Galaxy of the Month in Gemini

• NGC 2389 Group in Gemini

  February 2021 - Galaxy of the Month

  Although rather late in the season this small group of galaxies in Gemini is still high in the sky at a reasonable hour.

  The group, consisting of the galaxies NGC 2389, NGC 2388 and NGC 2385, was all discovered by William Herschel. He first found NGC 2389 itself in 1788 and then the other two galaxies in 1793, perhaps by this time he had moved to front view mode and gained an extra magnitude or so in what he could see.

  There are a number of non-existent NGC objects in the area in NGC 2386, NGC 2390 and NGC 2391. These are all stars that were discovered by the Rosse team at Birr and thought to be nebulae but which later turned out to be stars. One suspects that they were fooled on a night of poor seeing/transparency when the stars looked nebulous, an issue that still plagues visual observers in the UK.

  The group is also catalogued as WBL 142 which contains just these three galaxies. The group would appear to lie about 200 million light-years from us. NGC 2388 itself is an interesting type of galaxy known as a Luminous Infra-red Galaxy (LIRG). These are normally galaxies where there is a lot of star formation going on that is hidden by dust, which is then heated by the starlight to glow in the Infra-Red. They are also usually very red in colour. All the galaxies in the group are classified as spirals but the type of NGC 2388 is unknown. All the galaxies in the group appear disturbed but there are no obvious signs of interaction, such as tidal tails etc..

  NGC 2389 is an almost face on spiral with a relatively bright nucleus and signs of a bar which fits with its SAB(rs)c classification in the rather involved de Vaucouleurs system. For some reason NED also lists this galaxy as NGC 2388E, although this may have come from the RNGC by Sulentic and Tifft. NGC 2389 is a well-developed spiral with lots of young blue stars whilst both of the others are somewhat reddish. The UV GALEX image backs this up with NGC 2389 itself showing lots of star formation and the other two being practically invisible. NGC 2385 appears close to edge on with a well-developed dark dust lane. The suggestion is that NGC 2389 and 2388 form a pair with NGC 2385 a more distant part of the group.

  The Night Sky Observer's Guide (NSOG) Vol 1 recommends the group as a target for 40-45cm telescopes but also suggests that the small faint edge on galaxy UGC 3879 nearby should also be visible. I suspect that from UK skies probably 45-50cm may be needed to see all the galaxies in the group. All four should be in the same FOV with a medium power widefield eyepiece. I suspect however that UGC 3879 is going to be a challenge for all but the best nights.

  Also in the same medium power field is the faint spiral NGC 2393, a Stephan discovery, so there are a lot of objects to go for in this field. There is also a nice pair of galaxies nearby associated with NGC 2275 which has been covered before in the GOM series.

  Owen Brazell - Galaxy Section Director

• January 2017 - Galaxy of the Month

  NGC 2289 Group in Gemini

  Winter is never an easy time to select galaxies for the GOM column as we are mostly looking into the Milky Way areas. There are however a number of galaxies near the head of Gemini and this month’s challenge is the small group of galaxies around NGC 2289.

  The group appears to be a physical one and is listed as WBL 126, which consists of the five galaxies NGC 2288, 2289, 2290, 2291 and 2294. Unfortunately this is a pretty faint group and as such will be a challenge for larger telescopes and will probably require telescopes in the region of 37cm aperture plus to see visually.

  William Herschel discovered NGC 2289 and NGC 2290 with his 18.7” reflector in the spring of 1793 but the other three galaxies in the group were found by George Stoney using Lord Rosse’s 72” reflector at Birr when following up nebulae discovered by the Herschels. Some sources suggest that NGC 2291 was discovered by John Herschel but this is almost certainly an error and he only saw the two galaxies his father saw. NGC 2290 may be the brightest galaxy in the group.

  The group were photographed early on by Francis Pease using the 60” reflector at Mt Wilson in 1920. In his paper Photographs of Nebulae with the 60-inch Reflector, 1917–1919 he interestingly thinks they are all spirals. Of course at this time it was still unknown whether the nebulae were inside our own galaxy. Hubble’s observations were still a few years in the future.

  The group is fairly tightly concentrated and all the galaxies will fit in the field of a high power, 300x, eyepiece. The group consists of three lenticulars, one spiral and an unknown type (NGC 2288, although possibly this is an E5). My suspicions are that NGC 2288 is going to be the most challenging of the galaxies to see.

  The distance to the group appears to be about 70 Mpc distant. There is some galactic extinction in this area which could be a contributing factor in the faintness of these galaxies as they don’t lie completely outside the Milky Way. I was surprised to find that, despite its faintness, the group is part of the Astronomical League's Galaxy group and clusters observing program.

