Pair of Galaxies NGC 2444/5

NGC 2444/5
NGC 2444/5: Pair of galaxies in Lynx; 500 mm Cassegrain f/7.2; SBIG STL11K; 590-120-120-120 min LRGB; Bernese Highlands; © 2017 Radek Chromik

History

This pair of galaxies was discovered on 18 January 1872 by the French astronomer Édouard Stephan using the 31 inch Foucault reflector at Marseille observatory. [277]

In Halton Arp's «Atlas of Peculiar Galaxies» from 1966 the two galaxies NGC 2444 and NGC 2445 are listed as Arp 143. He classified it as material emanating from an elliptical galaxy and noted: «diffuse counter filament». [199]

Physical Properties

NGC 2444/5
NGC 2444/5: Image taken with Hubble Space Telescope. © ESA/Hubble & NASA [516]

This object shows a spectacular head-on collision between two galaxies. They probably already passed through each other once, which has ignited the star-formation in the unusual triangular-shaped galaxy NGC 2445, which is rich in gas. Young blue stars have tinted the galaxy in a blue-ish colour. The age of the stars in this bridge is estimated to be between 50 and 100 million years, while those in the centre of NGC 2445 are no older than one to two million years. Another interesting feature of NGC 2445 are the dark filaments of gas in the bright core, which may have been formed by outbursts of material. Radio observations reveal a powerful source in the core that may be spearheading the outbursts. The radio source may have been produced by intense star formation or a black hole gobbling up material flowing into the centre.

NGC 2444 appears to be winning this battle as this galaxy is pulling gas from NGC 2445. NGC 2444 contains old stars and no new starbirth because it lost its gas long ago, well before this galactic encounter. The gravitational tussle has stretched NGC 2444 into an odd shape, yanking gas far from the galaxy. [516] The distance is estimated to 63.3 Mpc. [194]

«Catalogue of Principal Galaxies (PGC)», Paturel et al. 1989 [144]
NameRA [hms]Dec [dms]mTypeDim [']Btot [mag]HRV [km/s]PA [°]
PGC 2175407 46 18.8+39 04 00S1.0 x .715.1
PGC 21774, NGC 244407 46 53.0+39 02 00L M1.2 x .814.24032
PGC 21776, NGC 244507 46 54.7+39 01 01I M1.4 x 1.113.93998

Finder Chart

The pair of galaxies NGC 2444/5 is located in constellation Lynx. The best time for observation is November through April, when it is high in the sky during night.

Chart Pair of Galaxies NGC 2444/5
Pair of Galaxies NGC 2444/5 in constellation Lynx. Chart created using SkySafari 6 Pro and STScI Digitized Sky Survey. [149, 160]

More Objects Nearby (±15°)

References

144Catalogue of Principal Galaxies (PGC); Paturel G., Fouque P., Bottinelli L., Gouguenheim L.; Astron. Astrophys. Suppl. Ser. 80, 299 (1989); cdsarc.unistra.fr/viz-bin/cat/VII/119 (2021-02-18)
149SkySafari 6 Pro, Simulation Curriculum; skysafariastronomy.com
160The STScI Digitized Sky Survey; archive.stsci.edu/cgi-bin/dss_form
194NASA/IPAC Extragalactic Database (NED); ned.ipac.caltech.edu (2020-12-27)
199«Atlas Of Peculiar Galaxies», Halton Arp, 1966; Astrophysical Journal Supplement, vol. 14, p.1 (1966); DOI:10.1086/190147; Bibcode:1966ApJS...14....1A
277«Historische Deep-Sky Kataloge» von Dr. Wolfgang Steinicke; klima-luft.de/steinicke (2021-02-17)
516Hubble Looks at a ‘Space Triangle’ Spawned by a Galaxy Collision; esahubble.org/news/heic2201 (2022-04-29)