London: Scientists have claimed that a special category of stars, known as Type Ia supernovae or ‘Zombie’ stars, can help to probe the mystery of dark energy, which they believe is related to the expansion of the universe.
Invisible dark energy makes up about three-fourths of the universe.
“We only discovered this about 20 years ago by using Type Ia supernovae, thermonuclear supernovae, as standard or ‘calibrated’ candles,” said Andy Howell, adjunct professor of physics at UC Santa Barbara.
“These stars are tools for measuring dark energy. They’re all about the same brightness, so we can use them to figure out distances in the universe,” he claimed.
According to Howell, these supernovae are so bright that they shine with the approximate power of a billion Suns.
He calls Type Ia supernovae “zombie” stars because they’re dead, with a core of ash, but they come back to life by sucking matter from a companion star.
Astrophysicists are using Type Ia supernovae to build a map of the history of the universe’s expansion.
“What we’ve found is that the universe hasn’t been expanding at the same rate,” said Howell.
“And it hasn’t been slowing down as everyone thought it would be, due to
gravity. Instead, it has been speeding up. There’s a force that counteracts gravity and we don’t know what it is. We call it dark energy,” he added.
The new findings relate to Einstein’s concept of the cosmological constant.
The study was published recently in Nature Communications.