Latest news with #EdwardBryant
WIRED
09-07-2025
- Science
- WIRED
A Giant Planet and a Small Star Are Shaking Up Conventional Cosmological Theory
Jul 9, 2025 7:00 AM A gas giant comparable in size to Saturn has been found orbiting a small red dwarf star. The discovery is making experts reconsider conventional notions of how planets form. An illustration of the giant gas planet TOI-6894b orbiting the small, dim red dwarf star TOI-6894. Illustration: University of Warwick/Mark Garlick Many of the stars in the Milky Way galaxy are small, dim red dwarfs—stars much smaller than the sun in both size and mass. TOI-6894, located far away from Earth, is one of them. Astronomers previously thought a star like this could not have large planets circulating it, because its mass is only about 20 percent of the sun, meaning its planetary system—generated from materials surrounding the star—would not have contained enough mass to form a giant body like Saturn or Jupiter. But when observing TOI-6894, an international research team detected a clear transit signal—a temporary decrease in a star's brightness caused by a planet passing across it. This newly discovered planet, named TOI-6894b, blocks 17 percent of the star's light, indicating the planet is fairly large. The signal was picked up by the Transiting Exoplanet Survey Satellite (TESS), an observation instrument launched by NASA to hunt for planets orbiting stars outside of our solar system. This makes TOI-6894 'the lowest mass star known to date to host such a planet,' said Edward Bryant, Astrophysics Prize Fellow at the University of Warwick, in a press statement. The finding appears to upend conventional theory on how planets are formed. 'This discovery will be a cornerstone for understanding the extremes of giant planet formation,' Bryant said. Astronomers at University College London and the University of Warwick, as part of a global collaboration with partners in Chile, the US, and Europe, trawled through the data of about 91,000 red dwarf stars observed by TESS before discovering the planet TOI-6894b. After that, the nature of TOI-6894b was clarified by additional observations made with other telescopes. According to these, TOI-6894b's radius is slightly larger than Saturn's, but its mass is only about half that of the ringed giant. Its density is extremely light at only 0.33 g/cm³, indicating that it is an expanding gas planet. TOI-6894 is nearly 40 percent smaller than the previous record for the smallest star with a planet of this size. This fact poses a serious contradiction to conventional theories of planet formation. The widely accepted planetary formation model, the 'core-accumulation theory,' proposes that a ring of dust and rocks—known as protoplanetary disk—forms around a star, and that materials in this disk then gather together to form the cores of planets. After starting out this way, larger gas planets then accrete gases around their cores to become gigantic. But if the mass of the star is small, the mass of its protoplanetary disk tends to be small as well. In such a scenario, the nucleus necessary for the formation of a giant gas planet will not grow. Based on this theory, it is estimated that more than 120 times more solid matter than that of the Earth would be required to form TOI-6894b. However, the observed disk surrounding the star TOI-6894 contains only 58 times the mass of the Earth at most. This raises the possibility of an alternative planet-formation mechanism existing. One suggestion by Bryant and the team is that planets could form by gradual gas accumulation, without the initial formation of a massive core. 'Alternatively, it could have formed because of a gravitationally unstable disc,' Bryant says. 'In some cases, the disc surrounding the star will become unstable due to the gravitational force it exerts on itself. These discs can then fragment, with the gas and dust collapsing to form a planet.' However, the press statement goes on to explain that neither of these theories can could completely explain the formation of TOI-6894b, based on the data gathered. For now the planet's origin remains a mystery. Analyzing the atmosphere of the newly discovered exoplanet might yield answers; it is possible that chemical traces of its formation process remain. Observations of TOI-6894b by the James Webb Space Telescope over the next 12 months are expected to reveal details about its interior structure and atmospheric composition, which will have a major say on whether current theories about planet formation are supported or new ones are needed. The discovery may force us to rethink our unified model of planet formation, says Andrés Jordán of the Millennium Astrophysics Institute at Adolfo Ibáñez University in Chile. Years of steady observations are pushing the limits of theory, and it may even be time to fundamentally rethink our estimates of the total number of giant planets in the galaxy. This story originally appeared on WIRED Japan and has been translated from Japanese.
