Because RR Lyrae stars have the same average brightness, astronomers use them as standard candle distance indicators.

FORBES: Astronomers Confirm Milky Way's Most Distant Stellar Stream

The confirmation, based on analysis of 10 billion year-old dying RR Lyrae stars in the Gemini constellation, was done by an international team of astronomers who report their findings in The Astrophysical Journal.

FORBES: Astronomers Confirm Milky Way's Most Distant Stellar Stream

By analyzing measurements of 1207 RR Lyrae stars taken by the Catalina Mount Lemmon Telescope in Tucson, the team was able to observe dramatic brightness variations in these stars, taking place over periods as short as half a day.

FORBES: Astronomers Confirm Milky Way's Most Distant Stellar Stream