Phil Harrington's Cosmic Challenge

Cosmic Challenge: Abell Galaxy Cluster 373

Nestled in the southeast corner of the dim late-fall/early-winter constellation Fornax, adjacent to the distinctive triangle formed by 6th-magnitude Chi-1 (χ-1), Chi-2 (χ-2), and Chi-3 (χ-3) Fornacis, is an attractive cluster of galaxies known as Abell Galaxy Cluster - Southern Supplement (AGCS) 373.

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Cosmic Challenge: The Southern Pinwheel

Have you ever heard of NGC 300, the Southern Pinwheel Galaxy? Were it positioned high in our autumn sky in a prominent constellation, you certainly would have. In fact, NGC 300, an Sc spiral tilted nearly face-on to our view, would be one of the season's showpieces, especially through large backyard telescopes. Because it lies in the far southern sky, nestled among the faint stars of Sculptor, it remains the purview of diehard deep-sky fanatics only.

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Cosmic Challenge: The Elephants Trunk

Take a look at just about any star atlas and you will find a huge, irregular cloud of ionized hydrogen suspended to the south of Mu (μ) Cephei, Herschel's Garnet Star. That's IC 1396, one of the largest nebulae in the night sky. Even from a distance of about 2,450 light years, this complex cocktail of bright glowing gas mixed with dark dust clouds spans 3° of our sky. At that distance, 3° translates to a linear diameter of nearly 160 light years, more than three times greater than the Orion Nebula, M42.

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Cosmic Challenge: A Trio of Binaries

How close can two stars appear and still be resolvable as two? The single most important factor that influences the result is a telescope's aperture. All other things being equal, the larger the aperture, the finer the level of detail resolved. Of the many observational experiments that have been conducted to determine the resolution limits of telescopes, the two most often cited are the Rayleigh Criterion and the Dawes Limit.

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Cosmic Challenge: Planetary Nebula GJJC-1

What is your favorite globular cluster? Apart from those two southern hemisphere beauties, Omega (ω) Centauri and 47 Tucanae, my answer has to be M22 in Sagittarius. Admittedly, the star chains and "propeller" formation within M13 in Hercules (profiled in the July 2017 Cosmic Challenge) are visually intriguing. But there is just something about the remarkable richness of M22 and its surrounding star field that calls to me.

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Cosmic Challenge: Mons Hadley and Rima Hadley

Fifty years ago this month, on July 30, 1971, Commander David Scott and Pilot James Irwin navigated their Apollo 15 lunar module, nicknamed Falcon, to land among the lunar Apennine mountains, while Alfred Worden remained in orbit aboard the command module, Endeavor. Scott and Irwin guided Falcon to a soft landing between the edge of a deep precipice and the base of a tall mountain to establish Hadley Base, as the landing site became known.

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Cosmic Challenge: Alcor and Mizar

Is there any constellation in the sky more universally known than Ursa Major, the Great Bear? Most of us learned of it as a child, perhaps from a relative or friend, or possibly as a Scout working our way toward a merit badge in astronomy. The seven brightest stars in the group, known in North America as the Big Dipper or in England as the Plough, always draw our attention, especially in the spring when they ride highest in our sky.

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Cosmic Challenge: Markarian's Chain

Aim your telescope anywhere in the large, seemingly empty gap between the stars Denebola [Beta (β) Leonis] and Vindemiatrix [Epsilon (ε) Virginis] and, given sharp eyes and a dark sky, you are bound to see one or more faint splotches of light somewhere in the eyepiece's field of view. You've entered the Coma-Virgo Realm of Galaxies, a collection of upwards

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Cosmic Challenge: Abell Galaxy Cluster (AGC) 1060

Finding AGC 1060 is a simple task as long as you can spot 4.5-magnitude SAO 179041. This red giant sun overlaps the center of the cluster and lies 4¼° north of Alpha (α) Antliae. Of course, finding Alpha Antliae presents its own challenge, since it shines at only magnitude 4.2 and lies far from any handy reference stars.

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Cosmic Challenge: Zeta (ζ) Cancri

Although it is one of the faintest constellations along the zodiac, Cancer the Crab hosts a variety of targets to test our mettle during the early spring. Spotting M44, the Beehive Cluster, by eye alone may prove very challenging for suburban observers, while the Crab's underappreciated second open cluster, M67, may also reach naked-eye visibility from more rural environs. While the constellation boasts a variety of challenging galaxies, in the test here, we will try our luck with one of the constellation's prettiest binary stars, Zeta (ζ) Cancri.

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