Two Newly-Found Stars Hold Secrets to Milky Way Galaxy's History
The reach of our Milky Way galaxy just grew a little farther, thanks to the recent discovery of two new stars located an estimated 700,000 and 900,000 light years out, respectively.
A team of astronomers led by John Bochanski, a visiting assistant professor at Haverford College in Pennsylvania, set their telescopes toward in our home galaxy's outer halo, a relatively sparse number of stars that surround the disk-like Milky Way and generally reach outward to approximately 500,000 light years away. And on July 3, the researchers discovered two stars since confirmed as the most distant ever discovered in the galaxy.
According to a paper published in Astrophysical Journal Letters, Bochanski and his colleagues managed to zero in on two red giants, ULAS J0744+25, situated about 775,000 light years away, and ULAS J0015+01, at about 900,000 light years.
The distances of the stars, deduced from two separate sky studies -- one a digital analysis and the other a survey of infrared light emanated from the celestial bodies in the sights of astronomers.
Red giants are relatively few when compared to cool red dwarf stars, which vastly outnumber giants across the sky. But, giants are also nearly 10,000 times brighter than dwarfs, making them visible even at extremely large distances.
Nevertheless, said Bochanski in a school news release, detecting and then verifying red giants "really is like looking for a needle in a haystack ... except our haystack is made up of millions of red dwarf stars."
Bochanski and his team, which includes astronomers from Boston University, Michigan State University, the Harvard-Smithsonian Center for Astrophysics and the Kapteyn Astronomical Institute, in the Netherlands, used a variety of methods to estimate the distances to ULAS J0744+25 and ULAS J0015+01, with every technique showing the same thing: these stars are extremely far away, more than 50 percent farther from the sun than any other known star in the Milky Way, about five times farther than the Large Magellanic Cloud.
The two stars are, in fact, about one third the distance to the Andromeda Galaxy, the Milky Way's sister spiral in the Local Group of neighboring galaxies.
"The distances to these two stars are almost too large to comprehend," said 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."
The discovery of ULAS J0744+25 and ULAS J0015+01 is important to us on Earth because they exist in the Milky Way's halo, which at least some astronomers think assert is like a cloud of galactic crumbs, the result of the Milky Way's merger with other smaller galaxies.
Therefore, by assembling a larger sample of distant red giants, Bochanski and his team hope to test model predictions for the formation of the Milky Way.
"Most models don't predict many stars at these distances," Bochanski said. "If more distant red giants are discovered, the models may need to be revised."
Said Daniel Evans, lead for Individual Investigator Programs at the National Science Foundation's Division of Astronomical Sciences, which funded the research: "These results will undoubtedly shed new light on the formation and evolution of our galactic home."