Artist’s impression of the HD265435 system in about 30 million years, with a smaller white dwarf distorting the hot bottom dwarf into distinct “teardrop” shapes. Photo credit: University of Warwick / Mark Garlick
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Astronomers brought the rare sighting of two stars to their doom by finding signs of a teardrop-shaped star.
This tragic shape is caused by a large white dwarf nearby, which distorts the star with its strong gravity, which will also be the catalyst for a possible supernova that will eat both of them up. Discovered by an international team of astronomers and astrophysicists led by the University of Warwick, it is one of the few star systems to be discovered one day. white dwarf star to revive the point.
New research posted by the team today at. published Natural astronomy confirms that the two stars are in the early stages of a spiral that is likely to end in a Type Ia supernova, the kind that helps astronomers determine how fast the universe is expanding.
This research was funded by the German Research Foundation (DFG) and the Science and Technology Facilities Council, part of UK Research and Innovation.
HD265435 is about 1,500 light-years away and consists of a hot sub-dwarf star and a white dwarf that orbit each other at a speed of about 100 minutes. A white dwarf is a “dead” star that has burned all its fuel and collapsed on its own, making it small but very dense.
It is widely believed that Type Ia supernovae occur when a white dwarf’s core re-ignites, resulting in a thermonuclear explosion. There are two scenarios where this could happen. In the first case, the white dwarf gains enough mass to reach 1.4 times the mass of our sun, which is known as the Chandrasekhar limit. HD265435 fits the second scenario, in which the total mass of nearby star systems of several stars is close to or above this limit. Only a handful of other star systems have been discovered that reach this threshold and produce Type Ia supernovae.
First author dr. Ingrid Pelisoli of the Department of Physics at the University of Warwick, which used to belong to the University of Potsdam, explained: “We don’t know exactly how this one is. Supernova explode, but we know it has to happen because we see it happening elsewhere in the universe.
“One possibility is that if the white dwarf accumulates enough mass from the hot sub-dwarf that as the two orbit and approach each other, matter begins to escape from the hot sub-dwarf and falls onto the white dwarf. Another possibility is that because you lose energy through the emission of gravitational waves, they get closer until they merge. As soon as a white dwarf gains sufficient mass using either method, it becomes a supernova. “
Using data from the NASA Transiting Exoplanet Survey Satellite (TESS), the team was able to observe hot sub-dwarfs, but not white dwarfs, as hot sub-dwarfs are much brighter. However, this brightness varied over time, suggesting that the star was distorted into a teardrop shape by a nearby massive object. With the help of radial velocity and rotational velocity measurements from the Palomar Observatory and WM Keck Observatory and by modeling the effects of massive objects on hot sub-dwarfs, astronomers were able to confirm that the hidden white dwarf was as heavy as our sun, but only slightly smaller than its radius. earth finger.
Together with the hot subdwarf mass, which is slightly more than 0.6 times the mass of our sun, the two stars have the mass required to cause a type Ia supernova. Like the two of them star are close enough to roll closer together, the white dwarf will surely become a supernova in about 70 million years. A theoretical model created specifically for this study predicts that the hot sub-dwarf will also contract into a white dwarf before merging with its companion.
Type Ia supernovae are important as “standard candles” for cosmology. Its brightness is constant and of a certain type of light, meaning that astronomers can compare its brightness to what we observe on earth and calculate the distance with great accuracy. By observing supernovae in distant galaxies, astronomers combine their knowledge of the speed of those galaxies with our distance from the supernova and calculate the area of the universe.
dr. Pelisoli adds, “The more we understand how supernovae work, the better we can calibrate our standard candles. This is very important today because there is a difference between what we get from this standard type of candle and what we do through other methods.
“The more we understand about supernova formation, the better we can understand whether these differences we see are due to new physics we don’t know about and haven’t considered, or simply because we are dealing with underestimated uncertainty. these distances.
“There is another difference between the estimated and observed rate of galactic supernovae and the number of precursors we see. We can estimate how many supernovae there will be in our galaxy by observing multiple galaxies or by what we know from stellar evolution, and the numbers are consistent. But when we looked for objects that could become supernovae, we didn’t have enough. This discovery is very useful in measuring what hot sub-dwarfs and white dwarfs can contribute. Looks like there’s still not much, none of the channels we’re observing seems to be enough.”
White dwarfs that live on the edge
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Chandrasekhar’s super-candidate white sub-dwarf hot sub-dwarf for supernova precursor Ia, Natural astronomy (2021). DOI: 10.1038 / s41550-021-01413-0 , www.nature.com/articles/s41550-021-01413-0–
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University of Warwick
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Quote: Teardrop Star Reveals Hidden Supernova Doom (2021, 12 July), accessed 12 July 2021 from https://phys.org/news/2021-07-teardrop-star-reveals-hidden-supernova.html
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