Picture of the Month for 2026

• November 2026 - Picture of the Month

  NGC 869 and NGC 884 in Perseus

  

  This month I have a favourite and familiar sight of the Double Cluster in Perseus. To the usual view David has added some narrowband data to show the nebulosity that surrounds this region of the Perseus arm of our galaxy. The Double Cluster comprises the two massive open clusters NGC 869 (on the left) and NGC 884 (on the right), also known as η Persei and χ Persei respectively. They share a common origin in a massive molecular cloud and they now form the core of the Perseus OB association.

  All open clusters form inside molecular gas clouds, and I frequently feature images of this in action, but the Double Cluster is a great example of a close binary open cluster (CBOC). These clusters are physically associated in the sense that they're identified not only by their proximity in space but also their similar ages and movement through space. CBOCs are thought to form by either the fragmentation of their shared molecular cloud or through tidal capture. The Double Cluster appears belong to the first of these categories.

  The pair are amongst the most massive young open clusters in the Milky Way and in a 2001 study photometric estimates of the their ages found that NGC 869 appeared to be older at nearly 20 Myr than NGC 884 which was only 12.6–14.1 Myr old.¹ Using data collected by the Mosaic Imager at the 4m Mayall telescope at the Kitt Peak National Observatory in 2006, Currie et al. estimated NGC 869 and NGC 884 to have cores containing 4,700 and 3,700 solar masses respectively.

  In addition they conclude that the pair's extensive halo must add at least another 11,000 solar masses, giving a combined mass of 20,000 solar masses and about 15,000 stars, 5,000 of which lie within 10 arcminutes of the cluster centres.² It's suspected that the halo may extend well beyond 30 arcminutes and Zhong et al. have extended NGC 869 to 5,500 and NGC 884 4,300 solar masses with an analysis of Gaia DR2 data.³

  Very recently, based on a probablistic analysis of the Double Cluster using Gaia DR3 data, Tașdemir et al. found distances of 2,378pc (7,750 light-years) for NGC 869 and 2,279pc (about 7,430 light-years) for NGC 884 and both clusters to be about 20 Myr old. The same analysis also identified 808 and 707 high probablity members of NGC 869 and NGC 884 respectively ⁴, somewhat less than the studies above, but certainly more than the 317 and 303 given by Archinal and Hynes.

  Further, their analysis appears to confirm the their common origin and also suggests that the two clusters might be in for some interaction in about 11 Myr when they're expected to be 26 pc (85 light-years) apart.⁴

  It's entirely possible to see the Double Cluster as a hazy patch with the naked eye, and it's a much more impressive sight in a pair of 10x50 binoculars. Both clusters are at least 18 arcminutes in diameter with condensed cores, as reflected in their I3r Trumpler classification. The clusters contain a large number of Washington Double Star Catalog pairs within these boundaries: 10 for NGC 884 and 22 for NGC 869.

  This part of the night sky is full of deep-sky objects and David's also captured the nearby open cluster NGC 957, on the extreme left of his image, which is home to double star HJ 2143.

  James Whinfrey - Website Administrator.

  References

  1. Marco, A. and Bernabeu, G., “Photometric study of the double cluster h & chi Persei”, Astronomy and Astrophysics, vol. 372, EDP, pp. 477–494, 2001. doi:10.1051/0004-6361:20010441.
  2. Currie, T., “The Stellar Population of h and χ Persei: Cluster Properties, Membership, and the Intrinsic Colors and Temperatures of Stars”, The Astrophysical Journal Supplement Series, vol. 186, no. 2, IOP, pp. 191–221, 2010. doi:10.1088/0067-0049/186/2/191.
  3. Zhong, J., Chen, L., Kouwenhoven, M. B. N., Li, L., Shao, Z., and Hou, J., “Substructure and halo population of Double Cluster h and χ Persei”, Astronomy and Astrophysics, vol. 624, Art. no. A34, EDP, 2019. doi:10.1051/0004-6361/201834334.
  4. Tașdemir, S., Elsanhoury, W. H., Çınar, D. C., Haroon, A., and Bilir, S., “Comprehensive Gaia DR3-based Astrometric, Photometric, and Kinematic Studies of the Binary Open Cluster h and χ Persei”, Research in Astronomy and Astrophysics, vol. 26, no. 4, Art. no. 045016, IOP, 2026. doi:10.1088/1674-4527/ae3d11.
  5. Brent Archinal and Steven Hynes, Star Clusters, Willman-Bell, 2003.

• October 2026 - Picture of the Month

  Planetary nebula Jones 1 in Pegasus

  

  This month we have another planetary nebula, this time an image of the entire object, which was discovered on photographic plates in 1941 by astronomer Rebecca Jones and named accordingly. Jones 1, also PK 104-29.1 and PN G104.2-29.6, is an large nebula nearly 5½ arc-minutes in diameter and has an integrated visual magnitude of about 15, which results in it being rather faint.

