Potentially habitable exoplanet candidate spotted around Alpha Centauri A in Earth's backyard

[Judi Lynn]

By Mike Wall 3 hours ago

Alpha Centauri A may have its own habitable-zone planet.

The nearest solar system to our own may actually host two potentially life-supporting planets, a new study reports.

In 2016, scientists discovered a roughly Earth-size world circling Proxima Centauri, part of the three-star Alpha Centauri system, which lies about 4.37 light-years from Earth. The planet, known as Proxima b, orbits in the "habitable zone," the range of distances from a star at which liquid water could exist on a world's surface. (A second planet, Proxima c, was later discovered circling the star as well, but it orbits farther away, beyond the habitable zone's outer limits.)

There's considerable debate about the true habitability of Proxima b, however, given that its parent star is a red dwarf. These stars, the most common in the Milky Way, are small and dim, so their habitable zones lie very close in — so close, in fact, that planets residing there tend to be tidally locked, always showing the same face to their host stars, just as the moon always shows Earth its near side. In addition, red dwarfs are prolific flarers, especially when they're young, so it's unclear if their habitable-zone worlds can hold onto their atmospheres for long.

The other two stars in the Alpha Centauri trio, however, are sunlike — a pair called Alpha Centauri A and B, which together make up a binary orbiting the same center of mass. And Alpha Centauri A may have its own habitable-zone planet, according to the new research, which was published online today (Feb. 10) in the journal Nature Communications.

More:
https://www.space.com/exoplanet-candidate-spotted-alpha-centauri-a?utm_source=notification

[PoindexterOglethorpe]

1. Fascinating.

I just had a conversation with My Son The Astronomer about exoplanet atmospheres and what counts as a biosignature. Apparently, they are looking at NO2 (nitrogen dioxide) as a possible biosignature. Elevated amounts of carbon aren't terribly useful, as lots of things contribute to that.

I also learned from him that the total amount of carbon on our planet is pretty much fixed.

I really, really appreciate all your science postings.

[Judi Lynn]

2. Astronomers' hopes raised by glimpse of possible new planet

Bright speck in space near Alpha Centauri A may be evidence of asteroids or dust – or a technical glitch

Ian Sample Science editor
@iansample
Wed 10 Feb 2021 05.00 EST

Astronomers have glimpsed what may be a previously unknown planet circling one of the closest stars to Earth.
Researchers spotted the bright dot near Alpha Centauri A, one of a pair of stars that swing around each other so tightly they appear as one in the southern constellation of Centaurus. The stars form what is called a binary system 4.37 light years away, a mere stone’s throw in cosmic terms.

So tentative is the sighting that scientists are referring to it only as a “planet candidate”, aware that the bright speck in the darkness of space may be evidence of alien asteroids, streaks of dust, or more prosaically, an unforeseen glitch in their equipment.

“We detected something,” said Pete Klupar, the chief engineer of the Breakthrough Initiatives, which are a raft of space projects funded by Yuri Milner, an entrepreneur based in Silicon Valley. “It could be an artefact in the machine or it could be a planet, or it could be asteroids or dust.”

The international team observed the star as part of the “New Earths in the Alpha Centauri Region” (Near) experiment backed by Breakthrough Watch, an effort to find and study Earth-sized rocky planets around Alpha Centauri and other nearby stars.

More:
https://www.theguardian.com/science/2021/feb/10/astronomers-hopes-raised-by-glimpse-of-possible-new-planet-alpha-centauri