Are You Ready, Willing, and Abell?

A cosmic rabbit hole in the tail of Leo will take you to Abell 1367, a wonderland of galaxies more than 300 million light-years from Earth. Step in and lose yourself in the vastness.

Knots of Fuzz in Leo's Tail

Abell 1367 is easy to locate. Look above Denebola in Leo's tail to find 93 Leonis. At least 70 galaxies occupy a 1° circle immediately west of the star.
Bob King; created with Stellarium

Care to join me for a little adventure? There's no better time to stalk external galaxies than on April nights, when the dusty Milky Way hunkers along the east and west horizons, giving center stage to the hordes of spiral, elliptical, and irregular galaxies that cross the meridian from nightfall till the wee hours.

Tucked in the tail of Leo, the Lion, just 5.5° north of the bright star Denebola, you'll find one of the brightest galaxy clusters in the sky, Abell 1367. Also known as the Leo Cluster, this fabulously rich degree of sky contains some 70 major galaxies and many minor ones. On a dark, moonless night, an amateur astronomer with a 10-inch or larger telescope and an hour or two to spare might pick off nearly 100 fuzzy, extragalactic cocoons residing more than 300 million light-years from Earth, or 120 times farther than the Andromeda Galaxy. Far out, man.

Standing at the Edge of Night

Paul Beskeen's photo encompasses all of Abell 1367 and also shows the "jump-off" star, 93 Leonis. Other stars are labeled with magnitudes (decimals omitted). In this and all the photos following, south is up and east to the right to match the field orientation in the larger Dobsonian-style reflectors many amateurs use to look for faint fuzzies. Click the image for a high-resolution view.
Paul Beskeen

The brightest galaxies in the cluster shine around magnitude +12.5 to +13 with the majority a magnitude and more fainter. Sounds challenging, doesn't it? Yes, but take galaxy magnitudes with a grain of stardust. You can almost always see deeper and fainter than you think if you follow these guidelines:

A Deeper Look

I've labeled the brighter NGC ("N"), IC, and UGC galaxies in this wide slice of Abell 1367 that features the busy core and brightest cluster member, NGC 3842. Click the image to see the original, unlabeled photo.
Fritz Kleinhans

  • Dark skies: Start out on the right foot by finding the best, un(light)polluted skies in your area and observe when the target is near the meridian. Abell 1367 culminates in the southern sky around 10 p.m. local time in late April.
  • Dark adaption: Allow at least 15 minutes for your eyes to get "owly."
  • High magnification: Start with low magnification to get oriented, then switch to between 200–250× when you're ready to really dig in. At low powers, you'll only see the brightest galaxies in a cluster. High magnification expands the apparent size of the smaller and fainter objects, allowing the eye to distinguish them from the sky background. Don't go too high, though, or these faint fuzzies will be so spread out, they'll disappear!
  • Averted vision: At night, we use our rod cells to find our way in darkness and soak up photons from dim galaxies. Rods are concentrated away from the center of vision, so to see faint things more clearly, play your gaze around the object rather than staring directly at it. Averted vision will get you at least a magnitude deeper. For more deep-sky observing secrets, read Alan MacRobert's excellent article, Observing Secrets of Deep-Sky Objects Revealed.
At the Root of It All

This artist's conception depicts stars moving around the central supermassive black in a giant elliptical galaxy like NGC 3842.
Gemini Observatory / AURA artwork by Lynette Cook

Most dense galaxy clusters are dominated by elliptical galaxies that grow to titanic sizes through the merger of smaller galaxies members as they fall toward the center of the cluster. Abell 1367 is a little different from other rich clusters in having a sizable population of spiral galaxies. Astronomers interpret the significant number of spirals as a sign of the cluster's relative youth.

That's not the cluster's only stand-out attribute. Its brightest member, the heavyweight 12th-magnitude elliptical galaxy, NGC 3842, possesses one of the largest black holes of any galaxy known with a mass of 9.7 billion suns.

The cluster, along with the Coma Cluster (Abell 1656), form the heart of the Coma Supercluster, the nearest supercluster to our own Virgo Supercluster and the heart of the Great Wall, a huge filament of galaxy clusters and superclusters 500-750 million light-years long said to be one of the largest structures in the observable universe. Abell 1367 forms the Wall's "near" end, with the far end represented by rich clusters in Corona Borealis and Hercules.