  Nonetheless, this planetary nebula can be observed visually with enough aperture, a good sky and perhaps a suitable eyepiece filter. But it's not an easy target. Even with a camera at your disposal you should be prepared to spend some imaging time on this object, particularly if you'd like a result like Peter's image above. I believe that there are about 79 hours of integration in this one, most of it with narrowband filters.

  Jones 1 can be found about 710pc (2,315 light-years) away in the constellation of Pegasus, just north of the midpoint of the square. It is a bipolar planetary nebula that we're viewing more or less along its axis resulting in its irregular annular disc. It's estimated to be about 36,000 years old based on its size and rate of expansion.^1,2

  WD 2333+301, also known as Gaia DR2/DR3 2871119705335735552, is the star which shines from the centre of Jones 1 at about magnitude 16.² The Gaia DR2 distance to this star is about 808pc (2,634 light-years). Its PG 1159 spectral type indicates that it is still in transition to its eventual degenerate white dwarf state, whilst a DOZ designation suggests that it is a hydrogen-poor helium core with a hint of nitrogen in its spectrum that will cool to an effective temperature of the order of 70,000K. It's hot and obviously blue.

  There are a couple of very nearby stars that match the expected distance to the nebula: Gaia DR3 2871119701039325696 (737pc) and Gaia DR3 2871119705335735296 (707pc), both are a little fainter and yellower, but they form a nice looking close and even double star about 19 arc-seconds to the north of WD 2333+301.

  I would expect this to be a very tough challenge at 16th magnitude and separated by only 1.8 arc-seconds. Has anyone other than Gaia tried? There's a nice image of Jones 1 on the NoirLAB website in which this pair is almost resolved but a little better than just elongated. Resolution is where a 4 metre aperture is helpful.

  James Whinfrey - Website Administrator.

  References

  1. Napiwotzki, R. and Schoenberner, D., “Spectroscopic investigation of old planetaries. III. Spectral types, magnitudes, and distances.”, Astronomy and Astrophysics, vol. 301, EDP, p. 545, 1995.
  2. González Pérez, J. M., Solheim, J.-E., and Kamben, R., “A search for photometric variability of hydrogen-deficient planetary-nebula nuclei”, Astronomy and Astrophysics, vol. 454, no. 2, EDP, pp. 527–536, 2006. doi:10.1051/0004-6361:20053468.

• September 2026 - Picture of the Month

  Helix nebula (NGC 7293) in Aquarius

  

  The Helix Nebula in southern part of Aquarius is very well known to and observed by the amateur astronomy community. It's one of the closest planetary nebulae with its central white dwarf star, WD 2226−210, about 199.9±3 parsecs (651.6±3 light-years) distant. As a result it's also large for a visual planetary with an apparent size of around 12 arc-minutes.

  However observers might find its apparent magnitude of about 7.3 is deceptive because its large size results in a very low surface brightness. This makes it a challenge to see much of NGC 7293's outer structure, but Patrick has some suggestions that might help. It's an good imaging target.

  Planetary nebulae form when an intermediate-mass star reaches the end of its life, swells into its asymptotic giant branch (AGB) phase, and ejects much of its gaseous envelope in the process leaving a white dwarf star at the centre of a glowing shell of expanding gas.

  For NGC 7293 this process seems to have started with a 1.5 solar mass star about 12,000 years ago with the material ejected forming what is now the outer ring of the nebula, a portion of which we see in most of this image. About 5,500 years later the current inner ring started to expand into this earlier material photoionised by the 13.5 magnitude central DAO-type white dwarf star, now about 0.7 solar masses and with an effective temperature well in excess of 100,000K. ^1,2 Whilst this star is out of shot in this fabulous image, we're looking at the consequences this expansion.

  This image from JWST’s NIRCam (Near-Infrared Camera) is full of cometary knots, named for their extended structure, that formed as the faster moving hot gas of that inner ring ploughs into the gas and dust of the earlier outer ring. There are several layers of these knots that become less dense as they're progressively eaten away by the solar winds in this young expanding nebula.

  The knots are dense regions that maintain temperatures low enough for the formation of the complex molecules from the elements present in the envelope of that long dead star. The interest for astronomers and planetary scientists is that these at the materials that will eventually find their way into the formation of other solar systems.

  I'm surprised by the number of galaxies that can be seen in larger versions of this image, they are very detailed and worth downloading. I'm not sure whether all the galaxies on display could be captured in a single image as this would suggest the nebula is extremely tenuous. There are galaxies that appear superimposed on some of the densest parts of the nebula. I wonder whether this might it be an artifact of the image processing?

