Messier Object 77

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M 77

Spiral Galaxy M77 (NGC 1068), type Sb,

in Cetus

Cetus A

[m77.gif]

Right Ascension 02 : 42.7 (h:m)
Declination -00 : 01 (deg:m)
Distance 60000 (kly)
Visual Brightness 8.9 (mag)
Apparent Dimension 7×6 (arc min)

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

Vesto M. Slipher of Lowell Observatory in 1914; it was the second galaxy

with a large measured redshift after the

Sombrero galaxy, M104 (R. Brent 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; the higher values would make M77 the most remote

Messier object).

This galaxy is unique and peculiar because of several reasons. First of

all, 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 was first discovered by

Edward A. Fath of Lick Observatory in 1908

(Lick Observatory Bulletin 5, p. 71, 1909) who identified six

“Planetary Nebula type” emission lines (H Beta, [O II] 3727, [N III] 3869,

[O III] 4363, 4959, 5007), confirmed by Vesto M. Slipher at Lowell

Observatory in a much better spectrum in 1917

(Lowell Observatory Bulletin 3, 59),

and particularly mentioned by Edwin P. Hubble in his historic paper on

“extragalactic nebulae” of 1926 (Ap.J. 54, 369).

It 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.

This remarkable class of galaxies is named after its discoverer,

Carl K. Seyfert, who described them first in 1943

(Ap.J. 97, 28-40).

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, has 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).

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