SA astronomers discover stars on edge of Milky Way

16 May 2014

A team of South African and Japanese astronomers, using the Southern African Large Telescope as well as an infra-red survey facility at Sutherland in the Northern Cape, has discovered the first known stars in the flared disk of the Milky Way galaxy, the South African Astronomical Observatory (SAAO) announced on Wednesday.

The stars, known as Cepheid variables, are situated on the far side of the galaxy, approximately 80 000 light years from the Earth.

“The discovery is important because stars like these will allow astronomers to test theoretical ideas about how galaxies, like the Milky Way in which we live, formed,” the SAAO said in a statement. “In particular these stars, which are close to the effective edge of the Milky Way, will help astronomers trace the distribution of the very mysterious dark matter.”

Dark matter is known to be an important component of all galaxies, but its nature and distribution remain elusive.

“The five stars involved in this discovery are very special ones whose brightness changes regularly on a cycle time of a few days,” the SAAO said, adding: “These Cepheid variables have characteristics that allow their distances to be measured accurately.”

The team used observations made at the SAAO’s site in Sutherland to determine the distances of these stars and their locations within the galaxy.

“The majority of stars in our galaxy, including our own sun, are distributed in a flat disk,” the SAAO explained. “Early in the 21st century, radio astronomers discovered that hydrogen gas, of which the galaxy contains a great deal, flared away from the disk at large distances from the galactic centre, but until now no one knew that stars did the same thing.”

The team comprised University of Cape Town professor Michael Feast, John Menzies and Patricia Whitelock, both from the SAAO, and Noriyuki Matsunaga from the University of Tokyo.

Their findings were published online in international scientific journal Nature on Wednesday.

SAinfo reporter