Galaxy of the Month in Pegasus

• NGC 7469 in Pegasus

  November 2022 - Galaxy of the Month

  Our challenge this month is the tight galaxy pair in Pegasus catalogued as NGC 7469 or Arp 298. Arp included the pair as part of his double galaxies classification. The brighter of the pair, NGC 7469, was discovered by William Herschel in 1784. The other galaxy in the pair, IC 5283, was found by Bigourdan in 1891 using a 12.4” refractor.

  Both galaxies are spirals with NGC 7469 being a barred spiral hosting an AGN of the Seyfert I type. NGC 7469 was one of the 6 galaxies that Carl Seyfert included in his original 1943 paper on Type I Seyfert galaxies. It is also a luminous infrared source (LIRG) with the source powered by a starburst in a circumnuclear ring.

  The two galaxies are gravitationally interacting and the interaction appears to have pulled a tidal tail from IC 5283 and also initiated a strong burst of star formation in IC 5283. The interaction may also be the cause of the starburst in NGC 7469. The UV images from GALEX show strong star forming activity in both galaxies and this may be the reason it was included by Markarian in his blue galaxies catalogue. There also appears the be a neutral hydrogen bridge (HI) between the two galaxies.

  The pair lies about 200 million light-years away. If they are at this distance then NGC 7469 will be about the same size as our Milky Way galaxy. The galaxies appear to be an isolated pair, i.e. not part of any galaxy group. There was some thought that they might be part of the Pegasus I galaxy group but they have been shown to lie much further away than that group.

  The pair were selected to be one of the first targets for the James Webb Space Telescope (JWST). There is also a nice Hubble image of the pair on the ESA/Hubble website.

  Two supernovae have been recently found in NGC 7469: SN 2000ft and SN 2008ec (type Ia).

  As this galaxy pair is so close together it is going to require high power to separate them. NGC 7469 itself should be fairly easy to see but IC 5283 is much fainter at around 14.8th magnitude so it is going to require a large telescope to find. It is also an edge on galaxy that will make seeing it even harder.

  The Night Sky Observer's Guide Vol. 1 suggests that 30cm may be needed to see NGC 7469 and 45cm to see IC 5283 which will appear as not much more than a faint oval patch. The pair do lie in a pretty star field however. Alvin Huey’s observations suggested that with a 55cm (22”) telescope NGC 7469 is very bright but IC 5283 is still no more than a faint streak.

  Owen Brazell - Galaxy Section Director

• NGC 7771 Trio in Pegasus

  September 2022 - Galaxy of the Month

  For the September GOM I have chosen the tight galaxy trio in Pegasus around NGC 7771.

  There are three NGC galaxies in the trio, NGC 7769, NGC 7770 and NGC 7771. All three of the galaxies were discovered on the same night by William Herschel in September 1784. For EAA observers there are two much fainter galaxies in the same field. The three galaxies appear to form a physical group along with LEDA 214993, also known as NGC 7771a. They are also classified as Holmberg 820. They also make it into both the WBL (726) and LGG (483) galaxy group catalogues.

  Both NGC 7770 and NGC 7771 appear to be slightly distorted from a gravitational interaction. All three appear to be spiral galaxies with all of them appearing to have a lot of star formation going on from the brightness in the UV images from GALEX. NGC 7771 is also classified as a luminous infrared galaxy (LIRG) starburst which also suggests that a lot of star formation going on is hidden by dust. It will be interesting to see if Webb images it as Hubble used its near infra-red camera to get an image of the centre of NGC 7771.

  The distance to the group is thought to be about 60Mpc. The group appears to have been interacting for some time as there are numerous star streams in the group. Over cosmic time all three galaxies are likely to merge. It is not clear if NGC 7771a is part of the triplet as there is very little hard information on it. Unfortunately deep images of the group are complicated by the presence of dust (IFN) in our own galaxy in front of the group, although there is a fine amateur image of the group by Capella observatory showing some of the interaction details. Despite the group not make the Arp atlas it is added as VV 2003 in the revised Vorontsov-Velyaminov catalogue, although this may only apply to NGC 7770.

  The Type II supernova SN2022mxv was discovered in NGC 7769 but only reached maybe 15th magnitude. NGC 7769 is also suspected to be a LINER, a weak form of AGN.

