Scientists discover another exoplanet that theories say should not exist

The uncertainty of science: Scientists using telescopes both in orbit and on the ground have discovered a small red dwarf star with only 20% the mass of our Sun with a gas giant exoplanet with about half the mass of Saturn but a bit larger in size.

The problem is that the theory for the formation of such gas giants predicts that they should not form around small red dwarfs such as this star.

The most widely held theory of planet formation is called the core accretion theory. A planetary core forms first through accretion (gradual accumulation of material) and as the core becomes more massive, it eventually attracts gases that form an atmosphere. It then gets massive enough to enter a runaway gas accretion process to become a gas giant.

In this theory, the formation of gas giants is harder around low-mass stars because the amount of gas and dust in a protoplanetary disc around the star (the raw material of planet formation) is too limited to allow a massive enough core to form, and the runaway process to occur.

Yet the existence of TOI-6894b (a giant planet orbiting an extremely low-mass star) suggests this model cannot be completely accurate and alternative theories are needed.

You can read the paper here. The exoplanet orbits the star every 3.37 days, and each transit across the face of the star has been easily detected by numerous telescopes. Further spectroscopic observations using the Webb Space Telescope will be able to characterize the exoplanet’s atmosphere more fully.

Earth-sized exoplanet discovered orbiting dwarf star 55 light years away

Using a number of ground-based telescopes worldwide, astronomers have discovered an Earth-sized exoplanet orbiting what the scientists label an “ultra-cool” dwarf star only about 55 light years away.

You can read the paper here.

Though Earth-sized, this exoplanet is not habitable. It orbits the star every 17 hours and is believed to be tidally locked, with one side always facing the star. More important, though this red dwarf star has likely existed for many tens of billions of years and will continue for many tens of billions of years into the future, the star is too dim and lacking in the kind of resources needed for life. It also drenches the planet with bursts of radiation, which is also believed to have stripped the planet of an atmosphere.

Astronomers discover an exoplanet with the density of a marshmallow

Using ground-based telescopes to gather more data about an exoplanet discovered by the orbiting TESS telescope, astronomers have found that it has the density of a marshmallow.

The planet orbits a red dwarf star, the most common star in the universe, and is the “fluffiest” yet seen around this type of star.

Red dwarf stars are the smallest and dimmest members of so-called main-sequence stars — stars that convert hydrogen into helium in their cores at a steady rate. Though “cool” compared to stars like our Sun, red dwarf stars can be extremely active and erupt with powerful flares capable of stripping a planet of its atmosphere, making this star system a seemingly inhospitable location to form such a gossamer planet.

Astronomers remain puzzled how such a large fluffy planet could have formed around such a dim small star.