Newly-discovered planet is hot, metallic and dense as Mercury

  • A hot, metallic, Earth-sized planet with a density similar to Mercury—situated 340 light years away—has been detected and characterised by a global team of astronomers, including the University of Warwick.
  • Named K2-229b, the planet is almost 20% larger than Earth but has a mass which is over two-and-a-half times greater—and reaches a dayside temperature of over 2000°C (2330 Kelvin).
  • It finds itself very close to its host star (0.012 AU, around a hundredth of the distance between the Earth and the Sun), which itself is a medium-sized active K dwarf in the Virgo Constellation. K2-229b orbits this star every fourteen hours.
  • Led overall by researchers at Aix-Marseille Université in France, Dr. David Armstrong and colleagues at the University of Warwick’s Astronomy and Astrophysics Group independently detected the planet in the first instance, alongside researchers at the Universidade do Porto.
  • Using the K2 telescope, Dr. Armstrong and colleagues employed the Doppler spectroscopy technique—also known as the ‘wobble method’ to discover and characterise this faraway planet.
  • The astronomers knew the planet was there due to dips in the light from its host star as it orbited, periodically blocking starlight.
  • They then calculated the size, position and mass of K2-229b by measuring the radial velocity of the star, and finding out how much the starlight ‘wobbles’ during orbit, due to the gravitational tug from the planet, which changes depending on the planet’s size.


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