Our Earth could ultimately survive the predicted death of the Sun
Illustration of an Earth-like planet facing its sun in the process of becoming a red giant. © Generated on Bing Creator by Brice Haziza
In the midst of bad news about the state of our beautiful planet, this one would almost bring a smile back. Indeed, the Earth may not be swallowed up by the Sun when it becomes a red giant star, approximately a hundred times larger than its current diameter!
We must then imagine a sky entirely filled with an immense incandescent, blood-colored ball, a vision of horror that is nevertheless astrophysically accurate. But all is not lost: astronomers have once again discovered a rocky planet orbiting the ultimate stage of solar-type stars, namely a white dwarf.
The stages of evolution of a star like the Sun. © Wikipedia Commons
The stars that have become white dwarfs are only the diameter of the Earth. The most massive ones are even smaller because of the gravity which compresses them. The one in the study would be approximately the size of Procyon B. © C.Tombry
We wrote above “almost a smile”because let's not kid ourselves, all life will then have disappeared from our beautiful blue planet. Let's see all this.
A star like the Sun consumes its hydrogen by transforming it into helium, which will ultimately cause it to swell prodigiously because the temperature in its core has become more than 10 times hotter than currently (around 200 million degrees). From then on, the volume of our star, under the action of the thermal pressurewill increase and the star will transform into a red giant.
Its surface temperature, then dropping to around 3000°C, will thus match that of our planet. That said, all life here will be gone long before then, as the solar luminosity flux will gradually increase over the next 200 million to 1 billion years, until it evaporates our oceans, eradicating every living thing (unless 'Humanity hasn't done worse long before).
4,000 light years away, an Earth-like planet orbits a dead star
Let's come to this discovery made initially by a South Korean network, then from the Keck observatory on Mauna Kea in Hawaii, thanks to a gravitational microlens caused by the white dwarf star with such powerful gravity. The light amplification was by a factor of 1000. The system discovered thanks to this event is threefold: a white dwarf, a brown dwarf (a sort of failed star, more massive than a gaseous planet) and a rocky planet comparable to the Earth.
Series of images from different dates where we see in b) the gravitational microlensing effect which allowed the discovery of the triple system. © OGLE, CFHT, Keck Observatory
The Earth will then move away from its dead sun
This rocky exoplanet located 4,000 light years away from us is approximately 150 to 300 million kilometers from its dead star, approximately the distance Mars is from the Sun. But by becoming a white dwarf, the star lost about half of its original mass and the orbit of the planets thus widened. It was therefore much closer initially and was not destroyed during the red giant phase, which remains surprising.
A window into the future
This type of discovery is very fascinating, because it sheds light on the future of the Solar System and advances our knowledge of what we could call “the plurality of worlds” (Fontenelle, 1686). Was this surviving rocky planet in fact a Neptune-type planet that had its atmosphere blown away by the red giant? In 5 billion years, subjected to the heat of an enormous sun, will the icy worlds of Europe and Enceladus melt, revealing liquid oceans on the surface, favorable to microbial life?
