A planet described as the ‘single most promising exoplanet discovered to date in terms of habitability’ and a ‘natural location where our civilization could aspire to move to’, has been found orbiting the closest star to our Sun.
This artist’s impression shows Proxima b orbiting Proxima Centauri, which at only 4.23 light-years is the closest star to our Solar System. The double star Alpha Centauri AB also appears in the image between the exoplanet and Proxima itself. Image credit: M. Kornmesser / ESO.
The discovery, made by a team led by Dr. Guillem Anglada-Escudé, from Queen Mary University of London, of a planet orbiting Proxima Centauri has been published in the journal Nature.
The rocky planet, named Proxima b, is slightly larger than Earth and sits within its star’s habitable zone, where liquid water could theoretically exist on the surface.
“Many exoplanets have been found and many more will be found, but searching for the closest potential Earth-analogue and succeeding has been the experience of a lifetime for all of us,” Dr. Anglada-Escudé said.
“The search for life on Proxima b comes next…”
This artist’s impression shows a view of the surface of Proxima b orbiting Proxima Centauri. Alpha Centauri AB also appears in the image to the upper-right of Proxima itself. Proxima b is a little more massive than the Earth and orbits in the habitable zone around its star, where the temperature is suitable for liquid water to exist on its surface. Image credit: M. Kornmesser / ESO.
The discovery was warmly welcomed by scientists involved in the Breakthrough Starshot project which earlier this year unveiled plans to send light-propelled nanocrafts 40 trillion km to the Alpha Centauri system, where Proxima Centauri and its orbiting planet reside.
On hearing the news Breakthrough Starshot’s chairman Professor Avi Loeb from Harvard University described Proxima b as “an obvious target for a flyby mission,” which could “take color images of the planet and infer whether it is green and harboring life, blue with water oceans on its surface, or just brown, dry rock.”
Prof. Loeb added that because the lifetime of the star is several trillion years, “a habitable rocky planet around Proxima would be the most natural location to where our civilization could aspire to move after the Sun will die, five billions years from now.”
Astronomer Royal Lord Martin Rees who sits on the project’s Advisory Board said: “it is excellent news to have strong evidence for a planet around such a nearby star, on which perhaps life could have emerged.”
This infographic compares the orbit of Proxima b with the same region of our Solar System. Proxima Centauri is smaller and cooler than the Sun and the planet orbits much closer to its star than Mercury. As a result it lies well within the habitable zone, where liquid water can exist on the planet’s surface. Image credit: M. Kornmesser / G. Coleman / ESO.
The discovery was made with the ESO 3.6-m telescope at La Silla in Chile (alongside other telescopes around the world), as part of the Pale Red Dot campaign to find a tail tell wobble of our second nearest star that could indicate the gravitational pull of an orbiting planet.
The wobble they discovered shows Proxima Centauri approaching the Earth at about 5 km per hour – normal human walking pace – and then receding at the same speed.
This regular pattern repeats every 11.2 days, and when compared against natural fluctuations in the star’s brightness indicated the presence of a planet slightly more massive than the Earth, orbiting its star at only 5% of the distance from our planet to the Sun.
Despite this close orbit, the fact that Proxima Centuri is far fainter than our own star keeps Proxima b in the crucial habitable zone.
Professor Ed Turner, from Princeton University, another member of the Breakthrough Starshot project advisory board, described the newly discovered planet as “the single most promising exoplanet discovered to date in terms of habitability.”
“That this planet is orbiting the nearest star to the Sun is an extraordinary and wonderful piece of good luck. It could hardly be more exciting from the perspectives of both astrobiology and interstellar flight,” he added.
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G. Anglada-Escudé et al. A terrestrial planet candidate in a temperate orbit around Proxima Centauri. Nature, published online August 25, 2016
