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Lindsay-Shapley Ring

A Peculiar Galaxy, an interesting Target for Big Telescopes, Resides in the Far Southern Skies

As a visual observer, galaxy morphology has always been a very exciting topic for me. To observe different kinds of galaxies, from the classic elliptical and spiral ones to those in groups and clusters showing peculiar shapes is something very interesting, especially if you have a chance to use a big telescope that allows you to detect the fainter and finer details of them. Among the peculiar members in the world of the galaxy morphology, we have the so-called annular galaxies or ring galaxies. As James L. Higdon et al. state in their paper "Why Are Ring Galaxies Interesting?" (2010), these objects are formed by the near central passage of a companion through a spiral along the rotation axis. The brief additional gravitational force induces epicyclic motions throughout the disk, which act to form radially propagating orbit-crowded rings of gas and stars. On other of their papers, James L. Higdon et al. argue that ring galaxies are striking examples of the ability of collisions to transform both the morphology and star-forming activity of a spiral galaxy. Numerical studies since the mid-1970s argue persuasively that the optically prominent rings are in fact outwardly propagating zones of strong orbit crowding within the disk of a spiral induced by the near central passage of a companion galaxy ("Wheels of Fire. IV. Star Formation and the Neutral Interestellar Medium in the Ring Galaxy AM1 0644-741" 2011).

The 24-inch telescope at the "Altos Limpios" Nature Reserve. 
Photo by the author.
If you are observing in the Southern Hemisphere during the summer season take a look, for a moment, to the Large Magellanic Cloud. It is a must-to-see object because of its size, brightness, and remarkable structure. Well, now aim your eyes about 8 degrees southeast of that galaxy. In that region of the sky, more specifically in constellation Volans, an interesting annular galaxy resides, 300 million light-years away. I´m talking about PGC 19481, also known as Graham A, the Southern Ellipse, AM 0644-7411 (Arp & Madore 1987), or Lindsay-Shapley Ring.

A way to find this peculiar galaxy is to look for the 5.1 magnitude star alpha Mensae, one of the stars that are part of the inconspicuous constellation Mensa. The galaxy lies about 2.1 degrees east-northeast of it. The J2000 coordinates of the nucleus of this galaxy are R.A. 06h43m06.s18   Dec. −74◦14 10".7.

The Lindsay-Shapley ring galaxy (AM 0644-741) appears in Category 6 of the Arp Madore catalog of Southern Peculiar Galaxies and Associations, a category that includes any galaxy with an apparent luminous ring around it, and attempts to exclude objects which appear to be spiral galaxies which have had their arms tightly wound into nearly circular appearance.

Below, there is a short video by Chandra Observatory about this enigmatic object in the Southern Sky,

Figure 1. Field of view of the Lindsay-Shapley Ring galaxy. 
"In AM 0644 741, we see a strong ring of bright blue stars in the Cerro Tololo Inter-American Observatory (CTIO) and Hubble Space Telescope (HST ) images, with associated HII regions. Unlike the Cartwheel, which shows spokes and is presumed to be a second ring-formation event (Struck-Marcell & Higdon 1993), AM 0644-741 is likely to be the first ring formed" (see the paper "Dynamical Parameters for AM 0644 741" Alex Antunes and John Wallin (2007).

As can be read on the paper "Morphology and enhanced star formation in a Cartwheel-like ring galaxy", F. Renaud et al. 2017), the Lindsay-Shapley Ring galaxy also displays an enhanced star formation activity in the furthest quadrant of its ring to the nuclei (Higdon et al. 2011).

The picture at the top of this article shows the 24-inch (0.61 meters) used to observe this galaxy. It was set up in a good field in the ranger station at the nature reserve named "Altos Limpios". You need to drive for almost 2 hours northeast from Mendoza City, in Argentina, to reach it. It is important to say that I saw this galaxy when it was about 32 degrees high in the sky (it reaches 48 degrees at its highest) and seeing was not the best that night, so maybe better results regarding the structures seen in this galaxy can be achieved with better-seeing conditions and with the galaxy at higher altitude.

