Orbiting an M-type star (red dwarf) just inside the habitable zone, Gliese 887b and Gliese 887c are the two super-earths found in our solar neighborhood and whose discovery is detailed in studies published in the journal Science.
It could be even three super-earths orbiting one of the brightest red dwarf stars in the night sky. According to experts, GJ 887, which is about half the mass of our Sun, is only 11 light years away, making it one of the closest multi-planet systems to our solar system, offering us the opportunity to study exoplanet atmospheres.
A super-earth is an exoplanet more massive than Earth but less massive than Uranus or Neptune.
“We now know of thousands of super-Earth-mass or smaller planets, but most of those planets orbit distant, faint stars,” explains Chris Tinney from the University of NSW in Australia, and a co-author of the work. “Planets orbiting nearby stars are key to future telescope searches for both exoplanetary atmospheres, and eventually evidence of life.”
Yes indeed; Since the planets are on the ‘inner edge’ of the habitable zone, which is the region where liquid water can remain on the surface, they may be too hot to support life. However, the other world might be able to support liquid water.
How have they been discovered?
M-type stars are so faint that even the closest star to the Sun, Proxima Centauri, requires a powerful telescope to observe it. Gliese 887 (also known as Lacaille 9352) is the brightest red dwarf.
The new planets were found using a high-precision planet-finding instrument at the 3.6-meter telescope of the European Southern Observatory at La Silla in Chile using the radial velocity method ( Doppler oscillation ). Australian astronomers were working with the international RedDots team searching for terrestrial planets around red dwarf stars when they stumbled upon this discovery.
Called GJ 887b and GJ 887c, the planets could be rocky worlds like Earth, but it is very likely that they are blocked by the tide of their star, which means that one side will always face the star and in perpetual day, while that in the other it will always be night. An eternal darkness. Gliese 887b has an orbit of only 9.3 days and Gliese 887c of 22 days and is estimated to have an average temperature of 79ºC. Their masses are about 4.2 and 7.6 times those of Earth, respectively. If the third exoplanet exists, – at the moment there is evidence of its possible existence – Gliese887d, it is believed that it would have a 51-day orbit, which would make it slightly warmer than Earth.
For a star like the Sun, the habitable planets must be located far enough away that their orbits take a long time to complete (not a few days). If Gliese 887 were as active as our Sun, which it is not, it is likely that a strong stellar wind would sweep the atmospheres of the planets. This red dwarf has very few sunspots, unlike our star. This means that the newly discovered planets can retain their atmospheres, or have thicker atmospheres than Earth, and potentially host life, even though GJ887 receives more light than Earth. The other interesting feature the team discovered is that the brightness of Gliese 887 is almost constant. Thus, it will be relatively easy to detect the atmospheres of the super-earth system, making it a prime target for the James Webb Space Telescope, a successor to the Hubble telescope.
“These planets will provide the best possibilities for more detailed studies, including the search for life outside our solar system,” says Sandra Jeffers of the University of Göttingen and lead author of the study.
If future observations confirm the presence of the third planet in the habitable zone, it is clear that GJ 887 could become one of the most studied planetary systems in our solar neighborhood.
Referencia: S.V. Jeffers el al., A multiple planet system of super-Earths orbiting the brightest red dwarf star GJ 887.Science (2020). science.sciencemag.org/cgi/doi … 1126/science.aaz0795
Multiple, quiet, and close by. Science (2020). science.sciencemag.org/cgi/doi … 1126/science.abb0217
