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Indian Express
02-07-2025
- Science
- Indian Express
Can a star die twice? Scientists spot rare cosmic ‘double detonation'
For a long time, scientists believed that just like humans, stars died only once. Now, a rare sighting seems to change the widely held belief. Scientists from the European Space Observatory (ESO) have spotted the first-ever visual evidence of a double detonation of a star, meaning death twice. 'This tangible evidence of a double-detonation not only contributes towards solving a long-standing mystery, but also offers a visual spectacle,' said Priyam Das, a researcher from University of New South Wales who led the SNR 0509-67.5 study, in a statement. By using the Very Large Telescope (VLT) and the Multi Unit Spectroscopic Explorer (MUSE) instrument, ESO scientists observed the remains of supernova SNR 0509-67.5. Located more than 160,000 light-years away, the supernova remnant is believed to have formed more than 300 years ago. The remnants reportedly showed clear indications of the supernova's progenitor star exploding twice. This can give an indication that a small number of stars could become supernovas without having reached the Chandrasekhar limit. This limit indicates the minimum mass of a star in order to become a supernova, which is around 1.4 times the mass of the Sun. As per ESO's research and data from observatories using the Hubble Space Telescope, the SNR 0509-67.5 was confirmed to be a white dwarf star. These stars undergo supernova explosions termed as 'Type Ia supernovas', which are useful to scientists while measuring cosmic distances. This is since the light that these supernovas emit is uniform, giving them the nickname 'standard candles' by astronomers. Astronomy places importance on the explosions of white dwarfs. However, the exact mechanism that triggers their explosion is still a mystery. The common consensus among scientists is that the genesis of Type Ia supernovas is a binary system of stars, with one dying and becoming a white dwarf. If the dead white dwarf ends up orbiting too close to the second living star, then the white dwarf becomes a 'stellar vampire'. This subsequently draws material from its living companion star, until the white dwarf crosses the Chandrasekhar limit. Then, the white dwarf explodes in a Type Ia supernova, which was previously believed to cause an eruption that destroyed the white dwarf. However, this was never considered a closed-book by scientists, and this recent research has further established the possibility of double detonations in white dwarfs. As per the latest theory, when white dwarfs become stellar vampires and are drawing material from their donor stars, they end up engulfing themselves in stolen helium. This then becomes unstable and ignites, leading to the first detonation. This explosion then generates a shockwave rippling inward, which goes on to strike the white dwarf's core. This subsequently leads to the second detonation, which then leads to the formation of the actual supernova. This is notable since it can occur before the white dwarf's mass exceeds that of the Chandrasekhar limit. Scientists were able to determine that a double-detonation would cause a long-lasting 'fingerprint' with the wreckage of the supernova. This has been confirmed by its presence in the SNR 0509-67.5 wreckage. (This article has been curated by Purv Ashar, who is an intern with The Indian Express)
Yahoo
18-03-2025
- Science
- Yahoo
Several planets found orbiting star less than 6 light-years away
Astronomers have confirmed the existence of four planets orbiting a star less than 6 light-years away with help from some of the world's most powerful telescopes. Research published in October 2024 revealed that one planet was rotating around Barnard's Star, the second-closest single star system to Earth. But a combination of telescopes all over the world confirmed the presence of four small exoplanets, according to a study published last week in The Astrophysical Journal Letters. MORE: How global warming could threaten satellites, according to new study The Gemini Telescope in Hawaii and the Very Large Telescope in Chile were used to detect the additional rocky planets, the astronomers said. "It's signaling a breakthrough with the precision of these new instruments from previous generations," said Ritvik Basant, Ph.D student at the University of Chicago and lead author of the paper, in a statement. The first planet was detected using a 27-foot diameter telescope at the European Space Observatory's Paranal Observatory in Chile and a spectrograph that could quickly detect changes in the star's velocity, according to the 2024 paper, published in the journal Astronomy & Astrophysics. MORE: 3.5 billion-year-old crater created by meteorite impact found in Australia, scientists say Barnard's Star, a low-mass red dwarf, was discovered in 1916. Since then, astronomers have discovered that at least 70% of all stars in the Milky Way are this type of star, which is why researchers want to know about the types of planets that orbit them, according to the University of Chicago. "It's a really exciting find -- Barnard's Star is our cosmic neighbor, and yet we know so little about it," Basant said. The planets are 20% to 30% the mass of Earth and make a full orbit around the sun in days, according to the paper. They are likely rocky planets, rather than gas. Since they are so close to Barnard's Star, they are likely too hot to sustain life. The researchers ruled out the existence of other planets within the habitable zone of Barnard's Star. MORE: Parade of planets this month will feature celestial bodies in alignment The planets are difficult to detect because their stars shine so brightly next to them, the researchers said. Scientists from the Gemini Observatory, National Science Foundation NOIRLab, Heidelberg University and the University of Amsterdam calibrated and analyzed data taken during 112 different nights over three years, where they found "solid evidence" to the existence of the additional planets orbiting Barnard's Star, according to the paper. "We observed at different times of night on different days," Basant said. "They're in Chile; we're in Hawaii. Our teams didn't coordinate with each other at all." MORE: Binary star system found near the Milky Way's black hole: An 'amazing' discovery, astrophysicists say He added, "That gives us a lot of assurance that these aren't phantoms in the data." Several planets found orbiting star less than 6 light-years away originally appeared on
