Galaxy of the Month in Ursa Major

• Abell 1185 in Ursa Major

  March 2022 - Galaxy of the Month

  This month’s challenge is the often-overlooked galaxy cluster Abell 1185 in Ursa Major. Perhaps not unsurprisingly it was covered 40 years ago in the Webb Deep-Sky Society Observer's Handbook (WSDSOH) Volume 5.

  The core of the group contains 6 galaxies listed in the NGC, with the brightest being NGC 3350. NGC 3350 was discovered by William Herschel in 1785. Herschel also found NGC 3552, along with an outlier to the main group in NGC 3527 at the same time. John Herschel found NGC 3554 along with 3561 whilst revisiting his father’s observations. Heinrich d’Arrest found NGC 3558 in 1866. The sixth is classified as NGC 3561A.

  The cluster is thought to be about 400 million light-years from us and perhaps 1 million light-years in width. It does feature in a Hubble image at ESA/NASA website. Here you are of course just viewing the very centre of the cluster. There is also a wider field view of the cluster. Abell 1185 is thought to be a member of the Leo Supercluster and is the brightest member of that grouping. The suggestion is that the cluster contains at least 85 galaxies and has an Abell richness class of 1, i.e. not very rich 😊

  The cluster seems to contain a large number of interacting galaxies with two appearing in the Vorontsov-Velyaminov (VV) catalogue with NGC 3561 being VV 237 and NGC 3530 being VV 1419. The cluster also contains Ambartsumian’s knot (a dwarf galaxy at the end of the banjo like tidal feature associated with NGC 3561A, also known as Arp 105). This feature is also known as the Guitar. NGC 3561 also contains a weak AGN of the LINER type. The group does seem to contain quite a few spirals and perhaps lenticulars which suggests it is quite a young cluster still coming together. There are also various sub clumps within the cluster which supports this theory. Abell 1185 also seems to be home to a large number of wandering globular star clusters that are not attached to any galaxy.

  The cluster is a very compact one with all the major NGC galaxies fitting in the same field in a high power (345x) modern hyperwide eyepiece. This will probably be the best way to see them as the individual galaxies are not that bright, even NGC 3550 comes in around 14th magnitude photographic. The field also contains a number of other galaxies that have been catalogued in the MCG catalogue. Interestingly NGC 3550 appears to have three cores (or other galaxies superimposed on it). Are these visible? The other galaxy that Herschel found in this area, NGC 3527, which is also thought to be part of the group lies over 45’ away from NGC 3550. The group also makes the Astronomical Leagues Galaxy group and Cluster list. The faintness and tightness of the group means it may also be a suitable challenge for EAA observers. Andrew Robertson using his 24” managed to find 7 members of the cluster.

  You may also need to look this group up as ACO 1185 which is now the preferred prefix for Abell galaxy clusters supplanting the older AGC description which is now used for a different catalogue.

  Owen Brazell - Galaxy Section Director

• NGC 3202 in Ursa Major

  January 2022 - Galaxy of the Month

  The small triplet of galaxies in the hind feet of UMa, comprising NGC 3202, NGC 3205 and NGC 3207, were all discovered by William Herschel and must be amongst the faintest of his discoveries. They were all found in February 1788 using the large 20ft which had the 18.7” speculum mirror.

  The group is also included as Holmberg 179, although strictly speaking that is only NGC 3205 and NGC 3207, and WBL 264 which includes just the three galaxies in the trio.

  All of the galaxies in the trio are spirals and NGC 3205 and NGC 3207 show some signs of distortion. The Pan-STARRS image shows NGC 3205 wrapped in shells which suggests a recent merger. It is also suggested that NGC 3205 contains a weak AGN known as a LINER. NGC 3207 it also reported to have an AGN of the same form but is also a low power radio galaxy. It is possible that there is much more activity going on but it is obscured by dust surrounding the nucleus. Perhaps unsurprisingly then NGC 3202 is also thought to contain a weak AGN, also classified as a LINER.

