Skywatch Line for Friday, January 19 through Sunday, January 21, 2018

This is Dudley Observatory’s Skywatch Line for Friday, January 19 through Sunday, January 21, written by Sam Salem.

On Friday, Sun rises at 7:21am and sets at 4:52pm; the Waxing Crescent Moon rises at 8:50am and sets at 7:30pm.

Mercury, Saturn, Mars and Jupiter are arrayed across the southeast roughly 45 minutes before sunrise. Jupiter, at magnitude –0.9, is the brightest and the highest, sitting a little less than 30 degrees above the horizon. Mars, at 1.3-magnitude, is just five degrees to the left of Jupiter. Saturn, at magnitude 0.5, shines only at five degrees altitude. Mercury, at –0.3 magnitude, sits below and to the left of Saturn by about 5½ degrees. You’ll likely need binoculars to be able to spot it.

On Friday morning, see the first brief double-shadow transit of the new Jupiter apparition. The double transit begins at 4:45am when the shadow cast by Ganymede lands on Jupiter’s disk, joining Europa’s shadow, positioned near the planet’s northwest limb. The show ends ten minutes later when Europa’s shadow egresses. Jupiter’s Great Red Spot will also be visible at that time.

The Milky Way runs vertically up and across the zenith by mid evening. It runs from Canis Major low in the southeast, up between Orion and Gemini, through Auriga and Perseus almost straight overhead, and down through Cassiopeia, Cepheus, and Cygnus to the northwest horizon.

Constellation Auriga, the charioteer, is nearly overhead around 10pm. Capella is the leading light of the pentagon-shaped group. Auriga is home to three open clusters M36, M37, and M38. These stellar clumps are members of the Milky Way Galaxy and relatively nearby. M36 and M37 are around 4,000 light-years distant, while M38 is nearly 6,000 light-years away. Each cluster is a rewarding sight in binoculars or a small telescope if your viewing conditions are good enough. M36 is the most compact member of the trio. In a telescope, M36 displays a spider-like appearance with rows of faint stars radiating from the cluster’s center. To find M36, move west just across an imaginary line from the Auriga stars “El Nath” and “theta Aurigae”. M37 is the most spectacular of the three. Also, it is the most easily found as it lies midway between stars “El Nath” and “theta Aurigae”. Telescope users likely find M37 to be the most rewarding Auriga cluster, as it’s richly packed with stars. M38 is just to the north west of M36.

Friday marks the birthday of the German Astronomer Johann Elert Bode. Bode was director at the Berlin Observatory. Born on January 19 1747, Bode was known for his popularization of the Titius-Bode law. In 1766, his compatriot Johann Titius had discovered a curious mathematical relationship in the distances of the planets from the Sun. The mathematical formula suggests that, extending out-ward, each planet would be approximately twice as far from the Sun as the one before it. The hypothesis correctly anticipated the orbits of Ceres, in the asteroid belt, and planet Uranus. However, it failed as a predictor of Neptune’s orbit and has eventually been superseded as a theory of solar system formation.

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