Downtown Galaxyville

The core of the cluster will reward observers with 10 or more galaxies dominated by the large elliptical, NGC 3842. See below for annotated version. Abell clusters are named for American astronomer and cosmologist George Abell, who cataloged them from visual inspection of the Palomar Sky Survey plates in the late 1950s. There are 4,073 in total.
Fritz Kleinhans

Finding your way to Abell 1367 couldn't be easier. Center your finder on 4.5-magnitude 93 Leonis, look through a low magnification eyepiece, and you're there! The star is pinned to the cluster's eastern edge. Using the maps, you can star hop from there, stopping at small clumps of galaxies, while edging ever closer to the cluster's core, a magnificently busy downtown where careful scrutiny will repay with a brain-boggling 10 or more galaxies visible in the same 200× field of view.

A Negative View

Click for a high-resolution annotated version to use at the telescope. "C" is short for CGCG. Don't forget — south is up! For a wide-field finder map (with labels) that includes many more galaxies, check out this one by Albert Highe.
Fritz Kleinhans

What I especially like about exploring this cluster are the numerous conveniently placed field stars you can use to navigate this galactic archipelago. The stars also help greatly in pinpointing some of the fainter members. I'll use two or three stars to create a figure, say a triangle or trapezoid, with the sought-for fuzzball at one apex. Once you know exactly where to look, bear down with averted vision, and give it all you've got. Using stars to create makeshift geometric figures will make your hunt easier and more successful.

Galactic Celebs

Rather than make a list of all the galaxies, I've selected a few to highlight. As you might expect, the NGC galaxies are generally larger and brighter than the other cluster members, but not always. Some of the small CGCG objects (Catalog of Galaxies and Clusters of Galaxies) and UGC galaxies (Uppsala Galaxy Catalog) were equally easy to spot.

  • NGC 3837 — Magnitude +13.3. Bright, compact elliptical with a bright stellar nucleus. Touches fainter CGCG 97-143 to the east.
  • NGC 3861 — Magnitude +12.7. Large, easy spiral with a bright, nearly stellar nucleus. I couldn't discern tiny, 15th-magnitude MGC +3-03-94 poking out of its southeastern edge. Note to self — use higher magnification next time.
  • NGC 3860 and companions — Magnitude +13.4. A fuzzy, oval glow with a stellar nucleus located just north of three smaller CGCG galaxies. CGCG 97-114 was faintest, a diffuse patch of haze shining at photographic magnitude +15.3 (+15.3p). Persevere and use averted vision to dig out this rad tetrad.
  • CGCG 97-88 and companions CGCG 97-93 and 97-94 — The first was relatively easy at magnitude +15.2p, but CGCG 97-33 (mag. +15.5p) and CGCG 97-94 about cracked my eyeball at magnitude +15.7. Both appeared as faint wisps at the limit of vision.
  • IC 2951 — Magnitude +13.6. Bright spiral, noticeably elongated east-west with a bright stellar nucleus. A magnitude +13 star touches the eastern end. Smaller, fainter but similarly elongated UGC 6683 lies 1′ to the west. Nice pair!
  • Cluster core / NGC 3842 — In the space of just 10′ at least 11 galaxies pop into view here, dominated by the blobby NGC 3842, a large elliptical with a bright, non-stellar nucleus. I've seen it listed at both magnitude +11.8 and +12.8, so we'll just call it +12. Four small smudges, PGC 36468 (very faint), CGCG 97-90, and NGCs 3841 and 3845 (all easier to spot), ride up along the galaxy's west side.
Super Streak

The galaxy UGC 6697, located about 1.5 million light-years from the core of Abell 1367, is shown here in a composite X-ray (blue) and optical (red & green) image. Supernovae heat the gas to produce X-rays and optical light seen here as the bright cyan glow. The light from stars is shown in red. The faint blue X-ray tail extending to the upper right comes from gas being stripped from the galaxy by its interaction with the hot cluster gas. Over time, this stripping process will remove all the gas from the galaxy, so no new bursts of star formation can occur.
X-ray: NASA / SAO / CXC /M.Sun et al.; Optical: GOLDMine / G. Gavazzi et al.

But the real celebrity in my opinion is the faint, evanescent UGC 6697 that flashes in and out of view like the momentary glimmer of a salmon leaping a waterfall. This magnitude +13.7 needle of light is a peculiar spiral galaxy undergoing a massive wave of star formation. As it plunges toward the center of the cluster at several million miles per hour, cold gas clouds within UGC 6697 are compressed by the hot gas that permeates the cluster. The massive new stars that result from this process will self-destruct as supernovae 10 million years later.

I saw 42 galaxies in Abell 1367 in just one evening in my 15-inch scope, but I'm eager to return because there's are at least 20 more calling my name. Exploring distant clusters whisks our imagination to the furthest reaches of the universe. I wish you happy hours climbing the Great Wall of galactic light in the deepest hours of a dark night.

