Researchers from the Center for Computational Astrophysics at the Flatiron Institute published a paper that may explain the mysterious gap in the size of planets outside the solar system. Planets between 1.5 and 2 times the radius of the earth are extremely rare. This new study suggests that the reason may be that a slightly larger planet (called mini-Neptune) loses its atmosphere over time and gradually shrinks into a ‘super-Earth’ whose size is only slightly larger than our own planet . These ever-changing planets only briefly have the correct radius to fill the entire space, and then shrink quickly.
The importance of planetary science is exciting because it confirms that planets are not stationary objects, but dynamic worlds that are constantly changing. Exoplanet research is a very young field. Until 1992, no one had seen a planet outside the solar system. Today, we have discovered more than 4,700 such telescopes, and this number is growing rapidly due to the efforts of special space telescopes such as Kepler (now discontinued) and its successor TESS system. Suddenly we got a lot of new planet samples to investigate, instead of the eight planets that orbit the sun (sorry Pluto). Kepler, Theis, and other planet hunters have discovered entirely new planets, such as the so-called ‘hot Jupiters,’ which are large gas giants that orbit their stars. These are one of the first observed exoplanets because their large size makes them easy to find, and their small and fast orbital period means that we can see them pass several times in a short period of time in front of the star They (some hot Jupiters last only a few few Earth days per year). As the ability to find smaller planets increases, we begin to see a wide variety of planets, the smallest of which is even smaller than Mercury. But as the number of samples increases, there is still a strange gap between Earth’s radius of 1.5 and 2. For some reason, the planets just don’t like this size.
Previous theories indicate that asteroid bombardment can push the atmosphere away from planets of this size, or that certain planets can form in regions where there is not enough gas to form a thick atmosphere first, making the total size much smaller than the space. ‘ The research team led by Trevor David explored this mystery in a new way, considering whether the size changes over time. Planets usually form at the same time as stars. Therefore, if you know the age of a star, just The age of the star can be estimated. The age of the planets, which allowed the research team to group planets by age. They found that in the oldest planets (planets older than 2 billion years), the gaps are concentrated in a radius of 1.8, while gaps in the size of the planets
The smaller than 2 billion years of history is about 1.6 times the radius of the earth. Provided by the Simmons Foundation. This difference indicates that the smallest mini-Neptune was unable to maintain its atmosphere and contracted into a super Earth very early. Later, for the slightly larger mini-Neptune, the same process will occur, resulting in a change in ‘space’. As Thomas Sumner of the Simons Foundation put it, this gap is best understood as ‘the gap between the largest super-Earth and the smallest mini-Neptune, but it can still be maintained. Atmosphere.’ What is the reason for this atmospheric contraction? This may be due to the radiation entrained by the gas emitted by the planetary star or the residual heat inside the planet itself. These processes will affect all planets to a certain extent, but the largest planets have enough gravitational force, so the impact is not so great. After solving a mystery (or at least a reasonable explanation), you need to understand a lot of details about the process, such as examining how the magnetic field affects the size of the planet and atmospheric loss. The article was published in the Astronomical Journal.