Red Giant Star Pair Are Our Exceptionally Distant Neighbors

Two new stars have been discovered in the Milky Way galaxy, and they are the most distant stars ever detected at the edge of our galaxy.

The two stars in question, a pair of cool red giants, are helping researchers better determine the vastness of the Milky Way. According to a study published in the Astrophysical Journals detailing this discovery, the giants ULAS J0744+25 and ULAS J0015+01 are an estimated 775,000 and 900,000 light years away from Earth, respectively.

The ULAS twins, as we will call them, are the first stars identified this far out, but are most certainly still part of the Milky Way Galaxy, according to the study's authors.

A team of experts led by John Bochanski, a visiting assistant professor at Haverford College, first detected the ULAS twins while surveying the Milky Way's shrouded outer halo - a shell-like structure of obscuring dust and other natural space debris. They were reportedly looking for rare red giants, using specially designed filters to highlight near-infrared light signatures specific to the massive stars.

Cool red giants are exceptionally bright, shining nearly 10,000 times brighter than their dwarf-star cousins. However, even with their brilliancy, finding these stars took a little bit of luck.

"It really is like looking for a needle in a haystack," Bochanski said in a statement. "Except our haystack is made up of millions of red dwarf stars."

The team was initially just thrilled to find more red giants, but when they measured the distance of these stars, they were awed.

"The distances to these two stars are almost too large to comprehend," says Bochanski. "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."

Past theories have suggested that the Milky Way and its cloudy outer halo is at least 500,000 light years away. Now researchers understand that it could possibly be twice that distance.

"Most models don't predict many stars at these distances," said Bochanski. "If more distant red giants are discovered, the models may need to be revised."

The study was published in Astrophysical Journals Letters on July 3.