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Dwarf star and giant planet

(31 October 2017 - DLR) In theory, it is impossible. Current theories of planetary emergence dictate that only small, rocky planets – and not a giant planet – can form around a dwarf star. The most recent discovery by the Next-Generation Transit Survey (NGTS) system has thrown some doubt on this assumption.

NGTS-1b is a planet of a size equivalent to that of Jupiter, orbiting a star that is only half as big as the Sun. It is the first exoplanet discovered using the NGTS array in Chile. The system has been in operation since 2015, and eight of the 12 cameras were financed by the German Aerospace Center (Deutsches Zentrum für Luft- und Raumfahrt; DLR). "This initial success with the NGTS is an immense surprise for those that discovered it, and a challenge for theorists," says Heike Rauer, Head of the Extrasolar Planets and Atmospheres Department at the DLR Institute of Planetary Research.

dwarf 1

The first discovery by the Next-Generation Transit Survey (NGTS) system is a giant planet orbiting a dwarf star. NGTS-1b is a planet of a size equivalent to Jupiter, but it circles a star (NGTS-1) that is olny half as big ans the Sun. This should bot be possible according to standard theory of planetary emergence, as dwarf stars are believed to be unable to accumulate sufficient material to bring large planets into existence. (courtesy: University of Warwick, Mark Garlick)

Accepted theory cannot explain the phenomenon

Star NGTS-1 and the recently discovered planet NGTS-1b are located in the Columba constellation in the southern sky and are approximately 600 light years from Earth. Standard theories state that when a star is formed, only a certain percentage of mass is available for accompanying planets. In the Solar System, for instance, the Sun holds more than 99 percent of all mass, and the eight planets, comets and asteroids account for less than one percent. It is believed that dwarf stars are unable to gather enough material together to form large planets, so NGTS-1 and NGTS-1b are putting this theory of planetary formation to the test. This first discovery by NGTS was published in the MNRAS Journal (Monthly Notices of the Royal Astronomical Society) on 31 October 2017.


Located at an altitude of approximately 4000 metres in the Atacama Desert of northern Chile at the Paranal Observatory of the European Southern Observatory (ESO), the Next-Generation Transit Survey is operated by an international team, including scientists from the DLR Institute of Planetary Research. The air at this site is extremely dry, and it offers some of the most favourable observation conditions found anywhere on Earth for 350 days each year. The system is designed for large-scale observation campaigns, and consists of 12 comparatively small, individual telescopes, each with a diameter of just 20 centimetres. The transit method is used to scour the depths of space for extrasolar planets. The light emitted by the stars is absorbed by highly sensitive, digital sensors and then analysed using highly complex methods to identify so-called dips. Dips refer to a dimming of a star’s brightness in a range of between one tenth and one hundredth of a percentage point. This dimness occurs when a planet crosses in front of its star's disc. NGTS is fully automated to search for these exoplanet transits. It continuously measures the brightness of several hundred thousand, comparatively luminous stars in the southern sky with an accuracy of 1000th of a magnitude. "We have never before achieved this kind of precision for large-scale sky surveys with ground-based instruments," adds Rauer.

NGTS was built by a consortium of British, Swiss and German institutions. DLR played a key role in the system assembly, observations and analysis of the measurement data. The acquired data are stored in the ESO archive and made accessible to astronomers worldwide. The NGTS consortium includes experts from the University of Warwick, Queen’s University of Belfast, the University of Leicester, the University of Cambridge (UK), the University of Geneva (Switzerland) and the German Aerospace Center (DLR) in Berlin.