The galaxy was searched, at the beginning of the observation, using 98x. After several minutes scanning the area the target was found, appearing, at this magnification, as a subtle nebulosity close to a quasi-stellar hazy spot when observing with averted vision, which is, actually, the core of the galaxy. The ring diameter, in arcsec, is 85 x 49. An asterism formed by 4 stars of magnitudes between 12 and 12.9 for those labeled in Figure 1, and magnitude 14.5 for the fourth one in the asterism labeled with a blue circle, was useful to confirm that the area was the correct (see Figure 1). A star indicated with a black arrow in Figure 1, is visible close to the galaxy´s nucleus.

Figure 2. DSS image of the Lindsay-Shapley Ring galaxy and its 
The Lindsay-Shapley Ring galaxy seems to be a member, according to the SIMBAD Database, of a small group of galaxies. The two nearest galaxies (at least in projection on the sky) were also detected through the 24-inch telescope. I´m talking about the galaxies LEDA2 19455, situated about 1.2 arcmin southeast of the target galaxy, and LEDA 19454, 1.05 arcmin to the north- northeast (see Figure 2). The first one, a distorted elliptical, was visible using averted vision as a small hazy patch. Both Graham (1974) and Few, Madore, and Arp noted an extended and low surface brightness light distribution between the ring galaxy and LEDA 19455. Partly on the basis of this emission, these researchers concluded that LEDA 19455 was the intruder galaxy. The other companion, fainter, was hardly visible using also averted vision.

Applying a little higher magnification (i.e. 122x), the view was similar to that one at lower magnification. However, the nucleus of the galaxy seems to be a little easier to see, like a faint defocused star. The outer part of the galaxy, including of course the ring structure, shows up when averted vision is applied, appearing as a slightly elongated nebulosity. It is not easy to see, and the beautiful structure seen in those detailed and colorful pictures provided by ground-based telescopes and the Hubble Space Telescope is not detected. The view is rather blurry and faint. The nearby galaxies are again visible, looking faint. LEDA 19455 appears similar to the nucleus of Lindsay-Shapley Ring galaxy, both in size and brightness.

Figure 3Picture credit of James L. Higdon and John F. 
Wallin, appearing as Fig 2 in their paper "Wheels of 
Fire. III. Massive Star Formation in the "Double-Ringed"
ring galaxy AM 0644-741".  
203x is a good magnification to observe the group of galaxies. LEDA 19455 looks now brighter and its presence there is undoubtful, showing a round shape. The LEDA 19454 galaxy is fainter, as said before, but it can be detected. The central part of Lindsay-Shapley Ring galaxy looks bigger and its brightness seems to be smooth. When the galaxy is observed with averted vision, an arc-shaped structure of very faint nebulosity is visible just south of the nucleus.

The view of the galaxy is interesting at 244x. The nucleus is easily visible through this instrument. The whole galaxy looks like a rather elongated nebulosity, a ghostly nebulosity among the surrounding stars in the field of view of the telescope. At this power and observing more carefully, some of the structure, very faint, and indicated with an arrow in Figure 2, seems to be detected for moments. AM 0644-741 possesses twin interlocked rings, each with slightly different centers, position angles, and ellipticity. The double-ring structure makes AM 0644-741 unique among ring galaxies, much like the Cartwheel and its network of spokes. A total of 54 H II complexes were identified in the rings using Figure 2a of the paper "Wheels of Fire. III. Massive Star Formation in the "Double-Ringed" Ring Galaxy AM 0644-741" by James L. Higdon & John F. Wallin (1997). I think the slightly brighter portion visible there, barely visible even with averted vision, are some of the HII regions present in the galaxy. The authors of the mentioned paper state that the most luminous H II complexes tend to be found near the intersection of the A-ring and B-ring (see Figure 3 here) which occurs in an area of the galaxy coincident with the one I observed, indicated with the arrow in Figure 2.

In the SIMBAD Database web page, two x-ray sources are indicated as present in that area also (i.e. [WFM2018] AM0644x1, and [WFM2018] AM0644x2.).

A long time ago, something amazing happened in this distant galaxy, and you can be a witness of that when observing it from a dark sky site.

