NGC6438 is a 12th magnitude lenticular galaxy in the far southern constellation of Octans. Measuring about 1.5' across and located at a distance of approximately 100M light years, it displays a noticeably brighter core but is otherwise appears fairly structureless.
Of more interest is its immediate neighbour, informally referred to as NGC6438A. This has a complex structure and has variously been referred to as a Magellanic type galaxy, an incomplete ring galaxy or an interacting galaxy pair. Visually, the galaxy comprises a brighter and slightly yellow core and two distorted arms, one curled almost into a ring and the other a shallow arc. Both arms are highly irregular and lumpy.
Donzelli and Espindola [Astronomical Journal Vol 111 (3) pp 1057-1064] argue that the object can be best interpreted as a triplet interaction of an SO galaxy and two disc galaxies undergoing a merger. Altogether a fascinating if small and faint object in the far southern skies, and a
First on Astrobin - AstroBin object.
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