How was the earth in the 1000s

Confirmation of existence of a "second earth" in our neighboring system

It really doesn't get any closer if you want to find Earth-like planets in other star systems. Proxima Centauri is the closest star to us and only 4.244 light years away from us. When evidence of the existence of a planet roughly the size of the Earth was found there in 2016, the euphoria among astronomers was therefore great.

According to the latest measurements, the calculated minimum size of the planet Proxima b is 1.17 earth masses, but it could also be a little higher. Its (hoped for) resemblance to earth is not only due to its dimensions, but also to the fact that it could offer living conditions. This similarity is of course only achieved in a roundabout way.

Because Proxima Centauri is a red dwarf, a faint and cool star. Its habitable zone - the area in which water can exist in liquid form - is therefore much closer to it than that around our sun. But the planet Proxima b also moves in such a narrow orbit around the star that it only takes 11.2 days to complete one orbit instead of a year. Two major differences between the two star systems balance each other out so well that both could actually have their respective earths.

More precise measurements confirm the impression

The potential friendliness of Proxima b has now been confirmed once again by a study in the specialist magazine "Astronomy & Astrophysics". It is based on measurements by the Espresso spectrograph ("Echelle Spectrograph for Rocky Exoplanet and Stable Spectroscopic Observations") at the Very Large Telescope of the European Southern Observatory in Chile. Compared to the first measurements with the older Harps spectrograph ("High Accuracy Radial Velocity Planet Searcher"), thanks to Espresso, it was possible to triple the measurement accuracy.

With the so-called radial velocity method, the movements of the star and planet around the common center of gravity can be measured and conclusions can be drawn about the properties of the planet. This led once more to the result that the surface temperature of Proxima b should make it possible for water to be in liquid form - and that would theoretically make life on the planet possible.

Big open questions

The mere possibility, of course, does not mean that there actually is life there. And if it did, it would have to struggle with difficulties that we were fortunately spared. Its narrow orbit suggests that Proxima b is in a bound rotation, i.e. that its star, like the moon of the earth, always faces the same side. It would be too hot on this side, but too cold in the dark hemisphere. Life should then probably only be possible in the twilight zone in between - or even underground.

The proximity to the star is even more problematic for another reason: If radiation bursts occur on Proxima Centauri, they hit the planet with full force. And even the normal, constantly "blowing" stellar wind could, according to earlier measurements, be up to 2,000 times stronger than the solar wind that hits the earth. If Proxima b ever developed an atmosphere, it may have long since been blown away.

The discussion about whether Proxima b could protect a hypothetical biosphere from its star has been surging back and forth among scientists for years. Christophe Lovis, head of data processing for the Espresso team, relies on new tools. They are specially built to detect the light emitted by Proxima b and could soon provide an answer. Incidentally, one of them will continue the work of Espresso in more ways than one and will be called Ristretto. (jdo, May 29, 2020)