The Cocoon Galaxy (NGC 4490) and NGC 4485

Posted by Rod Pommier
on Monday, February 17, 2014

by Rod Pommier
Telescope/Mount: Celestron Compustar C14 with Astrophysics 0.75x focal reducer (f/8.3)
Location: Pommier Observatory, Portland, OR, USA
Camera: SBIG STL 11000M with Baader Planetarium LRGB filters.
Exposures: L:R:G:B=240:80:80:80=8 hours total exposure obtained between 2013/05/31 and 2013/06/04

This image shows two interacting galaxies lying 40-50 million light-years away in Canes Ventatici. They have already had their closest approach and are speeding away from each other, separated by 24,000 light-years. Both galaxies are thought to have originally been spirals that have been heavily distorted by the tidal forces of the interaction. The group is also known as the Cocoon Galaxy, due to its present shape. The larger galaxy, NGC 4490, has virtually no remaining spiral structure discernible along our line of site, while the smaller galaxy, NGC 4485, still displays hints of its spiral structure. The interaction has triggered bursts of star formation in both galaxies, visible as numerous clusters of hot blue stars emitting UV light that cause numerous HII nebulae to glow. This is also evident along a chain of star formation that connects the two galaxies. These hot blue stars have short lives that end in supernovae and the group has exhibited several supernovae in the past 4 decades.

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