Great Galaxy Grab
The spring sky opens up a new vista for observers, the Milky Way lying toward the west, the eastern portion of the sky reveling in extragalactic objects for small and larger apertures alike. Here the skills of star hopping and patience are needed to hunt down many faint and not so faint galaxies, some spectacular and easily seen in binoculars and many a challenge just to find. We will take a journey to some of these objects, crossing through different constellations as we do so to complete the Great Galaxy Grab.
SCULPTOR
Sculptor lies at right angles to the plane of our galaxy therefore we look out beyond the spiral arms into deep space. Here we can contemplate the vastness of the cosmos, many faint galaxies seemingly immersed within the backdrop of faint stars, though of course, we lose the dazzling open clusters and nebulae that inhabit the spiral arm regions.
Most galaxies are not alone, they huddle together like moths around a porch light. One such gathering is the ‘Sculptor Group of Galaxies’ which include NGC 55, NGC 253, NGC 300 and NGC 7793 though recent study (I. D. Karachentsev et al. (2003). "Distances to nearby galaxies in Sculptor". Astronomy and Astrophysics) suggests that NGC 55 and NGC 300 are foreground objects only.
Located near the southern border with Phoenix, NGC 55 is an outstanding (SB) barred spiral. James Dunlop discovered this beauty on August 4th, 1826. With an estimated distance of 7.5 million light years, it is one of the closest galaxies to our Milky Way. In terms of size, NGC 55 spans 70,000 light years in extent and appears nearly edge-on. A 25cm mirror will show some mottling across the surface and a prominent dark dust lane east of the nucleus. The best galaxy in Sculptor is NGC 253, sometimes called the ‘Silver Coin Galaxy’.
This marvellous object lies near the northern border with Cetus and is the brightest member of the Sculptor Group, lying around 13 million light years distant. NGC 253 is what is called a star-burst galaxy because of its energetic star forming antics. The highly successful space-telescope Hubble has imaged part of the core of NGC 253, revealing a region 1,000 light years across that includes a super compact star cluster amongst a region of hectic star formation and fingers of ionised gas and dust.
Caroline Herschel, devoted assistant to her brother William and a qualified observer in her own right, first discovered this large spiral in 1783 whilst searching for comets. The galaxy appears mottled and dark dust clouds can be seen silhouetted against the background glow. We see it from 17° above it’s rim, a bright elongated central region with a few bright foreground stars dominating the large, faint outer envelope.
NGC 253 is bright enough to be seen in binoculars as a hazy elongated smudge of light, a grouping of bright stars helps to orient the observer to its position. Use a low power eyepiece, especially so under a dreaded city sky to enhance contrast against the background pollution. This galaxy is visually large and takes up the whole low power field. Savour the intricacies of this extra-galactic ‘wonder’ then insert an eyepiece of high power, around 200x magnification for a 20cm mirror. Look for some of the detail that appear at this higher magnification.
NGC 253 impressed Sir John Herschel whilst observing from the Cape of Good Hope with his 18” reflector:
“very bright and large (24’ in length); a superb object…Its light is somewhat streaky, but I see no stars in it except 4 large and 1 very large one, and these seem not to belong to it, there being many near…”
Sir William Herschel wrote:
“Considerably bright, much elongated…much brighter in the middle. Above 50’ long and 7’ or 8’ breadth…This nebulae was discovered Sept. 23, 1783 by my sister Caroline Herschel with an excellent small Newtonian Sweeper of 27 inches focal length, and a power of 30…”
NGC 300 is an extremely large face on Sc-type spiral galaxy with an overall low surface brightness. It does have a fairly bright central region easily seen through though the outer glow is difficult. Binoculars in the 11x80mm range will show this galaxy under a dark sky with care, the low magnification taking in the whole galaxy (about the size of the Full Moon) and its surrounds thus improving contrast against the background sky. Use the lowest power available with a telescope. Unlike many other galaxies, NGC 300 is unusual because it is so normal in it's appearance and constitution, a model spiral galaxy to study.
NGC 613 lies near tau Sculptoris and is easily seen in a small telescope under a dark sky. Large telescopes show this barred spiral as having a bright and condensed nuclear region surrounded by a mottled fainter halo. Smaller mirrors show a bright stellar core surrounded by an unresolved glow. NGC 613 lies some 65 million light years distant and spans over 100,000 light years in length.
NGC 134 is another barred spiral the same size, shape and brightness as NGC 613. It lies near eta Sculptoris, a reddish magnitude 4.8 star. A large mirror may show the dark lane that runs the length of this edge on galaxy under high power.
NGC 24 is a bright spiral lying near the northern border with Cetus and is easily seen in finderscopes. No detail is visible in small mirrors though larger ones may show a bright almost stellar nucleus under high power. Distance is 22.5 ±9.8 million light years.
