 | Interacting galaxies Arp 273 This interesting pair of interacting spiral galaxies was first described in the Catalogue of Peculiar Galaxies, compiled by Halton Arp in 1966. It is also pair number 64 in Igor Karachentsev's catalog of binary galaxies. The larger member is strongly tidally distorted, looking almost as though one side of the galaxy has been placed under a magnifying glass. The edge-on companion, however, retains a relatively undisturbed spiral disk, but has a luminous, heavily obscured but infrared-bright, star-burst nucleus. The nucleus of the large spiral, by way of a contrast, contains a low-ionization nuclear emission-line region (LINER), which is indicative of much less activity than the bright nuclear HII region of its companion. |
 | The Nearby Spiral Galaxy M33 This true color picture was taken using Ektachrome film at the prime focus of the Kitt Peak 4m telescope on October 3rd 1973. This is unusual: normally color images are made by combining black and white images taken through different colored filters. Due to reciprocity failure during the quite long exposure needed, the image is slightly bluer than it should be. The spiral structure of the galaxy is clearly seen, as is the giant HII region designated NGC604 (the reddish spot in the upper left). The third largest galaxy in our own Local Group (after the Andromeda Nebula, M31, and our own Galaxy), M33 (NGC598) is over thirty thousand light years across, and more than two million light years away, appearing on the sky in the constellation Triangulum. Photograph by Bill Schoening. |
 | M83, NGC5236, Southern Pinwheel This is a type Sc spiral galaxy in the constellation Hydra. The galaxy has two principal arms and a third, fainter one. There has been a remarkable number of supernovae in M83 within less than a century - at least four since 1923 - compared to the theoretical incidence of one per 300 years. This is still a subject of current research and uncertainty. M83 is 10 million light years away and thirty thousand light years across. This picture was taken using color film directly at the Kitt Peak 4-meter telescope in 1973. This is unusual: normally color images are made by combining black and white images taken through different colored filters. Photograph by Bill Schoening. |
