One of planetary science's most puzzling puzzles could get some fresh insight from a newly discovered exoplanet that is just 200 light-years away.
The object known as TOI-1075b is one of the largest instances of a super-Earth exoplanet we've discovered so far, with a radius of around 1.8 times that of Earth. It also occupies a stable position in the area known as the small-planet radius gap, which seems to be deficient in planets between 1.5 and 2 Earth radii.
There have been discovered somewhat smaller rocky super-Earths. As a result, somewhat bigger worlds—also referred to as mini-Neptunes—have bulked out with puffy atmospheres. However, the area in between resembles a desert.
Not all of that extra bulk is fluff, though. The mass of TOI-1075b is 9.95 times that of the Earth. At the estimated density, the exoplanet is most likely rocky, like Mercury, Earth, Mars, and Venus. That's much too heavy for a gaseous world. It is the perfect candidate for testing theories of planetary creation and development because of its peculiarities.
The small-planet radius gap wasn't discovered until 2017, when there was a sufficient number of exoplanets (planets beyond the Solar System) for researchers to discern a trend. Very few worlds that lie on either side of that distance have been discovered for exoplanets that are in close proximity to their sun.
The most prevalent theory for this appears to be because, below a certain size, an exoplanet simply lacks the mass to maintain an atmosphere against the evaporating radiation so near to the host star. There are a number of other theories that might also account for this. This model predicts that exoplanets in the gap should have rather large atmospheres that are mostly made of hydrogen and helium.
I present TOI-1075b. It was found in data collected by NASA's TESS exoplanet-hunting telescope. TESS, short for Transiting Exoplanet Survey Satellite, is a satellite that searches for weak, regular dips in the light of other stars that would indicate the presence of an exoplanet in their orbit. Based on how much of the star's light is being dimmed, astronomers may also determine the exoplanet's radius.
According to TESS data, an extraterrestrial planet with a radius of 1.72 times that of the Earth and an orbital period of around 14.5 hours was orbiting the orange dwarf star TOI-1075. Astronomer Zahra Essack of MIT, who researches hot super-Earths, was alerted to this. The then-candidate world met the requirements for a radius-gap world at that radius and close by.
Weighing this exoplanet was the next stage in the process of trying to comprehend its makeup. This requires making use of the gravitational influence that an exoplanet exerts on its home star. The star supplies the majority of the gravitational pull during a star-planet interaction, but the planet also pulls back on the star in a very small way. That implies a star gently wobbles when it remains stationary, and astronomers may see this by noticing minute variations in the star's brightness.
These variations may be used to estimate the planet's mass that is rattling the star if we know its mass. Essack and her coworkers were able to accurately determine the exoplanet's mass to 9.95 Earth masses since TOI-1075 has a mass and radius that are around 60% of that of our own Sun. And 1.791 Earth radii were obtained from their exact measurements of the size.
You can figure out something's average density if you know how large and how heavy it is. Also, TOI-1075b? proved to be a complete chonk. 9.32 grams are included in every cubic centimeter of it. It is a candidate for the title of densest super-Earth as it is about twice as dense as Earth's average density of 5.51 grams per cubic centimeter.
In the mass gap, an exoplanet should have a sizable hydrogen-helium atmosphere. The density of TOI-1075b is not compatible with a dense atmosphere. This is quite strange. The exoplanet's alternative, though, could be much more exciting.
According to the researchers' study, "We do not anticipate the planet to have kept a H/He envelope based on TOI-1075b's estimated composition and ultra-short orbital period."
But since TOI-1075b's equilibrium temperature is hot enough to melt a rocky surface, it could either have no atmosphere (bare rock), a metal/silicate vapor atmosphere with a composition determined by the vaporizing magma-ocean on the surface, or, particularly at the low end of its permitted mean density range, possibly a thin H/He or CO2 or other atmosphere.
You read it correctly; Due to its proximity to its star, TOI-1075b is so hot that it may have a surface ocean of magma that generates an atmosphere of vaporized rock.
The good news is that we may find out in this situation. JWST is extremely skilled at peering into the atmospheres of exoplanets, as we have only recently discovered. By pointing it at TOI-1075b, it should be able to determine whether the planet has a silicate atmosphere, a thin atmosphere, or no atmosphere at all. This information may reveal previously unknown aspects of planet formation and evolution as well as how super-Earths lose their gas.
The study group's findings have been published in The Astronomical Journal and are accessible on arXiv.
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