  All three are face on spiral galaxies classified as red and dead, which means there is no star formation going on in them at this time. The group appears to be at a distance of about 330 million light-years from us, which suggests that NGC 3205 at least is quite a large galaxy, comparable in size to the Milky Way. The distances here come from the redshifts so there may be some variation in the actual distances to the group members. Otherwise not much research seems to have been done on the group.

  Perhaps unsurpingly the trio does not make it into the Night Sky Observer's Guide (NSOG) Vol. 2 but is included in Alvin Huey’s booklet on galaxy trios. The group is very tight and will probably require a high power to bring out all the galaxies as they are relatively faint. The group is very compact so will fit in the field of a modern high power wide field eyepiece. It lies only about 41’ from the 4th magnitude star lambda UMa so a high power will be required to keep the glow from this out of the field.

  If you find the main galaxies in the group too easy then try for the edge on spiral UGC 5578, which will also appear in the same medium power field as the rest of the trio. I had half expected the trio to be listed in Wolfgang’s book on Galaxies and How to Observe Them as they appear as a precanned list in Eye and Telescope but they are not there.

  Owen Brazell - Galaxy Section Director

• NGC 2805 in Ursa Major

  January 2021 - Galaxy of the Month

  The small group of galaxies around NGC 2805 has an interesting discovery history. Three of them, NGC 2805, NGC 2814 and NGC 2820 were discovered by William Herschel in 1791. The last galaxy in the group is listed as either NGC 2820A or IC 2458. However, it appears that Bigourdan, who discovered IC 2458 in 1899, really meant to apply that designation to a knot in NGC 2820 so the galaxy is not the IC object. This small galaxy is also known as Markarian 108. John Herschel also managed to add to the confusion in the area as he recorded another nebula that became NGC 2816. NGC 2816 is however just another observation of NGC 2820 so that number should be retired.

  The group also became known as Holmberg 124 after Erik Holmberg’s catalogue of double and multiple galaxies in 1937 that he found from early photographic plates, an effort that was corrupted by poor images and led to a number of false identifications. The group is also catalogued as LGG 173 which adds NGC 2880 to the group to make a 5 galaxy system, which is slightly odd as NGC 2880 is almost 2 degrees away from the others.

  The group is classified as a poor galaxy group and consists of mostly late type spirals. The distance to the core of the group is around 90 million light-years or so. GALEX images in the UV show a lot of active star formation going on which suggest that the group has interacted in the recent past to stir up the star formation. The group does not show up so well in the IR WISE images. NGC 2814 in particular shows a number of knots, a bit like M82, and almost looks like two galaxies in collision. NGC 2820A also appears very disturbed.

  

  NGC 2805 is a face on spiral with well-defined arms in the central part but somewhat asymmetric arms further out. On the Sloan Digital Sky Survey (SDSS) image there is a diffuse patch that I initially thought was another dwarf galaxy in the system but is more likely to be an artifact from the bright star in the field as it does not appear on other survey images. There is a nice image at ManTrapSkies.com. NGC 2805 was also host to the recent supernova 2019hsw. Interestingly although the galaxies around NGC 2820 show signs of interacting with each other from their radio emission and there is a tidal bridge between all of them, there is no tie up with NGC 2805. It also appears that there may be a tidal dwarf galaxy created in the streams from NGC 2820 to the NE of it.

  The group is fairly compact and will fit in the field of a medium power (say 260x) hyperwide eyepiece. None of the galaxies in the group make the Night Sky Observer's Guide (NSOG) which is perhaps rather surprising. They do however make Luginbuhl and Skiff (L&S) where they suggest that a 30cm telescope is required to see much. NGC 2805 is a fairly low SB galaxy so perhaps only the small diffuse nucleus will be seen. I suspect the use of high power may help on the smaller galaxies to see if any detail can be seen. The NGC 2820 triplet does make the Interstellarum Field Guide, although not NGC 2805. NGC 2805 does make the H400 II list but the others in the group don’t.

