Artist's impression of an exoplanet. Photo: University of Warwick/Mark Garlick

For the first time, scientists have found the core of a dead planet orbiting a star 730 light-years from Earth.

Why it matters: Our solar system only has a few types of planets by comparison to the diversity of worlds out there orbiting other stars. Finding this bizarre world adds to that tapestry — and opens up new avenues for discovery.

Details: A study about the newfound planet — named TOI 849 b — reveals the odd, Neptune-sized world orbits its star once every 18 hours and its surface temperature clocks in at an extreme 2,732°F.

  • "The planet is strangely close to its star, considering its mass," David Armstrong, one of the authors of the new Nature study said in a statement.
  • The planet's strange composition is what gave scientists the hint that the world is likely the core of what could have been a much larger gas giant.
  • The authors of the study found that TOI 849 b has only a small amount of hydrogen and helium and it's incredibly dense at 40 times heavier than the Earth with a radius 3.4 times that of our planet.
  • According to current models of planetary formation, a planet that massive would have sucked up much more helium and hydrogen than is present now, the study says.

The intrigue: The scientists are confident this world is a dead core of a planet, but they're less sure about how it came to be.

  • The paper's authors suggest the planet may have once been like Jupiter but lost its atmosphere through a possible collision with another world or tidal forces that disrupted the planet due to its close proximity to its star.
  • It's also possible at least some of the planet's atmosphere evaporated because of its close-in orbit.
  • The alien world might also represent a "failed" gas planet where the gas that usually would have been slurped up by the core wasn't available during planet formation.

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Miriam Kramer, author of Space
Oct 13, 2020 - Science

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