1 _ Catalogue of Southern Peculiar Galaxies and Associations (Arp, Madore): 6,445 peculiar and interacting galaxies found on IIIa-J southern sky survey plates, types, positions, and characteristic sizes, cross-identifications and selected photographs. 

2(Lyon-Meudon Extragalactic Database). Extension of PGC catalog in the Lyon-Meudon Extragalactic Database 1989: Catalogue of principal galaxies, 1ST edition: N=73197.
The first designation was PGC, but PGC and LEDA are now equivalent.

Planetary Nebula K1-22

This Ghostly Remnant of a Dying Star is a Good Target to Test Your Eye Acuity When is Observed With Small Instruments.

Figure 1. K1-22 planetary nebula seen close to the mountains. 
Photo by the author
Also known as ESO 378-1 and PK 283+25.1[1], this planetary nebula, nicknamed the "southern owl nebula" by some observers, is a challenging target for owners of 8-inch or similar size telescopes. April and May is a good season to observe it from the Southern Hemisphere because it is very high in the sky as soon as the sky gets dark, hidden among the stars in the long constellation Hydra (the water snake), specifically in R.A. 11h 26m 43.7s Dec -34° 22' 12".

I personally think that an 8-inch is a small telescope if we have in mind that some observers own much bigger instruments (e.g. 24, 30 or even 32-inch mirrors).

I observed this object from Potrerillos, a site you can reach driving for 1 hour to the West from Mendoza City (Argentina). It is a nearby site, so you will have some light pollution in the eastern sky if you go there. However, the sky is pretty dark at the zenith and toward the West where the high peak mountains of Los Andes are situated. I can say that the observation of this planetary requires a good dark adaptation (as with any other faint objects) and to improve as much as you can your environment to have a very dark site. I should say that covering your head with a black blanket is a must. I also suggest to slightly shake your telescope when using averted vision taking into account that, according to researchers, rods are better motion sensors than cones, thus getting the best of your night vision to catch this elusive planetary nebula.

It was a real surprise for me to be able to glimpse this member of our Milky Way through my 8-inch telescope even at very low magnification.

This video, by ESO Observatory in Chile, shows the intriguing planetary in Hydra.

At 42x, the 1° field surrounding the planetary, which has an angular size of  3.1'x2.9', is easily recognized by identifying the pairs of stars HD 99463 & HIP 55828 (visual magnitudes 8.5 and 8.7 respectively), and the fainter one composed by the stars CD --33 07733 & TYC 7223-280-1 (visual magnitudes 9.9 and 10.5). They are labeled in Figure 2. Once there, another two pairs of stars are useful as references to find the area where this elusive planetary nebula resides. Amazingly, even without any nebular filter, a very faint nebulosity seems to jump to the view. However, the view is very challenging so nebular filters (e.g. UHC, OIII, Orion Ultrablock) are necessary to enhance the view of this interesting object of our Milky Way. The use of different eyepieces (magnification) will make possible a comprehensive visual analysis of this deep sky object and its visibility through an 8-inch telescope.

Figure 2. The planetary nebula and the nearby brightest stars in the field.
If you have a UHC filter among your accessories do not hesitate to use it to have an improved view of K1-22[2]. At low magnification and through this filter the planetary looks round, smooth, and of course very faint. The ghostly image of K1-22 is a little better detected for moments when applying averted vision. Even a slight movement of the telescope seems to enhance a little the detection of the planetary. It shows a little more contrast but it is still very faint. The Orion Ultrablock filter offers an image of the planetary not so contrasted as that of UHC. However, the view improves a bit compared to that without a filter.

The Hubble Space Telescope (HST) images (see Figure 4 below) show two sources separated by 0".35 at the center of K 1-22; the blue northeast component is the CSPN (Central star planetary nebula) and the red southwest component is a cool companion (Ciardullo et al. 1999). The IR images show a source coincident with this close pair of stars, but cannot resolve them (paper "Spitzer 24μm Survey for Dust Disks Around Hot White Dwarfs" You-Hua Chu et al. (2011).

