Dwarf Star Caught Exploding After Years Of Hibernation, [VIDEO]
A team of Polish astronomers have captured rare images of a once dwarf star exploding into a "classical nova" after years of hibernation. In an event like this, it is said that white dwarf stars sucks gas from a much bigger partner star until it explode. This usually happens around every 10,000 to one million years.
According to CNN, this was the first time a transition of a dwarf star with low and unstable mass-transfer rate erupt into a classical nova had been observed, said Przemek Mróz, the study's first author and a PhD student at the Warsaw University Astronomical Observatory. "Classical novae attract attention during eruptions, when they are bright and easy to observe," Mróz said. "Because of their unpredictable nature, very little is known about pre-eruption behavior of novae. This is the first case that the evolution of a classical nova can be investigated so precisely with long-term pre- and post-eruption observations."
A classical nova explosion happens in stars with a binary system. This occurs when two stars are orbiting each other. The distance between the components is usually smaller than one solar radius so the strong gravitational interaction disfigures the other star, usually the "secondary" red dwarf star, which has been known to transfer matter onto the second star, in this case the white dwarf star. The matter piles up on the white dwarf surface, and when its mass reaches a critical value, it ignites, triggering a thermonuclear runway, wired.co.uk explained.
Originally, the observation published in Nature, was part of a long-running sky survey originally conducted to detect dark matter. The series of images captured for the said project, the Optical Gravitational Lensing Experiment, allowed researchers to go back and check what the star system looked like before and compare it to the explosion which caught their attention in 2009, the star known as Nova Centauri 2009.
The team of astronomers used data from before the eruption and were able to discover evidence of dwarf nova outbursts, also known as periodic brightening, in the last six years leading up to the explosion. They also found that the classical eruption happened within six days of the last explosion suggesting that the matter discharged onto the white matter during that time prompted the runaway thermonuclear reaction which later led to the explosion.
The findings revealed evidence of mass-transfer changes before, during and after nova eruptions. It also supports the "nova hibernation hypothesis". Mróz explained to BBC News that the hibernation hypothesis states that decades after the nova eruption, the mass-transfer rate in the binary system is increased as a result of the eruption which was caused by the extreme irradiation of the secondary star. "Subsequently, the mass-transfer should drop significantly or even cease. This state is called hibernation," Mróz added.
Mróz also predicted that in the next few decades, the mass-transfer rate in the white dwarf star will gradually decline and the star will slowly fade. "The star will again transform into a dwarf nova, this may take a few years or even several decades, and possibly fall into hibernation for thousands of years, until it will awake again and explode as a classical nova," he said.