CETUS
The brightest visual object is the galaxy NGC 1068 (M77), shining at an integrated magnitude of 9.0 and spanning an area of 2.5' x 1.7'. This galaxy is easy to find, located just 1° southeast of 4th magnitude delta Ceti. This spiral galaxy lies around 60 million light years away and is easy in a 10cm telescope, though a 20cm makes observation of the mottling seen across its face more certain. About 30" northeast of M77 resides a faint edge-on spiral galaxy, NGC 1055. Glowing at 10.6 magnitude and measuring 7.5' x 3.0', it is visible in a 15cm telescope as a bright central region surrounded by a faint outer envelope. Large scopes, with care, will show some mottling and possibly a dark lane of obscuring material across the nucleus.
ERIDANUS
NGC 1700 lies 19’.9 to the north of 62 Eridani. This elliptical galaxy is an easy object for smaller telescopes whilst mirrors in the 25cm range show a bright halo enclosing a small bright core with a definite stellar nucleus. 10° south and slightly west of eta Eridani lies tau 1, a magnitude 4.5 F-type pale yellow dwarf star. Here we take a small diversion to a group of faint galaxies around 5.5° to the northeast. NGC 1172 is the most northerly of the group. Easy in a 25cm mirror, it appears as a faint round glow with a brighter middle region. Look for it west southwest of a magnitude 9.5 star.
Around 55’ to the southeast lies NGC 1199, an elliptical galaxy which appears rather small with a stellar nucleus at high power. It is the brightest of a surrounding small group of even fainter galaxies that need a mirror in the 40cm range to see. Directly east of NGC 1199 by around 35’ is NGC 1209, the brightest galaxy in this immediate area. A 25cm mirror shows a double nucleus enclosed within an extended halo.
Moving back to tau 1, seek out one of the better galaxies in Eridanus. NGC 1300 lies 8.2° east and slightly to the south. Here is a classic example of a barred spiral galaxy, the bar easily seen in a 20cm mirror as an elongated smudge with a slightly brighter middle. Larger telescopes in the 40cm range should show mottling in the surrounding halo. Also evident with larger telescopes on excellent nights of seeing are the spiral arms. A faint companion, NGC 1297 lies close by.
Around 47’ to the north of magnitude 4.1 tau 3 lies NGC 1187, a barred spiral galaxy that shows a little mottling with a brighter central region. This one needs larger mirrors to see well.
To the northwest 2.5° of magnitude 3.7 tau 4 brings us to the lovely face-on spiral galaxy NGC 1232. Even a mirror of 25cm may start to show detail including mottling of the disk and perhaps several HII regions as well. These HII clouds are similar in type to the Orion Nebula, a larger telescope showing them with ease.
Heading southeast towards tau 6, we meet four galaxies aligned northeast – southwest, the brightest of this gathering being NGC 1395. Easily seen in a 25cm mirror, within the halo is a brighter central region with a stellar nucleus.
Just 1.5° to the northwest of upsilon 4, a magnitude 3.5 B9 dwarf star, lies a nice pairing of galaxies, NGC 1531 and NGC 1532. Use 100x magnification or greater to see these two easy spiral systems. NGC 1532 is the brighter, appearing as an elongated streak with an obvious nucleus. A medium telescope with care will show several HII regions that trace the spiral arms. NGC 1531 is aligned more face-on but shows no detail.
GRUS
Alpha or Al Nair, the ‘Bright One’ according to the Arabs, shines at apparent magnitude 1.7. Just 16’.3 to the southeast lies NGC 7213, an SO type spiral of reasonable surface brightness. However, nearby alpha’s all consuming brightness intrudes so high power must be employed to exclude unwanted alpha from the eyepiece field. Then and only then will a small, elliptical shaped glow be seen, brightening toward the middle. Here we have what is called a lenticular galaxy, similar in shape to spirals but containing only the older Population II stars usually seen in elliptical systems.
Moving to the northeastern portion of Grus, seek out theta, a magnitude 4.3 F5 yellow star. This is a triple system, a companion of magnitude 7.0 lies close and a further family member of magnitude 8.1 lies 160”.0 to the west and slightly north. A line of brightish galaxies runs northeast of theta, including a lovely triplet of NGC 7552, NGC 7582 and NGC 7590.
If we start our tour from theta, we move 32’.1 east to NGC 7496, a bright spiral galaxy with a brighter central region. A further 55’.6 to the east will bring us to the spiral NGC 7531. It is a lot smaller but shows a brighter central region as well. A hop of 1° to the north encloses a trio of bright spiral galaxies. NGC 7552 is the first of them, pretty small in size and round in shape with a small bright nucleus. NGC 7582 lies 27’.6 to the northeast, larger than the former, showing an extended form and a bright middle region. NGC 7590 lies a further 9’.8 to the northeast, also pretty large with an obvious extended shape and a brighter central region. All three show different orientations within a low power field.
A fourth galaxy, NGC 7599, lies east of NGC 7590 but it is extremely faint and needs large mirrors to see. In fact, Grus itself is littered with faint galaxies, all needing a dark sky and a large mirror to do them justice. The pick of the others is NGC 7410, lying 4.4° to the north northwest of theta. This bright and large spiral appears edge on with a much brighter central nucleus.
Here we leave things for now. Seek out those extra-galactic glows with a wide field eyepiece and once identified, change to a higher power to hopefully bring out any subtle detail. Sometimes the enjoyment is not in the quarry but in the hunt.
Clear skies and good hunting ~ CosMos