Astronomers have discovered that the planet is only 87 years away and is exactly the same size as Earth, orbiting its star at a distance without heating or cooling.
Sounds good for Earth 2.0, doesn’t it? Not so fast. The exoplanet known as LP 791-18d was pulled so far from another planet in such a spiral that its interior is a hot mess that erupts from its surface like volcanoes.
Although not local, the findings could help astronomers understand how things work on planets like Earth.
“LP 791-18d is well-locked, which means that the same side is always facing its star,” says astronomer Björn Benneke of the University of Montreal in Canada.
“It’s possible that during the day it’s too hot for liquid water to exist on the surface. But the volcanic eruptions that we think are happening around the world could cause air circulation, which would cause the water to freeze at night.”
LP 791-18 is a small, red dwarf star that has 14 percent of the mass and 17 percent of the diameter of the Sun. In 2019, astronomers discovered two exoplanets; The largest planet called LP 791-18b, 1.46 times the size of Earth and an orbit of 0.94 days, and the smaller Neptune called LP 791-18c, which is thought to be about 6 times the size of Earth and the orbit of Earth. 4.99 days.
Because the star is one of the coolest known to host exoplanets, a team led by astronomer Merrin Peterson of the University of Montreal used the Spitzer Space Telescope to observe the star for 127 hours continuously. There, they saw cool arrows in the light of a transiting star that were not caused by LP 791-18b, or Lp 791-18c as they circled between us and the star.
This indicated the existence of a third, previously unknown world. Following observations from ground-based telescopes, the researchers confirmed the existence of LP 791-18d, an exoplanet that enters 1.03 times the length of the Earth and 0.9 the mass of the Earth, on a path of 2.753 days around the star.
It is much closer than Earth to the Sun, but LP 791-18 is very cold, meaning that the newly discovered exoplanet still resides in the interstellar region, the region of space far from the star that allows water to form. water surface. It is not too hot that the water boils, or too cold that it freezes.
However, that proximity creates another problem. An exoplanet’s orbit “locks” in time parallel to its path; in fact, the same side of the earth always faces the stars, just as one side of the Moon always faces the Earth. In the case of LP 791-18d, ‘tidal closure’ means that one side is hot during the day, the other at eternal night.
The team has taken 72 missions – 43 from LP 791-18d, and 29 missions from mini-Neptune LP 791-18c. This allowed them to measure something called a transit time shift, which occurs when the gravitational interactions between exoplanets cause small differences in the timing of their transits.
Then, the researchers were able to calculate the mass of the mini-Neptune with great accuracy, and realized that it was equal to 7.1 Earths. And they also learned that the two exoplanets pass so close to each other on their orbits that the mini-Neptune pulls the small planet into a clear orbit. This means that, as LP 791-18d moves closer and further away from the star, changes in gravity stretch and compress the planet, heating it from the inside.
This internal heat can be seen as a burst of fire – which can be seen as a thick atmosphere. Measuring it with an observatory like the James Webb Space Telescope can provide insight into how planets like Earth or Venus – both undergoing explosive processes, but taking very different evolutionary paths – end up the way they do.
“A big question in astronomy, the field that studies the origins of life on Earth and beyond, is whether tectonic or volcanic activity is necessary for life,” said astrophysicist Jessie Christiansen of the California Institute of Technology.
“In addition to providing oxygen, these processes can destroy things that would otherwise sink and be trapped in the crust, including things that we think are essential for life, like oxygen.”
This discovery shows how complex things can be, and the importance of studying each planetary system. It is no longer enough to find a small Earth in the hot atmosphere of a star. The impact of other countries in the system should also be carefully considered.
And it is important to continue to find and identify these countries, whether they are inhabited or not. They show us many possible outcomes for Earth-like exoplanets, and explore the possibility of living in a large galaxy.
“This discovery is just the first step,” says astronomer Karen Collins of the Harvard-Smithsonian Center for Astrophysics.
“Having the opportunity to continue learning about the world using the James Webb space telescope, we will be able to change what we have seen and learn more about how the world will be because of volcanic eruptions. living in countries other than ours.”
Research has been published in Nature.
