Galaxy of the Month Archive 2024

In this series of articles we draw your attention to galaxies particularly worthly of an observer's time.

• NGC 6368 in Ophiuchus

  July 2024 - Galaxy of the Month

  I apologise that the GOM is going to be rather short this month as there is a shortage of galaxies in the twilit summer skies. Our challenge this month may also be tricky on account of its faintness.

  The galaxy NGC 6368 in Ophiuchus was missed by William Herschel and was discovered in 1863 by Albert Marth using William Lassell’s 48” speculum metal mirror telescope in Malta. Marth was a prolific observer of faint nebulae and discovered 583 new objects that made it into the NGC, along with one that made it into the IC.

  As an aside many years ago Alan Dowdell wrote a paper in the Webb Quarterly Journal about Marth’s observations, and at that time it was very difficult to get access to the original paper whereas now it is freely downloadable.

  NGC 6368 itself appears to be a nearly edge on spiral galaxy of type Sb lying at a distance of perhaps 32 Mpc. NGC 6368 appears to be an isolated field galaxy and as far as I can see not much research has been done on it. SIMBAD suggests that it may be a candidate for having an AGN. There are also suggestions that it may be part of an outlying galaxy filament of the Virgo cluster. NGC 6368 is a relatively small galaxy with a calculated diameter of only 49,000 light-years.

  NGC 6368 lies very near the border with Hercules so it does rise pretty high as seen from the UK, this may help when observing it. I note that it can be seen from the UK with 40cm but is not described as terribly impressive, although it is not clear under what circumstances that observation was made. My suspicion is that probably only the central part of the galaxy was seen. Perhaps unsurprisingly NGC 6368 does not feature in any of the standard observation guides so any observations of it are of interest.

  Owen Brazell - Galaxy Section Director

  If you'd like to try out the Clear Skies Observing Guides (CSOG), you can download observing guide for the current Galaxy of the Month without the need to register. CSOG are not associated with the Webb Deep-Sky Society but the work of Victor van Wulfen.

• NGC 5614 in Boötes

  June 2024 - Galaxy of the Month

  Now into June only the brightest galaxies can be seen from the latitude of the UK and I have chosen NGC 5614 in Boötes, also known as part of the Arp 178 triplet, for this GOM.

  First discovered by William Herschel in 1785, NGC 5614 is a barred spiral galaxy lying at about 60 Mpc from the earth. The other members of the Arp 178 triplet are NGC 5613 and NGC 5615. NGC 5613 is however an unrelated galaxy lying almost twice as far away as the other two.

  NGC 5614 sports a large tidal plume that has come from a gravitational interaction with another galaxy in the past. It is perhaps logical to assume this has come from NGC 5615 which is buried in the arms of NGC 5614. It is interesting to note that it took Bindon Stoney using the 72” at Birr to discover NGC 5615 in 1851. It is likely that NGC 5615 is the remains of a galaxy being torn apart by NGC 5614. Currently however it seems to lie about 3 million light-years from NGC 5614 (further than the Milky Way M31 distance) if so it must be in a long looping orbit.

  Given their distances, NGC 5614 maybe about 130,000 light-years across and NGC 5615 only 10,000 light-years across.

  One arm of NGC 5614 shows up very prominently in the UV image from GALEX which suggests a lot of star formation going on, and indeed the PanSTARRS image shows a number of clumps in that arm which could be new large young star clusters.

  Observationally NGC 5614 should be relatively easy to find. The others given their discovery history will be much more challenging. NGC 5615 lies in the halo of NGC 5614 and will appear almost stellar and is probably going to be a challenge for large telescopes. NGC 5613 should be easier and in the range of 37cm or so. The group is very compact so a high magnification eyepiece will be required to split the group, perhaps of the order of 350x if the seeing conditions and telescope can take it.

  The The Night Sky Observer's Guide (NSOG) Vol. 2 suggests that using a 30-35cm scope NGC 5614 is a faint circular patch, but using a 40-45cm scope will show all the galaxies in the group, although here again NGC 5615 is a tough call in the halo of NGC 5614. Steve Gottlieb suggest that NGC 5615 is an averted vision object with 45cm and a faint spot with 55cm, so this is going to be a challenge to find. He also suggests that NGC 5613 is similar in difficulty. There is a fine image of the group by Adam Block and the Mount Lemmon SkyCenter on Wikipedia.

