by Steve Gottlieb
The planetary was easy to identify as it blinked well, but of more interest is research that strongly suggests M 3-33 actually belongs to the Sagittarius Dwarf Spheroidal Galaxy, our nearest neighbor that was discovered just 10 years back and which is in the process of being assimilated by the Milky Way. A 1996 journal article "Two planetary nebulae in the Sagittarius Dwarf Galaxy" (http://cdsads.u-strasbg.fr/cgi-bin/nph-iarticle_query?1996A%26A...312L..21Z&data_type=PDF_HIGH&type=PRINTER&filetype=.pdf) gives the details. In addition to the two planetaries discussed in the article, there are also four associated globulars including M54, which may be the nucleus of the highly disrupted galaxy.
So, here's the completion of an unusual observing project -- the extragalactic objects within the Sagittarius Dwarf Galaxy!
| Wray 16-423 = PK 006-19.1 = PN G006.8-19.8 | 19 22 10.5 -31 30 39 | V = 13.4; Size stellar |
|---|---|---|
| 17.5" (8/15/01): identified at 220x as a surprisingly easy mag 13.5-14 "star". Verified with UHC filter which gave a good contrast gain. Still stellar at 280x. Located 2.3' W of a mag 13.3 star. The paper "Two planetary nebulae in the Sagittarius Dwarf Galaxy", Astronomy and Astrophysics 312 L21-24 (1996) (Zijlstra and Walsh) suggests this PN is likely associated with the galaxy (along with Henize 2-436). | ||
| Henize 2-436 = PK 4-22.1 = PN G004.8-22.7 | 19 32 06.8 -34 12 57 | V = 14.2; Size <5" |
| 18" (6/28/03): easily identified at 161x as a mag 14.5 "star" using a GSC finder chart. Good contrast gain with a UHC filter. Without a filter, He 2-436 appears at least 1/2 magnitude fainter than a mag 13.5 star located 1.2' SE, but with the filter is ~1.5 magnitude brighter than the star. Appeared stellar at 257x. This planetary is a probable member of the Sagittarius Dwarf Galaxy! | ||
| Minkowski 3-33 = PK 9-10.1 = PN G009.6-10.6 | 18 48 12.2 -25 28 52 | V = 13.5; Size 6"x4" |
| 18" (9/3/05): verified by an excellent contrast gain using OIII blinking at 115x. Without a filter, a slightly soft mag 13 star is easily visible. Forms the western vertex of a small triangle with a mag 13 close following (~40") and a slightly fainter star is a similar distance SSE. A very small disc is visible at 300x, though seeing did not support higher power. This planetary is a possible member of the Sag Dwarf Galaxy. | ||
| Terzan 7 = ESO 397-SC14 | 19 17 44 -34 39.5 | V = 12.0; Size 2.6 |
|---|---|---|
| 17.5" (7/20/98): picked up at 220x as a very faint glow with weak concentration, perhaps 1.5' diameter but surprisingly easy for such an obscure globular (brightest of the Terzan catalogue) At 280x, two mag 14 stars are at the E edge [closest is 35" ESE of center] and a mag 15 star is symmetrically placed at the WNW edge. The globular has an irregular surface brightness with a fleeting glimpse of a couple of stellarings superimposed. Two brighter mag 12 and 13 stars are off the SW and SE sides. Located 4.4' W of a mag 10 star. | ||
| Arp 2 = ESO 460-SC6 | 19 28 44.1 -30 21 14 | V = 12.3; Size 2.5 |
| 17.5" (7/25/95): extremely faint, roundish, ~2' diameter. Appears as
an extremely low surface brightness glow with a very small brighter
core. At moments, a faint star or knot is visible at the center.
There is a distinctive 1.5' clump of five faint stars 5.5' NNE which
provides a good reference to center the globular. Located in a rich
star field and used a GSC finder chart to pinpoint the location.
Arp 2 is one of four young globulars that may have been captured by the Milky Way. Also Arp 2 and Terzan 7 lie very close to the recently discovered Sagittarius Dwarf galaxy (1994) and may be associated with that galaxy. | ||
| Terzan 8 = ESO 398-SC21 | 19 41 45 -34 00.0 | V = 12.4; Size 5.0 |
| 17.5" (7/20/98): at 220x initially appeared to have a small bright core surrounded by a very low surface brightness halo 1.5'-2' diameter (boundary difficult to trace) within a rich milky way field. With concentrated viewing, I noticed a couple of close mag 15 stars just SE of center contributed to the impression of a small bright core and the background glow was otherwise unconcentrated. The cluster is surrounded by several mag 13 and fainter stars. More difficult to view than Terzan 7 also observed on same evening. This globular (along with Terzan 7 and Arp 2) may be gravitationally bound to the Sagittarius Dwarf Spheroidal galaxy. | ||
Posted on sf-bay-tac Sep 05, 2005 15:33:05 PT
Converted by report.pm 1.2 Mar 10, 2006 21:59:49 PT