They locate an Earth-sized planet wandering aimlessly through the universe

which planets float freelyDark, isolated celestial bodies that roam the universe without a star to protect them simply do not appear in the midst of cosmic nowhere. It is likely that they formed in the same way as other planets: in The inside of the disc is made of gas and dust surrounding the newborn star.

But unlike their planetary brethren, these worlds are violently expelled from their heavenly quarters.

Astronomers estimate that billions of planets have disappeared in the Milky Way. And now, scientists from NASA and Osaka University (Japan) have brought this up Estimates in billions. In two papers accepted for publication in The Astronomical Journal, the researchers concluded that the number of these planets is six times greater than the number of planets orbiting their own sun. The second rogue planet the size of Earth disclosed so far.

The existence of rogue worlds, orphaned by their star systems, has been known for a long time, but little has been studied. Previous results indicated that most of these planets were from our own planet the size of Jupiter, the largest planet in our solar system. However, this conclusion drew a lot of criticism. Even the scientists who announced it found it amazing.

To better study these drifting worlds, David Bennett, an astronomer at NASA’s Goddard Space Flight Center, and his team used Nine years of data From observations of microlensing at the Astrophysical Telescope at the Mount John Observatory at the University of Canterbury in New Zealand. Exoplanets have been detected indirectly by measuring how much their gravity warps and stretches light from distant stars behind them, an effect known as microlensing.

The largest image of the Milky Way ever taken without the use of professional telescopes. An image that completes 70% of the galaxy.

With the help of experimental models, the researchers calculated the mass dispersion of more than 3,500 cases of microlensing. (The data from one of these candidates was convincing enough for the team to claim it had discovered a new wandering Earth.) Based on this analysis they estimate that there 20 times more floating worlds Of the stars in the Milky Way, Earth-mass planets are 180 times more common than rogue Jupiters.

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According to Bennett, the conclusion that most wandering worlds are small makes more sense than the idea that they are the size of Jupiter. This is because it is believed that the planets become asteroids When two protoplanets collide with each other. The force of the collision is so strong that one of them is completely outside the budding star system.

But planets can only be expelled from their star systems by larger bodies. If most of these orphan stars are the size of Jupiter, many so-called super-Jupiters will orbit their host stars, but these are rare. On the other hand, these results indicate that planets with less mass are at risk of being ejected.

“So things are serious for the territory,” Bennett said.

He also pointed out the large number of planets that Floating freely in the Milky Way He suggests that planetary-sized objects colliding with each other during the formation process “may be more common than theorists might assume”.

“very common”

Przemyk Mroz, an astronomer at the University of Warsaw who was not involved in the work, said the group’s findings support previous indications of rogue worlds from observations made using the gravitational lensing optical experiment and the Korea Network of Space Telescopes. “We now have three independent studies and three independent pieces of evidence that low-mass floating planets are very common in the Milky Way,” he wrote in an email.

There is still some mystery as to whether or not these planets are They are really free Or they simply orbit wide enough that scientists can’t relate them to the host star. Mroz thinks the observed population probably includes A mixture of bothbut it would be difficult to deduce the relative number of each from microlensing measurements alone.

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Astronomers in the new studies eagerly await better data on freely orbiting planets captured using the Nancy Gress Roman Space Telescope, a NASA mission scheduled for launch in 2027. As well as data from the European Space Agency’s Euclid Telescope or Earth Telescope. in a good position. Observatories, scientists will be able to measure it dough more directlywithout relying too much on models.

Could any of these planets be habitable? Possibly, Bennett predicted, explaining that it would be dim without a host star, but not necessarily icy. Hydrogen in a planet’s atmosphere can act as a greenhouse, trapping heat from its interior, which sustains microbial life in deep-sea vents on Earth.

But for now, the search for life on these lonely worlds is a long way off. “Maybe a hundred years from now there will be a way to do it,” Bennett said. “But scientists are now looking for things we can actually do.”

The team did not look beyond the boundaries of the Milky Way. “But we expect other galaxies to be quite similar,” Bennett said, implying that these outcast galaxies could be scattered throughout the universe.

New York times. private

Translation: Elisa Carneli

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