  Owen Brazell - Galaxy Section Director

• NGC 4365 in Virgo

  May 2024 - Galaxy of the Month

  Early May ends the serious galaxy observing season for the Spring in the UK, not that we really had one with the terrible weather in Spring 2024 here, as astronomical dark disappears until mid-August.

  I am indebted to Mark Stuart for bringing my attention to this interesting galaxy group in Virgo. NGC 4365 is an interesting and bright galaxy that should be visible in small telescopes, however the interest here lies in the small group of galaxies below it including NGC 4341, NGC 4342 and NGC 4343 along with the fainter galaxies IC 3259 and IC 3267.

  All of the NGC galaxies here were found by William Herschel in 1784. The two IC galaxies were found by Bigourdan using the 12.4” refractor from Paris in 1895. Unfortunately, observations in the classical period also rather scrambled the NGC and IC numbering of the galaxies in this group as William and John did not give positions for the individual galaxies they discovered. There does seem to have been a lot of confusion over the galaxy identification in the field but I think what we have now is correct. See Harold Corwin’s notes on these in his Historically-aware NGC/IC Positions and Notes.

  The E3 galaxy NGC 4365 is the central galaxy of the W cloud in the Virgo cluster lying about 6 Mpc behind the main supercluster with a distance of about 22.8 Mpc. NGC 4365 appears to be stripping globular clusters and stars from NGC 4362 and the two galaxies are tidally interacting. For more on NGC 4365 see ESO's article Elliptical Galaxy NGC 4365 With Numerous Young Star Clusters.

  Interestingly the galaxies in this area appear to be assigned to different galaxy groups in LGG 292 and LGG 295 and the area does seem rather confused as to what galaxies go where. The group is also included in the WBL catalogue of poor clusters as number 403. I note that the group is also suggested to be a Hickson like compact group. There is an interesting wide field view of this region on Jim Thommes' website.

  NGC 4341 and NGC 4342 are suspected to be lenticular galaxies, whilst NGC 4343 is an edge on spiral that hosts an AGN of the LINER variety at its centre. NGC 4342 has been suggested to have an unusually massive central black hole for its size and is X-Ray luminous. Both the IC galaxies appear to be spirals, and according to their brightness in the UV from the GALEX satellite are currently undergoing a lot of star formation. The same would apply to NGC 4343. It seems that Hubble imaged part of the galaxy, although I only see this in the Wikipedia entry. Chandra also observed the group in X-Rays and showed that both NGC 4341 and 4342 are surrounded by a large amount of very hot gas.

  The observations of this group in the The Night Sky Observer's Guide (NSOG) Vol. 2 are confused as they refer to NGC 4341 and NGC 4342 by IC numbers rather than the NGC numbers assigned to them today. The suggestion is that a 30-35cm scope is needed to see the brighter ones but a 40-45cm will do better. There are no observations of IC 3259 and IC 3267. It is probably worth remembering that the observations the NSOG are based on are over 40 years old now. Steve Gottlieb’s notes suggest that at least 32cm is needed and he normally observers from a high altitude site, to see these galaxies. He suggests that at least a 17.5” is needed to see the IC pair which suggests from the UK that maybe 50cm is needed from a good site. This is the size of scope that Mark Stuart was using for his own observations.

  Owen Brazell - Galaxy Section Director

• NGC 5903 in Libra

  April 2024 - Galaxy of the Month

  With the month of April comes the real end of the galaxy observing season at higher latitudes as the increase in daylight combined with the move to Daylight Savings Time means we have less hours of useable darkness.

  My choice of galaxy this month is NGC 5903 in Libra. Discovered in 1784 by William Herschel, NGC 5903 is an elliptical galaxy classified as an E2. It is going to be a challenge to observe from the latitude of the UK as it never rises that high above the horizon.

  It forms a non-interacting pair with the elliptical galaxy (E0) NGC 5898 and also a triplet with the lenticular MCG-4-36-7, which is a very much fainter galaxy. It is also part of a small 5 galaxy group catalogued as LGG 398. The group is thought to lie at a distance of perhaps 36 Mpc. More recent observation suggest that there may be as many as 30 members of the group, although most of these are small and faint.

  The faint galaxy MCG-4-36-7 appears to be a strong double lobed radio and X-Ray source.

  NGC 5903 is unusual in that it appears to have a long filament of neutral hydrogen lying across the galaxy. The filament is approximately 100kpc long. Its origin is unknown but it is probable that it was caused by AGN activity in NGC 5903 in the past.