Yomiuri Shimbun
11-06-2025
- Science
- Yomiuri Shimbun
Scientists Puzzled by Discovery of Giant Planet Orbiting Tiny Star
University of Warwick / Mark Garlick / Handout via Reuters A newly discovered giant planet named TOI-6894, top right, is seen orbiting a red dwarf star in this artist's impression released on June 4. WASHINGTON (Reuters) — 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. 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 June 4 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 coauthor 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.
NDTV
06-06-2025
- Science
- NDTV
Discovery Of Small Star Giving Birth To Huge Planet Leaves Scientists Puzzled
Astronomers were left stunned after they found a giant planet, about the same size as Saturn, orbiting a really small red dwarf star, a study published in Nature Astronomy revealed. The star, named TOI-6894, is only about a fifth the mass of the Sun. The observation is quite intriguing, as notable planet formation theories suggest that it shouldn't have happened, as small stars should host small planets similar to Earth and Mars, not big ones. Astronomers believe that small stars are not expected to have suitable conditions for planet formation. TOI-6894 is roughly 240 light-years from Earth in the constellation Leo. It is the smallest-known star to host a large planet. Meanwhile, the planet, called TOI-6894b, is a gas giant, like the Milky Way has Saturn and Jupiter. The planet is completing an orbit in approximately three days, as it is about 40 times closer to its star as compared to Earth is to the Sun. Its location suggests that TOI-6894b's surface must be hot. In size, it is bigger than Saturn but slightly smaller than Jupiter. In mass, it is 56% that of Saturn and 17% that of Jupiter. "I was very excited by this discovery. I originally searched through TESS observations of more than 91,000 low-mass red-dwarf stars looking for giant planets," says astrophysicist Edward Bryant of the University of Warwick in the UK, who led the international research team. "Then, using observations taken with one of the world's largest telescopes, ESO's VLT, I discovered TOI-6894b, a giant planet transiting the lowest mass star known to date to host such a planet. We did not expect planets like TOI-6894b to be able to form around stars this low-mass. This discovery will be a cornerstone for understanding the extremes of giant planet formation," Bryant said. Bryant added, "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." The star and planet system was discovered during an investigation of NASA's TESS (Transiting Exoplanet Survey Satellite) and the European Southern Observatory's Chile-based Very Large Telescope (VLT). "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. How are planets formed? The formation process starts with the Giant Molecular Cloud, in which a giant cloud of gas and dust collapses under its own gravity. After that, the centre of the cloud becomes a protostar, which eventually becomes a star. Then a disk of gas and dust forms around the protostar. The small particles in the disk stick together, growing into larger bodies called planetesimals. Then the collision and merger of Planetesimals happen, forming larger planetary embryos. The embryos undergo differentiation, where heavier elements sink to the centre.
Yahoo
05-06-2025
- General
- Yahoo
A tiny star gave birth to a giant exoplanet, but no one knows how
When you buy through links on our articles, Future and its syndication partners may earn a commission. Like a family in which short parents have tall children, a tiny red dwarf star is defying our understanding of how planets form by existing alongside a giant exoplanet. Giant planets are not rare per se — after all, we have four in our own solar system. Such large worlds are, however, rarely found around the smallest stars, red dwarfs. Red dwarfs simply shouldn't have enough material to form such huge worlds. Well, tell that to the red dwarf star TOI-6894, which is located 238 light-years away. It has just 20% of the mass of the sun, but has been found to host a giant planet, TOI-6894b, that's a little larger than Saturn, albeit with only about half the mass of the ringed planet. Statistical work has shown that only about 1.5% of red dwarfs harbor gas giant planets, so TOI-6894 is among a rare breed indeed. And it is by far the least massive star to be found with an orbiting giant planet: 60% less massive than the next lowest-mass star with a gas giant. Given how scarce such worlds around red dwarfs are, finding this new planet in data from NASA's Transiting Exoplanet Survey Satellite (TESS) was not easy. (The "TOI"' in the system's name refers to a "TESS object of interest.") "I originally searched through TESS observations of more than 91,000 low-mass red dwarf stars looking for giant planets," Edward Bryant of the University of Warwick, who led the discovery, said in a statement. Upon discovering that TESS had recorded TOI-6894b transiting