An extrasolar super-Earth planet circling a red dwarf lying about 40 light-years from the Sun could be the new title holder, the best place to search for signs of life outside the Solar System. An international team of astronomers has been able to observe it using a HARPS instrument at the ESO / La Silla Observatory and other telescopes around the world.
The planet is circulating in a habitable zone around a weak star with the catalog designation LHS 1140. It is a body larger and more massive than Earth, presumably preserving most of its atmosphere. In addition, the planet passes through observation from the Earth through the disc of its parent stars, making it one of the most promising targets for future research on planetary atmospheres. The results were published on April 20, 2017 in the scientific journal Nature.
The newly discovered extrasolar super-Earth planet is labeled LHS 1140b. It runs in a habitable zone around a weak red dwarf LHS 1140 that lies in the Earth’s sky in the constellation Cetus.
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Red dwarves are much smaller and much cooler than the sun. That is why the planet LHS 1140b receives only about half the amount of energy compared to Earth even though it circles around its star ten times closer than the Earth around the Sun.
The planet moves near the center of the habitable zone around its star, and from the Earth we observe its path practically from the side. Every 25 days, we can see the planet’s crossing over the star disk in which it shields some of its radiation.
„It’s the most exciting exoplanet I’ve seen in the last ten years,“ says Jason Dittmann, Harvard-Smithsonian Center for Astrophysics, Cambridge, USA. „That we could find a better target for one of the most challenging tasks of contemporary science – the search for the evidence of the existence of life outside Earth – we could not have hoped.“
„The current features of this red dwarf are particularly well suited – the LHS 1140 rotates more slowly and produces less energy with high energy than similar tiny stars,“ explains team member Nicola Astudillo-Defru (Geneva Observatory, Switzerland).
For the existence of life we know, the planet must have the atmosphere and the surface of the liquid water. It is known that when the red dwarf stars are young, they emit a considerable amount of radiation that can be devastating for the planet’s planetary atmosphere.
But the size of the planet, in this case, offers the possibility that the body could have a fully molten surface for millions of years. The glowing lava thus enriched the atmosphere of water vapor long after the mother’s star had calmed down into the relatively quiet, radiant phase and eventually flooded the planet with liquid water.
The object was found within the MEarth project, whose binoculars detected the first characteristic diminishes of the star’s brightness when the exoplanet crossed its disk. With the High Accuracy Radial Velocity Planet Searcher (HARPS), important follow-up observations have been made to confirm the presence of a super-Earth planet. HARPS also refined the period of circulating the body to allow it to derive its weight and density.
Astronomers estimate that the planet is at least 5 billion years old. They also deduced that its average is almost 18,000 kilometers – about 1.4 times larger than Earth. At 7 times the weight of Earth and much higher density, it is probably a stone exoplanet with a dense iron core.
This super-Earth could be, for the time being, the best candidate for future exploration and the detailed characteristics of the atmosphere, if any. A pair of European research team members, Xavier Delfosse and Xavier Bonfils (both CNRS and IPAG, Grenoble, France), adds:
„It could eventually prove that the LHS 1140 star system will be far more important than the Proxima b or TRAPPIST-1 from the perspective of future exploration of the exoplanet in the habitable zone. It was an extraordinary year of exoplanetary discoveries! “
Specifically, they will soon be followed by NASA / ESA Hubble Space Telescope observations to estimate how much high-energy radiation falls on the LHS 1140b to better assess the planet’s assumptions as to how to maintain Life.
Also in the future – as new devices such as ELT (ESO / Extremely Large Telescope) are available – it is likely that scientists will be able to conduct a detailed observation of the atmosphere of extrasolar planets and the LHS 1140b is an extremely suitable candidate for such research.