Proxima b: water of comets?

Earth twins could be watery thanks to the impact of exokomets

Does Proxima Centauri b have water on the surface of the nearby twin earth? Astronomers have now investigated this. © ESO / M. Grain knife, CC-by-sa 4.0
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Icy water suppliers: The four-year-old Earth Twin Proxima Centauri b could be rich in water. Because in orbit around his star there are enough comets that could have served him as a water supplier, as researchers have now determined. According to their calculations, impacts of these icy chunks over the last two million years could have caused up to 30 Earth oceans of water on the exoplanets.

The red dwarf Proxima Centauri is only four light-years away from us - and it has a planet in the habitable zone, as astronomers discovered in 2016. The roughly earth-sized and potentially life-friendly planet could not only be a worthwhile target for a first interstellar mission - it could also be an extraterrestrial life. However, this assumes that there is also liquid water on the earth twin.

Replenishment must come

But how likely is the presence of water on Proxima Centauri b? Although the temperatures on the earth twin are mild enough to allow this. But because its central star tends to frequent outbreaks of radiation, strong stellar winds could evaporate the existing water again and again and blow out into space.

But that means: In order to permanently preserve oceans and other waters on the planet, the water supply of the planet would have to be replenished again and again - for example, by the impacts of water-rich comets. In fact, images of the Proxima Centauri system show that the star is surrounded by several dust belts that could contain chunks up to 50 kilometers in size.

In the system of Proxima Centauri there are several dust belts - from them could come the ice-rich comets. © ESO / M. Grain knife, CC-by-sa 4.0

Comets from the dust belts

Whether these dust belts could serve the earth twin Proxima b as a water supplier has now been determined by Richard Schwarz from the University of Vienna and his colleagues. For their study, they modeled the system in a physical computer model and investigated whether and how comets from the dustballs could be directed to the planet, how often they hit, and how much Water would bring that. display

The result: Both the influence of gravity of the adjacent Alpha Centauri double star, as well as the existence of a possible second planet around Proxima Centauri could again and again throw out ice-rich chunks from the G rteln. These race through the system as comets and also cross the path of the earth's twin inclusions of such icy chunks would therefore probably be, the astronomers said.

30 Earth oceans full of water

This means that throughout its long history, the Earth twin Proxima b could have been getting water through impacts of ice-rich comets. "Our simulations indicate that water transport from a comet-rich area near the planet is most effective, " says Schwarz. Above all, the dust belts, which surround the star at a distance of one to four astronomical units, would be an obvious source of comets.

How much water the planet gets Proxima Centauri b by such Einschl ge, the researchers have also determined. "We were able to show that comet impacts on Proxima Centauri over a period of two million years can provide a mass of up to 30 earth oocytes in water, " says Schwarz. If the simulations also include extremely close approaches and crossings, the comets could bring much more water to the planet.

Whether or not our nearest neighbor is actually a "second earth" with oceans of full-bodied water, however, future observations have yet to be substantiated. However, the models of Schwarz and his team at least show a way in which the earth's twin could have gotten enough water. (Monthly Notices of the Royal Astronomical Society, 2018; doi: 10.1093 / mnras / sty2064)

(University of Vienna, 19.11.2018 - NPO)