  Both NGC 5903 and NGC 5898 are about half the size of the Milky Way given their distances. Perhaps surprisingly there does not seem to have been much other research done on this group.

  The group is in the Astronomical Leagues Herschel 3 list of mostly faint galaxies. It is also in Alvin Huey’s guide to galaxy triplets and in Miles Paul’s atlas of compact galaxy triplets (downloadable from the Webb Society’s web site).

  Both Luginbuhl and Skiff (L&S) and the The Night Sky Observer's Guide Vol.2 suggest a 20-25 cm scope are needed to see this pair, which may well translate to 25-30cm from the UK given the fact that they never rise that high. The best chances to observe them, as ever, will be when they are on the meridian and with a good light pollution free southern horizon. As both of the main galaxies are ellipticals there will not be much detail to be seen and smaller telescopes may only show the bright cores. Larger ones may show the haze surrounding the core. The triplet is close enough together that they will all fit in the field of view in a high power eyepiece and this may be the best way of finding them as it will increase the contrast between the galaxies and the background sky.

  Owen Brazell - Galaxy Section Director

• NGC 3169 in Sextans

  March 2024 - Galaxy of the Month

  My choice this month is the galaxy trio in Sextans NGC 3169, NGC 3166 and NGC 3165. I can’t believe I have not covered this trio before so my apologies if I have.

  NGC 3166 and NGC 3169 were discovered by William Herschel in December 1783 but it took until 1856 when Mitchell observing with the 72” at Birr found the much fainter NGC 3165. It appears that NGC 3166 and NGC 3169 are interacting strongly from the distortions seen in NGC 3169. The distance to all three galaxies is about 65 million light-years so it is likely that they form a physical group. It is probable that all three galaxies will eventually merge and for a single elliptical galaxy.

  There is an excellent deep image of the group on Mark Hanson's website showing the tidal tails and interactions between NGC 3166 and NGC 3169. NGC 3165 is the bluer galaxy off to the right. There is also a fine image of the group taken with a 4m telescope at Kitt Peak. Images in the UV from GALEX show that NGC 3169 and NGC 3165 are showing signs of elevated star formation whilst NGC 3166 does not seem to show so much. Both NGC 3166 and NGC 3169 have active galactic nuclei of the LINER type. For a detailed view of NGC 3169 Hubble also shot the field.

  The galaxies are also part of the galaxy group LGG 192 which contains 5 galaxies, including the three in this field and the nearby NGC 3156. They are also part of the larger Leo I group which is part of the Virgo cluster, see the Atlas of the Universe for more information on the Leo I group.

  It is suggested that the activity in the central region of NGC 3169 is powered by a supermassive black hole. NGC 3166 and NGC 3169 are separated by only 160,000 light-years, so less distance than that separating us and the Magellanic clouds. NGC 3169 was also host to two supernovae in the last 25 years. Whilst NGC 3169 is classified as a spiral galaxy, albeit very distorted, NGC 3166 appears to be a lenticular with a smooth bar (SAB0(a)rs), although deep images do show some dust lanes. It also hosted a supernova in 2012. NGC 3165 is also classified as a spiral.

  Both NGC 3166 and NGC 3169 appear in the Webb Society Deep-Sky Observer's Handbook (WSDSOH) Vol. 4 with observations with 16cm up to 40cm. The Night Sky Observer's Guide Vol. 2 suggests that 20-25cm will show NGC 3166 and NGC 3169 as elongated patches but not with much detail. They suggest that 40-45cm maybe needed to find NGC 3165. Luginbuhl and Skiff (L&S) suggest that NGC 3165 maybe glimpsed with averted vision with 25cm, however I suspect this was from a high altitude site. Hartung also briefly covers them suggesting that from his location they are right in 15cm (although this was rural Australia) and show in a nice star field.

  For those that like collecting lists, NGC 3166 and NGC 3169 are in the Astronomical League's Herschel 400 list as well as Stephen O’Meara’s The Secret Deep book (numbers 40 and 41), along with many others.

  Owen Brazell - Galaxy Section Director

• ACO 779 in Lynx

  February 2024 - Galaxy of the Month

  This month’s challenge is the galaxy cluster ACO 779 in Lynx. Containing at least 7 galaxies found in the NGC this should be a decent target for medium to large scopes.

