Object of the Week February 12th, 2017- A Southerly Grand Design Spiral NGC2997

Object of the Week February 12th, 2017- Grand Design Spiral NGC2997

NGC2997
UGCA181
PGC27978

Antlia

Galaxy

RA 09 45 39
DEC -31 11 23

Mag 10.2

Size 9.2' x 7.4'

Class SAB(rs)c

Antlia the Air Pump is a small nondescript constellation in the southern hemisphere just beneath Crater and Hydra. Originally coined Antlia Pneumatica in 1763- giving recognition to the recently invented pneumatic air pump - the name was shortened to just Antlia by John Herschel in 1844. A rather 'boring' area of the sky visually, the constellation is comprised of just 4 stars approximately 4th magnitude with the rest being even dimmer. Absent of any proper Milky Way objects, Antlia does house a beautiful grand design spiral that tends to be missed by many deepsky observers.

Using his 18.7" f/13 speculum mirrored telescope, Sir William Herschel discovered NGC2997 on March 4th, 1793. Both large and faint, NGC2997 is a nearly face on spiral armed galaxy with a bright core. Tilted away from us at approximately 50°, it isn't as face on as M51 but it still provides us a beautiful view of its arms all the while giving the galaxy a bit of an elliptical shape to it.

Sadly, NGC2997 isn't visible from my 40° latitude. But I was fortunate enough to observe it on February 24th, 2009 from Ft Davis Texas using Jimis 48". Recognizing I was being spoiled considering the telescope, the view was just astounding. Using a 13mm Ethos at 375x the galaxy filled the view. My notes read "Damn nice! Very M51 like. Very apparent arms. 2 arms on N side, single arm on the other twisting CCW. Bright core. HII regions throughout" Sadly, this was my first and only view of this galaxy. Having been observing in Australia twice (in march/april no less) since my observation in 2009, I have yet to observe this galaxy from the southern hemisphere. One day I will.

Online notes reveal that scopes as small as 5" can see NGC2997s glow. Stephen O'Meara in Southern Gems wrote "Very beautiful, bright ellipse of light about 5' across with a starlike core" while using his 5" refractor. So those with smaller scopes need not be intimated.

One bit of uncertainty I found while researching this object was its distance. Though the consensus appears to be that NGC2997 lies approximately 25 million light years away, I found reports indicating distances at 55Mly away as well as one at the European Space Agency placing it at 140Mly away!

Nevertheless, if you have the opportunity to observe under southern skies this spring (or autumn depending on where you live) be sure to point your scope towards a rather blank piece of real estate named Antlia. There you will find one of the skies grandest spiral galaxys either hemisphere has to offer, NGC2997. Enjoy.

And as always,


"Give it a go and let us know!
Good luck and great viewing!"

Attachment 2468
©AAO

Attachment 2469
©capella observatory

Attachment 2470
©ESO

Hi Dragan,

I've observed NGC 2997 only once, in 1994 with my old 20 inch, and didn't see much because it was so low on the horizon:

"A good sized galaxy, and is listed at magnitude 9.5, but at -31 declination and in (mild) sky glow it was barely seen at all. 182x."

I've thought of this one a few times since then but for a variety of reason have yet to take another look. Thanks for the reminder, hopefully I'll have better luck this year.

Hi Dragan,

with -31° Dec it is visible from Southern Germany but only between summit crosses and pine needles.

I went to Namibia to observe this highlight.
With 12-inch I noted: "impressive, very nice spiral, bright E arm with quarter turn and a brighter portion in its middle, bright NW arm with half turn, fainter third arm to the W with faint extensions to the N"

12", 214x, NELM 7m+
Attachment 2471

I haven't seen NGC 2997 from Jimi's, but I have seen it from Australia! These notes were taken using a 24" f/3.7 on a observing trip in April 2008.

At 215x, this beautiful, asymmetric face-on spiral extended ~7'x4.5' and was sharply concentrated with a very bright 40" core. The spiral structure is unusual with a very long, relatively thick arm that curves from west to east on the north side of the core. This arm then bends south on the east side and contains a very faint 20" HII knot situated northeast of the core [1.6' from center] and symmetrically placed opposite a mag 12 star in the outer halo on the SW side. A mag 14.5 star is near the end of this arm and due east of the core. To the west of the end of this arm the light level noticeably dips [this is a gap between the arms] as well as on the southeast side of the halo, giving an asymmetric appearance.

A second fainter outer arm running roughly SW to NE also wraps around the galaxy on the west and north side but at further distance from the core. This outer arm nearly reaches a mag 12 star on the southwest side (the one opposite the knot mentioned above) and then can be followed with more difficulty to the east where it attaches on the south side of the core.

