Phil Harrington's Cosmic Challenge

Cosmic Challenge: Schröter's Valley

Technically, Schröter's Valley, also known as Vallis Schröteri, is not a valley at all. It's a sinuous rille, the largest and most prominent sinuous rille on the Moon's near side. Although the "valley" looks to be connected to Herodotus, it actually begins at a 4-mile-wide (6 km) crater some 15 miles to the north called the "Cobra Head." It then meanders its way for over 100 miles (160 km) across the Aristarchus plateau, narrowing to less than 1/4 mile wide at its thinnest. It eventually empties into Oceanus Procellarum.

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Cosmic Challenge: M84 and M86

Look at any deep-sky map of the spring sky, and it's pretty clear that when it comes to galaxy hunting, the constellations of Coma Berenices and Virgo are the places to be. The Virgo Cluster hosts an estimated 1,300 individual galaxies (though some sources suggest it may have as many as 2,000) and forms the heart of the Local Supercluster, of which our Milky Way’s Local Group is considered an outlying member. Of those 1,300+ galaxies, two of the brightest are M84 and M86, found not far from the Virgo Cluster's geometric center.

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Cosmic Challenge: Hickson Compact Galaxy Group 50

Observing compact galaxy groups from Paul Hickson's 1982 study is an interesting challenge for owners of the largest backyard telescopes. Most are at the edge of detection, even from dark sites, and so offer great tests of our observing skills as well as the quality of our instruments' optics.

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Cosmic Challenge: Hickson Compact Galaxy Group 44

In 1982, astronomer Paul Hickson, professor of astronomy at the University of British Columbia , published a study of 100 compact galaxy groups scattered throughout the sky. In his paper "Systematic Properties of Compact Groups of Galaxies", Hickson defined a compact galaxy group as a small, relatively isolated collection of four or five individual systems that are set in close proximity to one another, and that differ in brightness by no more than 3 magnitudes. Further, so as to avoid including the central regions of dense galaxy clusters, Hickson stipulated an "isolation factor" requiring that there not be a non-member galaxy of similar magnitude within three radii of the group's center. Surveying the Palomar Observatory Sky Survey, Hickson created an inventory of 100 such groupings. The entries in the Hickson Compact Group, or HCG, catalog are ordered numerically according to increasing right ascension.

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Cosmic Challenge: NGC 2371 - 2372

Gemini offers two intriguing planetary nebulae for stargazers: the well-known Eskimo Nebula (NGC 2392) and the lesser known but equally fascinating NGC 2371 - 2. While the Eskimo Nebula dazzles with its bright, structured halo resembling a face framed by a parka, NGC 2371 - 2372 (traditionally abbreviated NGC 2371 - 2) presents a more subtle, ghostly charm.

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Cosmic Challenge: M1, the Crab Nebula

The story of M1, of how it is the expanding remnant of a massive star that detonated in a huge supernova explosion, is well known to most. That explosion was witnessed by ancient Chinese and Anasazi Native American stargazers in July 1054 AD. Although half a world away from each other, both recorded the exploding star's sudden appearance. At its peak, the supernova may have shone as brightly as magnitude -6 and was visible in broad daylight for nearly a month.

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Cosmic Challenge: Galaxy UGC 2838

The Pleiades is one of everyone's favorite winter sights. You and I probably look up at that tiny pot of stellar jewels every winter night we head out, just as we have ever since we first became fascinated with the night sky. It’s a seasonal rite. But did you know there was a small galaxy lurking behind the Pleiades? Not many people do. Its faint disk was never seen by the Herschels or known to John Dreyer when he assembled the New General Catalog and supplemental Index Catalogs.

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Cosmic Challenge: Palomar 13 and Friends

Pegasus is best known to deep-sky observers as a breeding ground for faint galaxies, with more than 100 faint NGC galaxies littering this winged steed. Floating seemingly out of place among those systems is the globular cluster M15, one of the season's finest targets. Did you know that there is a second globular within Pegasus lying just within the grasp of your 10-inch telescope? That little known target is Palomar 13, one of those nasty globulars discovered by Abell and company while surveying the Palomar Observatory Sky Survey half a century ago.

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Cosmic Challenge: IC 5067 and IC 5070 (Pelican Nebula)

My September 2018 Cosmic Challenge dared you to see the North America Nebula without optical aid. How did you do? If you didn’t see it back then, can you now? If you passed that trial, then pick up your binoculars and see how you do with this month’s test. The North America Nebula is easy to see compared to spotting this month's challenge, the Pelican Nebula by binoculars.

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Cosmic Challenge: IC 4997

This month’s challenge, the planetary nebula IC 4997 lies within the borders of Sagitta, and is surprisingly bright, but extremely small. That combination makes this a great object for everyone, whether you are observing under the veil of light pollution or from a dark, rural location. Its intensity should shine through all but the most extreme situations.

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