However, an international team of astronomers have found the unmistakable signature of a giant planet, called TOI-6894b, orbiting this tiny star.
This discovery will be a cornerstone for understanding the extremes of giant planet formation.”
The star (TOI-6894) is the lowest mass star to have a transiting giant planet discovered to date and is just 60% the size of the next smallest star to host such a planet.
So, 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.”
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.
As a small red dwarf with only about 20% of the mass of our sun, star TOI-6894 is similar to many others in our galaxy. It is not anticipated to offer favorable circumstances for the formation and support of a large planet, similar to many small stars.
The unmistakable signature of a giant planet, TOI-6894b, orbiting this tiny star has been discovered by an international team of astronomers. The article appears in the journal Nature Astronomy.
Under the direction of Dr. Edward Bryant, who conducted this work at the University of Warwick and UCL’s Mullard Space Science Laboratory, this system was found as part of a comprehensive analysis of TESS (Transiting Exoplanet Survey Satellite) data in search of giant planets orbiting low-mass celebrities.
Dr. “I was really thrilled by this discovery,” stated first author and Warwick Astrophysics Prize Fellow Edward Bryant. To find giant planets, I first looked through TESS observations of over 91,000 low-mass red dwarf stars.
“Then, using observations made with ESO’s VLT, one of the biggest telescopes in the world, I found TOI-6894b, a giant planet transiting the lowest mass star that has ever been known to host such a planet. The formation of planets like TOI-6894b around stars of this low mass was unexpected. In order to comprehend the extremes of giant planet formation, this discovery will be essential. “..”.
The planet, TOI-6894b, is a low-density gas giant that has about half of Saturn’s mass but a slightly larger radius. At only 60% the size of the next smallest star to host a transiting giant planet, the star (TOI-6894) is the lowest mass star with a transiting giant planet found to date.
Doctor. According to Daniel Bayliss, an associate professor at the University of Warwick, “The majority of stars in our galaxy are small stars just like this, with low masses, and were previously believed to be incapable of supporting gas giant planets. Therefore, the number of giant planets we estimate to exist in our galaxy is significantly impacted by the fact that this star is home to a giant planet. “,”.
An argument against the dominant theory.
Dr. Vincent Van Eylen of the Mullard Space Science Laboratory at UCL stated, “It’s a fascinating finding. How such a massive planet can form from a star with such a small mass is beyond our comprehension. This is one of the objectives of the exoplanet search. We can test our models and learn more about the formation of our own solar system by identifying planetary systems that are distinct from our own. “.”.
The core accretion theory is the most popular explanation for how planets form. Accretion, or the slow buildup of material, is the primary process by which a planetary core forms. As the core gets bigger, gases that make up an atmosphere are eventually drawn to it. It then grows to a size that allows it to become a gas giant through a runaway gas accretion process.
According to this theory, the formation of gas giants is more difficult around low-mass stars because there is not enough gas and dust in the protoplanetary disk surrounding the star—the raw material used to form planets—for a massive enough core to form and for the runaway process to take place.
However, the massive planet TOI-6894b orbiting an extremely low-mass star indicates that this model is not entirely accurate and that other theories are required.
Edward continued, “Considering the planet’s mass, TOI-6894b might have formed via an intermediate core-accretion process, which is a process where a protoplanet forms and gradually accumulates gas without the core growing sufficiently massive to cause runaway gas accretion.
It might have formed as a result of a disk that was unstable due to gravity. Because of the gravitational pull the star exerts on itself, the disk around it may occasionally become unstable. Afterward, these disks may break apart, causing the gas and dust to collapse and create planets. “..”.
However, the group discovered that neither theory could fully account for TOI-6894b’s formation based on the information at hand, leaving the giant planet’s origin up in the air for the time being.
atmospheric solutions.
To solve the puzzle of how TOI-6894b formed, a thorough atmospheric analysis is one way to go. Astronomers can ascertain whether TOI-6894b formed via accretion or an unstable disk by identifying the size and composition of the planet’s core through measurements of the distribution of material within the planet.
The atmosphere of TOI-6894b is oddly cold for a gas giant, but this is not the only intriguing aspect of the planet. Exoplanet hunters typically discover hot Jupiters, which are enormous gas giants with temperatures between 1,000 and 2,000 Kelvin.
In contrast, TOI-6894b is only 420 Kelvin. Astronomers find this planet to be one of the most promising giant planets to describe with a cool atmosphere due to its cool temperature and other characteristics, such as its extremely deep transits.
Co-author and SPECULOOS collaboration member Professor Amaury Triaud of the University of Birmingham stated, “We anticipate that methane chemistry, which is extremely difficult to detect, dominates the atmosphere based on the stellar irradiation of TOI-6894b. The temperature is so low that we might even detect ammonia in atmospheric observations—the first time we’ve seen it in an exoplanet’s atmosphere.
“TOI-6894b is probably the best ‘laboratory’ for studying a planetary atmosphere with carbon, nitrogen, and oxygen outside of the solar system and a benchmark exoplanet for studying methane-dominated atmospheres. “.”.
Within the next 12 months, the James Webb Space Telescope (JWST) is already planned to observe the atmosphere of TOI-6894b. This ought to enable astronomers to ascertain which of the two potential theories—if any—can account for the emergence of this surprising planet.
“This system presents a new challenge for models of planet formation, and it offers a very interesting target for follow-up observations to characterize its atmosphere,” Co-author Dr. Andrés Jordán, a professor at Adolfo Ibáñez University and researcher at the Millennium Institute of Astrophysics, stated.
