The Tycho supernova remnant
NASA/CXC/RIKEN & GSFC/T. Sato et al; DSS
It’s broadly been thought that our universe is increasing at an ever-accelerating price. However might we have now that incorrect? That’s what a bunch of scientists from South Korea has claimed in a brand new paper, however different scientists have cited main issues with the work.
Our universe has been increasing for the reason that massive bang 13.8 billion years in the past. A number of strands of proof, together with observations of distant dying stars referred to as Kind 1a supernovae, have prompt this enlargement is accelerating. One of many predominant theories for the motive force of this acceleration is a mysterious pressure referred to as darkish vitality, the invention of which received the 2011 Nobel Prize in Physics.
Younger-Wook Lee at Yonsei College in South Korea and his colleagues now say this may be incorrect. Kind 1a supernovae are brought on when the remnant core of a star like our solar, often called a white dwarf, explodes in a binary system. Astronomers use these so-called “normal candles” as reliable measurements of distance throughout the cosmos as a result of they’re regarded as uniformally vivid.
However Lee and his workforce say the brightness varies strongly with the age of the celebs, based mostly on their evaluation of 300 host galaxies. They recommend this leads to distant supernovae that seem fainter due to the accelerated enlargement of the universe however, as soon as this “age bias” is taken under consideration, the accelerated enlargement of the universe disappears.
As an alternative, Lee says their findings recommend the enlargement of the universe started decelerating 1.5 billion years in the past, and will even reverse sooner or later, a situation astronomers name the “massive crunch” by which the universe might finish in a reverse massive bang. Beforehand, he says, “a giant crunch was out of the query. However now it’s a chance.”
Adam Reiss on the Area Telescope Science Institute within the US, one of many recipients of the 2011 Nobel Prize in Physics, disagrees with that declare, pointing to earlier work by the group in 2020 that had been refuted. “The identical group’s new work repeats the argument with little change,” he says, noting that making measurements of stellar ages for Kind 1a supernovae at giant distances may be very tough. He says Lee’s workforce used a imply stellar age derived from the host galaxy. “The speculation behind that is weak due to an absence of certainty about how the [star] kinds,” says Reiss.
There are identified points with how age impacts the brightness of Kind 1a supernovae throughout the universe says Mark Sullivan on the College of Southampton, however these are already accounted for in measurements of darkish vitality. “I’m very sceptical this can result in a decelerating universe,” he says.
Upcoming observations with the Vera C. Rubin Observatory in Chile are anticipated to enormously increase the variety of identified Kind 1a supernovae within the universe, from the 1000’s catalogued as we speak to tens of 1000’s. That can enable us to “map the enlargement historical past” of the universe a lot additional again in time, says Sullivan, doubtlessly ruling out the claims from Lee’s workforce.
The precise nature of darkish vitality, nonetheless, stays mysterious. Earlier this yr, outcomes from the Darkish Power Spectroscopic Instrument (DESI) survey prompt that darkish vitality won’t be a continuing pressure, however might range over time. Whereas that wouldn’t imply the universe was decelerating proper now, it would recommend the enlargement price has modified over the historical past of the universe.
“The needle is pointing much more to darkish vitality being some type of dynamical factor, not a cosmological fixed,” says Ed Macaulay at Queen Mary College of London. “Precisely what that’s I believe is a extremely fascinating query.”
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