HOW PULSATING STARS unlock our universe.

FEATURES Earth is fortunate to be orbiting a star that is fairly constant in its light production. Images such as this have revealed numerous RR Lyrae stars in our galaxy's bulge, hinting that it is old and may have been built up as primordial star clusters merged together over time. RR Lyrae variables are standard candles - objects for which their intrinsic brightness is known, so that a comparison with their observed apparent brightness allows astronomers to calculate their distance. With the high-resolution imaging capabilities of the Hubble Space Telescope (HST), it is routinely possible to identify and characterize RR Lyrae stars in galaxies well beyond the Milky Way. [Extracted from the article]