  The Night Sky Observer's Guide (NSOG) Vol. 1 suggests that to see the whole group then you will require a telescope in the 40-45cm class and even then NGC 7770 will only appear as a faint smudge. The brightest galaxy in the Trio is actually NGC 7769 so that should be the easiest to find. As the group is so tight it will be worth using the highest power you can get away with to separate them and to increase the contrast to see NGC 7770.

  The group also makes it into the Cambridge Photographic Atlas of Galaxies. They are also included in Alvin Huey’s guide to Galaxy Trios as well as Miles Paul’s Atlas of Galaxy Trios, downloadable from the Webb Society website. The group has been included in the Herschel 300 list, an extension to the better known H400 and H400 II list.

  Owen Brazell - Galaxy Section Director

• NGC 7463 in Pegasus

  September 2021 - Galaxy of the Month

  Our target this month is the tight triplet of galaxies around NGC 7463 in Pegasus. NGC 7643 itself was discovered by William Herschel in 1784 along with the other brightish galaxy in the group, NGC 7465. The other galaxy in the triplet, NGC 7464, was discovered by d’Arrest in 1864, although it was independently rediscovered by Marth and Vogel later that year.

  The WBL has it as part of a small galaxy group listed as WBL 695 which includes the 3 NGC galaxies and UGC 12321. The faint edge on spiral UGC 12313 nearby is not listed as part of the group, however HI observations suggest that it may be connected with the others.

  NGC 7463 itself appears to be a barred spiral galaxy with the outer spiral arms distorted by interactions, possibly with NGC 7464. NGC 7464 is itself an interesting system as it is classified as E1pec, although its colours are very blue and it shows emission lines. There are other morphological classifications which suggest it maybe an irregular galaxy however. The NGC 7463/7464 group is also known as Holmberg 802.

  The third galaxy in the trio, NGC 7465, is also classified as a distorted form of a barred spiral. The nucleus of NGC 7465 seems to be a LINER, a mild form of AGN and the galaxy contains a lot of dust. It has also been classified as a Seyfert 2 type system. It appears to have a ring of star formation, or a shell of material which may come from interactions within the system or from a merger in the past. It could perhaps also be a polar ring galaxy. The core of the NGC 7465 also appears to have some intense star forming going on.

  The main interactions in the group appear to be currently between NGC 7464 and NGC 7465. Interestingly the Lyons Groups of Galaxies (LGG) has NGC 7465 and 7464 as part of the NGC 7448 group as LGG 469. NGC 7463 is not part of that group.

  The group is fairly small and faint and thus it is of interest that the Night Sky Observer's Guide (NSOG) Vol 1 suggests it as a target for 12/14 inch telescopes. It does not appear in Luginbuhl and Skiff (L&S). Steve Gottlieb suggests that even in a 18” telescope NGC 7464 was faint. The group is very tight and as such is probably going to require high magnification in order to be able to split all the components, in the range I would think of 250-350x.

  Owners of large telescopes may also be able to pick up the two UGC galaxies associated with the core trio, although I expect finding these may require the most transparent nights, although Steve Gottlieb reports that they are faint even in Texas skies with a 48”.

  Owen Brazell - Galaxy Section Director

• NGC 7436 in Pegasus

  November 2019 - Galaxy of the Month

  This small tight group of galaxies in Pegasus has an interesting discovery history. The brightest galaxy NGC 7436 was discovered by William Herschel in December 1784. However he was not able to resolve the other members of the group and it took Mitchell using the 72” at Birr to find NGC 7433 and NGC 7435 in 1855 and then Bigourdan added the last NGC member of the group (NGC 7431) in 1886.

  The group are also listed as VV 84 in the Voronstov-Velyaminov catalogue of interacting galaxies where he included it in his group of triples with a tight pair, although the group did not get the attention of Arp.

  Dreyer did note another galaxy in the group in 1875 but was not confident enough in his sighting as it was a bad night to list it. This may be the faint galaxy MCG +4-54-7.

  Unfortunately there is some confusion about the NGC designations in this group with the nomenclatures NGC 7436A and B being used for the central galaxy and not necessarily for the same objects.

  Mitchell and Dreyer did provide drawings of the field however which helps in trying to establish what galaxies they saw. The associated chart and image below will show how different galaxies are assigned different numbers.

