Picture of the Month for 2024

• November 2024 - Picture of the Month

  Van den Bergh 24 and XY Persei in Perseus

  

  So more glowing dusty goodness in my Picture of the Month, I should think that you can probably see a long term trend by now. This image from the Mosaic camera on the Mayall 4-meter telescope at Kitt Peak National Observatory provides another look at star creation. We have a dark nebula (LDN 1442) to the left of the blue reflection nebula which is illuminated by the bright star emerging just below.

  That star is XY Persei, which is a type INA variable star, one of the Orion variables of early spectral types (A2II+B6e in this case) that are noted for their abrupt Algol-like instances of fading. Normally around magnitude 9 this star fades to somewhere near 11^th magnitude, so it's a visual observing target as well as photometric.

  Although it isn't obvious in this image, SIMBAD Astronomical Database reveals that XY Persei is also a double star which the Washington Double Star catalog gives as HU 1067 with the component magnitudes of about 9.7 and 10.6. The separation is 1.30 arc-seconds which hasn't changes much between 1904 and 2015.

  As I mentioned above, it's this star that's responsible for the reflection nebula that's just above it in this image, and that's known as Van den Bergh (VdB) 24. I guess that VdB 24 itself isn't that easy to image in detail. Most of the images I've found are wide-field, but then the nebula is only around 9 arc-minutes across and quite faint. That's why I've gone for a professional image that reveals a wealth of detail.

  Frankly, there's not a lot of information available for the nebula itself, but it can be observed visually as a brief discussion on the Deep Sky Forum shows, as does its inclusion in Reiner Vogel's Young Stellar Objects guide, which is mentioned in that thread and available for download from his website, which also has a nice article about these objects. I expect that it'll need a large telescope to see much of the nebula since Reiner was using a 22 inch Newtonian and the observation in The Night Sky Observer's Guide (NSOG) Volume 4 recommends 16–18 inch telescopes.

  James Whinfrey - Website Administrator.

• October 2024 - Picture of the Month

  Van den Bergh 152 (and the Wolf's Cave Nebula) in Cepheus

  

  Well, there's a lot going on in David's image which shows nearly three degrees of the sky in Cepheus. Such a rich and colourful view of nice large piece of one of my favourite constellations made this my Picture of the Month. It also contains many of examples of my favourite kinds of deep-sky objects.

  The main feature of this month's article, Van den Bergh (VdB) 152 (also known as CED 201), is glowing at the lower end of that long dark nebula (Barnard 175 aka the Wolf's Cave Nebula it seems), all of which is about 1,400 light-years from us.

  The reflection nebula VdB 152 is illuminated by BD+69 1231, a magnitude 9.4 type ELL variable star (CzeV4335). It's a close binary system which is one of the class of Rotating ellipsoidal variables, but it probably isn't worth your time observing since its period is less than a day and amplitude only a few of thousandths of a magnitude.

  Speaking of stars, there's also a past Double Star of the Month from September 2021 nearby, STF 2883, that bright one just to the right of VdB 152.

  This end of B 175 comprises a Bok globule which hides the Herbig-Haro object HH 450 just to the left of VdB 152. A jet being driven by the formation of a new star has been detected within it, as it collides with local dust and gas. NOIRLab have a close-up from Kitt Peak National Observatory which reveals this feature well.

  It also shows the red filaments an expanding supernova remnant (SNR 110.3+11.3). Whilst you can't see the jet in David's image, the supernova remnant is just visible arcing all the way towards that yellow star on the left edge of the field, BD+70 1240.

  James Whinfrey - Website Administrator.

• September 2024 - Picture of the Month

  R Aquarii and Ced 211 in Aquarius

  

  Something a bit different from the usual nebulosity, although there is still a nebula associated with R Aquarii. This month I'm featuring the variable star, or perhaps that should be stars at the heart of this nebula: R Aquarii is a symbiotic binary system with the larger of the pair also being a Mira-type variable star from which a white dwarf that is accreting material.

  The variability of R Aquarii has been known for a long time, first noted by Karl Ludwig Harding in the early 1800s, because of the amplitude of the light-curve. The Mira component has a range of over four magnitudes during its broadly annual cycle. However the system as a whole has been seen to range between 5th and 12th magnitude. This is far from a simple light-curve and there's still conjecture surrounding the causes of its variability.

  Typically these binary system undergo periodic outbursts during which material is ejected from the accreting star. This is the theorised source of the nebula surrounding the binary which is designated as Cederblad (Ced) 211. There are a couple of shells visible in Peter's image which are thought to be from two separate events about 640 and 185 years ago. Additionally you can see the bright and roughly 'S' shaped feature which comprises superheated material being accelerated in jets.

