Messier 77, Cetus A + NGC 1055

Messier 77
Messier 77: Image taken with Hubble Space Telescope [215]


The galaxy M 77 was discovered by Pierre Méchain on October 29, 1780. Charles Messier verified the observation on December 17, 1780 and wrote: «A cluster of small stars with nebulae, in the whale on the parallels of the star δ [Ceti], third magnitude, which M. Messier estimated only to be fifth. M. Méchain saw the cluster on October 29, 1780 in the form of a mist.» [281] Wilhelm Herschel also saw a «poorly defined star surrounded by nebula» in his 7 feet focal length telescope in 1783. In his large 10 feet telescope he saw «a kind of greatly enlarged star cluster with a few bright stars in the middle». Only Lord Rosse recognized the spiral nature of this galaxy in 1850. [217] Halton Arp included the galaxy M 77 in his «Atlas of Peculiar Galaxies» published in 1966 as Arp 37, since he suspected small companion galaxies in the bright nodes. A few smaller, much more distant galaxies can also be seen at the edge of M 77. [199]

Physical Properties

Messier 77
Messier 77: Image taken with the VLT of ESO in Chile [284]

At a distance of about 44 million light years, M 77 is the closest and brightest Seyfert galaxy, a group of galaxies with a very active core, lots of hot, ionized, brightly shining gas and a high rate of star formation. In the core there is a supermassive black hole of about 15 million solar masses, which is also a strong source of X-rays and radio radiation. Hence the name «Cetus A». [215]

Only half a degree away is the galaxy NGC 1055, which we can see directly from the side. This was discovered by Wilhelm Herschel on December 18, 1783. The distance is estimated to be about 45 to 50 million light years and the diameter to about 115'000 light years. It belongs to the same group as M 77. It could also be a starburst galaxy similar to M 82. [196]

The small, faint galaxy NGC 1072 is much further away with 114 Mpc (approx. 372 million light years) and does not belong to the group. The best observation time is September to December.

«Catalogue of Principal Galaxies (PGC)», Paturel et al. 1989 [144]
NameRA [hms]Dec [dms]mTypeDim [']Btot [mag]HRV [km/s]PA [°]
NGC 105502 41 44.7+00 26 32SB7.6 x 3.011.4995105
NGC 1068, M 7702 42 40.1-00 00 48S7.3 x 6.39.7113570
NGC 1072, IC 183702 43 30.9+00 18 30SBR1.5 x .514.2802111

Finder Chart

The galaxy group is located in the constellation Cetus (Whale), less than 1 ° from δ Ceti.

Chart M 77
Chart created using SkySafari 6 Pro and STScI Digitized Sky Survey. [149, 160]


144Catalogue of Principal Galaxies (PGC); Paturel G., Fouque P., Bottinelli L., Gouguenheim L.; Astron. Astrophys. Suppl. Ser. 80, 299 (1989); (2021-02-18)
149SkySafari 6 Pro, Simulation Curriculum;
160The STScI Digitized Sky Survey;
196Celestial Atlas by Curtney Seligman; (2020-12-28)
199Atlas Of Peculiar Galaxies, Halton Arp; (2020-12-28)
215Explore - The Night Sky | Hubble’s Messier Catalog; (2020-12-31)
217The Messier Catalog (SEDS); (2021-01-01)
281«Catalogue Nébuleuses et des Amas D'Étoiles» Observées à Paris, par M. Messier, à l'Observatoire de la Marine, hôtel de Clugni, rue des Mathurins. «Connoissance des temps ou connoissance des mouvements célestes, pour l'année bissextile 1784 » Page 227; (2021-02-21)
284The edge-on galaxy NGC 1055; (2021-02-26)