14 thoughts on “Are You Ready, Willing, and Abell?

  1. Ernie OstunoErnie Ostuno

    Thanks for another excellent observing article, especially the labeled chart. You also described several tricks of the trade that I have found helpful such as averted vision and using field stars to locate the elusive glow of galaxies on the threshold of visibility. I am going to try to see more galaxies in this cluster. I have been there once before. My observing notes from April 18, 1988 include many of the galaxies brighter than magnitude 14.5 from the RNGC. For instance, I saw NGC 3842 at 13.5, but not nearby NGC 3841 at 15.0. That was with a 10 inch reflector from the skies of northwest Connecticut. I now have similar skies in Michigan with a 13 inch scope. So hopefully 3841 and others fainter than 14.5 will be visible.

    A few weeks ago I was able to spot IC 928 , one of the brightest galaxies of a faint galaxy cluster in Ursa Major. It was close to a field star, which helped identify it. IC 919 was another member of the cluster of similar magnitude that I failed to spot because of a lack of field stars near it. According to the DSO Browser, IC 928 is 939 million light years away…so it must be a super massive, luminous elliptical to be visible in my scope.
    https://dso-browser.com/deep-sky/11494/ic-928/galaxy

    1. Bob KingBob King Post author

      Thanks so much, Ernie. I’m guessing you’ll find 3841 with that 13-inch and most of the rest of those fuzzies in the core. The toughest one in the core for me was PGC 36468. I used the “conga line” of CGCG 97-90, NGC 3845 and 3841 to spot it. Good luck!

  2. Tom-Reiland

    I just checked my observing log and noticed that two years ago I observed at least five of the NGC objects on the image you posted. I’ll have to check this field again the next clear night. Keep these observing articles coming. I’m waiting for CTA 102 to return to the sky to see what has happened to it. BTW, I completed my Herschel Catalogue quest Wednesday night with five galaxies in Hydra. I’m as much relieved as I’m excited to have finished this project. All of my observations are done via Star-Hopping.

    1. Bob KingBob King Post author

      Congratulations Tom on completing the Herschel Catalog – a wonderful achievement. One of the great things about completing that and any of those type of challenges is the confidence an observer gets when it comes to seeing ANYTHING in the sky. If you hear about an object or phenomenon you’d like to see, you have the skills to go out and look for it.
      About CTA 102, it was still at 14.6 in late January and according to the AAVSO is currently fainter than magnitude +14.9.

      1. Genac

        Excellent comment regarding “confidence”, which I lack. I also lack a telescope, and find little through binoculars I can’t see without magnification. Please recommend a “next step”: 15x binoculars, 7″ telescope, 15″ telescope, 30 meters? Should the primary constraint be budget or skill level?

        I’m facile with Stellarium and can find my way around the sky, but intimidated by your “amateur” knowledge; I can’t imagine what skills a professional has that you don’t. I will look for your book. THANK YOU very much. RMO

        1. Bob KingBob King Post author

          Hi Genac,
          I think wide-field, comfortable eye-relief 10×50 binoculars are essential equipment for enjoyable views of brighter comets, the moon (earthshine, craters and conjunctions) and the brighter deep sky objects. But I wouldn’t stop there. An 8-inch Dobsonian telescope would be a great “next step.” This size scope is easy to set up, very portable and will show you enough of planets, deep sky and the moon for a lifetime of enjoyment and education.

  3. Owen-Brazell

    Bob it may be worth noting that the preferred shorthand for Abell galaxy clusters is now ACO rather than AGC according to Harold Corwin. This will undoubtedly cause issues with older guides and notes but things move on.

    1. Bob KingBob King Post author

      Hi Owen,
      Thanks for the update. I wonder why the change as AGC is an easy acronym for “Abell Galaxy Cluster.” Would the “O” be to give Corwin credit for his work extending the catalog?

      1. Owen-Brazell

        Hi Bob . it stands for (Abell, Corwin, Olowin) which is the updated catalogue that included the southern extension. That was published posthumously after Abell’s early death. AGC is now apparently being used for an Arecibo galaxy catalogue in professional cricles.

  4. West Coast Astronomer

    I tracked down about five of the brighter ones last night with an eight inch SCT. Quite a fun group to observe, being so close to 93 Leonis.

All comments must follow the Sky & Telescope Terms of Use and will be moderated prior to posting. Please be civil in your comments. Sky & Telescope reserves the right to use the comments we receive, in whole or in part, and to use the commenter’s username, in any medium. See also the Terms of Use and Privacy Policy.

COMMENT