Sydney: Old stars, called red giants, have offered insight into what our sun will look like after five billion years -- its outer layer will expand and cool down, so it`ll look red, and the core will contract and become extremely hot and dense.
Tim Bedding and Dennis Stello, professors of astronomers at the University of Sydney, and colleagues discovered that red giants have slowed down on the outside while their cores spin at least 10 times faster than their outer layers.
The finding tells what the sun will look like in five billion years when it develops into a red giant, the journal Nature reports.
"The heart of a star determines how it evolves, and understanding how a star rotates deep inside helps us to understand how stars like our sun will grow old," said Bedding, according to a university statement.
Using NASA`s Kepler space telescope, the team observed deep inside ageing red giants to make their discovery of the difference in rotation rate between the core and outer layers of the stars.
The team, led by Paul Beck from Leuven University in Belgium, analysed waves inside the stars, which appear as rhythmic variations in the surface brightness of the stars.
The effect of rotation on the frequencies of the waves is so small, it took the scientists nearly two years of almost continuous data gathering from the Kepler satellite to make their discovery.
"Red giants were once stars like our sun, but as they age their outer layers expand to more than five times their original size and cool down significantly, so they look red," explained Stello.
"The opposite actually happens to the cores of red giants, as the core contracts and becomes extremely hot and dense," said Stello.