Are there any other planets whose environments are similar to ours? Thanks to the progress of astronomical technology, we now know that there are thousands of planets orbiting distant stars. A new study shows that some exoplanets in the universe have helium rich atmospheres. The reason for the uneven size of the planets in the solar system is related to the helium content. This discovery may further our understanding of planetary evolution.

Mystery about the size deviation of extrasolar planets

It was not until 1992 that the first exoplanet was discovered. The reason why it took so long to find planets outside the solar system is that they are blocked by starlight. Therefore, astronomers have come up with a clever way to find exoplanets. It checks the dimming of the time line before the planet passes its star. In this way, we now know that planets are common even outside our solar system. At least half of the sun like stars have at least one planet size ranging from Earth to Neptune. These planets are believed to have “hydrogen” and “helium” atmospheres, which were collected from the gas and dust around the stars at birth.

Strangely, however, the size of exoplanets varies between the two groups. One is about 1.5 times the size of the earth, and the other is more than twice the size of the earth. And for some reason, there is hardly anything in between. This amplitude deviation is called “radius valley”. Solving this mystery is believed to help us understand the formation and evolution of these planets.

The relationship between helium and the size deviation of extrasolar planets

One hypothesis is that the size deviation (valley) of extrasolar planets is related to the planet’s atmosphere. Stars are extremely bad places, where the planets are constantly bombarded by X-rays and ultraviolet rays. It is believed that this stripped the atmosphere, leaving only a small rock core. Therefore, Isaac Muskie, a doctoral student at the University of Michigan, and Leslie Rogers, an astrophysicist at the University of Chicago, decided to study the phenomenon of planetary atmospheric stripping, which is called “atmospheric dissipation”.

To understand the effects of heat and radiation on the Earth’s atmosphere, they used planetary data and physical laws to create a model and run 70000 simulations. They found that, billions of years after the formation of planets, hydrogen with smaller atomic mass would disappear before helium. More than 40% of the Earth’s atmosphere mass may be composed of helium.

Understanding the formation and evolution of planets is a clue to the discovery of extraterrestrial life

To understand the effects of heat and radiation on the Earth’s atmosphere, they used planetary data and physical laws to create a model and run 70000 simulations. They found that, billions of years after the formation of planets, hydrogen with smaller atomic mass would disappear before helium. More than 40% of the Earth’s atmosphere mass may be composed of helium.

On the other hand, planets that still contain hydrogen and helium have expanding atmospheres. Therefore, if the atmosphere still exists, people think it will be a large group of planets. All of these planets can be hot, exposed to intense radiation, and have a high-pressure atmosphere. Therefore, the discovery of life seems unlikely. But understanding the process of planet formation will enable us to more accurately predict what planets exist and what they look like. It can also be used to search for exoplanets that are breeding life.