Astronomers have discovered a planet the size of Saturn, orbiting the smallest star ever, to host such a huge companion, challenging, challenging fundamental theory.
This discovery published in Natural Astronomy shows that TOI-6894b (a giant planet with half the mass of Saturn) circles a red dwarf star, which is only 20% of the mass of our sun every 3.37 days. This unexpected pairing suggests that the universe may have much more planets than previously thought.
The finding comes from international collaborations, including researchers from Leg University, working with teams from the UK, Chile, the United States and across Europe. This discovery is particularly striking that current planetary formation models predict that such small stars cannot form or retain giant planets.
Cosmic contradictions
Red dwarf stars like TOI-6894 represent the most common star type in our Milky Way, accounting for 75% of all stellar objects. However, so far, astronomers believe these dwarf stars lack the raw materials needed to build large numbers of planets in surrounding gas and dust disks.
“We used to think that this small star could not form or stick to giant planets. But stars like Toi-6894 are the most common type in the Milky Way, so our findings suggest that Professor Jamila Chouquar, an astronomer at the time of the discovery, said.
The planet was first discovered by NASA’s Exoplanet Survey Satellite (TESS), part of a systematic search of giant planets around small stars. Ground telescopes, including telescopes operated by Speculos and Trappist projects, confirm the planetary nature of the signal through extensive follow-up observations.
Extreme transit signals
TOI-6894b creates one of the most dramatic transit signals ever observed. When a planet passes in front of its host star, it blocks 17% of the star’s rays, a depth that makes it very easy to obtain in atmospheric studies. Most planets reduce their host starlight by less than 1%.
Dr. Khalid Barkaoui, who is responsible for the critical follow-up observations, explained: “In our data, the transit signal is clear. Our analysis excludes all alternative explanations – the only thing that works is that this little star has a huge observation over three days, and over three days, its mass is halfway.
The planet is extremely close to the star (nearer than mercury to our sun), giving it an equilibrium temperature of about 418 kelvin (145°C or 293°F), placing it in the “Warm Jupiter” category.
Formation Problems
The existence of TOI-6894b poses a significant challenge to established planetary formation theory. According to the core model, giant planets form when solid cores grow large enough to trigger the accumulation of runaway gas in the surrounding disk. However, low-mass stars usually host disks do not have enough solid material to build such a huge core.
Dr. Mathilde Timmermans, a member of the Speculos team, noted: “The existence of TOI-6894b is difficult to reconcile with existing models.
The composition of the planet adds another layer of complexity. Analysis shows that TOI-6894b contains about 12 heavy elements of Earth mass (in astronomy as the word), accounting for 23% of its total mass. This metal content is about 12 times higher than that of its host star, indicating an abnormal formation process.
Alternative formation pathway
The researchers proposed several mechanisms that might explain the existence of Toi-6894b. One possibility involves a modified core process, which is formed by a stable accumulation of heavy elements and gases, avoiding the traditional out-of-control phase and requiring a large number of initial cores.
Another scenario causes gravitational instability, where the region of the proto-disk collapses directly into the planet without the need for a solid core. However, simulations of this process have produced paradoxical results, some of which suggest that it can form planets such as TOI-6894B, while others suggest that it will produce larger objects.
The massive metal content of the Earth may also be due to subsequent bombing by planetary explosions, which has caused the already formed gas giants to bombard heavy elements.
Atmospheric gold mines
In addition to the mystery of its formation, TOI-6894B also provides great opportunities for atmospheric research. The combined star, short orbital period and low density of the planet creates the ideal conditions for the transmission spectrum, a technology that analyzes the filtration of starlight through the planet’s atmosphere during the transition.
The planet’s Transmission Spectroscopic Index (TSM) score is 356, making it the easiest giant planet to be found in atmospheric research among all known planetary spinning stars, rather than 0.7 solar energy. At moderate temperatures, astronomers will be dominated by methane chemistry, similar to the cooler planets in our external solar system.
Computer models show that a single transit observation using the James Webb space telescope can detect key atmospheric molecules including methane, water vapor and carbon dioxide. Such measurements not only reveal the composition of the Earth’s atmosphere, but also provide important clues about its formation history.
Detection methods and verification
This discovery requires careful verification to eliminate false positive scenarios. Tess’s large pixels sometimes mix signals from multiple stars, possibly mimicking the planet’s leap. The team used multiple telescopes and filters to conduct extensive ground observations to confirm signals originating from TOI-6894 itself.
High-resolution spectral observations of espresso instruments at very large telescopes measure changes in the radial velocity of stars caused by planetary gravity. These measurements confirm the planet’s mass and exclude scenes involving backgrounds of eclipse binary stars.
Archive images dating back to 1952 have no pollution background pollution at the current location of the system, while high-resolution imaging shows no companion stars that may confuse the signal.
Impact on exoplanet demographics
Professor Michaël Gillon, the head of the trappist program, concluded: “This huge planet orbits a tiny star reveals that the diversity of planets in the Milky Way is even greater than we think. Most of the targets observed by Speculos and Trappist are similar stars, even smaller – so we are easily eliminated, which is the effect of cossmic fore of fore oferover oferover ofere ofere ofere ofere ofere ofere ofere ofere ofere.
The finding suggests that surveys focusing on low-mass stars may spot previously hidden giant planetary populations. Given that the Red Dwarfs make up most of the stars in our galaxy, even a small portion of hosting giant planets could significantly increase the planet’s overall census.
Future observations of the TOI-6894b atmosphere will help determine which formation mechanism best explains its existence and potentially address long-standing problems regarding the formation of planets around the most common stars in galaxies. Now, the system is a key benchmark for testing and refining our understanding of how planetary systems emerge in the universe.
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