This is Dudley Observatory’s Skywatch Line for Friday, November 23 through Sunday, November 25, written by Sam Salem.
On Friday, the Sun rises at 6:57am and sets at 4:26pm; Full Moon sets at 7:05am and rises at 5:12pm. The full Moon occurs at 12:39am on Friday. As the Moon rises, it is positioned near Aldebaran, the brightest star in the constellation Taurus. Watch the Moon draw farther away from Aldebaran through the hours of the night. On Saturday, the Moon rises around the end of twilight and climbs high through the evening. It’s now below the horns of Taurus, Beta (β) and fainter Zeta (ζ) Tauri. On Sunday and Monday night look for the bright waning gibbous Moon in eastern sky. Notice the two bright stars in its vicinity, noticeable for being both bright and close together on the sky’s dome. These stars are Castor and Pollux in the constellation Gemini.
Saturn shines at magnitude 0.6 and is slowly slipping away into twilight. One hour after sunset, Saturn sits just 10 degrees above the southwest horizon. Mars, at magnitude –0.2, shifts each night a bit more than one Moon diameter along the ecliptic. As a result, Mars remains essentially due south each evening while the background stars appear to slowly advance westward.
At dawn, enjoy observing Venus at magnitude –4.8. Venus rises about 2 hours and forty-five minutes before the Sun. Venus’ overwhelming luminosity presents the greatest viewing challenge. About all you can see of Venus is its phase. Generally, a dark background sky makes the phase more difficult to discern. Locate Venus with your telescope before sunrise then continue to follow it as the sky brightens to deep blue. This allows you to observe the planet while keeping its glare to a minimum. This weekend Venus reaches the meridian, when it’s due south and highest, a little before 10am. At present, Venus is an attractive, 47 arc-second diameter waxing crescent. If you watch over the coming weeks, you’ll see its disk size shrink as the distance between Earth and Venus increases.
Neptune appears stationary on Sunday. Neptune right high in the south, in Aquarius, is harder to locate at magnitude 7.9 in a bright Moon night.
The phrase spring up and fall down gives you some idea of the Big Dipper’s place in the evening sky. On fall evenings the Big Dipper sits way down low in the northern sky. On spring evenings, the Big Dipper shines high above Polaris, the North Star. This weekend use the Big Dipper’s pointer stars, which point to the North Star Polaris, to find the bright golden star Capella in the constellation Auriga, the Charioteer. The top two bowl stars point toward Capella, the Goat Star. Capella is the Latin word for nanny goat. Near Capella, you’ll find a tiny asterism consisting of three fainter stars. This little triangle of stars is called the Kids.
Saturday marks the 379th. anniversary of the first observed transit of Venus. On November 24, 1639, Jeremiah Horrocks, an English astronomer and clergyman, measured a transit of Venus, the first ever to be observed. Applying Kepler’s prediction made in 1631, Horrocks calculated that these transits occurred not
singly but in pairs, eight years apart. Horrocks prepared his simple telescope mounted on a wooden beam to project a solar image onto a piece of paper marked with a six inch graduated circle. From this, he made measurements and calculated that the value for the solar parallax was smaller than previously recorded. He concluded that the Sun was further away from the Earth than previously thought.