M4
Spider Globular Cluster
Properties
Position & Identifiers
Visibility
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About M4
Description
M4 is the nearest globular cluster to our solar system, at only about 7,200 light-years away in Scorpius. Despite being relatively loose and diffuse for a globular, it contains tens of thousands of stars spread across about 75 light-years. A distinctive central bar of 11th-magnitude stars runs through the core, making it unique among globulars.
Observing Tips
Located just 1.3 degrees west of Antares (Alpha Scorpii), making it very easy to find. Visible to the naked eye from dark sites. Binoculars show a large, diffuse glow. Even a small telescope resolves individual stars — M4 is one of the easiest globulars to resolve due to its proximity and loose concentration. Look for the characteristic bar of stars across the center at 100x. Best observed from May through August.
History
Discovered by Philippe Loys de Cheseaux in 1745-46. Charles Messier cataloged it in 1764. It was possibly the first globular cluster in which individual stars were resolved. In 1987, the first millisecond pulsar in a globular cluster was discovered in M4.
Fun Facts
M4 contains one of the oldest known extrasolar planets — a gas giant orbiting the pulsar PSR B1620-26, estimated to be 12.7 billion years old, earning it the nickname the Methuselah planet. The Hubble Space Telescope identified white dwarf stars in M4 that are among the oldest burned-out stars known.
Community Photos (1)
Credit: ESO Imaging Survey. License: CC BY 4.0. (Wikimedia Commons)
Skybred Feb 28, 2026