  There's also a wonderful image combining one of the whole nebula by ESO's VISTA with this image for those that need to find their bearings.

  James Whinfrey - Website Administrator.

  References

  1. O'Dell, C. R., McCullough, P. R., and Meixner, M., “Unraveling the Helix Nebula: Its Structure and Knots”, The Astronomical Journal, vol. 128, no. 5, IOP, pp. 2339–2356, 2004. doi:10.1086/424621.
  2. Iskandarli, L., Farihi, J., Lothringer, J. D., Parsons, S. G., De Marco, O., and Rauch, T., “Novel constraints on companions to the Helix nebula central star”, Monthly Notices of the Royal Astronomical Society, vol. 534, no. 4, OUP, pp. 3498–3505, 2024. doi:10.1093/mnras/stae2286.

• August 2026 - Picture of the Month

  Supernova remnant W63 (Westerhout 63) in Cygnus

  

  The supernova remnant (SNR) Westerhout 63 (W63) or G82.2+5.3 is rather a large object in the night sky with an angular diameter in excess of a degree. As is sadly the case with many of the largest objects, it's also a very faint making observation difficult. W63 is certainly not a visual target.

  A further complication is that W63 is superimposed on that background of H-II nebulosity that you can see in this wonderful image. This nebulosity is designated as LBN 310, or a small portion of that object at least, and it makes W63 challenging to observe optically and in other wavelengths too.

  In fact, W63 was original identified in the radio frequency survey of Westerhout in the late 1950s, being too faint to appear on the plates of the Palomar Observatory Sky Survey (POSS) around the same time, and observation remained in the domain of radio telescopes until the 1970s. ¹

  Fortunately the shell-type structure of W63 is bright in O-III wavelengths, which is blue in this image, which helps to distinguish it from rest of the local nebulae. This O-III structure turns out to be very well correlated to radio observations, particularly on the right side of our image where the H-II nebula is less dense. The O-III emission from the filaments that make up most of W63's structure are the result of shock heated gas, however the more diffuse O-III emission in the upper part of this image seems to be from photoionization processes unrelated to the supernova. ^1,2

  The distance to this object has been estimated at 1.6—3.3 kpc (5,200—10,800 light-years) and it may be 13,500—26,700 years old. However these estimates appear to be far from certain since the data don't clearly indicate the SNR's stage of development. As such, the age range in particular could be as much as an order of magnitude too short. ¹

  I'm unaware of any success in identifying the remains of a progenitor for this SNR.

  James Whinfrey - Website Administrator.

  References

  1. Mavromatakis, F., Aschenbach, B., Boumis, P., and Papamastorakis, J., “Multi-wavelength study of the {G 82.2+5.3} supernova remnant”, Astronomy and Astrophysics, vol. 415, EDP, pp. 1051–1063, 2004. doi:10.1051/0004-6361:20031694.
  2. Gao, X. Y., Han, J. L., Reich, W., Reich, P., Sun, X. H., and Xiao, L., “A Sino-German λ6 cm polarization survey of the Galactic plane. V. Large supernova remnants”, Astronomy and Astrophysics, vol. 529, Art. no. A159, EDP, 2011. doi:10.1051/0004-6361/201016311.

• July 2026 - Picture of the Month

  Cometary Globule CG4 in Puppis

  

  I was going to bring you an image by an amateur this month, but things (not least a heat wave) have conspired against me, hopefully next month.

  All the same, I think that this stunning image of a dark cloud, check out CG 4 on SIMBAD and the Digitized Sky Survey (DSS), which looks anything but dark is a worthy alternative. It was captured by the Department of Energy-fabricated Dark Energy Camera on the U.S. National Science Foundation Víctor M. Blanco 4-meter Telescope at Cerro Tololo Inter-American Observatory.

  Apparently CG 4 (G259.43-12.72) in Puppis to left of centre in this image is nicknamed ‘God’s Hand’, however its structure reminds me more of the sandworms in Dune, and I believe that it's the edge-on barred spiral galaxy PGC 21338 that's about to be swallowed. It does make for a fabulous image, and even this larger jpeg version still pales in comparison with the full original which is extremely detailed.

