Skywatch Line for Friday, November 30 through Sunday, December 2, 2018

This is Dudley Observatory’s Skywatch Line for Friday, November 30 through Sunday, December 2, written by Sam Salem.

On Friday, the Sun rises at 7:06am and sets at 4:24pm; The waning crescent Moon sets at 1:10pm.

On Saturday, Venus is at greatest brightness, shining at magnitude –4.9 in the morning sky. Venus appears brilliant from the time it rises a little before 4am until close to sunrise some three hours later. It stands about 25° above the southeastern horizon an hour before the Sun comes up. The “morning star” reaches an altitude of nearly 30 degrees by sunrise. When viewed through a telescope, Venus spans 40″ and appears one-quarter lit.

Saturn sits less than 10 degrees above the southwest horizon 45 minutes after sunset. It will be impossible to spot in just a few more weeks. Saturn shines at magnitude 0.5, more than a full magnitude brighter than any of the background stars in its host constellation, Sagittarius the Archer. This weekend, the planet’s disk measures 15″ across while the ring system spans 35″ and tilts 26° to our line of sight. Mars, at magnitude –0.1, climbs due south to the meridian at roughly 6:30pm.

Try to spot Uranus, at magnitude 5.7, with your naked-eye this weekend. Uranus sits near the Aries-Pisces border. It is pretty easy to see in binoculars if you know the constellations well enough and with the use of a finder chart.

This weekend moonless evenings are a good opportunity to have the first look at Comet 46P/Wirtanen. Although it won’t be at its brightest until mid-December, the comet should be visible in binoculars or a small telescope as a magnitude 6 fuzz-ball. Comet Wirtanen is currently located in the constellation Cetus and heading northward. The best time to view it is roughly 10pm, when the comet is at its highest and positioned due south. This region of sky lacks bright stars. You’ll have to sweep carefully with your binoculars to catch the comet. Hopefully, in the coming weeks, Comet Wirtanen will brighten to naked-eye visibility as it continues to move northeast into better position.

The Andromeda Galaxy, M31, and the Perseus Double Cluster are two of the most famous deep-sky objects. They’re both cataloged as 4th magnitude. In a fairly good sky you can see each with the unaided eye as faint fuzzies. They’re located only 22° apart, very high toward the east early these evenings. They are located to the right of Cassiopeia and closer below Cassiopeia, respectively.

Vega still shines brightly in the west-northwest after dark. The brightest star above it is Deneb, the head of the big Northern Cross, which is made of the brightest stars of Cygnus. At nightfall the shaft of the cross extends lower left from Deneb. By midnight, it plants itself more or less upright on the northwest horizon.

Saturday marks the 400th anniversary of the first comet observation using a telescope. The Swiss mathematician and astronomer Johann Cysat was one of the first to make use of the then newly developed telescope. Cysat’s most important work was on comets. Cysat concluded that comets circled around the Sun. He demonstrated that the orbit of the comet was parabolic, not circular. Cysat’s observations on the comet are characterized by their great detail. Cysat saw enough detail to be the first to describe cometary nuclei and was able to track the progression of the nucleus from a solid shape to one filled with starry particles.

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