NASA scientists explained why — UNIAN
Researchers are studying a group of planets that appear to be shrinking. The reason may be radiation.
There are many different worlds outside our solar system. Distant alien planets, called exoplanets, can be gas giants like Jupiter, rocky layers the size of our planet, or even “super-chubby” with the density of cotton candy.
But there is a mysterious gap in which there should be planets approximately 1.5-2 times the width of the Earth, writes Business Insider. A study published in The Astronomical Journal may reveal the mystery of missing exoplanets.
A mysterious hole where there should be planets
Among the more than 5,000 exoplanets discovered by NASA, there are many super-Earths (which are 1.6 times the width of our planet) and many sub-Neptunes (approximately two to four times the diameter of the Earth), but there are almost no planets in between.
“Scientists who study exoplanets now have enough data to say that this discontinuity is not a coincidence. Something is happening that prevents planets from reaching and/or staying that size,” said Jessie Christiansen, a researcher at Caltech and Head of the NASA Exoplanet Archive.
Scientists believe that this happens because some sub-Neptunes shrink – lose their atmosphere and quickly overcome the difference in size until they become as small as a super-Earth.
In the latest study by Christiansen, it is assumed that these worlds are shrinking because radiation from the cores of the planets pushes their atmospheres into space.
The planets themselves probably repel their atmospheres
Compressible exoplanets may lack the mass (and, therefore, gravity) to keep their atmospheres dense. However, the exact mechanism of atmospheric loss remains unclear.
The new study supports one hypothesis, which scientists call “loss of mass due to nuclear energy.”
Loss of mass with the help of the core is when the core of a planet emits radiation that pushes its atmosphere from below, which eventually leads to its separation from the planet.
The second hypothesis, called photoevaporation, states that the planet’s atmosphere dissipates under the influence of radiation from the parent star.
But it is believed that photoevaporation occurs by the time the planet is 100 million years old, and the loss of mass due to nuclear energy may occur closer to the planet’s billionth birthday, the study says.
To test these two hypotheses, Christiansen’s team studied data from the former Kepler space telescope.
They studied star clusters whose age exceeds 100 million years. Since the planets are considered to be roughly the same age as their parent stars, the planets in these clusters must be old enough to undergo photoevaporation, but not old enough to lose mass due to nuclear energy.
Scientists have found that most of the planets there have preserved their atmosphere, which makes the loss of mass caused by the energy of the core a more likely cause of the possible loss of atmosphere.
“However, recent work suggests an ongoing mass loss sequence in which both processes operate,” Kristiansen noted.
Other news about space
As reported by UNIAN, dozens of objects the size of a planet were discovered earlier in the course of observing the Orion nebula, which may indicate the existence of a new astronomical category.
Free-floating objects have been called Jupiter-mass double objects, or jumbos. They are too small to be stars, but they do not lend themselves to the generally accepted definition of a planet, since they do not revolve around a parent star.
