Skywatch Line for Monday and Tuesday, January 22nd and 23rd, 2018

This is the Skywatch Line for Monday and Tuesday, January 22nd and 23rd.

The Sun sets at 4:55 PM; night falls at 6:34. Dawn begins at 5:39 AM and ends with the Sun rising at 6:37.

While the drought of visible evening planets continues, the Moon dominates the twilight sky. Monday’s Moon blazes in Cetus, the Sea Monster, at minus 8.5 magnitude and appears about 1/3rd full. The 5-day-old Moon rose this morning and sets at 10:35 PM. Tuesday’s Moon migrates to Pisces, is brighter and fuller. It is best observed at 5:09 PM and sets at 11:39 PM.

Neptune continues its residence in Aquarius, shining at 8th magnitude and sets at 8:17 PM. Uranus, still in Pisces, glows at 5.8 magnitude and sets at 11:55 PM. However, the Moon’s proximity to Uranus will probably make observation difficult. Neptune, though fainter, may be visible through telescopes.

The Dwarf Planet 1Ceres still hovers above Leo’s nose. It shines at 7th magnitude, appears a tiny 0.7 arc-seconds in size and is best observed at 1:17 AM. Neptune, Uranus and 1Ceres require detailed sky maps from astronomical media.

Two constellations display the bright, easily seen pre-dawn planets. Libra, hosts Jupiter, which rises first at 1:59 AM near the star Zubenelgenubi. It blazes at minus 1.9 magnitude, is a large 30 arc-seconds in size through our telescopes and binoculars and is best observed at 6:56 AM. Libra also houses Mars about 8 degrees east of Jupiter; it rises at 2:39 AM. The Red Planet is dimmer at magnitude 1.3, a small 5.3 arc-seconds in size, and appears 91 percent illuminated. Mars is heading down toward Antares, 12 degrees below. Sagittarius contains Saturn and Mercury. Saturn rises at 5:28 AM, about 35 degrees below Mars. Mercury, rising at 6:31 AM, is brighter at minus 0.4 magnitude, appears a third smaller then Saturn, and about 90 percent lit. Both Saturn and Mercury are so low on the horizon that binoculars are recommended to find them out of the rising Sun’s glare.

Throughout the night, star clusters abound. In early evening, we find the Pleiades above the shoulders of Taurus. The Bull’s face is made of another star cluster, the Hyades. The nearby constellation Auriga harbors three clusters. Finally, Cancer contains the Beehive and M 67.

All these are called “Open Clusters.” They appear to contain, at most, a few hundred stars, which are widely spaced and irregularly shaped. Open clusters are relatively young, less than a billion years old. They reside in the disk of a galaxy and are fairly small, about 50 light-years across.

There is another class of star clusters. These are called “Globular Clusters.” Globular clusters are usually found around galaxy halos and central bulges.
Globulars may contain up to a million stars and are quite large, in a sphere about 100 light-years across. These stars are quite old.

If tonight’s weather is clear, binoculars can show many Open Clusters. Just dress warmly and observe the Hyades, Pleiades and the nearby pentagon shaped constellation Auriga.

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