4 Attachment(s)
Object of the Week December 6th, 2015: The NGC 1600 family of galaxies.
Object of the Week December 6th, 2015: The NGC 1600 family of galaxies.
NGC 1600, Eridanus
RA 04 31 40
DEC -05 16 16
Type: Galaxy
Class: E2
Size: 2.5' x 1.7'
Magnitude: 11.5
The NGC 1600 family of galaxies.
During December evenings the sky is dominated by the magnificent constellation of Orion. Observers of all levels and ages spend hours and hours observing the gems of the Great Hunter, yet relatively few amateurs manage to detach themselves from Orion and explore the skies for goodies that literally “hide” in the shadow of the Hunter. This week’s Object of the Week is such a goodie, being located only a few degrees west of blazing Rigel, at the beginnings of the great river Eridanus: NGC 1600 and its “family” of galaxies (NGC 1601, 1603, 1604, and 1606), located between Nu and Xi Eridani.
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Deep Sky Survey of the NGC 1600 area
NGC 1600 is a large elliptical (E2) galaxy, located at the staggering distance of more than 60 Mpc (200 million light years away). Some sources even suggest a distance in excess of 300 lmy away, which indicate a huge system. There are several indications that NGC 1600, which is a weak X-ray source, is the result of galactic mergers. The visual magnitude of NGC 1600 is 11.5, and its apparent dimensions are 2.5 x 1.7 arc minutes. There are several fainter galaxies near NGC 1600, and a study by F.J. Balletseros et al suggests that NGC 1600 is indeed the main galaxy in a loose gravitationally connected group of galaxies that include the much fainter NGC 1601, 1603, 1604, 1606, and IC 373 (hence my using of the term “family”!).
I personally “discovered” these galaxies during an extensive star-hop to explore the more southerly areas of Eridanus. NGC 1600 seemed too prominent on the star charts to pass. Indeed, NGC1600 was a real treat in my 18” Obsession. Located next to a zig-zagging line of 12th and 13th magnitude stars, NGC 1600 appeared as a tiny but bright elongated ellipse in the 1-degree field given by my 31mm Nagler. In addition to NGC 1600, I could detect a couple of fainter smudges. Increasing the magnification provided more details in the brighter galaxies and brought some even fainter ones into view.
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The NGC 1600 group as photographed from my home. The field is nearly one-degree across.
NGC 1600 is the dominant galaxy in all magnifications. The galaxy is though best seen at 275X, appearing as an ellipse elongated north – south. A very bright star-like nucleus lies in the center of a bright roundish core, which in turn is surrounded by a bright elliptical halo. A few arcminutes to the north – northeast, a much smaller (0.5x0.3’) and fainter elliptical smudge of uniform surface brightness can be seen, this being magnitude 14 NGC 1601. To the east of NGC 1600 another 14th magnitude galaxy is visible, the tiny roundish (0.6’ diameter) NGC 1603. Like 1601, this galaxy has a uniform surface brightness. NGC 1606, further to the northeast of 1600 is by far the hardest galaxy of the family. It is a tiny roundish 15th magnitude glow that I could not hold steady all the time with direct vision. NGC 1604 is located about 15’ to the south of NGC 1600 it is 0.5’ roundish glow of magnitude 13.7, and slightly easier to see than other members of the group. Finally, IC373 is located about 15’ to the NW of NGC 1600 and is a roundish 1’ smudge glowing feebly at magnitude 14 but with a low surface brightness.
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All galaxies (except faint NGC 1606) could be seen together in the 0.6-degree field of view of my Ethos 13, and somehow reminded me of a parent taking his kids out for a walk in the park, the shyer kids staying close to the parent while the more playful ones daring to venture a bit further away. NGC 1606 was only visible in the higher power given by my Takahashi LE 7.5mm eyepiece.
As usual, I tried for the 1600 family with my smaller scopes. With my 6” achromatic refractor I could detect NGC 1600 even at medium powers, but was more defined at 128X. Unlike in the Obsession, the refractor showed NGC 1600 as a tiny roundish blob of faint light. No trace of the other galaxies could be detected. Going down to my 4.7” achromatic refractor, again I could detect NGC 1600 at 85X as a very faint tiny roundish glow. I believe that NGC 1600 should be detectable even with my 4” refractor but I have yet to try.
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So next time you are out in a dark winter evening looking at Orion, remember this cute family of faint galaxies near Rigel, and…
"Give it a go and let us know!
Good luck and great viewing!"
