Astronomers in the framework of the project RedDots opened two super-earths have a cold red dwarf Gliese 887, which is just 10.7 light years from the Sun. Both exoplanets are in the habitable zone, and the system became one of the most interesting targets for a future space telescope “James Webb”. Article published in the journal Science.
The goal of the project RedDots — the search for earth-like exoplanets closest to the Sun low-mass stars (e.g. red dwarfs) using Doppler spectroscopy. The observations involved a number of ground-based instruments around the world, including the spectrographs HARPS and UVES, installed on the telescopes in the observatories of La Silla and Paranal.
In 2016, the project managed to find exoplanet the nearest star to the Sun — Proxima Centauri, and in 2017, the astronomers reported the discovery of corselli the star Barnard. In 2018, began the second observational campaign, the objectives of which are red dwarfs Gliese 887, Gliese 1061 and YZ whale, and in 2019, announced the opening of three exoplanets have a single red dwarf star Gliese 1061.
A team of astronomers led by Sandra Jeffers (Jeffers Sandra) of Gottingen University, reports the discovery of two exoplanets have a cold M-dwarf Gliese 887 — 12th of a distant star system from the Sun, the distance to which is a 10.74 light-years. The mass of the star is 0.48 solar masses, the radius is 0.47 radius of the Sun. The researchers analyzed data from the HARPS spectrograph, PFS, HIRES and UCLES, installed on ground-based telescopes, covering a 20-year period of observations of the star, and photometric data obtained with space telescope TESS.
Orbital periods GJ GJ 887b and 887c are, respectively, 9.3 and 21.8 to earth day, and their minimum weight is estimated at 4.2 and 7.6 of the mass of the Earth, which can be attributed to the newfound exoplanets to the supertall category. Semi-major axes of their orbits have lengths 0,068 and 0.12 astronomical units: for comparison, the length of the semimajor axis of the orbit of mercury, is 0.38 astronomical units. The radiation flux from the star, we get GJ GJ 887b and 887c, 7.95 and 2.56 times higher than the flux of solar radiation received by Earth, both planets are close to the inner boundary of the habitable zone, which means that the surface water can exist in liquid form. The estimated surface temperature of Gliese 887c is about 70 degrees Celsius.
When you consider that the star is characterized by a low variability of the radiation flux, then the system is for astronomers one of the most interesting objects for further observations, including those with a future space telescope “James Webb”, which tries to find exoplanets atmosphere.
One of the most unusual of the known planetary systems red dwarfs is considered a TRAPPIST-1, which includes seven exoplanets, four of them are in habitable zone.