Astronomers Have Found Two Super-Earths In A Very Close Red Dwarf
Astronomers in the RedDots project have discovered two super-earths near the 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 itself has become one of the most interesting targets for the future James Webb space telescope. The article is available in the journal Science.
The goal of the RedDot's project is to search for earth-type exoplanets near low-mass stars (such as red dwarfs) using Doppler spectroscopy. The observations involve several ground-based instruments around the world, including the HARPS and UVES spectrograph mounted on telescopes at the La Silla and Paranal observatories.
In 2016, the project managed to find an exoplanet near the nearest star to the Sun — Proxima Centauri, and in 2017, astronomers reported the discovery of a super-earth near the star Barnard. In 2018, a second observation campaign began, targeting the red dwarfs Gliese 887, Gliese 1061, and YZ Kita, and in 2019, the discovery of three exoplanets in the single red dwarf Gliese 1061 was announced.
A group of astronomers led by Sandra Jeffers (Sandra Jeffers) from the University of Göttingen reports the discovery of two exoplanets in the cold M-dwarf Gliese 887 — the 12th most distant star system from the Sun, the distance to which is 10.74 light-years. The star has a mass of 0.48 Solar masses and a radius of 0.47 Solar radii. The scientists analyzed data from HARPS, PFS, HIRES, and UCLES spectrographs installed on ground-based telescopes, covering 20 years of observations of the star, as well as photometric data obtained by the TESS space telescope.
The orbital periods of GJ 887b and GJ 887c are 9.3 and 21.8 earth days, respectively, and their minimum masses are estimated at 4.2 and 7.6 Earth masses, which allows the newly discovered exoplanets to be classified as super-earths. The large semi-axes of their orbits have lengths of 0.068 and 0.12 astronomical units: for comparison, the length of the large semi-axis of the orbit of mercury is 0.38 astronomical units. The radiation flux from the star received by GJ 887b and GJ 887c is 7.95 and 2.56 times higher than the solar radiation flux received by Earth. both exoplanets are located near the inner boundary of the habitable zone, which means that water in liquid form can exist on their surface. The estimated surface temperature of Gliese 887c is about 70 degrees Celsius.
If we consider that the star is characterized by low variability of the radiation flux, then its system is one of the most interesting objects for astronomers to observe further, including with the help of the future James Webb space telescope, which will try to find the atmosphere of exoplanets.
One of the most unusual known red dwarf planetary systems is considered to be TRAPPIST-1, which includes seven exoplanets, and four of them are located in the habitable zone.