Messier three is likely one of the largest and most sensible globular clusters within the sky, a spectacular tapestry of stars in even modest telescopes, making M3 a favorite goal for beginner astronomers. Considered by the Hubble House Telescope, the eight-billion-year-old cluster takes on a completely totally different character, revealing a shocking focus of a half-million suns, together with almost 300 identified variable stars. At the least 170 of these are RR Lyrae variables, which recurrently pulse with a interval associated to their precise brightness. Evaluating their obvious and intrinsic brightness, astronomers can decide the space to certainly one of these “standard candles,” making them essential parts in calibrating cosmic distances.
This Hubble picture captures quite a few “blue stragglers,” main-sequence stars that seem like youthful than their siblings. However all stars in globular clusters are thought to have shaped at roughly the identical time, and the blue stragglers doubtless have acquired mass from close by companions, making them shine with blue depth.