NASA's Hubble captures a star-spangled sea of 500,000 stars

Key Points:

• Globular clusters are ancient, tightly packed star groups formed billions of years ago, preserving a record of the Milky Way's history; about 150 such clusters orbit the galaxy's outskirts.
• Messier 3 (M3) is a large globular cluster notable for its large population of over 240 RR Lyrae variable stars, which help astronomers accurately measure cosmic distances due to their predictable brightness cycles.
• M3 also contains around 70 blue straggler stars, which appear younger and hotter due to mass gained from companion stars, a phenomenon first discovered in this cluster.
• The presence of two distinct stellar populations in M3 suggests it may have formed from the merger of two globular clusters originally part of a dwarf galaxy absorbed by the Milky Way.
• Hubble Space Telescope observations of M3 use color imaging to reveal stellar temperatures and contribute to a broader survey of globular clusters, aiding scientists in reconstructing the Milky Way’s formation and evolution over billions of years.