  There are plenty of these dark nebulae around the galaxy which are known as Bok globules. The cometary variety, of which CG 4 is an example, are characterised by their dense 'head' which fades into a diaphanous tail. In fact there's another example in the upper right of this image, CG 6 which is is more classically cometary with its pointed tip. CG 4 is about 1 pc wide and 3 pc long containing about 60 solar masses of hydrogen, and that mouth is 0.5 pc in diameter. CG 6 is smaller, only about 0.25 pc wide and 1 pc long, and only contains about 5.5 solar masses. ¹

  There's some uncertainty about the origin of these structures. For the 32 cometary nebulae found around the edge of the Gum Nebula it's been noted that they 'point' roughly towards a common centre, perhaps in the direction of the Vela Supernova Renmant, suggesting that this event about 11,000 years ago, and the resulting Vela pulsar, may have some part in their development. However the leading theory is that the stellar wind of hot nearby O-type stars, principally γ² Velorum in the case of the two objects in this image, caused the stripping of gas from the dense nebula to form the tail. ²

  CG 4 is relatively close at about 400 pc (1,300 light-years) and is certainly not an object for visual observation. The Very Large Telescope (VLT) captured an excellent image of the gaping maw full of stars, but sadly no sign of PGC 21338 which lay outside the field. In reality PGC 21338 is in no danger from this particular sandworm as it's somewhere around 45 Mpc (147 million light-years) further away.

  James Whinfrey - Website Administrator.

  References

  1. Gonzalez-Alfonso, E., Cernicharo, J., and Radford, S. J. E., Molecular gas in cometary globules: CG4 and CG 6 in the GUM Nebula., Astronomy and Astrophysics, vol. 293, EDP, pp. 493–506, 1995.
  2. Sridharan, T. K., Kinematics of the Cometary Globules in the GUM Nebula, Journal of Astrophysics and Astronomy, vol. 13, no. 3, Springer, pp. 217–239, 1992. doi:10.1007/BF02702292.

• June 2026 - Picture of the Month

  Cat’s Paw Nebula (NGC 6334) in Scorpius

  

  This is very small piece of bright nebula NGC 6334, also known as the Cat's Paw Nebula. The whole object is approximately 30 arc-minutes in extent and 4,000–5,800 light-years away from us, nestled amongst the abundant clouds of Scorpius and the Carina-Sagittarius arm of the Milky Way.

  This nebula has featured in Picture of the Month before as part of a fabulous and very widefield mosaic view of the centre of the Milky Way by Robert Gendler which really shows the richness of this part of the sky. That was the article for July 2016, nearly ten years ago! In that image there were sections of at least three different constellations; in sharp contrast this James Webb Space Telescope (JWST) image is only about 6 arc-minutes across.

  NGC 6334 contains some of the most active sites of massive star formation in our Galaxy, which the whole region appears to be undergoing an accelerated rate, possibly due to a collision of molecular clouds ¹.

  Of course, given that it's a JWST near-infrared image, we can see features that are normally completely hidden in the dense clouds that fill the region, in particular those massive O-type stars etching bubbles in the surrounding cloud and compressing dense knots of dust and gas where protostars are protected around their edges. You can clearly see the fiery glow of stars forming within the dust in the centre of this image.

  At the top of the right side of this image is a bright orange-red flare which is part of NGC 6334-I, the densest star-forming region in the area. However the same location looks like empty space above the most northern part of the Cat's Paw in optical images (celestial north is broadly to the right in this image) such as this fabulous example from 2007 taken with the Mosaic-2 imager on the Blanco 4-meter telescope at Cerro Tololo Inter-American Observatory.

  It was in NGC 6334-I that the Atacama Large Millimeter/submillimeter Array (ALMA) was used to study water vapour jets issuing from a massive protostar in 2018, a fascinating radio-frequency image, and the chemical richness of the environment around these forming stars. ALMA data was also used to investigate star formation in the area around NGC 6334-I, finding that nearby NGC 6334-E contained the most evolved HII region, whilst clusters to the north were less developed ², thus still heavily shrouded in the molecular cloud.

  In fact, outside of optical wavelengths NGC 6334 displays a filamentary structure that can be seen in a wide infrared image from ESO's VISTA in 2010 extending for some 100pc (326 light-years), which doesn't look all that paw-like anymore. NGC 6334-I and E can also be seen in this image as the bright emission region. Our JWST view is aligned with one of these filaments, NGC 6334 M, the very one that was studied with ALMA, which runs between those obvious blue reflection regions broadly from the lower left corner to the top right of this image.

  So with all of those links I suppose that this has become Pictures of the Month in a sense, but multi-wavelength observation is the theme of this article.

  This object is going to be tricky of more northern visual observers, being less than a couple of degrees above the horizon from most of the UK. However The Night Sky Observer's Guide Volume 4 suggests that it's accessible to very modest telescopes and enhanced with a UHC filter in larger ones.

  James Whinfrey - Website Administrator.

