Colossal extraterrestrial sheds light on a planetary mystery
One of the largest ever discovered
A new exoplanet just 200 light years away may provide answers to one of the mysteries of planetary science. TOI-1075d is one of the largest exoplanets we have discovered, with a diameter 1.8 times that of Earth.
Smaller rocky exoplanets have been found, as well as larger worlds with dense atmospheres known as mini-Neptunes. However, not many worlds have been found between 1.5 and 2 times the diameter of Earth, creating a planetary size gap. TOI-1075b’s mass is 9.95 times that of Earth, making it unsuitable for a gas planet. At this density, it is probably rocky like Earth, Mercury and Venus.
This “planet gap” in sizes was defined in 2017, when the list of exoplanets available to us grew enough for scientists to detect patterns. So they found that of the exoplanets that are at a certain distance from their stars, very few have been found in this gap.
There are possible explanations. One of them is that below a certain size, an exoplanet does not have enough mass to maintain an atmosphere so close to its star and its radiation. According to this model, exoplanets in the vacuum must have a fairly dense atmosphere consisting mainly of hydrogen and helium.
TOI-1075b orbits an orange dwarf, the star TOI-1075, with a 14.5 hour orbit. The star has 60% the diameter and mass of the Sun. Knowing the mass of the star and the exoplanet, the researchers were able to calculate the density of TOI-1075b at 9.32 grams per cubic centimeter, almost twice the density of Earth at 5.51 grams per cubic centimeter.
Based on the predicted composition and proximity to the star, we do not expect TOI-1075b to have an H/He atmosphere. However, it may have a metal/silica vapor atmosphere, with the composition determined by the evaporating magma ocean at the surface, since its temperatures are high enough to melt its rocky surface.
Yes, you read that right. TOI-1075b is so hot that its surface may be a magma ocean producing an atmosphere of vaporized rock. A future survey by the James Webb Space Telescope will provide more answers, revealing details that will enrich our knowledge of planet formation and evolution, as well as how exoplanets lose their gases.
The research is available on arXiv .