its star, which gave Bryant the planet's radius, his team then observed it with the ESPRESSO (Echelle Spectrograph for Rocky Exoplanets and Stable Spectroscopic Observations) spectrograph on the Very Large Telescope in Chile, and SPIRou (Spectropolarimétre Infrarouge) spectrograph on the Canada–France–Hawaii Telescope on Mauna Kea to determine its mass. However, "we don't really understand how a star with so little mass can form such a massive planet," team-member Vincent Van Eylen of University College London's Mullard Space Science Laboratory said in the statement There are two models to describe the formation of giant planets. One way, which we think is how Jupiter, Saturn, Uranus and Neptune formed, is via a process called core accretion. A giant planetary core, up to ten times the mass of Earth, forms first out of elements heavier than hydrogen and helium. The gravity of the resulting large rocky body is then able to pull in huge swathes of gas in a runaway process from the surrounding planet-forming disk. Given that red dwarfs are scaled down stars, the material available in their planet-forming disk is then similarly scaled down — hence why we find many more smaller planets around red dwarfs than gas giants. Calculations suggest the core of TOI-6894b contains 12 times the mass of Earth. However, in a previous survey of 70 planet-forming disks around red dwarfs with between 15 and 25% the mass of our sun, only five were found to contain more than 12 Earth masses of heavy elements, and only one had an abundance significantly greater than 12 Earth masses. The odds are that TOI-6894b shouldn't have been able to support core accretion. However, Bryant has tried to envisage a process of core accretion by halves. Given that TOI-6894b's overall mass is less than Saturn, a runaway accretion process might not have been required to build up its mass. "Given the mass of the planet, TOI-6894b could have formed through an intermediate core-accretion process, in which a protoplanet forms and steadily accretes gas without the core becoming massive enough for runaway gas accretion," he said. An alternative means by which giant planets form is from a disk instability, whereby a section of a planet-forming disk becomes unstable and collapses under its own gravity, coalescing into a planet. This is a top-down formation process rather than the bottom-up of core accretion, but there is disagreement within the astronomical community over whether such low-mass stars can even experience a disk instability. So, the origin of TOI-6894b remains an open question, but the James Webb Space Telescope (JWST) could potentially discover the answer in the planet's atmosphere. TOI-6894b orbits close to its star every 3.37 days at a distance of just 3.89 million kilometers (2.42 million miles). A gas giant so close to a sun-like star would be classed as a "hot Jupiter" with an atmospheric temperature in the high hundreds, if not more than a thousand, degrees Celsius. However, as a red dwarf, TOI-6894 is cooler than our sun by more than 2,500 degrees Celsius, meaning TOI-6894b has an atmospheric temperature of just 147 degrees Celsius (296 degrees Fahrenheit) – still warm, but by no means hot. This has repercussions for the chemistry of its atmosphere. "Based on the stellar irradiation of TOI-6894b, we expect the atmosphere is dominated by methane chemistry, which is very rare to identify," Amaury Triaud of the University of Birmingham said in the statement. "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." Related Stories: — 'Cosmic miracle!' James Webb Space Telescope discovers the earliest galaxy ever seen — James Webb Space Telescope unveils fiery origins of a distant, hellish exoplanet — Scientists question possible signs of life on exoplanet K2-18b in new study: 'We never saw more than insignificant hints' A proposal to observe TOI-6894b's atmosphere has already been accepted as part of the JWST's fourth cycle of science observations, to take place over the next 12 months. Besides searching for the likes of methane and ammonia, the characteristics of the planet's atmosphere discernible to JWST could point to which formation model – core accretion or disk instability – is the correct one, or even whether a brand new formation model is needed. Although giant planets around red dwarf stars are rare — other examples include the worlds LHS 3154b, GJ 3512b and c, and TZ Ari b — the numbers may still be on their side. That's because red dwarfs are the most common type of star in the galaxy, making up three-quarters of the estimated 100 billion stars in the Milky Way. So even 1.5% of 75 billion is a huge number of red dwarf stars – 1.125 billion to be exact — that could host giant planets. "This discovery will be a cornerstone for understanding the extremes of giant planet formation," concluded Bryant. The discovery of TOI-6894b was published on June 4 in the journal Nature Astronomy.
GMA Network
05-06-2025
- 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
