Many planets could have atmospheres rich in helium, study finds
An artist’s illustration of a faraway planet with an atmosphere rich in helium. A new study explains how these types of planets may be very common and why. Credit: NASA/JPL-Caltech

No one knew if we were alone in the universe or if there were other planets like us.

Thanks to new telescopes and methods in the past decades, we now know that there are thousands and thousands of planets out there in the universe.

A study by scientists with the University of Chicago, the University of Michigan and the University of Maryland suggests that there is a planet with a helium atmosphere. The discovery suggests a new step in our understanding of the planet.

Over time, it is likely that the atmospheres of certain types of exoplanets will be filled with helium. This would explain the puzzle about the size of these exoplanets.

"There are so many weird and wonderful kinds of exoplanets out there, and this finding not only adds a new kind but may have implications for understanding the evolution and formation of planets in general," said University of Chicago astronomer and co-author of the new paper.

There is a mystery surrounding the valley.

It took us a long time to find planets that are close to the stars. Scientists were able to spot them by looking for a dip in the light of a star when a planet passes in front of it. The size of the planet is told by this.

It is now known that planets are very common. Our sun has at least one planet between the size of Earth and Neptune that is very close to the star. The planets have atmospheres with a lot of hydrogen and helium, collected when the planets first formed.

The scientists noticed that the planets were separated into two different groups. There were two groups, one of which was twice the size of Earth and the other of which was about the size of a half Earth.

There is a gap between the two populations of planets known as theradius valley. The answer will help scientists understand how planets form and evolve.

The explanation may have to do with the atmospheres of the planets. Being a planet close to your star can be hard because you're bombarded with X-rays and UV light.

The study's first author, a graduate student at the University of Michigan, began exploring the question with Rogers for his undergrad thesis.

Rogers and Malsky decided to take a closer look at atmospheric escape.

The models they created were based on the data we have about the planets and the rules of physics. Over time, they modeled what would happen to the planets when they were different sizes, types of stars, and the temperature of the atmosphere.

After several billion years, the hydrogen in planetary atmospheres may escape faster than the helium. Malsky explained that hydrogen has a lower atomic mass.

Simulations suggest that 40% or more of the atmospheres could be made up of helium.

Confirmations of telescopes.

A way to confirm their results was suggested. A reading of the atmosphere's elements and their amounts can be obtained with the James Webb Space Telescope. There is a chance that some of the planets have a large amount of helium in their atmosphere.

If the theory is correct, these planets with rich atmospheres should be common at the lower end of the larger-radius group because the helium builds up as the planet shrinks.

Malsky explained that the two distinct planet-size groups are created because of the large amount of hydrogen and helium in the atmosphere. They will be in the larger-radius group if there is no atmosphere left.

None of these planets are thought to be good candidates for life because they are hot and bombarded with radiation.

The scientists said that by improving our understanding of the processes that drive the formation of planets, we can better predict what other planets are like, as well as directing the search for more hospitable planets.

A better understanding of this population could tell us a lot about the origins and evolution of sub-Neptune-size planets.

There are Helium-Enhanced planets along the upper edge of the radius valley.

Journal information: Nature Astronomy