  

  The group also exists as part of WBL 692, which appears to consist of just the galaxies catalogued in the NGC. The group, also known as Holmberg 800, lies on the outskirts of the galaxy cluster Abell 2153 and is at about 340 million light-years distant from us.

  NGC 7436 itself appears to be an elliptical galaxy with a large outer halo, suggestive of it snacking on other galaxies in the past. That fuzziness makes it difficult to decide if the little galaxy next to it lies in front or behind NGC 7436. NGC 7435 shows signs of an interaction with its distorted spiral arms although it is probably not with NGC 7436 as its recession velocity suggests that it lies behind it. It may be that NGC 7436 is only marginally part of the group of galaxies that we see. There are a number of other faint galaxies in the field including UGC 12274.

  The compactness of the group suggests that to get much out of this will require a night of steady seeing and high power. Observations from Andrew Robertson using a 24” and Mike Wood using a 15” Obsession with an EAA system are included below. Also see Steve Gottlieb’s observations with a 48” dobsonian on his website.

  

  

  The group is also included in Alvin Huey’s selected small galaxy groups atlas and his VV atlas Part 1.

  Owen Brazell - Galaxy Section Director

• NGC 7042 in Pegasus

  August 2019 - Galaxy of the Month

  August sees the return of astronomical dark to UK skies and also sees the 100th GOM. I can’t believe that so many of these have been written, almost 40000 words.

  For this occasion, I have chosen the galaxy pair NGC 7042/7043 in Pegasus. This may feel like an inauspicious choice for such a landmark column but it is getting progressively more difficult to find interesting objects that fit within reach of medium sized telescopes.

  NGC 7042 itself was discovered by William Herschel in 1784, but it took Albert Marth using William Lassell’s 48” speculum metal reflector to discover NGC 7043 in 1863.

  Both galaxies appear to be face on spirals and appear to be a physical pair. They both appear to be part of an 11 galaxy group designated as LGG 442. This group also contains the galaxies NGC 7015 and NGC 7025 as well as a number of UGC galaxies.

  NGC 7042/42 may be of the order of 210 million light years away, which would make NGC 7042 perhaps 110000 light years in diameter and NGC 7043 perhaps 70000 light years in diameter. Despite being physically associated NGC 7042 and NGC 7043 do not show any signs of tidal interactions.

  As both the discoverers described their respective objects as faint it is perhaps not surprising that they do not appear in any of the standard references such as the Night Sky Observer's Guide (NSOG) or Luginbuhl and Skiff (L&S). NGC 7042 does however make the H400 II observing program, which admittedly is mostly non-descript galaxies. NGC 7042 was also home to the Type Ia supernova SN 2013fw.

  Perhaps unsurprisingly given their nature there is not a lot of information in the research literature on either of these two galaxies as they would appear to be just run of the mill spirals.

  Visually NGC 7042 itself would appear to be visible in a 14” (32-cm) telescope but only as a faint glow. I am not sure what size telescope is needed to see NGC 7043, although I have seen an observation of it which suggests that with averted vision it may be visible in 30-cm, although I would think this observation may be questionable. NGC 7043 has a listed magnitude of 14.8B which suggest that it is probably around 14th magnitude in V. The tightness of the pair would suggest that high power can be used on them and keep both galaxies still in the field of view.

  Owen Brazell - Galaxy Section Director

• NGC7385 in Pegasus

  October 2018 - Galaxy of the Month

  Staying in Pegasus for another month, we look at the small group of galaxies surrounding NGC 7385.

  The New General Catalogue of Nebulae and Clusters of Stars (NGC) lists eight galaxies in this area, with the group also known as WBL 688. The two brightest galaxies, NGC 7385 and NGC 7386, were discovered by William Herschel in 1784. The rest may have been discovered by the Rosse team in 1850. However in the accompanying chart some of the numbers are incorrectly attached to galaxies when it would seem that the Rosse team actually only saw stars. So the numbers for NGC 7384 and NGC 7388 appear to have been randomly assigned to galaxies that were not actually seen by the Birr observers, but by later researchers.

