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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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The Skies of February, 2025

Highlights: Comet Journal, Martian Landers, Meteor Showers, Planet Plotting, February Moon Focus Constellations: Ursa Major, Draco, Ursa Minor, Cepheus, Cassiopeia, Camelopardalis, Lynx, Leo Minor, Leo, Cancer, Gemini, Orion, Taurus, Auriga, Perseus, Andromeda, Triangulum, Aries, Pisces

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