At 78x, K1-22 looks faint, so averted vision is necessary to improve the detection. UHC filter clearly enhances the view of the planetary. For a brief moment, a stellar feature seemed to show up inside the planetary. However, the stars "inside" or in projection on K1-22`s disk are very faint to be detected through an 8-inch telescope taking into account that they have a visual magnitude around 15.3. Sources state that at 80x an 8-inch telescope should show (under ideal conditions of course) stars up to visual magnitude around 14.4, so surely the view of that faint stars was just a false signal of my eye.  
Figure 3. The central star of this planetary nebula (CSPN K 1-22) 
is labeled on this picture.
Photo credit: ESO.

"The discoverer of this planetary nebula (Kohoutek 1971) noted that three stars appear near the center of the nebula and proposed that the brightest of these was the PNN, paper "New Planetary Nebulae". Smith & Gull (1975) confirmed that this star is very blue. Instead, Kaler & Feibelman suggested that a fainter object 4" east of Kohoutek´s candidate was the PN's true central star. Given the low stellar density in the field, the pair almost certainly form a bound system. Our derived distance of 1.3 kpc is reasonably consistent with distances based on statistical techniques (1.0 kpc, CKS ; 3.4 kpc, Zhang 1995)." (paper "A Hubble Space Telescope Survey for Resolved Companions of Planetary Nebula Nuclei" Robin Ciardullo et al. 1999. On the other hand, T. Rauch et al. claim, in their paper "Classification and spectral analysis of faint central stars of highly excited planetary nebulae" (1999), that absorption features is the spectrum of the central star of PN G283.6+25.3[3] (by the way another name for this planetary nebula) suggest the presence of a cool companion with the planetary being a circular object with two lobes and without a central hole.

The view of the planetary is very faint and difficult at 106x also. A good suggestion to better detect this elusive object is to cover your head with a black carpet. Once again, the UHC filter is useful to improve the contrast of K1-22. Averted vision is always necessary to glimpse this round and smooth disk. No stars were visible at this magnification through the mentioned filter. The performance of the Orion Ultrablock filter was, as with the lower magnifications, worse than that with the UHC filter.

Figure 4. Picture taken from the paper  "Spitzer 24 µm Survey for Dust 
Disks around Hot White Dwarfs"  by  You-Hua Chu et al. showing optical 
and IR images of CSPN K1-22.

166x did not show new features or something different beyond the smooth and faint patch "hidden" among the stars in this southern constellation.

I decided to go back and make a final observation using very low magnification (i.e. 32x). Knowing in advance where this planetary lies, something seems to be visible there, very elusive. However, you can use this low power to catch it if you have, of course, a detailed star chart and a good eyepiece field chart to know the precise position of K1-22.

I used an OIII filter with this eyepiece and I got a beautiful view, with K1-22 faint but visible with direct vision. Averted vision makes possible to improve the detection with this object appearing big, smooth in brightness, and round.

H-Beta was a totally useless filter for this planetary nebula.

K1-22 is a faint planetary nebula in the autumn southern sky to study visually and photographically. If you have seen the well-known "Owl nebula" Messier 97, try to observe its southern cousin, K1-22 if you have a chance to travel to this part of the planet and enjoy the starry skies.


[1]   Perek and Kohoutek. Catalog of Galactic Planetary Nebulae.  Academia publishing house of the Czechoslovak Academy of Sciences,  Prague, 1967, 276 pages. Compilation of all Planetary Nebulae known in the Milky Way Galaxy in 1964. 

[2]   K is the acronym after Kohoutek.

[3] The nomenclature for the Strasbourg-ESO catalog of planetary nebulae.

The Coddington`s Nebula

This Member of the Nearby M81 Group Shows an Intriguing Structure 
that Amateur Astronomers can Observe Through their Telescopes

Figure 1IC 2574, in constellation Ursa Major. Photo by the author.
A summer night in the Northern Hemisphere, the sky looks good for observing deep-sky objects. However, it is important to say that the conditions were not the best at all. I consider important to mention this in case you want to compare your own observation of this faint galaxy with the report posted here. 

