Messier 88 (NGC 4501) is a spiral galaxy in the constellation Coma Berenices, and is one of the giant spiral members of the Coma-Virgo Galaxy Cluster.
M 88 is one of the eight galaxies found on March 18, 1781 by Charles Messier in the Coma-Virgo region, and described by him as a "nebula without stars". M 88 was among the first galaxies recognized as a spiral, listed by Lord Rosse in 1850 as one of the fourteen "spiral nebulae" known at that time.
Amateur Observation
Messier 88 is a bright galaxy, appearing at magnitude 9.6, and is about 7' x 4' in size. It lies near the northern end of a 3° long arc of galaxies that begins to the southwest in Virgo, with M 84 and M 86, then curves east and northeast to M 88.
M 88 is one of the more rewarding galaxies in the Virgo cluster for smaller instruments. It is a compact spiral whose equatorial plane is inclined by about 36° to our line of sight; its appearance is similar to the Andromeda galaxy, M 31, although in miniature! The galaxy's 2.5' x 2' core is bright and elongated. Its disk has a mottled texture around the core. With averted vision, spiral structure can be seen, especially along the southwest flank. Knots can be seen northwest and southeast of the core.
M 88 is classified as an Sbc spiral, with moderately-wound spiral arms. The arm structure is very regular and can be followed into the galactic core. In 1999, the Type Ia supernova 1999cl was discovered in this galaxy, and reached magnitude 13.6.
Physical Properties
At the Virgo Cluster's distance of 65 million light years, M 88 has the impressive absolute magnitude of -22, a luminosity of 52 billion suns. Its true diameter probably is in excess of 125,000 light years. This galaxy has a considerable radial velocity away from us, receding at about 2000 km/sec.
M 88 may be on a highly elliptical orbit that is currently carrying it toward the Virgo cluster's center, near the giant elliptical galaxy M 87. Currently 1.5 million light years from the center, it will come closest in 200 to 300 million years. The galaxy's motion through the intergalactic medium of the Virgo cluster creates "ram pressure" that is stripping neutral hydrogen away from its outer regions, especially along its western, leading edge.
M 88 is also classified as a Seyfert galaxy, which means that it produces narrow spectral line emission from highly ionized gas in its nucleus. In the core region, there is a central condensation, 230 parsecs in diameter, which is being fed by inflow from the spiral arms. The supermassive black hole at the core of this galaxy contains about 80 million times the mass of the Sun.