Waid Observatory

Arp 269 - NGC 4490, NGC 4485

Date: June 11 13 14 15, 2021  -   Location: Davis Mountains, TX
Telescope: 10in. RC   Mount: Paramount MX   Camera: Apogee ALTA F8300M
Exposure:   L = 180 min. (bin 1x1 - 20 min. exp.)
R = 160 min. - B&G = 120 min. each - Ha = 180 min - (all bin 2x2 - 10 min. exp.)

Click on the image to view at higher resolution.


Arp 269


Arp 269 1,2,3

Located in the constellation Canes Venatici approximately 25 million light years distant is Arp2691..  This celestial object consists of two interacting galaxies. The larger galaxy is designated NGC 4490 and is commonly referred to as the Cocoon Galaxy.  The smaller of the two is designated NGC 4485.  This galaxy pair has interacted during a close encounter.  Their mutual gravity has greatly distorted both.  NGC 4490 is classified as a barred spiral galaxy; however, since the interaction, this form is difficult to discern.  Both galaxies now resemble irregular galaxies.  The gravitational force between the two continues and their shapes are still in the process of warping and evolving.  The gravitational tug-of-war between these two galaxies is not all destructive.  It has created areas of intensive star birth.  Such areas are known as HII regions and appear as redish or pink in the image above.  These regions are distinguished in hydrogen alpha (Ha) filtered exposures.

NGC 4490 actually contains two cores3.  One core is visible in the optical part of the spectrum and one only visible in infrared wavelengths.  This is speculated to be the result of a previous merger with another galaxy.


Copyright Donald P. Waid