NGC 4676 A/B, Mice Galaxies

NGC 4676
NGC 4676: Galaxy in Coma Berenices. North is right; 500 mm Cassegrain 3625 mm f/7.2, SBIG STL11K; 180-60-60-60 min LRGB; Bernese Highlands; © 2011 Radek Chromik


These two interacting Galaxies were first seen by William Herschel on March 13, 1785. As usual he was observing with his large his 18.7 inch reflecting telescope of 20 feet focal length, located in Bath, England. He cataloged it as II 326 and noted: «faint, much extended in the direction of the meridian.» [463] His son John cataloged it later as h 1425 (GC 3207) and thought he had seen two nucleus. He noted: «extremely faint, query if not bicentral». [466] John L. E. Dreyer added it 1888 as NGC 4676 in his «New General Catalogue». [313]

On March 3, 1892 the Austrian astronomer Rudolf Spitaler observed the same galaxy with the 27 inch refractor at Wien University Observatory. He saw two objects which were later added as IC 819 and IC 820 by Dreyer in his «Index Catalogue». He described both as «double nebula, connected, very faint, very small, south following, one brighter». [314] Because John Herschel described the nebula as having two nuclei and Spitaler listed them as two individual objects, they ended up as duplicate entries of NGC 4676 by mistake.

In Halton Arp's 1966 «Atlas of Peculiar Galaxies», the two interacting galaxies are listed as Arp 242 in the group #233-256 with «appearance of fission». [199]

NGC 4676
NGC 4676: Image taken by Hubble Space Telescope in 2002 with blue, orange and near-infrared filters [476]

Physical Properties

The distance to NGC 4676 A/B is given as 102 Mpc (circa 331 million light years). [145] These are two nearly identical spiral galaxies approximately 160 million years after their closest encounter. Gravitational forces have deformed their spirals into long, stretched tidal tails, giving the nickname «The Mice» for this interacting pair of galaxies. The long, stretched arm is actually curved. We see it edge-on why it appears straight. Simulations show that the pair will eventually merge and form a large elliptical galaxy. The stars, gas and luinous clusters of stars in the tidal tails will either fall into the merged galaxies or remain in a orbit in the halo. Our own Milky Way will probably look similar when it collides with our neighbour the Andromeda Galaxy (M 31) in several billion years from now. [476]

«Catalogue of Principal Galaxies (PGC)», Paturel et al. 1989 [144]
NameRA [hms]Dec [dms]mTypeDim [']Btot [mag]HRV [km/s]PA [°]
NGC 4676A, IC 81912 46 10.1+30 44 00LB M2.1 x .613.86619
NGC 4676B, IC 82012 46 11.2+30 43 28S M2.7 x .714.06597146

Finder Chart

The pair of galaxies can be found in the constellation Coma Berenices. Best observation time is in the months December through July.

Chart NGC 4676
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)
145SIMBAD astronomical database;
149SkySafari 6 Pro, Simulation Curriculum;
160The STScI Digitized Sky Survey;
199Atlas Of Peculiar Galaxies, Halton Arp; (2020-12-28)
313«A New General Catalogue of Nebulae and Clusters of Stars, being the Catalogue of the late Sir John F.W. Herschel, Bart., revised, corrected, and enlarged» Dreyer, J. L. E. (1888); Memoirs of the Royal Astronomical Society. 49: 1–237; Bibcode:1888MmRAS..49....1D
314«Index Catalogue of Nebulæ found in the years 1888 to 1894, with Notes and Corrections to the New General Catalogue» Dreyer, J. L. E.; Memoirs of the Royal Astronomical Society, Vol. 51, p.185; 1895; Bibcode:1895MmRAS..51..185D
463«Catalogue of one thousand new nebulae and clusters of stars» William Herschel, Philosophical Transactions of the Royal Society of London, 1 January 1786; DOI:10.1098/rstl.1786.0027
466«Observations of nebulæ and clusters of stars, made at Slough, with a twenty-feet reflector, between the years 1825 and 1833» John Frederick William Herschel, Philosophical Transactions of the Royal Society of London, 1 January 1833, Pages: 359-505; DOI:10.1098/rstl.1833.0021
476The Mice (NGC 4676): Colliding Galaxies with Tails of Stars and Gas; (2022-01-29)