  References

  1. Yasuo Fukui, Mikito Kohno, Keiko Yokoyama, Kazufumi Torii, Yusuke Hattori, Hidetoshi Sano, Atsushi Nishimura, Akio Ohama, Hiroaki Yamamoto, Kengo Tachihara, Molecular clouds in the NGC 6334 and NGC 6357 region: Evidence for a 100pc-scale cloud–cloud collision triggering the Galactic mini-starbursts, Publications of the Astronomical Society of Japan, Volume 70, Issue SP2, May 2018, S41, https://doi.org/10.1093/pasj/psy017
  2. Physical properties of the star-forming clusters in NGC 6334 - A study of the continuum dust emission with ALMA, M. Sadaghiani, Á. Sánchez-Monge, P. Schilke, H. B. Liu, S. D. Clarke, Q. Zhang, J. M. Girart, D. Seifried, A. Aghababaei, H. Li, C. Juárez and K. S. Tang, A&A, 635 (2020) A2, DOI: https://doi.org/10.1051/0004-6361/201935699

• May 2026 - Picture of the Month

  Planetary nebula NGC 3699 in Centaurus

  

  Around 2015 this planetary nebula was imaged by ESO from its La Silla Observatory in Chile using an instrument on their 3.6-metre telescope. Adam's image was also taken from Chile but, 11 years on, he's using a 0.61m telescope and 32 hours of exposure time to produce this detailed, confusing and fascinating view of NGC 3699 in the southern constellation of Centaurus.

  Adam has a great article on this object and his imaging process on Astrobin and, rather than repeat what he's said here, I suggest you read it. As Adam notes, this is probably a polypolar planetary nebula with a binary system at its heart, but there appears to be very little written about it.

  The article for NGC 3699 on French Wikipedia claims that the GAIA DR3 parallax corresponds to a distance of about 1228–1534 pc (4,000–5,000 light-years). There's little data available for NGC 3699 anywhere else.

  I checked this with Gaia DR3 using Vizier and the location of this particular source (Gaia DR3 5336133687170599040) does appear to be that of Adam's suspected central star. However the estimated effective temperature of around 10,000K seems a little low, although it is easily the highest to be found in the area. Additionally, the Renormalized Unit Weight Error (RUWE) for this star is very close to 1, suggesting that this isn't an unresolved binary system... perhaps Gaia DR4 will help when it arrives.

  NGC 3699 is a relatively large and faint object which I suspect puts it beyond the scope of visual observers, and it's location will foil many imagers in the northern hemisphere. Fortunately the availability of remote telescopes under southern skies opens up the possibility to examine many fabulous objects of this kind.

  James Whinfrey - Website Administrator.

• April 2026 - Picture of the Month

  Copeland's Septet (Hickson Compact Group 57) in Leo

  

  This month I bring you a wonderful image of a group of galaxies just above the hind-quarters of Leo known as Copeland's Septet, Hickson 57, Arp 320 or a number of other designations, as is often the way.

  This group of galaxies was discovered in 1874 by Ralph Copeland with the Parsons 72-inch telescope whilst an assistant to Lord Rosse at Birr Castle in Ireland. For a while this group was lost due to a positioning error by Copeland which carried through to the compilation of the New General Catalogue of Nebulae and Clusters of Stars (NGC) by Dreyer in 1888. Being a septet, Copeland obviously identified seven members in this group, albeit over different nights of observing.

  Paul Hickson made it a group of eight members, with the addition his H component, when it was catalogued as Hickson Compact Group 57 (HCG 57) in 1982 ¹. In this paper, Hickson examined 100 compact galaxy groups from the Palomar Observatory Sky Survey –now available as the Digitised Sky Survey (DSS)– with respect to their overall morphology and that of their component galaxies. From this study he attempted to draw conclusions about the dynamical evolution of such groups and their extrapolation to larger galaxy clusters, in which it was believed the density of galaxies was broadly the same.

  HCG 57 comprises NGC 3753 (HCG 57A), NGC 3746 (HCG 57B), NGC 3750 (HCG 57C), NGC 3754 (HCG 57D), NGC 3748 (HCG 57E), NGC 3751 (HCG 57F), NGC 3745 (HCG 57G) and 2MASX J11375047+2200450 (LEDA 36010, PGC 36010 and also HCG 57H).

  Hickson estimated there to be three spiral galaxies amongst them, but this image would suggest that this was an underestimate, which is a shame because a low proportion of spiral galaxies was felt to set these groups apart from the general background.

  The NASA/IPAC Extragalactic Database (NED) gives the Hubble distance to HCG 57 as 136.04±9.53 Mpc (about 443.4 Mly) which matches closely with radio frequency based estimates of 135±3 Mpc, and places the group within the Coma Supercluster. The galaxies themselves range between 434.5 Mly (HCG 57A) and 470.7 Mly (HCG 57G) distant.

