Our Milky Way galaxy still remains a big mystery for our scientists. Its distant outskirts, i.e. Milky Way halo harbor some of the valuable clues of the endless space that may help us in understanding the formation and evolution of our Galaxy to a larger extent.
“Its halo is still a big mystery to us. Our current observations are very limited,” say the researchers.
According to the scientists, an extremely sparse population of stars and the overwhelming distances have still kept many objects that are beyond 400,000 light years unidentified. So far, only seven stars are known beyond this limit.
Initiating a hunt in this regard, John Bochanski, a visiting assistant professor at Haverford College, along with his team began targeting stars in the Milky Way’s outer halo.
Halo, a sparse shroud of stars that surrounds the disk of our Galaxy, stretches to at least 500,000 light years away.
Bochanski’s team, which includes Haverford College Associate Professor of Astronomy Beth Willman, has discovered two stars in this halo. Both the newly-found stars are the most distant ever discovered in our Galaxy.
The details of the discovery of two cool red giants, ULAS J0744+25 and ULAS J0015+01, was published a letter in Astrophysical Journal Letters on July 3.
These distant stars are at distances of 775,000 and 900,000 light years respectively. The importance of both the stars goes beyond their record-holding distances as they inhabit the Milky Way’s halo.
“It really is like looking for a needle in a haystack. Except our haystack is made up of millions of red dwarf stars,” Bochanski says.
Bochanski states, “The distances to these two stars are almost too large to comprehend. To put it in perspective, when the light from ULAS J0015+01 left the star, our early human ancestors were just starting to make fires here on Earth.”
Haverford College astronomer Beth Willman, who is a co-author of the study, says, “Theory predicts the presence of such an extended stellar halo, formed by the destroyed remains of small dwarf galaxies that merged over the cosmic ages to form the Milky Way itself,” Willman says. “The properties of cool red giants in the halo thus preserve the formation history of our Milky Way. These stars are truly ghosts of galaxies past.”