New exoplanet defies accepted theories of planet formation

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The uncertainty of science: A newly discovered exoplanet, the size of Jupiter and orbiting a star half the size of the Sun, should not exist based on all the presently favored theories of planet formation.

New research, led by Dr Daniel Bayliss and Professor Peter Wheatley from the University of Warwick’s Astronomy and Astrophysics Group, has identified the unusual planet NGTS-1b – the largest planet compared to the size of its companion star ever discovered in the universe.

NGTS-1b is a gas giant six hundred light years away, the size of Jupiter, and orbits a small star with a radius and mass half that of our sun.

Its existence challenges theories of planet formation which state that a planet of this size could not be formed by such a small star. According to these theories, small stars can readily form rocky planets but do not gather enough material together to form Jupiter-sized planets. The planet is a hot Jupiter, at least as large as the Jupiter in our solar system, but with around 20% less mass. It is very close to its star – just 3% of the distance between Earth and the Sun – and orbits the star every 2.6 days, meaning a year on NGTS-1b lasts two and a half days.

No one should be surprised by this. While the present theories of planet formation are useful and necessary, giving scientists a rough framework for studying exoplanets, they should not be taken too seriously. We simply do not yet have enough information about how stars, solar systems, and planets form.



  • LocalFluff

    Hot Jupiters can’t form where they are anyway (stellar winds quickly blow away all H and He that close), they must’ve moved inwards by tossing out a neighbor, which fits with the vagabond planets found. Star systems form out of a common cluster and can relatively easily trade material with each other as long as they are still co-moving. This star has had company.

  • Cotour

    If this planet is defying the accepted theory of planet formation, maybe its made of “Molten carpet”?

  • SteveC

    How can a star be half of both our suns radius and mass? Isn’t it a mater of square vs. cube?

  • wayne

    LocalFluff is on to it. “This star has had company.”

  • Judy

    SteveC, I would assume that the smaller star is more dense

  • LocalFluff

    @SteveC, like Judy writes. Larger stars are hotter because their greater mass causes higher pressure at their center, fusing more hydrogen and the heat puffs them up. Planets don’t get much larger volume than Jupiter, even if one adds ten Jupiter masses. It mostly just increases the density, until fusion ignites at the center.

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