An extensive "bridge" connects the 60 thousand light year wide M51 with its smaller companion, NGC 5195. Clusters of hot, bright young stars, and gases heated by their radiation, illuminate the spiral arms, and clearly define them. Thick dust lanes straddle the arms, sweep across the "bridge" and partially obscure the companion. The pair are just over 30 million light years away. (S. Beckwith (STScI) Hubble Heritage Team, (STScI/AURA), ESA, NASA, postprocessing by Robert Gendler, apod091226)

M60 is a 120 thousand light-year wide elliptical galaxy, in the Virgo Cluster, 60 million light years distant. It is a massive galaxy, with thousands of globular clusters, in addition to the trillions of stars in the galaxy, itself. In the image below, M60 is the bright elliptical at lower left. The more distant spiral galaxy above and to its right is NGC4647. (AURA, NSF, NOAO)

     Only 35 million light years away, this hundred thousand light year wide spiral is a member of the well-studied Leo Triplet of galaxies. Gravitational interaction with other members of the small group has probably influenced the structure of its dust-filled arms, and the formation of clusters of bright young stars which light up those arms. (M. Neeser (Univ.-Sternwarte Munchen), P. Barthel (Kapteyn Astron. Institute), H. Heyer, H. Boffin (ESO), ESO, apod060902)

Although in Coma Berenices, M88 is one of fifteen Messier objects which are members of the Virgo Cluster of galaxies, the nearest major cluster to our galaxy. It is about 60 million light years away, and over 100 thousand light years in diameter. (Jim Quinn/Adam Block/AURA/NSF, NOAO)

     M94 is a spiral galaxy about 15 million light years distant, in the constellation of Canes Venatici. The central, bright "spiral" is about 30 thousand light years across, but the galaxy also has a broad faint ring of stars extending an additional 30 to 40 thousand light years beyond the central region. Recent investigation has shown that the outer ring has a spiral structure, with currently active star formation, as well (click here for more images and discussion). (Adam Block, AURA, NSF, NOAO)

     M102 was long thought to be a duplication of M101, because its actual discoverer, Pierre Méchain, made an error in the position he sent to Messier, and later disavowed the discovery. Based on subsequent communications between the two, it now seems likely that the object was NGC 5866, a lenticular galaxy in Ursa Major which both Méchain and Messier observed in 1781. The tenth-magnitude NGC 5866 is the brightest member of the 45 million light-years distant NGC 5866 group of galaxies, and the dynamics of the group suggest that although NGC 5866 is only about 70 thousand light-years across, it has a trillion solar masses. This mass would include, as in the case of all galaxies of well-determined mass, large amounts of "dark matter"; but its oversized nucleus, presumably crammed with a multitude of faint stars, undoubtedly contributes to its large ratio of mass to size. (NASA, ESA, and The Hubble Heritage Team (STScI/AURA), W. Keel (U. Alabama), apod060612)

     M104 lies at the nearer edge of the 60 million light years distant Virgo cluster of galaxies, and at nearly a trillion solar masses, is one of the more massive galaxies in that group, even though relatively small (about 50 thousand light years across). The massive central bulge of the galaxy almost totally obscures the structure of the spiral disk, but a recent reworking of this image, seen on a page about M104, reduces the glare from the nucleus, allowing the spiral structure to be better revealed. (The Hubble Heritage Team (STScI/AURA), NASA)

     A satellite of M31, also known as NGC205, M110 is the elliptical galaxy below M31, in the image of that galaxy, above. About 15000 light-years across, M110 is comparable in size to the Magellanic Clouds, which are satellites of our galaxy. Elliptical galaxies usually contain little gas, and only old stars, but M110 has dust clouds, and young stars, perhaps as a result of its gravitational interaction with M31. (Robert Gendler, apod051222)