  A study of the distribution of neutral elemental hydrogen (HI) in 16 of the Hickson Compact Groups (HCG) using data from the Very Large Array (VLA) proposed an evolutionary sequence for these groups ²: in phase 1 HI is confined to the individual galaxies themselves; in phase 2 tidal forces are clearly having their effect and the hydrogen is becoming distributed throughout the group, such tidal features are well in evidence in this image of HCG 57; and by the end of phase 3 the galaxies lack any HI, in fact it may be missing from the group entirely.

  In a later paper this mechanism was revisited with an analysis of 38 HCGs and found little correlation between the evolutionary stage of the galaxy group based on its morphology and that of its HI deficiency ³ . The author notes that the phase 3 groups are all deficient in HI, however the difference between phases 1 and 2 is negligible and likely attributable to the amount of HI present in the galaxies at the time the group formed. Additionally, there's always the possibility of replenishment from captured galaxies at a later stage that requires consideration.

  Galex shows emission in the far-ultraviolet, which is characteristic of star formation in galaxies, is confined to HCG 57B and HCG 57D with perhaps a hint in HCG 57C. It's probably a coincidence that these three galaxies are also at nearly the same distance.

  HCG 57B was host to two supernovae since the turn of this century: SN 2002ar and SN 2005ba, type Ia and type II respectively. It has been noted that HCG 57D seems to be the least reddened of the galaxies in the group with clear signs of active star formation, it's also a LINER-type Active Galactic Nucleus (AGN).

  A recent paper examined this group from a high-energy perspective using data from Chandra and XMM-Newton X-ray ⁴. It identified point-like X-ray emissions from HCG 57A, HCG 57B and HCG 57D confirming the presence of AGNs. The authors also note that HCG 57A and HCG 57D form an interacting pair, right in the middle of this image, with HCG 57D having passed through the disk of HCG 57A about 50 million years ago, leaving a substantial gas bridge and areas of shock heating. The turbulent expansion of the resulting shock through the two galaxies are also suggested as a possible mechanism to explain the significant suppression of star formation in the larger HCG 57A. Being much smaller, the shock passed through HCG 57D long ago.

  Visual observation of the group doesn't appear to be easy by any means based on Steve Gottlieb's comments, and a large telescope will be necessary, probably 350mm (14-in) or bigger. He notes that the easiest of the galaxies is NGC 3753 (HCG 57A), which is coincidentally also the closest, and that the whole group is possible with persistence and a good sky. As you can see, these compact galaxy groups do make spectacular imaging targets.

  James Whinfrey - Website Administrator.

  Reference

  1. Hickson, P., “Systematic properties of compact groups of galaxies.”, The Astrophysical Journal, vol. 255, IOP, pp. 382–391, 1982. doi:10.1086/159838. https://ui.adsabs.harvard.edu/abs/1982ApJ...255..382H/abstract (Viewed on 25 March 2026).
  2. Verdes-Montenegro, L., Yun, M. S., Williams, B. A., Huchtmeier, W. K., Del Olmo, A., and Perea, J., “Where is the neutral atomic gas in Hickson groups?”, Astronomy and Astrophysics, vol. 377, EDP, pp. 812–826, 2001. doi:10.1051/0004-6361:20011127. https://ui.adsabs.harvard.edu/abs/2001A%26A...377..812V/abstract (Viewed on 25 March 2026).
  3. Jones, M. G., “Disturbed, diffuse, or just missing? A global study of the H I content of Hickson compact groups”, Astronomy and Astrophysics, vol. 670, Art. no. A21, EDP, 2023. doi:10.1051/0004-6361/202244622. https://ui.adsabs.harvard.edu/abs/2023A%26A...670A..21J/abstract (Viewed on 25 March 2026).
  4. O'Sullivan, E., “HCG 57: Evidence for Shock-heated Intergalactic Gas from X-Rays and Optical Emission Line Spectroscopy”, The Astrophysical Journal, vol. 979, no. 2, Art. no. 240, IOP, 2025. doi:10.3847/1538-4357/ada14b. https://ui.adsabs.harvard.edu/abs/2025ApJ...979..240O/abstract (Viewed on 25 March 2026).

• March 2026 - Picture of the Month

  Dwarf galaxy Sextans A

  

  This month's colourful image is of the irregular dwarf galaxy Sextans A. It's box shape, which has been sculpted by a succession of supernovae, is filled with bright young and massive stars and H-II regions around its periphery for that splash of colour.

  As the name suggests, it's a small galaxy with a diameter of about 2.45 kpc (8,000 light-years). It lies only around 1.4 Mpc (4.6 million light-years) away at the edge of our Local Group. Sextans A is also chemically primitive: it displays very low metallicity being comprised mostly of hydrogen and helium. This is largely due to its low mass as it lacks the gravitational strength to retain the the heavier elements that are energetically ejected in supernovae and which would then contribute to the generation of complex chemical species during the late evolution of massive stars.

