Thanks to a new instrument developed in part by the Geneva Observatory, an international team of astronomers discovered a giant planet around a star two times smaller than the sun. This planet challenges planetary theoreticians who thought that only small planets could form around small stars.
About the size of Jupiter and orbiting a star two times smaller than our sun, NGTS-1b is the largest planet compared to its star ever discovered in the universe. It was unveiled by NGTS a new instrument developed by a consortium including the Department of Astronomy of the University of Geneva, the universities of Warwick, Leicester and Cambridge and installed since a year and a half on the European Observatory Paranal site in Chile. NGTS is made up of a battery of 12 robotic 20 cm telescopes that examine the sky in search of transits. “The discovery of NGTS-1b is a surprise” exclaimed Dan Bayliss, postdoc of the PlanetS in Geneva and leader of the analysis of this discovery, “it is the first exoplanet that we detect with this new instrument and we are already questioning the formation of planets commonly accepted so far. ”
The huge planet around NGTS-1 (Artist view. credit University of Warwick/Mark Garlick)
The planet orbits a M dwarf cold star, the most common type of stars in the universe, implying that this kind of exoplanets may not be as rare as we thought. However, they are difficult to flush out because their host stars are small and dim. If NGTS has discovered and measured the size of the planet in question, it is another “Geneva” instrument, HARPS, which has been used to estimate its mass.
NGTS-1b is a planet the size of Jupiter but 5 times less massive. It turns in 2.6 days around its star. Having a mass equivalent to 60 times that of Earth, it questions the theory of planetary formation which until now ensured that during the formation of small stars there is not enough material to form large planets. This is clearly contradicted by the existence of NGTS-1b.
NGTS-1b: A hot Jupiter transitong a M-dwarf https://arxiv.org/pdf/1710.11099v1.pdf
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