In a first, NASA spots supernova split into four images

Astronomers using NASA's Hubble space telescope have spotted for the first time a distant supernova split into four images.

The multiple images of the exploding star are caused by the powerful gravity of a foreground elliptical galaxy embedded in a massive cluster of galaxies.

This unique observation will help astronomers refine their estimates of the mass of dark matter in the lensing galaxy and cluster, the US space agency said in a statement.

Dark matter is an invisible form of matter that makes up most of the mass of the universe.

"It really threw me for a loop when I spotted the four images surrounding the galaxy - it was a complete surprise," said Patrick Kelly from the University of California, Berkeley and lead author on the paper.

The elliptical galaxy and its galaxy cluster, MACS J1149.6+2223, are five billion light years away from the Earth.

The supernova behind it is 9.3 billion light years away.

When the four images fade away, astronomers predict they will have the rare opportunity to see the supernova again.

This is because the current four-image pattern is only one component of the lensing display.

The supernova may have appeared as a single image some 20 years ago elsewhere in the cluster field, and it is expected to reappear once more in about a decade.

Measuring the time delays between images offers clues to the type of warped-space terrain the supernova's light had to cover and will help the astronomers fine-tune the models that map out the cluster's mass.

"We will measure the time delays, and we will go back and compare to the model predictions of the light path," astronomers said.

The paper appeared in a special issue of the journal Science celebrating the centenary of Albert Einstein's Theory of General Relativity.