  There an interesting article about R Aquarii in the American Association of Variable Star Observers Variable Star of the Season archive from Summer 2003. The European Southern Observatory also turned their Very Large Telescope (VLT) on the Ced 211 back in 2012.

  Alternatively you might like to make a few magnitude estimates with binoculars or a modest telescope. Apparently Ced 211 is possible to observe visually, but it seems to take a relatively large scope, and I should imagine that it's best attempted with a good sky when the variable is near minimum.

  James Whinfrey - Website Administrator.

• August 2024 - Picture of the Month

  NGC 6769, NGC 6770 and NGC 6771 in Pavo

  

  This month I'm bringing you an fabulous image of a cosmic crash which appears to have been named either the Cosmic Ballet or the Devil's Mask by ESO, although it's the latter that seems to have stuck. Personally I prefer the NGC 6769 group or the Pavo Triplet. The ESO image is impressive enough, but I think that this more recent one of Adam's shows much more detail.

  The pair of galaxies principally involved are to the upper left are NGC 6769 and NGC 6770, both of which are spiral galaxies about 180–190 million light-years away in the constellation of Pavo, are around 11th magnitude and 300–400 kly in diameter. In the lower right we have another spiral galaxy that's edge-on designated as NGC 6771 which lies slightly further away at about 200 million light-years, is 12th magnitude and of comparable size.

  This image shows plenty of dust and star formation in the interacting pair, with an obvious dust lane around the middle of NGC 6771. The core of this galaxy has a strange box-like structure.

  Probably due to being southern sky objects there are relative few observations of this triplet, either by astroimagers or visual observers. These galaxies aren't particularly faint and they should be visible in fairly modest scopes. I suspect that a scope of 40-cm (16in) or more might show some detail.

  James Whinfrey - Website Administrator.

• July 2024 - Picture of the Month

  IC 4628 (Prawn Nebula) in Scorpius

  

  I had hoped to bring you this rather splendid image of IC 4628 by Josep Drudis, but I wasn't able to secure permission in time. So you'll have to make do with the smaller field in the version above by ESO, with some amateur data from Martin Pugh, that's still rather impressive. There's another spectacular close-up of the region in the top left of this field taken with the MPG/ESO 2.2-metre telescope at the La Silla Observatory in Chile.

  IC 4628 lies 6,000 light-years away from us in the Sagittarius Arm of the Milky Way, and it's about 250 light-years across, with an apparent size of roughly 90 arc-minutes. Despite varying reports of its apparent magnitude of 7.3–10.0, the fact that it covers an area of the sky about four times the size of the Moon means that this nebula is not particularly bright, and as such few people image it, which seems a pity.

  The majority of the colour in this image is the result of light emitted by the glowing gas and dust surrounding the hot young stars in this HII region. But there's some blue there too from reflected light. Of course, against such a background there's a fair amount of dark nebulosity on show.

  The majority of the stars in this image are part of open cluster Trumpler 24 (Tr 24), which so happens to be a subset of Collinder 316 (Cr 316). The Night Sky Observer's Guide (NSOG) Volume 4 reports that …the two groups appear as one huge object… in binoculars, and that the star field is rich. Archinal and Hynes in Star Clusters provide Tr 24 with a IV2p n classification, noting that Cr 316 is superimposed on top and might even be just the brighter members of Tr 24. How many members either of these open clusters might have, they're not saying.

  NSOG suggests that with a modest scope, but good skies, an OIII filter starts to bring out IC 4628 itself, arcing across the NE perimeter of Tr 24 and earning that 'n' in its classification.

  If you are foolish enough to try superimposing the SIMBAD data on this image it will disappear beneath a sea of Young Stellar Object (YSO) candidates, perhaps unsurprisingly.

  James Whinfrey - Website Administrator.

• June 2024 - Picture of the Month

  NGC 6164 in Norma

  

  This month I bring you an emission nebula some 4,200 light-years distant in the southern skies that's sometimes known as the Dragon's Egg. I think you'd agree that Martin's image of this object is spectacular enough to be a Picture of the Month.

  It's designated as both NGC 6164 and NGC 6165 since it was first observed by John Hershel in 1834 as two unconnected bars of nebulosity separated by about 5 arc-minutes. These nebulae are the brightest edges of that broadly rectangular opening that's being created by the central star. NGC 6164 is the bar at the bottom left (actually the NW), and NGC 6165 is at the top right (or the SE).

