(CN) — An international team of astronomers and astrophysicists accomplished the rare feat of imaging two stars locked in the early stages of a doomed dance orchestrated by the deadly pull of an eventual supernova.
The cosmic dance involves a high-temperature subdwarf star and a white dwarf star orbiting each other across the heavens at a rate of roughly 100 minutes.
After stars like our sun exhaust their nuclear fuel source, they become white dwarfs, expelling their outer material and eventually cooling their massively hot cores over billions of years.
United Kingdom-based astronomers were able to collect data on the subdwarf star using NASA's Transiting Exoplanet Survey Satellite, but the white dwarf was initially too bright to capture using the system.
The white dwarf’s brightness dimmed over time, suggesting a distortion caused by the immense gravity of a nearby object, the study said.
Using radial velocity and rotational velocity measurements from the Palomar Observatory and the W. M. Keck Observatory, astronomers imaged the hidden white dwarf and found it’s as heavy as our Sun, but smaller than the Earth's radius.
Scientists’ observations show the stars are still in the early stage of spiraling to their doom, according to the study published Monday in the journal Nature Astronomy.
Lead author Ingrid Pelisoli from the University of Warwick said in a statement released with the study the team of scientists don’t yet know how the supernovae explode, only that the explosion is a guarantee.
"One way is if the white dwarf accretes enough mass from the hot subdwarf, so as the two of them are orbiting each other and getting closer, matter will start to escape the hot subdwarf and fall onto the white dwarf,” Pelisoli said. “Another way is that because they are losing energy to gravitational wave emissions, they will get closer until they merge. Once the white dwarf gains enough mass from either method, it will go supernova."
The trajectory the two stars are on directs them toward a supernova — the largest explosion event found in the cosmos and one facilitated by collapse of a white dwarf’s dense core — set to occur in about 70 million years.
The supernova that will eventually consume the stars is known as Type Ia, a kind of cosmic event whose brightness allows astronomers to determine the rate at which the universe is expanding.
"The more we understand how supernovae work, the better we can calibrate our standard candles,” Pelisoli said. “This is very important at the moment because there's a discrepancy between what we get from this kind of standard candle, and what we get through other methods. The more we understand about how supernovae form, the better we can understand whether this discrepancy we are seeing is because of new physics that we're unaware of and not taking into account, or simply because we're underestimating the uncertainties in those distances.”
Type Ia supernovae occur when the reignition of a white dwarf star's core sparks a thermonuclear explosion.
The star system where the objects of the study were observed, categorized as HD265435, is located about 1,500 light years from Earth.
Scientists said the star system is also one of the few discovered systems containing a white dwarf with a core that will eventually reignite, according to the study.
“There is another discrepancy between the estimated and observed galactic supernovae rate, and the number of progenitors we see,” Pelisoli said. “We can estimate how many supernovae are going to be in our galaxy through observing many galaxies, or through what we know from stellar evolution, and this number is consistent. But if we look for objects that can become supernovae, we don't have enough. This discovery was very useful to put an estimate of what a hot subdwarf and white dwarf binaries can contribute. It still doesn't seem to be a lot, none of the channels we observed seems to be enough."
Follow Martín Macías on Twitter
Subscribe to Closing Arguments
Sign up for new weekly newsletter Closing Arguments to get the latest about ongoing trials, major litigation and hot cases and rulings in courthouses around the U.S. and the world.
