Astronomers Discover Gas Giant Orbiting Unusually Small Star

Astronomers Discover Gas Giant Orbiting Unusually Small Star

In a surprising breakthrough, astronomers have identified a massive planet revolving around an unexpectedly diminutive star, a pairing that challenges existing theories of planet formation. The star, designated TOI-6894, is a small red dwarf with only 20% of the mass of our Sun, and it was previously assumed that such feeble stars could not create or sustain large planets.

An international team of researchers has successfully detected the unmistakable signature of a gas giant, named TOI-6894b, orbiting this tiny star. This finding establishes TOI-6894 as the smallest known star to host a gas giant planet, suggesting that the conditions for planetary formation might be more flexible than previously thought.

TOI-6894b is noteworthy not only for its unusual pairing with a less massive star but also for its size and mass. The planet's radius is slightly larger than that of Saturn, although it weighs in at only about half of Saturn's mass. TOI-6894b completes an orbit around its star in just over three days.

The discovery was made while analyzing data from over 91,000 low-mass red dwarfs observed by NASA's TESS space telescope, and its existence was subsequently confirmed using ground-based telescopes, including the renowned Very Large Telescope in Chile.

Daniel Bayliss, a co-author of the study from the UK's Warwick University, remarked, "The fact that this star hosts a giant planet has big implications for the total number of giant planets we estimate exist in our galaxy." This statement underscores the potential impact of the discovery on our understanding of planetary formation and distribution in the universe.

Another co-author, Vincent Van Eylen from University College London, expressed excitement about the findings: "We don’t really understand how a star with so little mass can form such a massive planet! This is one of the goals of the search for more exoplanets." Their remarks give credence to the notion that this unique planetary system opens new avenues for exploring diverse planetary systems beyond our solar system.

Central to understanding planet formation is the core accretion theory. This model posits that a planetary core develops from a disc of gas and dust surrounding a newly formed star and eventually gathers enough mass to attract a gaseous atmosphere, transforming it into a gas giant. However, this mechanism struggles to account for the existence of gas giants around low-mass stars like TOI-6894, as the available materials for core formation are inherently limited.

Another theory suggests planets can form when the protoplanetary disc itself becomes gravitationally unstable, causing collapse and formation of a planet. Yet, neither theory fully explains the characteristics of TOI-6894b, suggesting the need for new theoretical perspectives on planet formation.

To add to the intrigue, TOI-6894b is relatively cool for a gas giant, with an equilibrium temperature of approximately 420 Kelvin. This temperature is significantly lower than that of most gas giants found, referred to as