Confirmation of Earth-like planet in orbit around Proxima Centauri's Habitable Zone

[EdZ]

ESO Press release

This is really incredible news. While the planet is not likely to be particularly hospitable due to the likelihood of tidal locking and the proximity to Proxima Centauri bathing it in radiation, it is still not only one of the most Earth-like exoplanets discovered thus far, but absolutely the closest exoplanet to us discovered (and will remain so barring discovery of any Rogue Planets with in 4ly).
It's absolutely amazing that not only does our closest neighbour star have a planet, that it is also so similar to ours!

 

[BirdofPrey]

Calling that a habitable zone is pushing it.

Still, finding anything that small in another solar system is eventful, and so is finding something in the next star system over.

 

[EdZ]

The Habitable Zone is mostly defined by temperature around/above the triple-point of water and below the boiling point. Proxima Centauri b's equilibrium temperature is 234K (compared to Earth's 255K), so depending on atmosphere (Proxima Centauri b is at least 1.3x Earth mass, so may well be able to sustain a denser atmosphere) and orbital characteristics (likely tidally locked) there could well be regions where liquid water can persist for long periods on the surface, if not planet-wide.
Radiation is another matter entirely. Proxima Centauri can at flare peak emit roughly the same energy in the X-ray band as the Sun, so being much closer the star-facing surface of Proxima Centauri b is often going to be a harsh radiation environment. That does not preclude life subsurface or on the far side, or life that is more resistant to ionising radiation.

the Habitable Zone is not necessarily habitable for squishy humans.

 

[BirdofPrey]

Oh I know what the habitable region is; I just think it's a silly thing to be bringing up every single time since the "habitable" zones of many stars still aren't conducive to life as we know it.

 

[EdZ]

With the range of extremophiles discovered on Earth alone, the only consistance factor we have observed life to requires is that liquid water be possible in some phase for some portion of the lifecycle. Boiling acid lakes, frozen arid deserts, reactor cores, deep underground, deep subsea volcanoes, the exposed outside of spacecraft (surviving, if not evolving there), etc, all sustaining life.

The Habitable Zone is the zone limited to chemistries for life that we have already observed. If we posit other chemistries being possible, that zone only widens.

 

[BirdofPrey]

I wasn't going to bring those up, but, in my mind, they make the concept of a habitable zone even more dubious.

Anyways back on topic, I do hope to see more smaller rocks discovered, though I doubt any will be explored in my lifetime. I'm sure we'll see faster spacecraft, but even at high fractions of C, Proxima centauri you're still looking at mission times longer than New Horizons, but requiring a vastly more powerful antenna and on-the-fly troubleshooting won't be viable.

 

[iFreilicht]

I read an article about this where the astronomer the journalist asked called it "temperate zone", which seems like a much better term in my eyes.

 

[EdZ]

Anyways back on topic, I do hope to see more smaller rocks discovered, though I doubt any will be explored in my lifetime. I'm sure we'll see faster spacecraft, but even at high fractions of C, Proxima centauri you're still looking at mission times longer than New Horizons, but requiring a vastly more powerful antenna and on-the-fly troubleshooting won't be viable.

This discovery couldn't have been timed better to boost to interest in Breakthrough Starshot and similar initiatives. As a 'space race' program it, like Apollo, has plenty of side-benefits to the research beyond launching probes: ground-to-orbit power beaming for high-power satellites (e.g. high-thrust electric propulsion for orbit/deorbit/plane change), power buffering (useful for renewable energy integration into existing grids), further integration of multiple electromechanical and electronic systems into monolithic units (micromanufacturing applications pretty much everywhere), etc.

 

[EdZ]

Pale Red Dot have a fascinating article on Proxima b's potential habitability, based on this paper.