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NGC 1961 (Arp 184)

Date:26.10.95 Time:4:19 UT Exposure:V:20m, I:20m
Field of View:14' x 11' (big image) Receiver: WWFPP, 20482 CCD Filter:V, I
Instrument: 1.23m Observatory: Calar Alto Observer:T. Credner, S. Kohle

© Copyright by the observers

Astronomical Institutes of the University of Bonn

NGC 1961 is a disturbed spiral galaxy located in the constellation Camelopardalis. Due to its peculiar asymetric appearence it is listed in Arp's Catalog of Peculiar Galaxies (number 184).

Its distance is 60 Mpc, adopting a Hubble value of H0=75 km/s/Mpc. NGC 1961 is known to be a very massive spiral galaxy with strong star formation. The upper wing shows this very blue star population, indicating the young age of this part. The bright blue stars are very massive, waste their hydrogen and so have a very short lifetime. Indeed, just back in 1998 the violant death of a star was observed as Supernova explosion in NGC 1961 (IAU Circular 7016).
The peculiar morphological appearance remains a puzzle to astronomers. The neighboring galaxies are too small and not close enough for gravitational interaction (see the small spiral companion in the big image). The possibility of interaction with a hot intergalactic medium (Shostak et al. 1982) could not be confirmed by recent X-ray observations (Pence & Rots 1997). And a former merging event should result in a different morphology and kinematics (Shostak et al. 1982).

The above image is a two color composit. Two exposures were taken with Johnson V and I filters and are represented with the two complementary colors blue and orange to show the data in a natural appearing way with the right chromatic order.


U. Lisenfeld et al.: 1998, MNRAS, 300, 30