  Strangely, most modern references point out that these observations were just stars, so I am not sure who assigned the numbers to the galaxies. The compilers of the Revised New General Catalogue (RNGC) in this case do not seem to be guilty as they also refer to them as stellar. It seems that it was the compilers of the original Principal Galaxy Catalogue (PGC) in 1989 who were responsible for assigning these faint galaxies to the NGC numbers.

  The WBL 688 group only lists 6 galaxies as physically associated in this area: NGC 7385, NGC 7386, NGC 7383, NGC 7389, NGC 7387 and NGC 7390. The group would appear to be at a distance of about 100 Mpc and to consist primarily of elliptical and lenticular galaxies. I wonder if this is the core of a fossil cluster. NASA/IPAC Extragalactic Database (NED) also lists the brighter galaxies as part of ACO 2506, which I struggle to understand, in fact discussions with Harold Corwin indicate this is an error.

  When you look at deep images of NGC 7389 it does look just like a barred spiral galaxy, just without any obvious signs of new stars. This is in essence what lenticular galaxies are. They have the light distribution of spiral galaxies but no gas to make new stars. In this case NGC 7389 would be classified as an SB0 galaxy. NGC 7383 also looks very similar and is also classified SB0, although it does not show such a well developed bar. These shapes do not show up well on the DSS images but do on the SDSS and PanSTARRS images.

  NGC 7385 appears to have radio jets, and in one of those an HII region has been detected at radio wavelengths which may be caused by the interaction between the jet and the ISM: one would not expect to see HII regions in a normal elliptical galaxy. Strangely SIMBAD refers to NGC 7385 as a quasar and, although it is certainly some form of AGN, most references suggest it is a low power one. NGC 7385 was home to SN 2005er.

  The group is fairly tight and most of the galaxies will fit in the field of a modern high power hyperwide field (100 degree) eyepiece. It would appear that a 16” (40-cm) telescope will show five of these galaxies in this field, so I guess that the challenge for owners of larger telescopes to see more of the cluster.

  If you wish to know more about this group then Mark Bratton published an excellent article on observing it in DSO 168, and for further reading on the observations by the Birr team see Wolfgang’s excellent book on Observing and Cataloguing Nebulae and Star Clusters.

  Owen Brazell - Galaxy Section Director

• Hickson 93 in Pegasus

  September 2018 - Galaxy of the Month

  The discovery history of the objects in the quintet of galaxies catalogued as Hickson 93 is a run through of some of the great visual observers of the 19th Century.

  The brightest galaxy in the group, NGC 7550, was discovered by William Herschel in 1784. The next brightest galaxy in the group, NGC 7547, was discovered by his son John when revisiting his father’s observations.

  Bindon Stoney, one of Lord Rosse’s assistants, discovered NGC 7549 in 1850 using the 72” telescope at Birr. Lord Rosse and his team also glimpsed another galaxy in the area which was added to the NGC as number 7553. Its position was not well defined and this galaxy was later catalogued as CGCG 454-14 by Zwicky from the POSS plates. (CGCG stands for Catalogue of Galaxies and Clusters of Galaxies). This object is almost certainly the one seen by the Birr observers.

  The last of the group to be discovered visually was NGC 7558 by Albert Marth using Lassell’s 48” reflector in 1864, it may however have also been seen by the Rosse team 14 years earlier as they described a fifth nebula in this group.

  The discovery history gives an idea of the challenge required to see all the galaxies in this group.

  Halton Arp in his famous catalogue of peculiar galaxies added the pair NGC 7549 and NGC 7550 as Arp 99. Arp thought he could see indications of an interaction between the two due to the shape and length of the spiral arms on the opposing sides of NGC 7549. There has been some debate as to whether Arp meant NGC 7549 or NGC 7547 as the spiral component of Arp 99 however it seems fairly clear from his description that it is NGC 7549 that should be the other component of the pair. Deep images also show shells of material around NGC 7550 and NGC 7547. It is likely however that NGC 7547 is part of a physical triple system with the other two.

  The group is interesting as it seems to consist of three spirals, one lenticular and one elliptical and many of the galaxies are obviously interacting. It is not often you see lenticular galaxies outside large galaxy groups however Hickson groups are often thought to be conglomerations within large loosely bound galaxy groups. In this case the group has a listing as WBL 700, although only 4 out of the 5 galaxies in HCG 93 are listed in this group in NGC 7547, NGC 7549, NGC 7550 and NGC 7553 (CGCG 454-15 on the chart). NGC 7558 may just be a line of sight object and not a physical member of the group, although to be fair Hickson did recognise this.