  However, its low metallicity makes Sextans A a good analogue for early galaxies, and a convenient target for detailed observation due to its proximity.

  A recent survey of asymptotic giant branch (AGB) stars in Sextans A with the James Webb Space Telescope (JWST) revealed the presence of Silicon Carbide (SiC) dust. These dwarf galaxies were expected to lack the heavier elements that are required to create SiC dust, in fact they didn't expect to find any dust at all, yet it turned out to be abundant and composed almost entirely of iron. The authors found that one of the stars surveyed was producing dust via an unusual mechanism, demonstrating that solid matter can be created even when many of the usual components are absent.¹

  The discovery of SiC dust in such a metal poor galaxy is evidence that solid particles can be created even at this apparently early stage of galactic formation.

  Polycyclic aromatic hydrocarbons (PAHs) are interpreted as signifying star formation, due to their catalytic effects on the formation of molecular hydrogen and moderation of ionising radiation. They were also thought to be absent in low mass galaxies, since the lack of dust to shield these compounds from the intense UV radiation from young stars would permit rapid decomposition.

  Another study used JWST data of Sextans A's interstellar medium to reveal dense pockets of PAHs. In large galaxies PAHs are distributed throughout the galaxy inside large dust and gas clouds, many of which have featured in this column. This result suggests PAHs might not be so rare in such low metal environments, rather it's the sparse distribution of these clumps within small distant galaxies that makes them hard to measure.²

  The low surface brightness of Sextans A makes it a better imaging target than one for the visual observer. We have an observation image of this dwarf galaxy on the website already, provided by David Davies, and there's another nice amateur image from the Gemsbock Observatory, both from 2025.

  James Whinfrey - Website Administrator.

  References

  1. M. L. Boyer et al, “Discovery of SiC and Iron Dust around AGB Stars in the Very Metal-poor Sextans a Dwarf Galaxy with JWST: Implications for Dust Production at High Redshift”, The Astrophysical Journal, Volume 991, Number 1. DOI 10.3847/1538-4357/adf06a
  2. Tarantino, E. J., “JWST Captures Growth of Aromatic Hydrocarbon Dust Particles in the Extremely Metal-poor Galaxy Sextans A”, arXiv e-prints, Art. no. arXiv:2512.04060, 2025. doi:10.48550/arXiv.2512.04060
  3. “NASA Webb Finds Early-Universe Analog’s Unexpected Talent for Making Dust”, NASA Webb Mission Team, 9 Jan 2026, https://science.nasa.gov/missions/webb/nasa-webb-finds-early-universe-analogs-unexpected-talent-for-making-dust/ (Accessed on 23 Feb 2026).

• February 2026 - Picture of the Month

  Ultra-Diffuse Galaxy (UDG) 32 in Hydra

  

  My feature object this month is the ultra-diffuse galaxy UDG 32 in Hydra, which can just be seen as a smudge to the lower right, although I have to admit that the more spectacular NGC 3314 in the upper left certainly lifts the image.

  Ultra-diffuse galaxies (UDGs) are very faint, as this image clearly shows, much like dwarf galaxies. In fact, they might be consider as the same class of object given their similar masses, except that UDGs are the same size as galaxies like the Milky Way, and far from being dwarf in their physical extent. Their faintness arises from their sparse old stellar populations that contain 100—1000 times fewer stars than similar sized galaxies.

  The cause of such large yet sparse galaxies remains an open question. They're a diverse group of objects with some comprised of almost nothing but dark matter and others having very little. The main contenders appear to be that UDGs are either failed galaxies or dwarf galaxies that have grown in size, possibly inflated by the action of supernovae. They may represent separate populations of both types of object. ¹

  There's suggestion that this month's feature, UDG 32, might have been formed from the stellar filaments from NGC 3314A, one of the pair of galaxies lending spice to this image, as it lies about 40 kpc away in its trail. ²

  NGC 3314 is a pair of overlapping and non-interacting galaxies imaginatively designated as NGC 3314A, the foreground face-on spiral galaxy of about 16.8 kpc (55,000 light-years) diameter, and NGC 3314B, which is a much larger spiral galaxy whose diameter is about 83 kpc (270,000 light-years). The Hubble Space Telescope has an excellent close-up of the NGC 3314 pair and for their apparent sizes to be so close there must be a large distance between them, about 26 Mpc (85 million light-years). ³

  The very nature of UDG 32 makes it unlikely to be a target for imagers, let alone visual observers, without the benefit of a very large telescope. However the NGC 3314 pairing is a possible target for both imaging and visual observation, although the latter will need a large scope. It will be challenging since it's faint and rises less than 10° above the horizon in the UK; those further south may have more luck.

  James Whinfrey - Website Administrator.