  The BCG (Brightest Cluster galaxy) is the giant elliptical galaxy NGC 2832, classified as a cD galaxy, also classified as E2, NGC 2832 itself was discovered by William Herschel in 1785. Most of the rest of the group appear to have been discovered by Stoney using Lord Rosse’s 72” at Birr. The Lord Rosse team found 12 galaxies in this area.

  The group seems to contain mostly spirals and lenticulars with an interacting group from the extended VV catalogue in the centre. The same pair is also known as Arp 315, although this may apply to the three galaxies NGC 2830, NGC 2831 and NGC 2832. The galaxies in Arp 315 do not appear to be interacting.

  ACO 779 is quite a small cluster with maybe 83 members and lies maybe 300 million light-years away. The Abell richness class however is 0 which suggests that there may be only 30 galaxies actually in the group. It covers roughly 50 arcminutes on the sky, although deep observations suggest it is more like 90 arcminutes, and lies roughly 40 arcminutes south of Alpha Lyn so it should not be that hard to find.

  The group also contains a number of blue compact dwarf galaxies which appear to be forming stars at this time. There are some suggestions given its distance and location that ACO 779 may be part of the extended substructure of the Coma galaxy filament. There does appear to be some confusion regarding the NGC numbers in the group. NGC 2832 is certain but the others have been shuffled around a bit over time.

  There is a decent amateur image of the group on Bernhard Hubl's website. I think observing this cluster will be best done with a chart as some of the fainter galaxies may look stellar. There is an interesting drawing available on X (Twitter) was made with a relatively small telescope, although this observers drawings appear to have some question marks about them.

  A chart for the cluster can be found in Alvin Huey’s guide to observing Abell Clusters at which can be downloaded from his website. Steve Gottlieb suggests that NGC 2832 is visible in 13” but the others require a larger telescope, which given he usually observes in the high mountains suggests the group may require 45-50 cm to pick up more than the main galaxy. The Night Sky Observer's Guide (NSOG) Vol.1 suggests that a 20cm may show NGC 2832 and 30-35cm will show one of the others but 40-45cm are needed to show more galaxies in the group. The group is included in the Astronomical League’s groups and galaxy clusters program as well as in the SAC list of galaxy clusters.

  Owen Brazell - Galaxy Section Director

• NGC 3414 in Leo Minor

  January 2024 - Galaxy of the Month

  Our galaxy this month is the lenticular galaxy NGC 3414 in Leo Minor. First discovered by William Herschel in 1785 it is the central galaxy of the rich galaxy group known as the NGC 3504 group, which in turn is also part of the Leo II group, a series of clusters on the edge of the Virgo cluster. The group is also catalogued as LGG 227, a cluster of 9 galaxies. For more information on the Leo II group see An Atlas of the Universe.

  NGC 3414 is also known as Arp 162 and has a weak AGN of the LINER type. The Arp listing also includes NGC 3418, another nearby lenticular galaxy, although recent classifications suggest that this is a spiral galaxy. Interestingly the gas flows in NGC 3414 appear to follow a spiral pattern, however the gas in the inner part rotates in a different direction for the outer part. Deeper images also show signs of shells so all of this could be due to a recent merger. NGC 3414 also has a very strong bar in images.

  NGC 3414 lies at a distance of perhaps 23 Mpc and NGC 3418 lies perhaps 800,000 lyrs from NGC 3414. If NGC 3414 is at this distance, then it is perhaps 40,000 light-years across, perhaps half the size of our Milky Way Galaxy. NGC 3414 is classified as S0pec.

  It is probable that UGC 5958, a nearby edge on galaxy, is also associated with NGC 3414. Observations in the UV part of the spectrum with the GALEX satellite shows the bright core of NGC 3414 but also shows active regions in both NGC 3418 and UGC 5958 suggesting the galaxies are interacting. There also appear to be a number of dwarf spheroidal galaxies associated with NGC 3414, although these are far beyond amateur visual observations.

  NGC 3414 is bright enough to make it into the Herschel 400 list of the Astronomical League. Observations from the UK suggest that NGC 3414 can be seen in 20cm but NGC 3418 is tough in a 40cm., however other observations suggest that NGC 3418 is visible in 30cm under very dark skies, although the quality of the site here was not defined. The The Night Sky Observer's Guide (NSOG) Vol. 2 suggests that 20-25cm telescopes will show NGC 3418 as a bright core but that 30-35cm is needed to show NGC 3818. Luginbuhl and Skiff (L&S) suggest that 25cm is needed to show NGC 3414 clearly and again it shows a bright core.

  Owen Brazell - Galaxy Section Director