Note: The HII region is identified in NED as NGC 2997:[MM 81] 306, from the 1981 paper "Morphology and Kinematics of the Ionized Gas in NGC 2997" by Milliard and Marcelin in A&A, 95, 59.

My only observation of NGC 2997 was in May of 2015 from my observing platform at the very southern tip of Vancouver Island Canada 48° 23' N. It was a tough object with my 20" almost horizontal and me on my knees. It wasn't very impressive and I'm sure all that I was seeing was the bright core and the inner part of the main body. No arms were detected. It wasn't the best night for transparency but at least the sky over that area of North western Washington State is fairly dark.

Bill

I drew NGC 2997 last May from Hakos, Namibia using a 16" Newtonian. The spiral structure was obvious at first sight. The arms were a little more extended than on Uwe's drawing. The HII region mentioned by Steve was visible as an elongated inhomogenious spot that is slightly brighter than the arm. All in all this is a beautiful galaxy. My sketch is not yet processed. It will hopefully be ready in a couple of months.

Amply deserves a detailed reobservation. I've only a crude sketch made with my travel 5.5" from Australia:

http://2.bp.blogspot.com/--IsshfG6YJ...Dunlop+100.jpg

Another favorite of mine.

I first found this one from Flagstaff, AZ with a (brand new at the time) 70mm TeleVue Pronto. I mentioned this in my customer-comment card that I sent back to TeleVue, and much to my surprise, found my comments used in a TeleVue ad in S&T and Astronomy Magazine.

I finally got around to re-observing it last spring, under difficult conditions from near Eugene, OR:

4/06/16
EAGLE’S RIDGE
MOON: 29 days, did not rise
SEEING: 6
TRANSPARENCY: 5
SQM: not taken
NELM: about 6.8
WEATHER CONDITIONS: temps in 50s, occasional cirrus blowing through, winds high (tapering off after midnight)

10:40

NGC 2997 (Ant)—down so low in sky I am seeing trees in the FOV—pretty blurry—galaxy 6’ x4’—slightly mottled, even in poor view so low—bright star maybe 10th/11th mag in galaxy’s halo, about 3’ from core on P side—core is about 3/4’ across—maybe stellar nucleus visible in averted, very elusive—galaxy framed in dipper-shaped group of stars of equal mags, bright line/zigzag of 7th/8th/9th mag stars to F side

This came up when I was proof reading Wolfgang's forthcoming book on Herschel's observations. I think it is the most southerly object he found but given he was observing from 51N one wonders whether this was through the grass :)

This one is large and bright, and displays a mottled surface and some nearby stars.
It culminates at roughly +25deg. for me, and a couple degrees higher than that at some of my observing sites.
It's about the same as M83 for me, in altitude.
It's a bit fainter than M83, but has the same classic close-to-ace-on spiral look, obviously not exactly round or oval.
One side extends out farther from the core than the other--one of the spiral arms I presume. The core is small and bright, not stellar.
In Australia, this was an obvious spiral, with a bright core and detailed spiral arms (in an 18").
Here in SoCal with a 12.5", it's less detailed and displays only an indistinct look at the spiral arms because of its low altitude.
(though it's higher than a lot of stuff in Sagittarius and Scorpius)
This is one of the grand southern galaxies I look at every year, along with NGC55, 300, 1365, 247, 253, 7793, 3109, etc.

Quote:

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Originally Posted by obrazell

This came up when I was proof reading Wolfgang's forthcoming book on Herschel's observations. I think it is the most southerly object he found but given he was observing from 51N one wonders whether this was through the grass :)

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Herschel had a few more southerly discoveries than NGC 2997. He made it down another 1.5 degrees further south to NGC 3621 in Hydra, which culminated at 7 degrees elevation. And he had no problem with it...

"cB, vgbM, E from about 70 degrees np to sf, about 6' or 7' long and near 4' broad. Within a parallelogram of stars."

Last night I finally observed this galaxy with my 20" from Rio Hurtado, Chile. The galaxy was already past the meridian but it still was high in the sky. At 197x it was visible as a large oval glow with two beautiful spiral arms. A third one split off from the tighter one near a bright star. This one definitely is one of the most beautiful spirals in the sky!

One note: at 40°N, this object culminates at an altitude of 19°. That's low, but not "dirt diving" low.
That's 6° HIGHER than the Bug Nebula in Scorpius, and a degree higher than Messier 70 in Sagittarius.