Planets don't need stars like the Sun: radioactivity will make them inhabited

Planets don't need stars like the Sun

If the Sun goes out, the Earth will survive. For this, there must be an increased radiation activity on Earth. Astronomers believed that for a planet on which life may be present, some conditions are important. The most important condition is that a star such as the Sun should not be too close, but not too far away. However, a new study challenges this condition. Scientists believe that the planet can hold water and other liquids on its surface if it is not heated by starlight, but by radioactive decay.

This discovery is relevant for many planets that are not associated with stars, because in this case, they can be open to life in any of its forms. The most important radioactive isotopes for this are uranium-238, thorium-232 and potassium-40. They are considered unstable and form energy when decayed. This is a small amount of energy, it makes up about one thirty-thousandth part of the energy that the sun gives.

Scientists believe that some planets, especially those that are born near the center of the Milky Way, may have enough isotopes. Isotopes on these planets can independently generate the necessary amount of heat. This heat will not allow the surface of the planet to turn into desert ice. Avi Loeb, an astrophysicist at Harvard University, believes that such a phenomenon can occur in outer space anywhere, in any galaxy, and a star such as the Sun is not important.

He and his fellow astrobiologist at the Florida Institute of Technology, Manasvi Lingam, studied three possible sources of heat to sustain life on the planet without starlight or solar radiation. This is the remainder of the heat from the formation of the planet, the radioactive decay of long-lived isotopes and the radioactive decay of short isotopes that have lived for hundreds of thousands of years. Then scientists created a computer model of the temperature of the planets, which have different masses and different amounts of radionuclides.

The model helped establish whether water, ammonia and ethane, these three liquid forms that exist in the solar system, can exist in the form of liquids. To maintain its liquid form, the warming of the planet will require thousand times more radioactive isotopes of both types than there are now on Earth. Other planets, the mass of which is close to the earth, have a hundred times more isotopes, and ethane remains liquid on their surface for millions of years.

On such planets, the radiation level will be hundreds of times higher than after the Chernobyl disaster. It is unlikely that cell life can survive such exposure. But many microbes on Earth can survive even in the most extreme situations, and they have a chance of exploring the planets. Whether the planet can have a sufficient supply of radionuclides is a moot point. If such planets exist, they are located near the center of the Milky Way, because heavy elements such as uranium and thorium are formed in collisions between neutron stars.

And such collisions are more likely to occur in the crowded center of the Galaxy. To discover such a planet would be a surprise since it would completely change the idea of the solar system. Tim Lichtenberg, a planetary scientist at the University of Oxford, believes it is difficult to say that this is impossible. But it could well be.