Potential Earth-like exoplanet turns out to be right at our figurative doorstep

A WORLD NEXT DOOR  Proxima Centauri casts a reddish glow over the surface of Proxima b (illustrated), the closest exoplanet to Earth, while two companion stars, Alpha Centauri A and B, appear as bright pinpricks of light.
ESO/M. Kornmesser
A WORLD NEXT DOOR Proxima Centauri casts a reddish glow over the surface of Proxima b (illustrated), the closest exoplanet to Earth, while two companion stars, Alpha Centauri A and B, appear as bright pinpricks of light.

Original news release was issued by the Scientific American, written by Lee Billings.

Ever since humanity journeyed for the first time into outer space, we’ve been fascinated to push the boundaries of interstellar travel. For decades, astronomers have been searching for a planet that would offer us habitable conditions or even indicate signs of life already existing there. So far either the nature of the planet and its surroundings or the remoteness makes any detailed research rather challenging. News reports that we found a similar planet to Earth are not uncommon. Only this time, Guillem Anglada-Escudé, an astronomer at Queen Mary University of London and his colleagues report signs of a potentially habitable exoplanet, that could be well within the reach of observing probes — given a certain plan by Breakthrough Starshot is carried out — in just 20 years after the launch.

Dubbed Proxima b, the planet orbits the closest neighboring star to our sun: Proxima Centauri — a dim red orb in the Alpha Centauri system about 4.2 light-years away. Despite very close proximity to its star — only 5 percent of the distance from Earth to the sun — its temperature is just right for liquid water to flow on its surface, so that makes it the closest known exoplanet where life might exist.

Its “sun”, Proxima Centauri, is a runt of a star. Temperatures at the surface run about 2,800 degrees Celsius cooler than our sun, giving the planet a feeble, ruddy glow. However, there is much uncertainty about the mass and atmosphere of Proxima b. The researchers only confirm that the planet is no lighter than 1.3 Earths. Their best bet to characterize its atmosphere relies on the planet to pass in front of Proxima Centauri, allowing starlight to filter through the planet’s atmosphere. If this occurs, NASA’s James Webb Space Telescopescheduled to launch in late 2018, should be able to further decipher it’s nature.

“A spacecraft equipped with a camera and various filters could take color images of the planet and infer whether it is green (harboring life as we know it), blue (with water oceans on its surface) or just brown (dry rock).” says Avi Loeb, Harvard University astrophysicist and chairman of Breakthrough’s advisory committee.

An eager and undoubtedly the fastest way to observe the exoplanet would be via sending probes. And Yuri Milner, a Russian entrepreneur funding the Breakthrough Starshot, wants to do just that. He announced to put $100 million toward developing technology that would send a fleet of nanocraft — robotic probes weighing just a few grams — toward Alpha Centauri, nudging them along with an Earth-based 100 gigawatt laser. Accelerating to roughly 20 percent the speed of light, the armada would arrive at Alpha Centauri about 20 years after launch. In comparison, the fastest spacecraft ever to leave Earth — the New Horizons mission to Pluto — would need roughly 90,000 years to complete the journey.

Proxima Centauri is also known for exuberant flames, which would buffet any orbiting planets with bursts of ultraviolet radiation and X-rays. Should Proxima b have any living organisms on its surface, the life might show in unusual ways. Scientists propose looking for biofluorescence, a glow from organisms triggered by ultraviolet light. Critters on Proxima b could have evolved biofluorescence as protection, transforming it into more palatable visible light — a flicker that might be detectable from an Earth-based telescope. Given the hypotheses, it is also speculated that life might have taken shelter underground or underwater.

eso1629c-1-1024x696
Source: ESO/M. Kornmesser/G. Coleman

At any rate, the discovery of the planet “could really usher new energy into the search for other nearby worlds,” says Margaret Turnbull, an astronomer with the SETI Institute and based in Madison, Wis. Most exoplanets are hundreds to thousands of light-years away. But little is known about the possible planet families huddled up to the stars nearest to us. “I’d love to see interstellar travel,” says Turnbull. “To really inspire that kind of effort, we need interesting destinations like this.”

Michal Madaras

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