Messier 60

Lore & Background

Messier 60 and nearby elliptical galaxy Messier 59 were discovered by Johann Gottfried Koehler in April 1779, while he was observing a comet in the same part of the sky. Charles Messier added both to his catalogue about three days after this discovery. The galaxy is classified as elliptical type E1+1⁄2 (E1.5), though some sources class it as S0 – a lenticular galaxy. Its isophotes are boxy in shape rather than simple ellipses, and it has a near-constant mass-to-light ratio of 9.5 in the V band. The effective radius is 128″ (about 10 kpc at its distance), with an estimated mass of ~10¹² M☉ within a threefold volume, nearly half of which is dark matter. X-ray emission estimates give a mass of (1.0±0.1)×10¹² M☉ within 5 effective radii.

At the center of M60 is a supermassive black hole of 4.5±1.0 billion solar masses, one of the largest ever found, which is currently inactive. X-ray emission reveals a cavity created by jets emitted by the hole during past active periods, corresponding to weak radio lobes, with the power needed to generate these features in the range (6–7)×10⁴¹ erg·s⁻¹. One supernova has been observed: SN 2004W (Type Ia-pec, mag. 18.8), discovered by the Lick Observatory Supernova Search on 28 January 2004, located 51.6″ west and 78.7″ south of the nucleus.

M60 has several satellite galaxies, including the ultracompact dwarf galaxy M60-UCD1, discovered in 2013. Its motion through the intercluster medium results in ram-pressure stripping of gas from the galaxy's outer halo beyond a radius of 12 kpc. NGC 4647 appears approximately 2.5′ from M60; their optical disks overlap, but photographic images show no evidence of gravitational interaction, suggesting they are at different distances and only weakly interacting if at all. However, Hubble Space Telescope studies indicate a tidal interaction may have just begun.

Reader's Guide

Messier 60 holds significance in the history of extragalactic astronomy as the fastest-moving galaxy included in Edwin Hubble's landmark 1929 paper concerning the relationship between recession speed and distance. Hubble used a recession speed of 1090 km/s for M60, 1.8% less than the more recent value of about 1110 km/s (based on a redshift of 0.003726). However, he estimated its distance, along with that of three other Virgo Cluster nebulas (Messier 85, 49, and 87), to be only two million parsecs, rather than the accepted value today of around 16 million parsecs. These distance errors led him to propose a Hubble constant of 500 km/s/Mpc, whereas the present estimate is around 70 km/s/Mpc. The galaxy's central supermassive black hole, one of the largest ever found, and its inactive state with evidence of past jet activity, make it a key object for studying black hole growth and feedback. Its membership in the M60 group, the closest-known isolated compact group of galaxies, and its possible tidal interaction with NGC 4647, provide a laboratory for understanding galaxy interactions and evolution in dense environments.

Did You Know?

• Messier 60 was discovered by Johann Gottfried Koehler in April 1779 while observing a comet.
• It was the fastest-moving galaxy in Edwin Hubble's 1929 paper on the recession speed–distance relationship.
• The galaxy has a satellite, the ultracompact dwarf galaxy M60-UCD1, discovered in 2013.