Object of the Week April 21, 2019 - NGC 1954, MCG -2-15-3, PGC 17422, HDCE 0361, in LEPUS
Object of the Week - NGC 1954, MCG -2-15-3, PGC 17422, HDCE 0361, in LEPUS
R.A.: 05h32m48.3s Dec.: -14°03'46" (2000)
Size: 3.4'x 1.8'
Magnitude: 12.60 B
Morphology; SA(rs)bc pec (as per NED)
Since the this is the Easter weekend I thought I would chose an object from the Easter Bunny constellation… well, OK, it’s Lepus, the Hare… but that’s close enough for me… even though it too late to observe this year!
NGC 1954 is an interesting galaxy, about 14° south of the celestial equator, and is part of a galaxy trio that also includes NGC1957 4.3’ SSE and IC 2132 9.3’ NNW, all strung out in a nearly straight line. All 3 galaxies are at about the same distance, about 150 million light years away. NGC 1954 is a very large galaxy. Its apparent diameter of about 4.6 arc-seconds corresponds to a diameter of about 200,000 light-years, bigger than the Milky Way (or about the same, depending on which source you choose to determine our galaxy’s diameter). The companion galaxies NGC 1957 and IC 2132 have diameter of 43,000 light-years and 83,000 light-years respectively, so each is much smaller than NGC 1954. In addition, IC 2132 has a morphology of Sa pec and is an example of what now are known as red and dead galaxies due to their lack of recent star formation.
I was originally drawn to the galaxy because I saw a terrific picture of it by an amateur astrophotographer named Kent Biggs…
… and I wanted to see what I could of any details. The photo shows 2 arcs of what appeared to be star-forming regions rather than being spiral arms or rings… but from my usual observing site in the local Anza Borrego State Park, all I could see was a bright compact core with a dim halo around it. Still, it was a nice view with NGC 1957 also showing in the same field of view, off to the side, and in the other direction, about twice as far away, is the third member of this trio, IC 2132.
The MCG says of NGC 1954… "Two extremely thin arcs do not appear as spirals, nor as dense rings. They consist of 15 to 20 HII regions." Reading this made me think: both NGC 1954 and NGC 1957 are so-called “peculiar” galaxies and both have suspected rings, and when you add to that those 2 arcs of HII regions, what do you suppose the chance is that these 2 galaxies have interacted in the not too distant past? That would sure explain a lot, wouldn’t you agree?
As always, give it a go and let us know.
Last edited by Paul Alsing; April 24th, 2019 at 04:28 AM.
Nice group. My journal says of NGC 1954, "Possibly the arm segment leading to the star pair." That would be the northern arc. 12", 125-375x, dark-blue zone site. 2015.
Wow, very deep photograph. I was not aware of the bridge between NGC 1954 and 1957 yet. Nice.
I had a look at the group at a windy but extremely transparent night on the top of the ORM observatory in La Palma with an 18-inch telescope. I could detect the hints of the thin spiral arms and the somewhat offset nucleus of NGC 1954.
sketch: 18", 274x, NELM 7m5+, Seeing IV NGC1954.jpg
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