  Photographically it looks rather like a planetary nebula doesn't it? And that's what it was considered to be by Karl Henize in 1959, but by the early 1960s it had been established as an emission nebula. The cause for some of this confusion lies at the middle of the nebula in the form of an unusual type of star. It's the one that you can see shining brightly in the centre of this image at visual magnitude 6.7: HD 148937, a spectroscopic binary.

  The components of HD 148937 are huge and hot O-type stars that have been in existence for 3–4 million years and will probably last the same again before ending life as a supernova. Yet one of the pair displays magnetic fields, and since stars as hot as these don't have convective interiors they're not meant to be magnetic. On top of that this magnetic star is about 1.5 million years younger than its companion.

  As for the nebula itself, including the extensive blue coloured halo, it is significantly younger, at about 7,500 years, than either of the stars at its centre. Additionally, observations by ESO have confirmed that it contains relatively large quantities of carbon, nitrogen and oxygen, not the kind of thing expected from the outer layers of a star, but rather its core. So it's not likely that the nebula was formed from gas ejected by these young stars as had been supposed.

  Recent observations by ESO have provided confirmation for an alternative hypothesis by Frost et al leading to a paper being published in April 2024 in Science. It seems likely that this was once at least a three star system, but that two of the companions were close enough to merge after 1.5 million years, forming a star with a magnetic field and ejecting the matter to create the nebula.

  James Whinfrey - Website Administrator.

• R Coronae Australis and the Coronet Cluster in Corona Australis

  May 2024 - Pictures of the Month

  

  This is not the first time that this region of Corona Australis has featured on Picture of the Month. Martin Pugh provided an amateur view back in June 2018, but this time I've a reason for choosing an image from ESO’s Chilean telescopes, as you'll discover below.

  The Coronet cluster in the image above is a young star forming region much like that in the Orion Nebula (Messier 42), visible in northern skies. It's embedded in the Corona Australis molecular cloud complex, and so comes complete the glowing gas and dust I enjoy so much. The Coronet lies about 170pc from us, whereas M 42 is about 412pc away, so due to its proximity it looks fairly sparse. It spans about 30 arc-minutes.

  Of particular interest is the fact that it's full of stars that are less than two million years old, some much less, and of varying mass, providing the opportunity to observe stellar evolution in progress. Many of these stars are of course of variable brightness, and I want to draw attention to a couple in particular: the variables T and R Coronae Australis.

  These two stars can be see near the centre of the image above, and they're embedded in a variable reflection nebula called NGC 6729. Below I've cropped into this nebula.

  

  You can clearly see the fan-shaped nebula in the optical view above. R Coronae Australis sits at its apex with and T Coronae Australis to the right in the middle of the fan itself. What's interesting though is that ESO have imaged this region in the infrared in order to peek through all the obscuring dust. As you can see, doing so reveals many more young stars and far more internal detail of this reflection nebula.

  In addition to valuable data, I think that these multi-wavelength studies provide some exciting new perspectives on well known objects that, so far, amateurs can't match. For those that agree, ESO have a fantastic slider view of the optical and IR versions covering the full field of the main image in this article.

  James Whinfrey - Website Administrator.

• Messier 85 and NGC 4394 in Coma Berenices

  April 2024 - Picture of the Month

  

  Just below the centre of this image we can see a 10.5 magnitude star, and above and to the right is the main subject of this article: Messier 85 (NGC 4382).

  This galaxy's morphology lies somewhere between elliptical and lenticular, perhaps in transition between the two types. It's populated by mostly elderly red stars, but there's a population of much younger stars near its central region. This may be connected to a merger event, and the outer regions of this galaxy are very disturbed, as shown in David's image. Another notable feature of Messier 85 is that direct star velocity measurements indicate that it completely lacks a central massive black hole, yet indirect methods suggest a black hole of substantial mass.

  Messier 85 is also disturbed by its interactions with another galaxy shown on this image directly below the core of Messier 85: the small elliptical MCG 3-32-28. To the left is the beautiful spiral of NGC 4394, and IC 3292 is also visible on the extreme right of the frame. These two are likely companion galaxies, although they may not be interacting. This group lies about 55–60 million light-years from us.

  As you can see, these galaxies make a nice group for an image, but they're also easily visible in smaller telescopes. Even I logged some clear observations of the main pair, Messier 85 and NGC 4394, from my garden with a 130mm (roughly 5 inch) Newtonian telescope.

  James Whinfrey - Website Administrator.

