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deepskytraveler
January 23rd, 2019, 02:30 AM
Object of the Week January 20, 2019 - ARP 217 The Bow and Arrow Galaxy

ARP 217, NGC 3310, UGC 5786, PGC 31650, VV 356, VV 406, MCG+09-18-008
Constellation: Ursa Major
Type: SAB(r)bc pec
Orientation: face-on
RA: 0h 39m 56.5s
Dec: +53° 24’ 03”
Magnitude: 11.2
Size: 2.2’ x 2.1’


NGC 3310 was discovered by William Herschel on April 12, 1789 during sweep #919. Cataloged as H IV-60 and h731, William Herschel recorded his observation as: “vB, R, planetary, but very ill defined. About 1’ of its diameter is equally bright, and 1/4 of a minute hazy or ill-defined round the margin.” John Herschel recorded his observation as “B; R; vsmbM, so as to for almost a disc 15” diameter. Surrounded by a very feeble atmosphere.”

On March 5, 1848, Lord Rosse and William Rambaut observed NGC 3310 (the earliest observation of Lord Rosse’s 1861 monograph) and reported: “See minute points in it at intervals, also spiral arrangement.” A week later on March 11 they noted: “Nebula well resolved into little stellar points. Saw a broad band across the bottom distinctly and two at the top.”

When compiling his 1966 Atlas of Peculiar Galaxies, Halton Arp identified NGC 3310 as a galactic merger candidate and described it briefly like this: “Much Ha emission including Half arc outside galaxy.” The galaxy was catalogued as Arp 217 and placed it in the Adjacent Loops category. Examples of other galaxies in this class are NGC 2782 (Arp 215), NGC 7679 and NGC 7682 (Apr 216), and IC 4553 (Arp 220).

Arp 217 lies 55 million light years away and is a starburst galaxy, similar to M82. It is commonly called the Bow and Arrow galaxy because of the odd stream of young blue stars piercing a diffuse arc of stars that possibly traces the path of the merging galaxy. Another name associated with this galaxy but less frequently used is the Bowstring Galaxy.

Arp 217 is located in Ursa Major, SW of the southwest corner of the Big Dipper and 10’ SSW of a beautiful reddish-orange magnitude 5.5 star. The galaxy is fairly bright, slightly elongated, and uniformly illuminated. In small to medium aperture scopes the core of the galaxy appears broadly concentrated but the surrounding halo is marginally visible.

Christian Luginbuhl and Brian Skiff in the Observing Handbook and Catalogue of Deep-Sky Objects share their observations of Arp 217 with a wide range of apertures. “Lying 10’ SSW of a reddish mag 5.5 star, 6 cm will show this galaxy easily. At 50x it is a small, evenly bright spot about 1’ diameter that looks much like a planetary nebula. A faint star is visible 3’ N. In 25cm it grows to about 2’ diameter and occasionally seems a bit elongated E-W. The core is a fairly large and broadly concentrated region, but no nucleus stands out. With 30 cm the 1’.5 core forms most of the object; the halo is only a very faint irregular extension to the ESE and WNW sides to an overall length of about 2’. Within the core is a somewhat brighter region about 40” across that has an uneven texture but no distinct central concentration.”

Though Arp 217 is readily visible in smaller apertures, it will benefit immensely from larger apertures and higher powers. Your challenge areas are the knots N of the nucleus, arcs NW and SW, and a jet piercing the NW arc. So…

Give it a go and let us know!

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Uwe Glahn
January 23rd, 2019, 05:55 PM
Wow, nice galaxy Mark. My notes are:

14.5", 283x-404x, NELM 6m5+, Seeing II
high surface brightness, E of the laminar core a short arm segment started to the N, N and S of the core faint extensions are visible but not in the photographic dimension
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27", 419x, NELM 6m5+, Seeing III
outer N arm not flashy but direct vision, ends in a stellar spot; S outer arm fainter and wider, ends at a 16mag star; conspicuous inner region - S and N arm visible as two small but bright shells, stellar peak (no star) at the end of the S arm

36", 500x, NELM 6m5+, Seeing II
impressive glow; in addition to the view trough the 27-inch some stellar spots are visible offset to the north; the inner arms are structured

Bertrand Laville
January 23rd, 2019, 08:25 PM
Hi Mark, Uwe, and All,

Here is my drawing and notes, with my 25" Obsession.
Southern Alps, March 8, 2014 1:15 UT, SQMZ SQMLZ 21.34 21.57 FWMH 2.0 " NELM (UMi) 6.4
( Detailed report at: http://www.deepsky-drawings.com/ngc-3310/dsdlang/fr )


x125 ES25 / 25mm 100
The galaxy is easy to find. At this G, the galaxy is bright, round (?), Fuzzy, and shows no structure

Ethos 8mm x390
After adaptation, and prior knowledge of the image of Block, the two arms appear: that of N visible on 30 "x 10", that of S as one stub.
The halo is blurred; the annular central zone is difficult, but knowing the view. The NS* is seen as a star m16.0 - 16.5V, much lower than the 12.v given by Veron.
Northern spots not known, not seen.

Clear skies (not very clear, presently in south-east France!)
Bertrand
http://www.deepsky-drawings.com


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