April 1, 2020

Astro Event: An Interesting Equatorial Galaxy.

Many northern hemisphere observers many not realize the wealth of galaxies that exist in the late fall sky. This week, we look at an interesting galaxy that transits to the south right around 9 PM local time; M77. Also known as NGC 1068, this large extended galaxy sports a bright nucleus shining a magnitude of about +10. Under moderate magnifications with a good-sized aperture telescope perhaps three distinct spiral arms can be seen.

About 1° degree southeast of Delta Ceti, M77 is the brightest in a group of Cetus galaxies including NGC 1090, 1087, 1073, and 1055. M77 was one of the first galaxies along with the Sombrero galaxy to display a large redshift and added to mounting evidence in the early 20th century that the universe was indeed expanding. Current estimates put the distance to M77 at about 47 million light years. Visually, its surface dimensions are about 7’x 6’ arc minutes in size. Its coordinates are;

Declination: -00 00’ 48”

Right Ascension: 2h 42’ 41”

This places it well above the murk for observers in middle latitudes during November at dusk. Do give this interesting galaxy a try as the light-interfering Moon doesn’t reach 1st Quarter this month until November 13th.

The astro-term for this week is Seyfert Galaxy. This particular class of galaxies was first noted by Carl Seyfert in 1943 as a source of moderately strong radio emissions. These are active galactic nuclei embedded in large galaxies and are classified either as type I (broad emission lines) and type II (narrow emission lines). M77 is a barred spiral type 2 Seyfert galaxy with an energetic core and a diameter of about 170,000 light years. M77 is one of closest and best studied of this class of galaxies.  This also has made it a target for several studies by the Hubble and Spitzer Space telescopes as well as the Very Large Baseline Array. M77 also has the standard radio source designation of 3C71.

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