  To see more than the two brightest members of the HCG 93 group is going to be a challenge, except from very dark skies, and even then, a telescope with an aperture of at least 40cm is likely to be needed. The galaxy group will benefit from using medium to high power when observing it, as well as keeping any extraneous light from reaching the eye, in order to find the fainter members.

  If Hickson 93 is not enough of a challenge then less than half a degree south east is the galaxy group Hickson 94. This will be much more challenging. The galaxy cluster Abell 2572 is also close by. Although ACO 2572 is not a particularly rich cluster it does contain four NGC galaxies. The whole area is worth spending some time in. There is a nice drawing of the group at SkyInspector.

  Owen Brazell - Galaxy Section Director

• November 2016 - Galaxy of the Month

  Abell 2666 in Pegasus

  This interactive image of the Abell 2666 group was provided by the Sloan Digital Sky Survey using Aladin Sky Atlas. We also have a finder chart should help you locate these galaxies.

  Located just inside the square of Pegasus the galaxy cluster AGC 2666 is often overlooked by observers. It appears in neither the Night Sky Observers Guide (NSOG) or L&S which is perhaps rather surprising. It even does not make the Webb Deep-Sky Society Observer's Handbook (WDSSOH) Vol. 5! Despite this it seems to be quite a common imaging target.

  The main galaxies in the group lie along a line anchored on the giant cD galaxy NGC 7768. At around 12th magnitude NGC 7768 was discovered by John Herschel in 1828, but the other three NGC galaxies in the group are much fainter and were discovered by Lord Rosse and his assistants using the 72” reflector at Birr. These are NGC 7765, 7766 and 7767 and they come in at around 14th magnitude. There are also a number of non NGC galaxies in the chain at around the same magnitude. As such I think this cluster will be a target for larger telescopes.

  With the exception of NGC 7768 the brighter members of the group appear to be disproportionally spiral galaxies. NGC 7768 has a number of interesting properties and as well as having a supermassive black hole at its centre it has far fewer globular clusters than might be expected for a galaxy of its size and location. Hubble did observe the galaxy and the image can be retrieved from the Hubble Legacy Archive but the original is not too interesting. Properly stretched however the centre of the galaxy does show a dust disk, unusual for this type of galaxy.

  

  A number of the galaxies in the cluster show signs of interactions but perhaps the most interesting is the galaxy labelled as MCG 4-56-14 in the accompanying chart. It shows signs of an enormous plume on deep images extending from its spiral arm, not unlike the more famous atoms for peace galaxy NGC 7252. It is almost certainly the remnant of a recent merger. One of the best amateur images can be found on the Rancho Del Sol Observatory website. Even the SDSS image does not show the plume well. MCG 4-56-14 is also a LINER galaxy, an active galaxy with emission lines from an AGN. Note that as always what name a galaxy is given tends to be at the choice of the article writer so MCG 4-56-14 is also referenced as CGCG 477-016 in some articles.

  NED suggests the diameter of the group is of the order of 50 arcmins but the main core is much smaller than that, with the main line perhaps 13 arcmin in length. The group lies at a distance of about 112 Mpc which gives it an Abell distance classification of 1 (where 0 is the closest). There are some very blue objects in the SDSS image which appear to be foreground sdO stars.

  Owen Brazell - Galaxy Section Director

• September 2014 - Galaxy of the Month

  NGC 7339 in Pegasus

  

  This image was provided by the Sloan Sky Survey and this finder chart was produced using Megastar 5.

  NGC 7332 and NGC 7339 are an isolated bound pair of galaxies about 67 million light years away. NGC 7332 is lenticular galaxy with a boxy nucleus. Lenticular galaxies have a light profile that makes them look like spiral galaxies but they have no gas and new stars. They are usually found in large galaxy clusters where it is believed that the gas is stripped out by ram pressure as the galaxy moves through the intra-cluster medium. It is relatively unusual to see them in isolated situations like this.