  Owen Brazell - Galaxy Section Director

• M101 in Ursa Major

  June 2018 - Galaxy of the Month

  It always feels slightly pointless writing a GOM article for June as it never gets dark here in northern latitudes so rather than going for something faint we will go with the relatively easy challenge of M101.

  M101 was first discovered by Pierre Mechain in March 1781 and has been the subject of some controversy as it has also been suggested that it is the same as M102 as Mechain listed M102 as a duplicate observation of M101. There are suggestions however that M102 was in fact really a different object and modern Messier books seem to randomly choose what object to associate with M102.

  Lord Rosse observing with the 72” at Birr added M101 to his list of nebulae that showed spiral structure and made a drawing of it that compares favourably with modern images.

  When it is dark and at a high altitude M101 is easily visible in binoculars, even my 10x42 Canon IS binoculars will show it, to see detail requires a somewhat larger aperture.

  M101 is such a complex galaxy that it has been given an Arp designation (Arp 26) and two designations in the VV catalogue of interacting systems (394 and 456). It is complex enough that it contains 10 objects within it that have NGC designations (mostly HII regions). The included finder chart shows many of these.

  A recent study suggested that there are upwards of 1264 HII regions in M101. This may be due to gravitational perturbations raised by its companion galaxies (in particular NGC 5474, just over 45’ south of M101, and NGC 5477). In return the gravitational effects on these two caused by M101 is making them form stars at a fast rate.

  M101 is about 23 million light-years away and has a size of perhaps 170,000 light-years, so substantially larger than our own Milky Way, despite recent estimates suggesting our galaxy is much larger than previously thought.

  M101 is part of a small group of galaxies catalogued as LGG 371 which contains perhaps 8-9 other galaxies. The distance of the M101 group is similar to that of the M51 and NGC 5866 groups which suggests they maybe subgroups within a much larger loose group.

  I have found that when observing M101 with my larger telescopes I am caught between using the widefield view which sets the galaxy nicely off in its surroundings and using higher power to tease out the detail. As M101 is a face on spiral then under poor conditions you may only see a haze with a central core but under better conditions the spiral arms and HII regions will leap out at you.

  Note that on the SDSS image the bright blue object on the left at about 9 o’clock is not a plate defect but the giant HII region NGC 5471. Under very steady conditions with a large telescope and high power NGC 5471 may also show structure. It shows up very prominently on the UV images from GALEX. To see multiwavelength images of objects I recommend using the free viewer Aladin.

  

  If finding M101 is not enough of a challenge then perhaps a nice observing project will be to see how many of the M101 group galaxies you can find. These are NGC 5204, NGC 5474, NGC 5477, NGC 5585, UGC 8837 and UGC 9405. Most of them are relatively bright but UGC 9405 is at around 17th magnitude so it may be rather more difficult to see.

  M101 has had one supernova in recent times with sn2011fe which was observed in August 2011 and reached 10th magnitude at its peak. I do remember observing this one although M101 was relatively low at the time using my 15”. Given the amount of star forming activity it is probably a likely source for more supernovae.

  M101 made the OOTW on the DSF forum in 2015 and there are some interesting drawings there made with large telescopes.

  There is interesting web page showing Lord Rosse’s drawings of the spiral nebulae. It is in German but if using Chrome you can ask it to translate the page.

  Owen Brazell - Galaxy Section Director

  I've received an image of M101 captured by Paul Whitmarsh in March this year.

• February 2014 - Galaxy of the Month

  NGC 4088 in Ursa Major

  

  Image Credit - Volker Wendel and Bernd Flach-Wilken, Spiegelteam Astrofotografie. Please click on image for a high resolution version.

