In five billion years, our sun will blow up into a red giant and then probably reach the orbit of Mars: Mercury, Venus and Earth will be swallowed up by it and burn up - at least according to current projections. However, a white dwarf located 4200 light years away suggests that Earth-like planets close to stars could possibly survive the red giant phase after all. This conclusion is suggested by the findings of a team led by Keming Zhang from the University of California, which were published in "Nature Astronomy".
The exoplanet has about 1.9 times the mass of our home planet and orbits its star at about twice the distance of the Earth from the Sun. It was discovered with the help of the microlensing effect. At a distance of around 26,100 light years on the same visual axis from Earth, a very large, bright star briefly lined up behind the white dwarf system. When the light from the more distant star crossed the white dwarf on its way, the path of the light was bent by the gravitational field, which led to a thousand-fold magnification effect. This allowed the Earth-like companion to significantly influence the magnification pattern, from which Zhang and co were able to draw detailed conclusions about the white dwarf's surroundings.
In addition to the Earth-like planet, they also discovered a brown dwarf with 30 times the mass of Jupiter, which also orbits the white dwarf. This dwarf still has about half the mass of our sun, which is why the working group assumes that the dwarf also had approximately the dimensions of our central star before it inflated. The orbit of the exo-Earth derived from the data also suggests that before the red giant stage, it orbited the star at a similar distance as the Earth currently orbits the sun.
As the star inflated, it then pushed the exoplanet into a more distant orbit. This could also happen to Earth in a few billion years: Current models therefore come to different conclusions about the fate of our planet. The expanding sun could swallow it up and destroy it - or push it into a more distant orbit. However, this only plays a minor role for life here: it will be destroyed much earlier because the sun's increasing radiation will vaporise our atmosphere and any surface water. This could be the case in a billion years at the latest.