  NGC 7339 is an edge on spiral that is unusually blue. The pair form number 57 0 in the catalogue of double galaxies by Karachentsev. Although NGC 7332 and 7339 appear to be a dynamically interacting pair there are no signs of tidal distortions in the system so the orbit is currently fairly wide. Deep radio observations of the system also show no evidence of tidal interactions although they have turned up some new dwarf galaxies associated with the pair. They do however show a stream of gas in NGC 73339 which could be the remains of a merger event which could account for the current star formation episode in it. Recent surveys looking for globular clusters suggest that both galaxies have a small number ~175 for NGC 7332 and perhaps 75 for NGC 7339. NGC 7339 was also home to supernova 1989L. Both the galaxies were discovered by William Herschel in 1784. NGC 7332 is catalogued as S0(pec) because of the box like shape of its nucleus. The box could be evidence for a bar in the galaxy. Unusually for an S0 type galaxy NGC 7332 does show evidence for a large amount of ionized gas so it maybe a young version of this type. NGC 7339 is probably an Sbc type spiral but is features are fairly low contrast.

  Both these galaxies are relatively bright and should be visible in telescopes of 20cm or above aperture from typical UK skies. The galaxies are an interesting pair because they are at right angles to each other. It should be noted that NGC 7339 is the fainter of the pair whne seen visually. It may be possible with larger telescopes to make out the box like shape. Of the nucleus of NGC 7332. They make a nice pair to warm up with before going are more challenging targets.

  Owen Brazell - Galaxy Section Director

• September 2013 - Galaxy of the Month

  NGC 7619 and the Pegasus I Galaxy Group

  

  Image Courtesy of Sebastam, France. For more images from Sebastam please visit his website. You can click on image for a high resolution version, a Megastar© finder chart of NGC 7626 & NGC7619 can be downloaded.

  NGC 7619 along with NGC 7626 was first discovered by William Herschel in 1785. They are both giant elliptical galaxies which form the core of the Pegasus I galaxy group. It would appear that both NGC 7619 and 7626 are the main members of two subgroups that are colliding to form the Pegasus I galaxy group.

  X-Ray observations show bright shock fronts in each galaxy which are part of the merging process. X-ray observations of NGC 7619 also shows a tail of material stripped out from it, presumably by ram pressure from the intra cluster medium, as it falls into the cluster around NGC 7626. Both NGC 7626 and 7619 are radio sources with NGC 7626 being the more regular with bipolar jets.

  The Pegasus I cluster itself contains perhaps 13 galaxies at a distance of perhaps 53 Mpc. These numbers are slightly down from a paper in 1976 by Rood which suggested there were perhaps 23 or so galaxies in this group. This maybe be due to either improved radial velocities for the galaxies themselves which separated them from the main cluster galaxies or the large angular diameter of the group of about 6.7 degrees which meant that perhaps not all have been surveyed.

  NGC 7619 itself is classified as a generic elliptical galaxy with a classification of E, perhaps 2 or 3 given it is slightly ovoid and it is fairly bright.

  NGC 7616 and 7626 should be visible in relatively small telescopes, although much larger ones may be required to pick up the fainter galaxies in this area.

  In 1929 Milton Humason used the 100" at Mt Wilson to obtain a spectrum of NGC 7619 which showed the largest radial velocity seen at that time. The exposure time was 45 hours, which was about 5 night’s worth of observing for a single spectrum!! It was integral to Hubble’s famous paper on the distance-redshift relation later in 1929.

  The Pegasus I galaxy group would appear to be a challenge for observers as despite the fact that the two main galaxies can be seen with relatively small telescopes being around 11th magnitude the rest will be a challenge for larger instruments and imagers. There are a lot of observations of the central two galaxies but not many of the others. Interestingly small galaxy groups like this did not make Webb Handbook Volume 5. The group however is covered in Alvin Huey’s guide to small galaxy groups which can be downloaded.

  Owen Brazell - Galaxy Section Director

• August 2012 - Galaxy of the Month

  NGC 7331 in Pegasus

  

  Image Courtesy of Ken Crawford, California. Click on image for a high resolution version (5.5 MB). For more images from Ken please visit his Rancho Del Sol Observatory website.

  Often suggested to be a twin of the Milky Way NGC 7331 is a steeply inclined spiral galaxy in Pegasus. Missed by Messier it was discovered by William Herschel in 1784 and is the brightest member of the NGC 7331 group of galaxies.