  Perhaps not surprisingly given the groups faintness there have been few studies made of the group apart from statistical ones to show it is a group. Given its faintness it is perhaps no surprise that it does not appear in the Night Sky Observer's Guide (NSOG) but Steve Gottlieb has observed all the galaxies in this group and his observations can be found on his website.

  

  Owen Brazell - Galaxy Section Director

• December 2016 - Galaxy of the Month

  NGC 2487 in Gemini

  This interactive image of the NGC 2487 group was provided by the Sloan Digital Sky Survey using Aladin Sky Atlas. We have a close in finder chart and also a wider field finder chart to help you locate these galaxies.

  This month’s challenge is NGC 2487, a barred spiral galaxy in Gemini.

  It was first discovered by Albert Marth in 1864 using William Lassells 48” speculum metal telescope from Malta which would suggest that it may be a target for larger telescopes.

  Fittingly being in the constellation of Gemini it is also part of a pair of galaxies along with NGC 2486, also discovered by Marth. The pair also feature as entry number 90 in Holmberg’s 1937 catalogue of multiple galaxies.

  The NGC 2486 and NGC 2487 are actually part of a small group of 4 galaxies called LGG 152 which also includes the galaxies NGC 2498 and UGC 4099. The group is interesting because all four members appear to be barred spirals, although there is some question over the classification of NGC 2486 and it may be type Sa. The group appears to be at a distance of 70 Mpc, however NED gives some quite discordant distances for the 4 galaxies so I wonder if they truly are a physical group.

  NGC 2487 was home to the type Ia supernova SN1975O and it is also classified as a radio galaxy, although there seems to be no form of AGN associated with it. NGC 2486 is also described as an emission line galaxy so perhaps there is some interaction going on between NGC 2486 and NGC 2487.

  The two main galaxies are discussed in Night Sky Observer's Guide (NSOG) Volume 1 as objects for 16/18” telescopes but are described as faint ovals. In theory with a modern medium power (say 200x) hyperwide field (100 degree) eyepiece all three NGC galaxies should fit in the same field of view, however NGC 2498 may be quite faint and difficult to find. It was originally discovered in 1885 by Stephan (of Stephans quintet fame) using a 31” sliver on glass reflector. Steve Gottlieb reports observations of all three NGC galaxies with a 17.5” reflector, but these would have been from altitude.

  UGC 4099 is quite a distance from the main pair being perhaps 44’ away in a SE direction from NGC 2487.

  For those with large telescopes there is a faint IC galaxy IC 482 forming an equilateral triangle with NGC 2487 and 2498. At 15th magnitude this galaxy will probably require telescopes in the 50cm+ class to find. This galaxy is unrelated to the others being a more distant object.

  Owen Brazell - Galaxy Section Director

• February 2015 - Galaxy of the Month

  NGC 2275 Group in Gemini

  

  This image the NGC 2275 group was provided by the Sloan Sky Survey, and this finder chart should help you locate these galaxies.

  Finding galaxies in the winter constellation is always a challenge as most are quite faint and in general overlooked. With Gemini riding high on the meridian on February nights the challenge was to find a galaxy that was not really just for imagers. The NGC 2274/5 pair seemed to be a good challenge. There are not many observations of this galaxy pair and it is not included in either the NSOG or L&S. Both galaxies were discovered by William Herschel (who else ☺) in 1786.

  NGC 2274 is the brighter of the two being an elliptical galaxy. At 12th magnitude this may be a challenge to find. Its companion NGC 2275 is actually much fainter and is an unclassified spiral. It appears to be undergoing some form of interaction as one of its spirals arms is much more obvious than the other. I am sure it would have made Arp’s famous catalogue if it was a brighter pair.

  The pair is actually part of a small group of galaxies which has been variously catalogued as LGG 139 or WBL 121. The group consists of the four galaxies, NGC 2274, 2275, 2290 and UGC 3537. NGC 2290 is actually quite a distance from the others at 47’ of arc away. It appears with another group of galaxies which are in fact unrelated. NGC 2290 was also discovered by William Herschel but in 1793. The separation is due to the fact that the group is relatively close to us at about 4.6 Mpc so the group is spread out on the sky.

  NGC 2274 and 2275 have been reported with apertures as small as 15cm from very dark sites but I suspect that probably 30cm will be needed from most normal sites, certainly to see NGC 2275. The other galaxy in the group UGC 3537 appears to be a face on spiral and is quite faint and is going to be a challenge to see unless you have a large telescope or use video or CCD imaging.

  

  This image of NGC 2290 was provided by the Sloan Sky Survey.

  The group of galaxies around NGC 2290 will also make a nice target but will be a challenge for large telescope owners as these galaxies are much fainter.

  Owen Brazell - Galaxy Section Director