• Galaxy NGC 3628 in Leo

  March 2024 - Picture of the Month

  

  I've seen a few excellent images of NGC 3628, but I don't recall another that made the full 300,000 light-year extent of the galaxy's tidal tail so obvious. My guess is that this has taken a lot of imaging time, in addition to which Mark's website mentions he used some large aperture telescopes to produce this mosaic.

  NGC 3628 is an edge-on spiral galaxy which contains plenty of star-forming dust which hides its inner structure. However it's not hard to see how disturbed those outer dust lanes appear, which lead to its inclusion in the Atlas of Peculiar Galaxies as Arp 317. This edge-deformation and the tidal tail are thought to be the result of gravitational interaction with the other two galaxies in the famous triplet, Messiers 65 and 66.

  Just above the centre of NGC 3826 you can see the faint glow of a satelite galaxy, of which ESO have a nice close-up image.

  There are also a number of faint galaxies along the length of its tail. Above the tail in a central position, and about halfway to the top, you can just see the thin profile of IC 2745 next to a magnitude 14 star. Further right near the top of the image is another faint and thin profile: IC 2776. Below that is the more substantial round glow of IC 2782 with IC 2786 just to its right, next to a sharp looking spear of a LEDA galaxy. Finally there's the obvious glowing ball below them, and just above the tail itself, of IC 2787.

  NGC 3628 is wonderful object for imaging and visual observing alike. It's easy to find in small telescopes, and spectacular in large ones so I'm told.

  James Whinfrey - Website Administrator.

• Spiral Galaxy NGC 2903 in Leo

  February 2024 - Picture of the Month

  

  Yes, I've used another image from a professional observatory, and a space telescope at that. I had something else in mind, but I couldn't get permission to use that image in time. All the same, I think that this is a glorious image of NGC 2903 filling the frame.

  This galaxy is roughly 30 million light-years away which would make it upto 110,000 light-years in diameter. You can clearly see its spiral nature and the dusty dark lanes that are home to those bright blue star forming regions. It was an investigation into the role of supermassive black holes and that bright central bulge surrounding them that drew the Hubble Space Telescope (HST) to image this galaxy.

  However as a kind of compensation I should point you to the wonderful images by Josep Drudis, and by Adam Block. Both have captured the features mentioned above beautifully whilst also showing the galaxy in its star field, capturing a few other galaxies in the process. The most obvious are at the bottom of both images, UGC 5086 on the left and PGC 1648681 on the right.

  Whilst neither of those are visual targets, NGC 2903 itself is so accessible that even I've observed it relatively easily in my 130mm and 150mm newtonian telescopes. It has a visual magnitude of about 9, and being relatively large and bright it's not hard to find.

  James Whinfrey - Website Administrator.

• Herbig-Haro 1177 in Mensa

  January 2024 - Picture of the Month

  

  You might says that I've started the year with another cheat! Which is true: this isn't an amateur image by any stretch of the imagination. In my defence all I can say is… dust and star formation again, but with a twist.

  I'm guessing that many will have seen this image at the end of last year, but what struck me is the way that different instruments have been used to build up the impressive story of a forming star and, at least in time, its planetary system. Accretion disks have been seen before, but this one caused excitement because it's the first seen in another galaxy, albeit the Large Magellanic Cloud (LMC) which is relatively close by.

  The large HII region in the Very Large Telescope (VLT) image on the left is catchily known as LHA 120-N 180B, but it also appears to broadly coincide with the more familiar designation of NGC 2122. Its likeness was captured along with that of Herbig-Haro (HH) 1177 in images released by ESO in February 2019. The Multi Unit Spectroscopic Explorer (MUSE) instrument provided the image of blue and red shifted jets issuing from the poles of the newly formed star, hidden in its surrounding cloud of dust and gas. You can see this in the central image.

  It was fairly safe to assume that a Keplerian disk might be hidden in that structure, feeding those jets, but the new story comes with the addition of data from the Atacama Large Millimeter/submillimeter Array (ALMA) that can show the rotation of the disk at wavelengths that penetrate that natal cloud. That's the small addition of the red and blue pixels between the HH jets in the image on the right.

  So this month I want to express my excitement about the cumulative use of measurements with different instruments and wavelengths to reveal more about the formation of stars, or indeed the nature of any other astronomical objects. Work such as this is well beyond amateurs, but there are many other fields where traditional imaging can be supplemented with techniques such as multi-band photometry and spectroscopy. It's always fascinating to hear about such projects.

  James Whinfrey - Website Administrator.