  This small group consists of NGC 7331, NGC 7320, DDO 213 and an anonymous galaxy. The group appears to be projected onto, i.e. in front of Stephans Quintet. The group also appears to be gravitationally stable. The galaxies in the group are separated by a fair distance on the sky, DDO213 being about 1.7 degrees from NGC 7331. This is because of the relative closeness of the group to us: at a distance of perhaps 45-50 million light years.

  Note that none of the apparent companions, known as the fleas, are associated with NGC 7331 but are merely background galaxies. NGC 7331 itself is classified as a supergiant SA(s)b galaxy of luminosity class I-II. The visual association of galaxies has also got the nickname (at least in North America) of the Deer Lick Group. A fine image of the whole grouping can be found at NASA's APOD.

  The NGC 7331 is interesting in many ways because the bulge of the galaxy appears to be rotating in in the opposite sense to the disk, something that is difficult to explain if this has been the case since the galaxy's formation.

  Although earlier I stated that NGC 7331 may be a twin of the Milky Way it size and mass indicates that it may be much larger and perhaps more similar in size to M31.

  Despite its size only one supernova has been observed in it in 1959 so perhaps it is overdue for another. Intriguingly it appears to contain a super massive black hole and may be a weak type of AGN known as a LINER. NGC 7331 was also chosen as one of the first galaxies to imaged by Spitzer as part of its infra-red survey. The images showed that the galaxy had a ring of dust and gas girdling the nucleus about 20,000 light years out. The rings mass was estimated at 4 billion solar masses. Observations in the ultraviolet from GALEX by contrast only show the star forming regions in the spiral arms.

  For visual observers NGC 7331 is a pretty easy target. It should be visible in binoculars from a dark site but a 100mm (4 inch) telescope shows it easily as a dim streak. As you increase the aperture more detail in the galaxy becomes visible and the companions will also start to appear. I find them very dependent on the sky transparency as to how many you can see.

  Although they all have NGC numbers most were discovered by Stoney in 1849, presumably using the 72" at Birr. NGC 7331 is also often used as a jumping off point for Stephans quintet which is only half a degree away.

  Owen Brazell - Galaxy Section Director

• September 2011 - Galaxy of the Month

  NGC7479 - A Barred Spiral Galaxy in Pegasus

  

  Image Courtesy of Adam Block, Mount Lemmon SkyCenter, University of Arizona. Click on image for a larger version. For more astrophotography images from Adam please visit his Caelum Observatory website.

  First discovered by William Herschel in 1784 NGC 7479 is a classical barred spiral galaxy. The orientation of the galaxy is almost face on making it one of the best barred spirals to observe from the northern hemisphere. Sometimes known as the Propeller galaxy it does however have some rather unusual features in that one of the spiral arms is much more prominent than the other. The spiral structure is also unusual in that the arms when observed in the radio spectrum appear to rotate in the opposite direction to those in the visible and near IR. This may have been the result of a merger with a smaller companion about 300 million years ago. The bar is also unusually long.

  The galaxy also appears to be a Seyfert with star formation going on in the nuclear regions as well is in the spiral arms. It is this active star formation that has given rise to a couple of supernovae in the galaxy 1990 and 2009. It is obviously one worth watching for further possible supernovae. Observations taken with the GALEX satellite in the Ultraviolet also show numerous HII regions and areas of active star formation.

  NGC 7479 is also unusual in that it is extremely isolated. Often starburst galaxies occur because the galaxies have been stirred up by close encounters with other galaxies but that appears not to be the case here. NGC 7479 appears to be at a distance of perhaps 105 million light years and may be associated with the Pegasus galaxy cloud. It is also thought to be about 150 thousand light years across.

  Visually the galaxy has been picked up as a faint smudge in telescopes as small as 4" but it will take much a much larger telescope to show the spiral structure. The bar is relatively easy to see as in one of the spiral arms. The other is much more difficult. I find that the visibility of the arms depends very much on the transparency as well as the size of telescope. For those interested in doing the Herschel 400 project NGC 7479 is part of this list. More information on the Herschel 400 project and other Astronomical League observing programs can be found on their website. NGC 7479 was also well observed in the Webb Society Observer's handbook Volume 4 which contains descriptions from a wide range of telescopes.

  Owen Brazell - Galaxy Section Director