  The major galaxies M81/82 and 108,109 and 101 in Ursa Major usually get all the attention but the constellation is filled with other interesting galaxies. One of the overlooked ones is NGC 4088. Classified as an intermediate spiral galaxy it forms a physical pair with NGC 4085. NGC 4088 was first discovered by William Herschel in 1788. The same observer found NGC 4085 the following year in 1789. Described as a grand design Spiral galaxy Halton Arp included it in his Atlas of Peculiar galaxies as Arp 18 because it appears to have a detached spiral arm. Both NGC 4088 and 4085 are members of the M109 group of galaxies. This group lying about 55 million light years away contains maybe 39 galaxies including M109. It is also known as the Ursa Major North group. Unusually the group contains no major elliptical galaxies. NGC 4088 and 4085 are at the front of this group at perhaps 50 million light years. Distances however to galaxies this close are notoriously unreliable if it is based on redshift because the peculiar motion of the galaxy maybe a substantial part of the Hubble flow. Recently NGC 4088 had a supernova (2009dd). Previous to that it had one in 1991 so it is a relatively prolific supernova generator. The image here shows Sn2009dd near the core of the galaxy. Visually NGC 4088 is bright enough to be seen in quite small telescopes, certainly in the 8-10” class. Larger telescopes will show much more detail and a series of observations made with a range of telescopes can be found at the DeepSkyForum.

  An interesting set of drawings of NGC 4088 can be found Bertrand Laville's Extreme Deep Sky Drawings website. Another view is at the Astronomy Sketch of the Day website. NGC 4085 should be visible in 8-10” telescopes but is considerably fainter. It is also an edge on spiral. For those who like collecting lists NGC 4088 is part of the original Herschel 400.

  The included PDF chart shows both of these galaxies.

  There is a fine image showing both galaxies at Kai Wiechen's Deep Sky Astrophotography website.

  Owen Brazell - Galaxy Section Director

• April 2011 - Galaxy of the Month

  NGC 3718

  

  Click on image for a larger version and for more images from Philip Perkins please visit his website

  Our galaxy of the month this month is the distorted spiral galaxy NGC 3718. Also known as Arp 214 the galaxy is distinguished by distorted spiral arms and a dust lane wrapped across its centre. NGC 3718 is also a Type 2 Seyfert AGN.

  First discovered by William Herschel in 1789 both NGC 3718 and the probable cause of its distortion NGC 3729 make a nice galaxy pair for northern observers . NGC 3729 also appears distorted but not as much as 3718 It appears that NGC 3718 could be evolving into a polar ring galaxy. The nucleus of NGC 3718 is not circular but definitely box shaped. Both 3718 and 3729 are classified as SB (barred spirals) but obviously they are both distorted from this basic designation.

  The Webb DSOH Volume 4 suggests that it is faint but visible in a 6" whilst more modern observations from the NSOG suggest that a 30cm scope is need to see pair well.

  In the same field is the small group Hickson 56. Comprised of 5 galaxies this will be a challenge for larger scopes. Three of the group appear to be interacting. I was quite surprised however when observing NGC 3718 with my 20" last spring at the Kelling Heath star party to see that the group appeared quite obvious. With one of the modern superwide field eyepieces both NGC 3718 and NGC 3729 will appear in the same field along with Hickson 56. Interestingly when the astronomers using the 72" telescope at Birr observed NGC 3718 they missed this small group of galaxies nearby. Must have been a murky night with a tarnished mirror. You may need a power of around 250x to split the group.

  NGC 3718 and 3729 are about 40 million light years away compared to the 400 million light years for Hickson 56. This grouping seems popular with imagers, witness the fine image from Philip Perkins, but I have not seen too many visual observations of it.

  Associated with this the BAA Deep Sky Section and the Webb Galaxy Section are looking at doing a joint project on observing the Hickson galaxy groups and we are putting together the plans for this project shortly.

  Owen Brazell - Galaxy Section Director