Skywatch Line for Friday, March 13, through Sunday, March 15, 2020

This is Dudley Observatory’s Skywatch Line for Friday, March 13, through Sunday, March 15, written by Sam Salem.

On Friday, Sun rises at 7:10am and sets at 7:00pm, the waning gibbous Moon sets at 9:40am. On Sunday morning watch for the waning gibbous Moon to pair up with Antares, the brightest star in the constellation Scorpius the Scorpion.

The illuminated side of a waning Moon points in the Moon’s direction of travel in its orbit around Earth. Relative to the stars of the zodiac, the Moon moves eastward at about half a degree per hour per hour. Half a degree is the Moon’s angular diameter. In 24 hours, the Moon goes about 13 degrees eastward in front of the constellations of the zodiac. Before dawn on Monday, the Moon will be at or near its half-lit last quarter phase. You’ll find its lit side pointing directly toward Jupiter, Mars and Saturn. In the the week ahead, watch for the Moon to pass all morning planets.

Venus, at magnitude –4.4, shines in the west in constellation Aries, during and after twilight. Venus remains up for a good two hours or more after the end of twilight. In a telescope, Venus is 20 arc-seconds in diameter and still slightly gibbous. It will enlarge in size and wane in phase for the rest of the winter and much of the spring, passing through a half-lit phase in late March before becoming a thin crescent in May. Uranus, at magnitude 5.9, in constellation Aries, is getting lower in the west after dark, hiding in the background of Venus.

Observe Mars in the last few hours before sunrise. By an hour before sunrise, Mars stands 17 degrees above the horizon, glowing at magnitude 1. Following a line east of the red planet, you’ll find first Jupiter, then Saturn. Use a telescope to search the sky roughly halfway between the two giant planets Jupiter and Saturn. There you may spot magnitude 14 Pluto, the solar system’s most famous dwarf planet. Mars is moving eastward closer and closer to the two giants. By Saturday they’re only 3 degrees apart.

Friday marks the 165th anniversary of Percival Lowell’s birth in 1855. Lowell is the American astronomer who predicted the existence of the planet Pluto and initiated the search that ended in its discovery. It was Lowell’s study of the orbit of Uranus that caused him to propose the presence of an unknown planet outside of Neptune’s orbit. That prediction sparked the years-long search that ultimately culminated in the discovery of Pluto by Clyde Tombaugh on February 18, 1930, 14 years after Lowell’s death. Lowell was also passionately committed to finding proof of intelligent life on Mars. Lowell was one of many astronomers who believed Mars hosted canals constructed by native life forms for irrigation purposes.

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