M80 is a small but compact globular cluster located in Scorpius. It shines at magnitude +7.5 and therefore within the range of popular 7x50 or 10x50 binoculars. At its core, M80 contains a large number of "blue stragglers", stars that appear much younger than the age of the globular cluster itself! The likely reason is they have probably lost part of their cooler outer layers due to close encounters with other stars. Since M80 contains more blue stragglers than average it implies exceptionally high core stellar interaction rates.
M80 was discovered by Charles Messier on January 4, 1781. Though not conspicuous, M80 is easy to locate as its positioned just 4 degrees northwest of brilliant red supergiant star Antares (α Sco - mag. +1.0). The globular is situated halfway along an imaginary line connecting Antares with Acrab (β Sco - mag. +2.6). Located just west of Antares is magnificent globular cluster M4.
The finder chart below shows the position of M80. The globular is best seen from tropical and Southern Hemisphere latitudes during the months of May, June and July.
When viewed with binoculars or small telescopes, M80 appears as a mottled ball of light. A small 80mm (3.1-inch) scope reveals a soft round structure that's not resolvable. Larger 200mm (8-inch) telescopes display a bright compact core and an outer halo that extends up to 5 arc minutes in diameter. On nights of good seeing and transparency the outer regions hint at resolution. Much better resolution is achieved with apertures of 300mm (12-inch) or greater, with the brightest member stars being of about 14th magnitude. On May 21, 1860 a bright nova (T Sco) reached magnitude +7.0 in M80 and for a short time it outshone the entire cluster.
M80 is located at a distance of about 32,600 light-years and contains at least 200,000 stars. In total it covers 10 arc minutes of apparent sky, which corresponds to a spatial diameter of 96 light-years. The cluster is estimated to be 12.54 billion years old.
M80 Data Table
|Object Type||Globular cluster|
|RA (J2000)||16h 17m 03s|
|DEC (J2000)||-22d 58m 30s|
|Apparent Size (arc mins)||10 x 10|
|Number of Stars||>200,000|
|Notable Feature||Contains a relatively large number of blue stragglers|