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Economic Times
3 days ago
- Science
- Economic Times
What's TOI-6894b that just showed up around a dwarf star only 2.5 times its size; here's why that's weird
Reuters An artist's impression of a newly discovered giant planet named TOI-6894 b (top right) orbiting a red dwarf star (center) about 20% the mass of the sun, the image was released on June 4, 2025. University of Warwick/Mark Garlick/Handout via REUTERS NO RESALES. NO ARCHIVES. THIS IMAGE HAS BEEN SUPPLIED BY A THIRD PARTY Astronomers have made a discovery that challenges long-standing beliefs about how planets form. A gas giant planet, roughly the size of Saturn, has been found orbiting an unusually small red dwarf star. This rare pairing defies current models, which say small stars don't have enough material in their surrounding disks to form such large planets. Named TOI-6894b, the planet was found about 241 light-years from Earth in the constellation Leo. TOI-6894b is about 1.07 times the diameter of Saturn but has just over half its mass. This makes the planet very low in density, similar to that of a beach ball. Despite its large size, the planet orbits extremely close to its host star, completing a full revolution in just under three Earth days. Also Read: Sun will die in 5 billion years but life could survive on Jupiter's moon Europa; here's how The star it orbits, TOI-6894, is a red dwarf with only about 21% the mass of the Sun and roughly 250 times dimmer. In terms of physical size, the star is just 2.5 times wider than the planet itself, a remarkable size ratio rarely seen in planetary systems. The formation of such a large planet around such a small star has puzzled astronomers. According to the well-accepted 'core accretion' model, large planets are thought to grow from small rocky cores that gradually gather gas from the star's surrounding protoplanetary disk. But small, dim stars like red dwarfs are believed to have disks too thin and short-lived to form massive planets before the gas disappears. Dr. Teruyuki Hirano, the lead researcher from the Graduate University for Advanced Studies in Japan, noted that this planetary system 'is completely inconsistent with what we thought we knew.' He said the discovery 'forces us to question our assumptions about planet formation.' The planet was first flagged by NASA's Transiting Exoplanet Survey Satellite (TESS), which detects periodic dips in starlight caused by planets passing in front of their stars. Follow-up observations using the European Southern Observatory's Very Large Telescope (VLT) confirmed the planet's mass and orbit. Also Read: Rare superorganism 'wormnadoes' caught on camera for the first time; what is it exactly? More data will be needed to determine how TOI-6894b formed. Future observations by the James Webb Space Telescope could reveal more about its atmosphere and structure, including how much of it is made up of hydrogen and helium and whether it has a large core. Red dwarfs are the most common type of star in the Milky Way, making up about 75% of the stellar population. They're also seen as good candidates for hosting habitable planets due to their long lifespans. Discoveries like TOI-6894b suggest there's still much to learn about the diversity of planetary systems these stars may this is not the first time a massive planet has been found orbiting a small star, it is one of the most extreme examples yet.
GMA Network
5 days ago
- Science
- GMA Network
Scientists puzzled by giant planet detected orbiting tiny star
An artist's impression of a newly discovered giant planet named TOI-6894b (top right) orbiting a red dwarf star (center) about 20% the mass of the sun, the image was released on June 4, 2025. University of Warwick/Mark Garlick/Handout via REUTERS WASHINGTON - Astronomers have spotted a cosmic mismatch that has left them perplexed - a really big planet orbiting a really small star. The discovery defies current understanding of how planets form. The star is only about a fifth the mass of the sun. Stars this size should host small planets akin to Earth and Mars under the leading theories on planetary formation. But the one detected in orbit around this star is much larger - in fact, as big as Saturn, the second-largest planet in our solar system. The star, named TOI-6894, is located roughly 240 light-years from Earth in the constellation Leo. A light-year is the distance light travels in a year, 5.9 trillion miles (9.5 trillion km). It is the smallest-known star to host a large planet, about 40% smaller than the two previous record holders. "The question of how such a small star can host such a large planet is one that this discovery raises - and we are yet to answer," said astronomer Edward Bryant of the University of Warwick in England, lead author of the study published on Wednesday in the journal Nature Astronomy. Planets beyond our solar system are called exoplanets. The one orbiting TOI-6894 is a gas giant, like Saturn and Jupiter in our solar system, rather than a rocky planet like Earth. The birth of a planetary system begins with a large cloud of gas and dust - called a molecular cloud - that collapses under its own gravity to form a central star. Leftover material spinning around the star in what is called a protoplanetary disk forms planets. Smaller clouds yield smaller stars, and smaller disks contain less material to form planets. "In small clouds of dust and gas, it's hard to build a giant planet," said exoplanet scientist and study co-author Vincent Van Eylen of University College London's Mullard Space Science Laboratory. "This is because to build a giant planet, you need to quickly build a large planet core and then quickly accrete (accumulate) a lot of gas on top of that core. But there's only so much time to do it before the star starts shining and the disk rapidly disappears. In small stars, we think there's simply not enough mass available to build a giant planet quickly enough before the disk disappears," Van Eylen added. No known planet is larger than its host star, and that is the case here as well, though the two are much closer in size than usual. While the sun's diameter is 10 times larger than our solar system's largest planet Jupiter, TOI-6894's diameter is just 2.5 times greater than its only known planet. The star is a red dwarf, the smallest type of regular star and the