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BERKELEY, California – The nearest exoplanet on Earth can have a neighbor.
Astronomers have detected a candidate planet surrounding the star Proxima Centauri, a pale red dwarf located just 4.2 light-years from our solar system. Proxima is already known for hosting a world, a planet the size of the Earth, called Proxima b.
So, the potential world of siblings is Proxima c. But "potential" is the key word.
Related: Proxima b: Discovery of the planet closest to the Earth in images
"This is just a candidate," said Mario Damasso of the University of Turin, Italy, during a presentation today (12 April) at the Breakthrough Talk conference at the University of California, Berkeley, which was also broadcast live. "It's very important to emphasize."
Damasso, presenter Fabio Del Sordo of the University of Crete and their colleagues analyzed the observations of Proxima Centauri made by the High precision radial velocity planet search instrument. HARPS, installed on a telescope at the La Silla observatory of the European Southern Observatory, in Chile, notices the tiny stellar movements induced by the gravitational tugs of planets in orbit. The data from the instrument contributed to the discovery of Proxima b (and many other extraterrestrial worlds).
The Proxima b circles are located in the Proxima Centauri habitable zone, this ideal range of distances where liquid water could exist on the surface of the world. It is unclear whether Proxima b could harbor a life similar to that of the Earth; For example, the exoplanet is probably tied to its star by the tides and perhaps therefore sports a hot day and an icy night. And flares from Proxima Centauri may havelong ago unleashed the atmosphere of the foreign world, say some scientists.
The debates on habitability will probably not participate in the confirmation of Proxima c, if that were to happen. The candidate world, which has a minimum mass about six times that of the Earth, revolves around 1.5 astronomical units (AU) of Proxima Centauri and is therefore probably very cold. Its equilibrium temperature hovers around minus 390 degrees Fahrenheit (minus 234 degrees Celsius), said Damasso and Del Sordo during their talk today.
(An AU is the average Earth-Sun distance – about 150 million kilometers, and Proxima Centauri is a dark and cold red dwarf, so 1.5 AU is well beyond the star's habitable zone.)
This large orbital distance made it difficult to detect Proxima c; the tug of the planet on the star is pretty weak after all.
Damasso and Del Sordo said that they were confident in the detection but pointed out that it was a preliminary step. For example, even though the outcome document has been submitted to a peer-reviewed publication, it has not yet been accepted.
The researchers said that the confirmation of the planet could come from additional observations of HARPS or similar instruments, or from measurements made by the European Gaia satellite of stellar mapping. Indeed, if Proxima is real, Gaia should spot the planet by the time the spacecraft's work is finished, Del Sordo said.
And if the planet exists, many exciting opportunities open up. For example, telescopes could soon take pictures of this alien extraterrestrial world.
"It's potentially a spectacular laboratory for direct imaging," Del Sordo said.
Stay tuned!
Mike Wall's book on the search for extraterrestrial life, "Over there"(Grand Central Publishing, 2018, illustrated by Karl Tate), is out now. Follow him on Twitter @michaeldwall. Follow us on twitter @Spacedotcom or Facebook.
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