Messier 3 (M3; also NGC 5272) is a globular cluster located 33.9 thousand light years from Earth in the northern constellation of Canes Venatici. It is one of the largest and brightest globular clusters discovered with around 500,000 stars.

Discovery

It was discovered on May 3, 1764, Since then, it has become one of the best-studied globular clusters. Identification of the cluster's unusually large variable star population was begun in 1913 by American astronomer Solon Irving Bailey and new variable members continue to be identified up through 2025.]]

Many amateur astronomers consider it one of the finest northern globular clusters, following only Messier 13.

Messier 3 is quite isolated as it is above the Galactic plane and roughly from the center of the Milky Way. It contains 274 known variable stars, by far the most found in any globular cluster. These include 133 RR Lyrae variables, of which about a third display the Blazhko effect of long-period modulation. The overall abundance of elements other than hydrogen and helium, what astronomers term the metallicity, is in the range of −1.34 to −1.50 dex. This value gives the logarithm of the abundance relative to the Sun; the actual proportion is 3.2–4.6% of the solar abundance. Messier 3 is the prototype for the Oosterhoff type I cluster, which is considered "metal-rich". That is, for a globular cluster, Messier 3 has a relatively high abundance of heavier elements.

See also

  • List of Messier objects
  • SEDS Messier pages on M3
  • M3, Galactic Globular Clusters Database page
  • M3 Photo detail Dark Atmospheres