  References

  1. Maria Luisa Buzzo, Duncan A Forbes, Thomas H Jarrett, Francine R Marleau, Pierre-Alain Duc, Jean P Brodie, Aaron J Romanowsky, Anna Ferré-Mateu, Michael Hilker, Jonah S Gannon, Joel Pfeffer, Lydia Haacke, “The multiple classes of ultra-diffuse galaxies: can we tell them apart?”, Monthly Notices of the Royal Astronomical Society, Volume 536, Issue 3, January 2025, Pages 2536–2557, https://doi.org/10.1093/mnras/stae2700
  2. “Formation of an ultra-diffuse galaxy in the stellar filaments of NGC 3314A: Caught in the act?”, Enrichetta Iodice, Antonio La Marca, Michael Hilker, Michele Cantiello, Giuseppe D’Ago, Marco Gullieuszik, Marina Rejkuba, Magda Arnaboldi, Marilena Spavone, Chiara Spiniello, Duncan A. Forbes, Laura Greggio, Roberto Rampazzo, Steffen Mieske, Maurizio Paolillo, Pietro Schipani, A&A 652 L11 (2021), DOI: 10.1051/0004-6361/202141086
  3. Data for the NGC 3314 pair of galaxies taken from NASA/IPAC Extragalactic Database (NED) on 27 January 2026. The dodgy maths of the conversions to light-years is my own.

• January 2026 - Picture of the Month

  Sharpless 261 (Sh2-261) in Orion

  

  This HII region in the northern part of Orion was discovered in 1939 by Harold and Charles Lower using an 8-inch f/1 Schmidt camera to make a 20 minute exposure on a photographic film. Brendan's SHO narrowband image above contains a total of 24 hours of exposure and a lot more detail.

  As a consequence of the discovery this region is sometimes known as Lower's nebula. It was later catalogued as Cederblad 64 (Ced 64), then Siméis 34 (Sim 34) before reaching Stewart Sharpless' list as number 261 (Sh2-261). The same region later produced three bright nebulae designations in the Lynds' Catalogue of Bright Nebulae: LBN 862, LBN 863 and LBN 864.

  Based on photographic plates, Stewart Sharpless estimated Sh2-261 to be 45 arc-minutes in diameter with an 'irregular' form in his 1959 paper ¹. In this paper Sharpless considered this HII region to be associated with star HD 41997 which he estimated to be B8.5 class.

  Radio measurements of CO emission appear to show that Sh2-261 lies beyond the western edge of the Gemini OB1 Molecular Cloud Complex ² at a distance of about 1.89 kpc (6200 light-years) ³, although other estimates of its distance vary widely. As a result it's uncertain whether it lies in the Perseus arm of the galaxy or our own Orion spur.

  HD 41997 (Gaia DR3 3345950879898371712) is now classified as an O7.5III star with a visual magnitude of 8.45 at a distance of around 1.75 kpc (5705 light-years) and it's a runaway ⁴ with significant peculiar velocity with respect to [its] environment having been ejected for wherever it formed.

  Brendan's wonderful image captures the runaway right where you might expect it, below the high energy blue structure in the central hollow, just to the right of centre, from where it illuminates this whole region of dust and gas. The brightest region surrounding the star corresponds to LBN 864.

  Unsurprisingly perhaps, according to The Night Sky Observer's Guide Volume 4, Sh2-261 is barely visible as a half-degree patch of very faint haze with a 16–18 inch telescope and, I assume, a good night sky. So, probably one for the imagers or an ambitious visual observer.

  James Whinfrey - Website Administrator.

  References

  1. Sharpless, S., “A Catalogue of H II Regions.”, The Astrophysical Journal Supplement Series, vol. 4, IOP, p. 257, 1959. doi:10.1086/190049.
  2. Wang, C., Yang, J., Xu, Y., Li, F., Su, Y., and Zhang, S., “Molecular Gas toward the Gemini OB1 Molecular Cloud Complex. I. Observation Data”, The Astrophysical Journal Supplement Series, vol. 230, no. 1, Art. no. 5, IOP, 2017. doi:10.3847/1538-4365/aa6c6b.
  3. Foster, T. and Brunt, C. M., “A CGPS Look at the Spiral Structure of the Outer Milky Way. I. Distances and Velocities to Star-forming Regions”, The Astronomical Journal, vol. 150, no. 5, Art. no. 147, IOP, 2015. doi:10.1088/0004-6256/150/5/147.
  4. Carretero-Castrillo, M., Ribó, M., and Paredes, J. M., “Galactic runaway O and Be stars found using Gaia DR3”, Astronomy and Astrophysics, vol. 679, Art. no. A109, EDP, 2023. doi:10.1051/0004-6361/202346613.