Source: Is there life on Proxima b, the planet next door?
It’s now perfectly respectable to talk about interstellar travel, says Cornell astronomer Lisa Kaltenegger. She’s coauthor of an unpublished paper speculating about how life could survive on a high-radiation planet, quoted by Maddie Stone at Gizmodo.
We’ll get to that hypothesis in a moment. The occasion for this optimism about interstellar travel is, as you probably know, the announcement that a planet is orbiting our closest star neighbor, Proxima Centauri.
One you delve into the details, though, the optimism may not seem terribly realistic. Even though Proxima Centauri is our Solar System’s closest neighbor and “only” 4.2 light-years away, our best current rockets would take 75,000 years to get there, the astronomer and veteran searcher for extraterrestrial intelligence Seth Shostak says at HuffPo.
But so what, astronomers declare. “We may not go there any time soon, but it will motivate us (and our funding agencies!) to design and build instruments to image and characterize this planet,” says Franck Marchis confidently at Cosmic Diary.
David Appell, of Quark Soup, says the first order of business should be a name change for the planet . “For now it’s just ‘Proxima b,’ which needs improvement; hopefully those who discovered it will get to name it. (Please don’t use ‘Earth 2,’ ‘Neoearth,’ or anything of the sort.)” He doesn’t care for “Vulcan” either.
Well, let’s not be mean-spirited and rain on the jubilant parade. Finding the planet Proxima b is undoubtedly a yuuuge deal, fully worthy of some dancing in the streets. Bad astronomer Phil Plait proclaims, “Did I mention wow? Because wow.”
A DIM BULB POSSESSES A PLANET WITH POSSIBLE WATER AND POSSIBLE LIFE
Shostak calls the planet’s sun, Proxima Centauri, “a dim bulb, a red dwarf that’s only one-seventh the Sun’s diameter.” It belongs to the abundant star class known as M dwarfs, which comprise 80% of the stars in our Galaxy, the Milky Way. Deborah Byrd explains Proxima Centauri basics at EarthSky.
But Proxima b is close enough to its sun so that there still might be liquid water, even oceans. And, therefore, the possibility of life of a kind familiar to us.
Proxima b is semi-sorta Earth size, minimum 1.3 Earth’s mass, and probably rocky like Earth. But in almost every other way, Proxima b cannot reasonably be called Earthlike. For example, the planet’s year is only a little more than 11 Earth days long.
Proxima b gets about 65% of the radiation we get here on Earth. Because it is much closer to its dimmer sun than we are to our much hotter one, that’s adequate to keep it warm enough for liquid water and therefore possibly life-as-we-know-it. That’s assuming it also has an atmosphere to hold in the heat and the water, which is entirely unknown at the moment, and in some ways not terribly likely. Otherwise, -40 degrees Celsius. No liquid water.
Also, Proxima Centauri may be a (relatively) cool star, but periodically it drenches Proxima b in potentially deadly flares of radiation, X-ray blasts more than 400 times what we get on Earth, and probably a lot of damaging UV radiation too.
But ever-creative scientists have thought of ways around that discouraging news. At No Place Like Home, Nadia Drake describes the new proposal I mentioned at the beginning: biofluorescence.
Drawing on a hint from some corals on Earth, the Cornell astronomers propose that Proxima b life might evolve to do what these corals do: make proteins that can can convert damaging radiation into safer longer wavelengths. Other Earth species have also evolved this capacity.
In corals, this converted light glows red, green, and orange. If such creatures existed on Proxima b, they might fluoresce during flares strongly enough to be detectable on Earth with future telescopes.
Earth organisms have also evolved other protections against damaging radiation, including living deep underground or in the ocean. If something like that happened on Proxima b, though, these buried lifeforms wouldn’t be detectable here.
Here’s another discouraging fact about the likelihood of life on Proxima b. Eric Berger explains at Ars Technica that the planet could be tidally locked to its star. That would mean it’s always sunny on one side of the planet, but the other is a perpetually dark side.
Some scientists are, however, determined to look on the bright side of a half-lit planet. Eric Betz speculates at The Crux that even if the planet does have a scorched side and a frozen side, there’s still a chance for Earthlike conditions in a strip between the light side and the dark side.
That narrow ribbon of Proxima b would be bathed in permanent twilight, according to Penn State astronomer Paul Robertson. Conditions would be like Alaska’s midsummer sky, sunlight all night as well as all day. Robertson told Berger, “That would be the only place that it would be temperate enough to stand there.”
HOW TO LEARN MORE ABOUT PROXIMA B: GO THERE
There are three ways to learn more about Proxima b, according to Ethan Siegel at Starts with a Bang. With ground-based telescopes. Or space-based telescopes.
Or just go there.
Believe it or not, there is a plan to do that, and it involves a journey of only a couple decades with no human passengers to slow things down. You may have heard about Breakthrough Starshot, announced in April, a collaboration between billionaire Yuri Milner and name-brand physicist Stephen Hawking.
The Starshot is nothing if not, um, ambitious. They propose launching a vast fleet of “nanocraft” the size of postage stamps. Each would contain a chip loaded with cameras, sensors, and communications equipment, plus a 10-foot “lightsail.”
The sails would be propelled initially by an enormous array of Earth-based lasers. Within minutes the nanocraft would achieve 20% of light speed, which would get them to the Alpha Centauri system within a (human) generation. Whereupon they would beam their findings back to Earth. More at Becky Ferreira’s post at Motherboard and the Breakthrough web site.
IF A TREE FALLS IN A PROXIMA B FOREST, WILL IT MAKE A SOUND?
The announcement that Proxima b is real came after years of suggestive observations by many scientists and was preceded recently by excited rumors.
But Proxima b was a quick payoff for the European Southern Observatory’s Pale Red Dot project, announced only in January. Using a telescope based in Chile, the project’s aim was to study Proxima Centauri for an Earthy kind of planet because previous data had been hinting that something was there. The Nature paper is paywalled, of course. But Nature has posted a words-of-one-syllable video at YouTube. It’s accompanied by–you’ll love this–a correction.
All of the data about Proxima b so far has emerged from indirect observations, for example of the star’s wobble. But direct imaging might be possible within a decade because of the European Extremely Large Telescope under construction in Chile. It’s expected to be open for business in 2024, according to Sean Raymond, part of the team that discovered the first Earth-size planet, Kepler-186f, writing at On Matter.
Shostak, a veteran of the search for extraterrestrial intelligence and senior astronomer at the SETI Institute, argues that we should use big antennas to study Proxima b. Don’t get too hopeful, though, because they would only yield data if the planet is already home to a civilization with enough technical smarts to have invented radio.
A similar past SETI Institute project in Australia aimed at Proxima Centauri detected no microwave radiation. “If there are aliens hanging out on this world, they were not broadcasting in our direction,” he says. But is he discouraged? Nah. “We should try again.”
In his Nature News and Views commentary (paywall), astronomer Artie P. Hatzes notes that M dwarfs are long-lived. “Proxima Centauri will exist for several hundreds or thousands of times longer than the Sun. Any life on the planet could still be evolving long after our Sun has died.”
Hmmm. If a tree falls in a forest on Proxima b eons after our Sun is extinguished and we are not around to hear it, will it make a sound? If H. sap is gone, how can we care?
