​New York, Feb 15 (IANS) Astronomers have spotted a rare pulsating star which is expanding and contracting in three different directions simultaneously.

It is situated 7,000 light years away from Earth in the constellation Pegasus, said astronomer Farley Ferrante, a member of the team that made the discovery at Southern Methodist University in Dallas, Texas.

The star is one that pulsates and so is characterised by varying brightness over time. 

Called a variable star, this particular star is one of only seven known stars of its kind in our Milky Way galaxy.

"It was challenging to identify it," Ferrante said in a university statement. 

The Milky Way has more than 100 billion stars. But just over 400,900 are catalogued as variable stars. 

Of those, a mere seven -- including the newly-identified one -- are the rare intrinsic variable star called a Triple Mode 'high amplitude delta Scuti' or Triple Mode HADS(B), for short.

"The discovery of this object helps to flesh out the characteristics of this unique type of variable star. These and further measurements can be used to probe the way the pulsations happen," Robert Kehoe, Professor at Southern Methodist University, said.

"Pulsating stars have also been important to improving our understanding of the expansion of the universe and its origins, which is another exciting piece of this puzzle," Kehoe said.

The astronomers discovered the variable star by analysing light curve shape -- a key identifier of star type -- created from archived data procured by ROTSE-I telescope.