Theories of planet formation.
According to conventional theories, planets are formed from the protoplanetary disk of a young star, the substance of which is gradually compacted. Because of this, there is a clear relationship between the size of specific stars and the planets that orbit them. But sometimes such calculations are interfered with by unusual facts of observation of the starry sky.
The new red dwarf-who is he?
Astronomers have discovered such a discrepancy: a giant exoplanet of the hot Jupiter class was found near the dwarf star. The corresponding article will be published in the journal Monthly Notices of the Royal Astronomical Society, the preprint is available.
We are talking about the newly discovered planet NGTS-1b, whose parent star is located 600 light-years from Earth, in the constellation of Dove. NGTS-Nesct-Generation Transition Survey, a system of small telescopes in the Chilean Atacama desert, controlled by robots. The discovered star and the planet with it are the first significant results of this project, so the star is named NGTS-1.
The star itself belongs to the class of red dwarfs, its diameter is from 40 to 70 solar, and its mass is about 0.6 solar. Red dwarfs are much smaller than stars like our Sun, and they shine much fainter. Their spectral class is M, and the nearest star to us, Proxima Centauri, belongs to this class.
What is remarkable about the new planet?
The planet NGTS-1b is 0.8 Jupiter in mass and 1.33 times the size of a gas giant from the Solar System. The system of a red dwarf and a hot Jupiter is all the more strange because the planet orbits the star very close — just 3% of the space between the Sun and the Earth. This is the third time a giant planet has been discovered near a red dwarf, despite the fact that the previous two planets were much smaller and lighter.
NGTS-1b belongs to the so — called hot Jupiters-planets with a mass of about 1.9·10.27 kg, but located close to their star. There are a lot of such planets found, as they significantly affect the parent star, and by this effect they can be tracked. This is how NGTS-1b was discovered: scientists used the transit method, detecting changes in the star’s luminosity during the planet’s passage through the star’s disk. Because part of the disk was obscured by the planet, the researchers were able to register changes in the spectrum. For this method, NGTS-1b fits perfectly — its period of revolution around the star takes only 2.6 earth days.
The main reason for the attention to this discovery is that hot Jupiters have not been found in red dwarfs before. It is believed that red dwarfs do not have enough protoplanetary matter for gas giants, and only small rocky planets, like Mars, orbit them.
In order to correct the existing theories, we need more facts about the observation of giant planets near M-class stars.