This article is devoted to IC 2574 (also  UGC 5666, DDO 81, and VII Zw 330), an interesting dwarf galaxy discovered by the american astronomer Edwin Foster Coddington on a photographic plate using the Crocker Photographic Telescope at Lick Observatory (University of California, USA), in 1898. This object is part of the M81 group which contains 30 members, being Messier 81, NGC 2403, and NGC 4236 the brightest ones (book "The Cambridge Photographic Atlas of Galaxies" by Michael Kônig Stephan Winnewies). M81 group is one of the nearest prominent groups in the vicinity of the Local Group. 

The IC 2574 galaxy is located at a distance D = 4.02 Mpc (1 arcsec = 19.5 pc) according to Karachentsev, Makarov & Kaisina (2013), paper "The Supergiant Shell with Triggered Star Formation in the Dwarf Irregular Galaxy IC 2574: Neutral and Ionized Gas Kinematics" O. V. Egorov,1‹ T. A. Lozinskaya,1 A. V. Moiseev1,2 and G. V. Smirnov-Pinchukov1 (2014).

Figure 2IC 2574 and its surrounding field.
When you are ready to observe, in a site as dark as possible because we are talking about a faint object, aim your telescope to the region indicated on Figure 1, just north of the Big Dipper. This galaxy lies about 22 degrees from the well known star Polaris.

IC 2574 hosts many HI holes and also an interesting structure to be observed through big telescopes, a Supergiant Shell1 (SGS) of ∼1000 × 500 pc in deprojected size (Walter et al. 1998; Walter & Brinks 1999; Cannon et al. 2005). The SGS, as well as many holes found in IC 2574, is surrounded with HII regions likely triggered by the stellar feedback related to the star-forming event that occurred in the hole center ∼25 Myr ago (Walter & Brinks 1999; Weisz et al. 2009). The SGS is located in the northwest region of IC 2574 and created by a significant burst of star formation in its center. It is likely responsible for triggering a ring of star formation around it (Walter et al. 1998; Walter & Brinks 1999; Pasquali et al. 2008) See paper "Hunting for Young Dispersing Star Clusters in IC 2574 "Anne Pellerin, Martin M. Meyer, Daniella Calzetti, and Jason Harris (2012).

A few questions arise now, how much details can we see in this galaxy through an amateur telescope? Are the components of the supergiant shell visible?

Figure 3. Working with a DSS image I tried here to reproduce 
how the galaxy looked through the 18-inch telescope. Faint target, 
with the two "brighter" areas indicated with squares on the picture.
North is down. South is up.
This article was written based on observations I made using an 18" (45cm) f3.5 telescope. I first found this galaxy using low power (45x). The group of stars labeled with a circle on Figure 2 was useful to identify the surrounding field and to find the galaxy which was visible at this low power. With a visual magnitude of 8.2 HD 90820 is the brightest star in the 1 degree field of view. 

At 45x, IC 2574 looks like a "rather smooth nebulosity" elongated northeast-southwest with a small area appearing slightly brighter, even though is faint and round. This area is indicated with an arrow in Figure 2 and is the aforementioned supergiant shell. We are talking of a rather faint object even for an 18-inch telescope, at least under the sky conditions in central Oregon in 2018 summer, when this observation was made. It is important to say that the sky conditions were good enough for carrying out this observation but it was not an excellent sky, so maybe observers with the same kind of telescope under a darker and more clear sky might be abble to see this galaxy and its features a little better or easier.

At 61x the galaxy looks again smooth and clearly elongated, faint in brightness. Using averted vision two areas are slightly brighter than the rest (see Figure 3). However, the whole object is hard to see.

Figure 4. Credit O.V. Egorov et al. 
While the structure to the south end looks smooth in brightness and bigger than the other one, the north patch appears round and smaller. Observing carefully, some star-like structures seems to be visible in this region. Figure 4 to the left is a picture taken from the paper  "The supergiant shell with triggered star formation in Irr galaxy IC 2574: neutral and ionized gas kinematics". O.V. Egorov , T.A. Lozinskaya , A.V. Moiseev , and G.V. Smirnov-Pinchukov. This picture shows the giant HII regions on the HST/ACS F658N image of the SGS area according to the list of Stewart & Walter (2000). Bottom panel on Figure 4: location of the star clusters on the same image. The clusters identified by Pellerin et al. (2012) are shown by blue. The red circles denote the clusters from Cook et al. (2012). The four largest green circles show the star clusters identified by Yukita & Swartz (2012).