most common kind found in the Milky Way galaxy. "Given these stars are very common, there may be many more giant planets in the galaxy than we thought," Bryant said. The star is about 21% the mass of the sun and much dimmer. In fact, the sun is about 250 times more luminous than TOI-6894. "These findings suggest that even the smallest stars in the universe can in some cases form very large planets. That forces us to rethink some of our planet formation models," Van Eylen said. The planet is located about 40 times closer to its star than Earth is to the sun, completing an orbit in approximately three days. Its proximity to the star means the planet's surface is quite hot, though not as hot as gas giants called "hot Jupiters" detected orbiting similarly close to bigger stars. Its diameter is slightly larger than Saturn and a bit smaller than Jupiter, though it is less dense than them. Its mass is 56% that of Saturn and 17% that of Jupiter. The main data used in studying the planet came from NASA's orbiting Transiting Exoplanet Survey Satellite, or TESS, and the European Southern Observatory's Chile-based Very Large Telescope, or VLT. The researchers hope to better understand the planet's composition with observations planned over the next year using the James Webb Space Telescope. "We expect it to have a massive core surrounded by a gaseous envelope made up of predominantly hydrogen and helium gas," Bryant said. — Reuters
CBS News
6 days ago
- General
- CBS News
Massive planet discovered orbiting tiny star, leaving scientists stumped
Astronomer breaks down "strongest evidence yet" of life on distant planet Astronomers announced Wednesday they have discovered a massive planet orbiting a tiny star, a bizarre pairing that has stumped scientists. Most of the stars across the Milky Way are small red dwarfs like TOI-6894, which has only 20% the mass of our sun. It had not been thought possible that such puny, weak stars could provide the conditions needed to form and host huge planets. But an international team of astronomers have detected the unmistakable signature of a gas giant planet orbiting the undersized TOI-6894, according to a study in the journal Nature Astronomy. This makes the star the smallest star yet known to host a gas giant. The planet has a slightly larger radius than Saturn, but only half its mass. It orbits its star in a little over three days. Artist's impression of the newly discovered giant planet - TOI-6894 b orbiting around a 0.2 solar mass host star. University of Warwick/Mark Garlick The astronomers discovered the planet when searching through more than 91,000 low-mass red dwarfs observed by NASA's TESS space telescope. Its existence was then confirmed by ground-based telescopes, including Chile's Very Large Telescope. "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," study co-author Daniel Bayliss of the UK's Warwick University said in a statement. Another co-author, Vincent Van Eylen, of University College London, said it was an "intriguing discovery." "We don't really understand how a star with so little mass can form such a massive planet!" he said. "This is one of the goals of the search for more exoplanets. By finding planetary systems different from our solar system, we can test our models and better understand how our own solar system formed." Planet is unusually cold The most prominent theory for how planets form is called core accretion. The process begins when a ring of gas and dust — called a protoplanetary disc — which surrounds a newly formed star builds up into a planetary core. This core attracts more gas that forms an atmosphere, eventually snowballing into a gas giant. Under this theory, it is difficult for low-mass stars to host giant planets because there is not enough gas and dust to begin building a core in the first place. A rival theory proposes that these planets instead form when their protoplanetary disc becomes gravitationally unstable and breaks up, with the collapsing gas and dust forming a planet. However neither theory seems to explain the existence of the newly discovered planet, TOI-6894b, the researchers said. The planet also interests scientists because it is strangely cold. Most of the gas giants discovered outside our solar system so far have been what are known as "hot Jupiters," where temperatures soar well over 1,000 degrees Celsius. But the newly discovered planet appears to be under 150C, the researchers said. "Temperatures are low enough that atmospheric observations could even show us ammonia, which would be the first time it is found in an exoplanet atmosphere," said study co-author Amaury Triaud of Birmingham University. The James Webb space telescope is scheduled to turn its powerful gaze toward the planet in the next year, which could help uncover some more mysteries of this strange planet. Recent cosmic discoveries The spotting of the giant planet orbiting the undersized star marks the latest in a string of recent celestial discoveries. Last month, a U.S.-based trio hunting the elusive "Planet Nine" said they instead stumbled on what appears to be a new dwarf planet in the solar system's outer reaches. Named 2017 OF201, the new object is roughly 430 miles across, according to a preprint study, making it three times smaller than Pluto. Also in May, an international team reported that a newly found celestial object — perhaps a star, pair of stars or something else entirely — is emitting X-rays around the same time it's shooting out radio waves. Meanwhile, scientists announced recently that a new planetarium show about the Milky Way helped them unlock one of the solar system's many secrets. Experts at the American Museum of Natural History in New York were fine-tuning a scene about the Oort Cloud that's far beyond Pluto. Scientists have never glimpsed this region, but when museum experts projected their scene onto the planetarium dome, created using simulation data, they saw a spiral shape. Scientists had long thought the Oort Cloud was shaped like a sphere or flattened shell, warped by the push and pull of other planets and the Milky Way itself. The planetarium show hinted that a more complex shape could lie inside. This image provided by the American Museum of Natural History shows a new planetarium show showing a backwards S-shaped spiral in what's known as the Oort Cloud far beyond Pluto. AP contributed to this report.
