Astronomie - Super-Erden sind möglicherweise tote Welten


In the last 20 years the search for Earth-like planets around other stars has accelerated, with the launch of missions like the Kepler space telescope. Using these and observatories on the ground, astronomers have found numerous worlds that at first sight have similarities with the Earth. A few of these are even in the ‘habitable zone’ where the temperature is just right for water to be in liquid form and so are prime targets in the search for life elsewhere in the universe.
Now a team of scientists have looked at how these worlds form and suggest that many of them may be a lot less clement than was thought. They find that planets that form from less massive cores can become benign habitats for life, whereas the larger objects instead end up as ‘mini-Neptunes’ with thick atmospheres and probably stay sterile. The researchers, led by Dr. Helmut Lammer of the Space Research Institute (IWF) of the Austrian Academy of Sciences, publish their results in Monthly Notices of the Royal Astronomical Society.
Dr. Lammer and his team modelled the balance of capture and removal of hydrogen for planetary cores between 0.1 and 5 times the mass of the Earth, located in the habitable zone of a Sun-like star. In their model, they found that protoplanets with the same density of the Earth, but less than 0.5 times its mass will not capture much gas from the disk.
Depending on the disk and assuming that the young star is much brighter in ultraviolet light than the Sun is today, planetary cores with a similar mass to the Earth can capture but also lose their enveloping hydrogen. But the highest mass cores, similar to the ‘super Earths’ found around many stars, hold on to almost all of their hydrogen. These planets end up as ‘mini Neptunes’ with far thicker atmospheres than our home planet.
The study was carried out by researchers within the Austrian FWF Research Network “Pathways to Habitability”.
Quelle: Royal Astronomical Society
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