121x. This is an intersting magnification to see IC 2574. It is a faint object so averted vision is always necessary to glimpse and identify its structures. A very challenging glimpse of a small nebulosity is possible for moments when observing carefully, I´m talking about [MH94a]3 IC 2574 203 and [MH94a] IC 2574 218, a small object composed of two HII regions. The bigger structure, to the south, looks again smooth (featureless). Although faint, the smaller northern feature is a little easier to detect, appearing slightly more detached against the surrounding stars. Some of the components on that zone (appearing star-like in shape) are barely visible. Using averted vision, PMC20122 13z, the brightest component according with what can see on a DSS image, seems to be the "easiest" part to pick up visually. PMC2012 13z is a star-forming complex – an extended (∼ 450 × 320 pc) fine-filamentary HII region, located in the northern wall of the SGS. Yukita & Swartz (2012) identified the young star cluster C1 inside Region.

162x. At this power the small object composed of two HII regions is visible with averted vision (see Figure 5). It is a faint feature of the galaxy however. At this magnification the aforementioned areas of the galaxy seems to be connected by faint nebulosity, without a doubt part of the galaxy, appearing clearly elongated. Observing carefully, some components of the supergiant shell seem to jump to the view but it is not possible to see them clearly and discern and identify each one. The component of the supergiant shell, PMC2012 13z, an association4 of stars according to SIMBAD Database and the STScI Digitized Sky Survey web page is certainly visible appearing cuasi-stellar in size and with a hazy nature. The UHC filter slightly improves the view of the smaller patch of the galaxy. Even PMC2012 13z appears more nebulous.

Figure 5The supergiant shell and its main components.
Both the STScI Digitized Sky Survey web page and SIMBAD Database agree that CVL20095 UGC 5666-3, the brightest nebula in the SGS, is an HII region that looks rather non-uniform and consists of a central nebula ≃ 120 pc wide, several more compact (≃ 10 − 20 pc) clumps that surround it, and two faint external shells southeast and northwest of the region with the sizes of ≃ 20 pc and 35 pc.

Another association of stars, PMC2012 21z, is a region that has the form of a bright ‘halfshell’ whose eastern part adjoins the dense wall of the SGS, with a fainter filamentary inner part. The full size of the region is about 250 × 150 pc.

While some star-like structures seem to be visible briefly and with difficulty in this galaxy, as was mentioned above, the view is difficult and unclear, so I can not claim to have identified these last two features of the SGS visually. The only patch visible there seems to be the brightest one on Figure 5PMC2012 13z. 

IC 2574, one of the many outstanding and enigmatic galaxies that we can find in a dark sky, is a good target to put your eyes and telescope under proof and see how much you can detect under ideal observing conditions.


1_ SGS Irregular galaxies reveal giant HI supershells and holes with sizes as large as 1 – 2 kpc and lifetimes up to several hundreds Myr. Giant supershells and holes in some galaxies represent the dominant feature of the ISM. Such large structures are usually called supergiant shells (SGS), or giant supershells. Formation mechanisms of supergiant shells have been discussed extensively in recent decades

2[PMC2012] - (Pellerin+Meyer+Calzetti+, 2012)

3[MH94a] (Miller+Hodge, 1994)= (MH)as appears in SIMBAD Database

4The concept of a stellar association was originally introduced in 1949 by V. A. Ambartsumian, who later separated them into OB and T associations (Ambartsumian 1968). Morgan, Sharpless, & Osterbrock (1952) considered as a stellar association any loose group of stars within an area where bright OB stars exist and with evidence of a common origin.

A recent definition of a stellar association (Kontizas et. al. 1999) refers to it as a single, unbound concentration of early-type luminous stars, embedded in a very young star forming region.

5[CVL2009] - (Croxall+van Zee+Lee+, 2009)as appears in SIMBAD Database