Astronomers have discovered an Earth-like planet around Proxima Centauri, the closest star to the sun.
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On Wednesday, a team of astronomers announced they had discovered a planet orbiting Proxima Centauri – and that the planet is rocky, has a mass similar to Earth’s and sits in the “goldilocks” zone where liquid water could exist on its surface.
From this data the scientists were able to infer the presence of a planet around 1.3 times more massive than the Earth orbiting at a distance of 7.5 million kilometres.
This discovery may persuade them to change their focus to the closer and considerably more interesting target of Proxima Centauri and its orbiting planet – or possibly even planets. Courtesy of ESO/G. Coleman. This 11-day cycle represents the exoplanet’s short orbit around its star.
For example, despite the temperate orbit of Proxima b every 11 days, the conditions on the surface may be strongly affected by the ultraviolet and X-ray flares from the star, which are far more intense than the Earth experiences from the Sun.
So what’s Proxima b like?
Scientists hope to be able to explore the planet more to try and find life.
A bit of backstory: in 1961 radio astronomer Frank Drake showed some very speculative math to another group of scientists about how many intelligent civilizations should be hanging around in the Milky Way. Because the star is so dim, temperatures on the planet would be mild enough that any water – if it’s there – would be liquid. Kepler, for instance measures the tiny decreases of light that happen when a planet goes in front of its star.
After over a week of silence, the European Southern Observatory (ESO) has confirmed “clear evidence” of a rocky planet capable of supporting liquid water in our neighbouring star system, Alpha Centauri. But one important factor is whether or not it has an atmosphere, which scientists don’t yet know. The Breakthrough Starshot mission, headed by entrepreneur Yuri Milner and physicist Stephen Hawking, aims to travel to Proxima Centauri (and its two sister stars, Alpha Centauri A and B) within a generation. In math, unity means one. And it receives more radiation from the star than Earth does from the Sun. It’s far closer than any previously discovered “exoplanet”.
The planet has some features that may lower likelihood of it actually supporting life. “I am 65”, he told VOA, “but I expect to still be alive when it happens”.
If there are lifeforms on Proxima b – even simple microbes – they may find the going rather tough, however. According to Paul Butler from the Carnegie Institute “the discovery of Proxima takes us from this vague fuzzy statistical abstraction, where we think potentially habitable planets are common, and makes the case concrete”.
The research was part of the Pale Red Dot campaign, a program that searches for exoplanets around Proxima Centuari while connecting science to the public.
This image of the sky around the bright star Alpha Centauri AB also shows the much fainter red dwarf star, Proxima Centauri.
The global team of astronomers that announced the discovery did not actually see the planet but deduced its existence indirectly, by using telescopes to spot and precisely calculate the gravitational pull on the star by a possible orbiting body – a tried-and-true method of planet-hunting.
The Pale Red Dot campaign data comes from the European Southern Observatory (ESO) 3.6-meter telescope in Chile and other telescopes around the world.
While observing Proxima Centuari, the researchers noted that on a periodic basis, the star’s light spectrum shifted toward red-or longer wavelengths-and then toward blue, or shorter wavelengths.
Pale Red Dot’s measurements were made each night for around three months at the beginning of 2016.
This kind of backlit observation could confirm not just the existence of an atmosphere but reveal perhaps something of its chemical properties. For Butler, “This is the culmination of 30 years of work”. In these wonderful ESO videos depicting such a voyage, an artist’s impression of Proxima b is rendered, creating what you might see during humanity’s first flyby of the alien world.
“We are all convinced that this is a planet”, Endl said, “especially because there’s such a long timeline of data”. Of course, to do that we would need to get a spacecraft moving really fast, about 10 percent of the speed of light.
This infographic compares the orbit of Proxima b with the same region of our Solar System.
That’s a lot of ‘ifs’.
“That cinches it”, Butler said.
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“The key question of our initiative was whether there were potentially life-bearing planets orbiting these stars”.
