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M 77

Spiralna galaksija - Spiral Galaxy M77 (NGC 1068), type Sb, in cetus

Cetus A

Rektascenzija 02 : 42.7 (u:m)
Deklinacija -00 : 01 (sto:m)
Razdalja 60000 (*1000 sv.l.)
Vizual. magnituda 8.9 (mag)
Zorni kot 7x6 (loc min)

This magnificient galaxy is one of the biggest galaxies in Messier's catalog, its bright part measuring about 120,000 light years, but its faint extensions (which are well visible e.g. in the DSSM image) going perhaps out to nearly 170,000 light years. Its appearance is that of a magnificient spiral with broad structured arms, which in the inner region show a quite young stellar population, but more away from the center, are dominated by a smooth yellowish older stellar population.

M77 is about 60 million light years distant, approximately the same distance but another direction as the Virgo Cluster, and is receding from us at about 1100 km/sec, as was first measured by Slipher of Lowell Observatory in 1914; it was the second galaxy with a large measured redshift after the Sombrero galaxy, M104 (Tully's Nearby Galaxies Catalog gives a somewhat smaller value for the distance, 47 million light years, and values in other sources are spread both below and above the Virgo Cluster value).

This galaxy is unique and peculiar because of several reasons. First, its spectrum shows peculiar features in the form of broad emission lines, indicating that giant gas clouds are rapidly moving out of this galaxy's core, at several 100 km/sec. This feature classifies M77 as a Seyfert galaxy of type II (type I Seyfert galaxies exhibit an even larger expansion velocity of several 1000 km/sec); it is the nearest and brightest representative of this class of active galaxies. An enormous energy source is required to generate this velocity, which must sit in the galaxy's core. This core was found to be a strong radio source (which was designated Cetus A), and it was investigated by the Hubble Space Telescope. Infrared investigations with the 10-meter Keck telescope by Caltech astronomers have revealed a strong pointlike source, less than 12 light-years in diameter, and surrounded by an elongated structure of 100 light years extension (a concentration of stars or interstellar matter); these structures were not apparent in the Hubble images in the visible light. M77, as well as other Seyfert galaxies, have been known to be bright infrared radiators since some time.

It were Donald E. Osterbrook and R.A.R. Parker in 1965 who brought up the hypothesis that Seyfert galaxies might be thought of as miniature quasars (quasi-stellar radio sources), according to Burnham.

In the inner disk of M77 surrounding the active nucleus, intense star forming activity in an inner bar was found to take place by the Ultraviolet Imaging Telescope on its Astro-1 Space Shuttle mission.

M77 is the dominating member of a small physical group of galaxies, which includes NGCs 1055 (type Sb) and 1073 (type SABc), as well as UGCs 2161 (DDO 27, type Im), 2275 (DDO 28, type Sm - designating a morphiological type between spirals and irregulars) and 2302 (DDO 29, type Sm), and the irregular galaxy UGCA 44 and the SBc barred spiral Markarian 600. NGCs 1087 (Sc), 1090 (S-), and 1094 (SABb-) are nearby background galaxies, as their much higher redshift indicates (Info from Burnham, Tully, and the Sky Catalogue 2000).

  • Vec posnetkov M77
  • Amaterski pos. M77

    Povzeto po:
    Hartmut Frommert (spider@seds.org)
    Christine Kronberg (smil@lrz.uni-muenchen.de)

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