162 is close enough to its stellar partner and the new planet that its gravitational pull could have affected planet formation.

This finding challenges the leading model of giant planet formation, called core accretion, they said.

In core accretion, according to them, dust and gas particles circling a young star cling together and gradually become larger, forming rocks, boulders and eventually the stony cores of planets. The process of creating rocks from scattered dust requires millions of years to form Jupiter-like planets.

According to models of the HR 7162 system's evolution, the second star's gravity should have disrupted the planet-forming gas and dust in just thousands of years, ejecting this raw material from the system. That a planet exists in spite of these predictions challenges core accretion as the singular model for gas giant planet formation, the researchers said.

Gravitational collapse offers an alternative method of forming giant planets, according to the team. In this theory, dense parts of the gas and dust cloud develop enough gravitational attraction within themselves to rapidly pull together into giant planets.
Simulations show these regions can collapse fast, well within a few thousand years -- meaning that the planet-forming materials could have survived in HR 7162 before the second star booted them out, said the researchers.

Some studies suggest that binary star systems produce more super-dense regions in their gas and dust clouds, because of the turbulent gravitational environment the two stars create. This would enhance the odds of giant planet formation by gravitational collapse, the researchers added.

(Published 24 October 2010, 07:55 IST)

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