Skywatch Line for Friday, November 16 through Sunday, November 18, 2018

This is Dudley Observatory’s Skywatch Line for Friday, November 16 through Sunday, November 18, written by Sam Salem.

On Friday, the Sun rises at 6:49am and sets at 4:32pm; the waxing gibbous Moon rises at 1:37pm and sets at 12:33am on the following day. The first quarter Moon occurred on Thursday at 9:54am. Try to locate the Lunar Straight Wall on Friday evening. The Lunar Straight Wall, or Rupes Recta in Latin, is a linear fault on the Moon in the southeastern part of the Mare Nubium. Straight Wall is challenging in a small telescope. Look for it as a hair-like shadow. The Sun illuminates the feature at an oblique angle at about 8 or 9 days after the new Moon. Straight Wall appears dark near the waxing half moon because it is a cliff casting a shadow on the surface to its west.

Saturn shines at magnitude 0.6 and hovers roughly 15 degrees above the southwest horizon as twilight fades. Mars, at magnitude –0.3, culminates in the early evening and doesn’t set until midnight. Venus beams at magnitude –4.7 more than two hours before the Sun. Venus is a thin crescent, thickening from 7% to 12% sunlit this week. For sharper telescopic views, follow it up higher past sunrise and into the blue-sky day.

On Saturday, Neptune sits 3 degrees north of the waxing gibbous Moon. Neptune, in Aquarius at magnitude 7.9, is well up in the southeastern side of the sky after dark.

On Friday, Asteroid 3 Juno, at magnitude 7.6, will be at opposition. Asteroid 3 Juno will be well placed for observation, lying in the constellation Eridanus, well above the horizon for much of the night. 3 Juno will reach its highest point in the sky at around midnight. This optimal positioning occurs when it makes its closest approach to the point in the sky directly opposite to the Sun. Since the Sun reaches its greatest distance below the horizon at midnight, the point opposite to it is highest in the sky at the same time. At the time 3 Juno passes opposition, it also makes its closest approach to the Earth, or its perigee, making it appear at its brightest in the night sky.

The Leonid meteor shower should be at its modest best in the three hours between moonset and the beginning of Sunday’s dawn. Moonless predawn skies help make this is a favorable year for the Leonid meteor shower, which peaks in the hours before morning twilight. Although famous for several spectacular outbursts in the past, the Leonids are now a relatively humble display with a rate of usually fewer than 20 meteors per hour under ideal conditions. The radiant for the Leonids is near the star Algieba in constellation Leo, the lion. Both Algieba and Regulus, the brightest star in Leo, belong to a noticeable pattern on the sky’s dome in the shape of a backwards question mark. This pattern is called “the Sickle.” The paths of Leonid meteors can be traced backwards to the Sickle asterism. The constellation Leo carrying the meteor shower radiant point will rise over eastern horizon around midnight. It reaches its highest point in the night sky just before dawn. You don’t have to locate a meteor shower radiant to watch the meteor shower. The meteors will appear in all parts of the sky. The Leonid meteor shower happens every year in November, when Earth’s orbit crosses the orbit of Comet Tempel-Tuttle. When Earth’s orbit crosses the comet’s trail of debris, pieces of the comet fall toward the planet’s surface. Air resistance in Earth’s atmosphere cause the comet’s crumbs to heat up and ignite into burning balls of fire or meteors.

The star marking the radiant Leonid meteor shower, Algieba, or Gamma Leonis, is a double giant with a planet. Named after its place in the foreparts of constellation Leo. The Arabic name Algieba means “the forehead”.

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