The researchers said that these 208 stars reside in the outermost regions of the outer halo, which is a spherical cloud of stars dominated by the mysterious, invisible substance that scientists call dark matter, whose existence is only known through the influence of its gravity.
The most distant of these stars is located at a distance of 1.08 million light-years from Earth. One light year is the distance that light travels in a full year, equal to 9.5 trillion kilometers.
These stars were observed using the Canada-France-Hawaii telescope on Mauna Kea in Hawaii, and they belong to the class of stars called (RR Laray), which has a relatively low mass and is characterized by a lack of elements heavier than hydrogen and helium. The mass of the most distant star is about 70 percent of that of the Sun.
No other stars have been reliably measured in the Milky Way at a greater distance than these stars.
These objects that inhabit the far outskirts of the galactic halo can be considered orphan stars, because, according to scientists’ interpretation, they originated in smaller galaxies that collided with the larger Milky Way at a later time.
“Our explanation for the origin of these distant stars is that they were most likely born in the halos of dwarf galaxies and star clusters that were attracted or, more bluntly, swallowed by the Milky Way,” said Yuting Feng, a doctoral researcher in astronomy at the University of California, Santa Cruz.