Astronomers have discovered two exoplanets similar to Earth and potentially habitable in our cosmic vicinity. They also discovered a mysterious “cold Neptune”, with record temperatures.
The two potentially habitable worlds revolve around red dwarf stars GJ229A and GJ180, which are respectively around 19 light years and 39 light years from Earth. It may seem extreme as a distance, but on the scale of the universe, it is not the case, since the famous disc of our galaxy, the Milky Way, is about 100,000 light years across (and that the closest neighbor star to the sun, Proxima Centauri, is about 4.2 light years away from Earth).
Red dwarfs, which make up around 70% of the stellar population of the Milky Way, are significantly smaller and darker than the sun (which is a yellow dwarf). Thus, the ” habitable areas “Of these stars (the range of orbital distances where liquid water could be stable on the surface of a planet) are much closer than they are in our solar system, for example.
Artist’s impression of the new exoplanet GJ180d: a real “super-Earth”. This is the closest temperate super-Earth to us. In addition, this planet does not have a tidal lock on its star, which makes it more conducive to the reception of life. Credits: Robin Dienel / Carnegie Institution for Science
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Planets in the habitable zone of red dwarfs tend to be locked by the tide, always showing the same face to their star (just like the Moon shows us only one and the same face, constantly). And this locking of the tides is not a good thing for the habitability of a planet, because the phenomenon can cause extremely hot days as well as freezing nights (although a thick atmosphere can distribute the heat on the scale overall and somewhat mitigate the extreme temperatures).
Discover and study potentially habitable Super-Earths
But, according to members of the discovery team, the new exoplanets found around GJ180 and GJ229A (known respectively as GJ180 d and GJ229A c) orbit far enough to avoid blocking the tides. And because of this, the exoplanet GJ180 d breaks a world record: ” The exoplanet GJ180 d is the closest temperate super-Earth which is not locked to its star, which increases its chances of being able to harbor and maintain life Said team leader Fabo Feng of the Carnegie Institution for Science in Washington.
Indeed, the exoplanet GJ180 d is a true super-Earth, a world slightly larger than ours: its mass is about 7.5 times that of Earth. Note that GJ229A is also a super-Earth, with a mass of about 7.9 Earths. Scientists have also reported that GJ180 d orbits every 106 Earth days and GJ229A c orbits every 122 Earth days.
Artist’s impression showing the surface of planet AJ229A c, a temperate super-Earth. Credits: Robin Dienel / Carnegie Institution for Science
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The exoplanet GJ229A c resides in a binary system composed of a red dwarf and a brown dwarf (GJ229B). Note that brown dwarfs are substellar objects whose mass is insufficient for them to be considered stars, but it is greater than that of a giant planet.
As the name GJ180 suggests, it is not the only known world in its system: in fact, astronomers had already discovered two other planets orbiting the red dwarf, namely GJ180 b and GJ180 c.
Map exoplanets orbiting neighboring stars
At present, astronomers do not yet have much information about the two recently discovered super-Earths, but that may soon change. Indeed, the relative proximity of these planets to our own solar system makes them good targets for study by powerful future instruments, such as NASA’s James Webb Space Telescope, which is expected to launch next year.
” Our discovery adds to the list of exoplanets that can potentially be directly imaged by the next generation of telescopes. Ultimately, we strive to determine whether the planets orbiting neighboring stars harbor or can harbor life. Said Feng.
” We want to map all the planets orbiting the nearest stars, our own solar system, especially those that are potentially habitable Added study co-author Jeff Crane, also of the Carnegie Institution.
Discovery of an extremely cold “Neptune type” planet
As for the recently discovered “cold Neptune”, known as GJ433 d, it doesn’t seem like a good candidate for shelter because of its extremely cold temperatures, but it remains interesting for other reasons.
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The planet, which is at least 4.9 times more massive than Earth, orbits a dark red dwarf, some 29.5 light years from Earth. ” GJ433 d is the closest, largest and coldest Neptune type planet ever detected Said Feng. Note that, for researchers, this planet is also a good candidate for a follow-up study, including on direct imagery.
We will still hear a lot about exoplanets in the future!
The researchers made these new discoveries after re-analyzing data collected by the UVES (Ultraviolet and Visual Echelle Spectrograph) instrument from the European Southern Observatory (ESO), during an investigation into 33 close red dwarfs, dating from 2000 to 2007. These were radial velocity measurements (ie observations that can reveal a stellar movement). The team then completed the UVES data with measurements made by three other instruments: Carnegie’s Planet Finder (PFS) spectrograph, at the Las Campanas observatory in Chile, High Accuracy Radial velocity Planet Searcher (HARPS). ) from ESO, at the Silla Observatory, in Chile, and the HIRES (High Resolution Echelle Spectrometer) from the Keck Observatory, in Hawaii.
The researchers’ work has resulted in a total of five new exoplanets discovered, as well as eight other potential candidates who are currently unconfirmed.
Artist’s impression of the exoplanet Proxima b, a probably telluric exoplanet, with a minimum mass of 1.3 Earth mass and orbiting the habitable zobe of the red dwarf star Proxima Centauri. By bringing together conditions similar to those of primitive Earth, the exoplanet could, and still could, harbor life. Credits: ESO
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Since the launch of the NASA Kepler space telescope in 2009 (whose purpose was specifically to detect existing exoplanets in a region of the Milky Way, through the use of the “transit method” – note that this since 2018), astronomers have confirmed the existence of more than 4,100 exoplanets, 70% of which have been identified using the Kepler space telescope.
It is certain that there are still many other exoplanets to discover in our galaxy, so we have not finished hearing about these worlds similar to Earth!
Sources: The Astrophysical Journal Supplement Series, Carnegie Science
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