Skywatch Line for Wednesday, March 29th, and Thursday, March 30th, 2017

This is the Dudley Observatory Skywatch Line for Wednesday, March 29th, and Thursday, March 30th, written by Louis Suarato.

The 5% illuminated, waxing crescent Moon sets alongside Mercury Wednesday night. On March 29, 1974, the Mariner 10 spacecraft took the first close-up photos of Mercury. Mariner 10 was the first mission to utilize the gravity assist from one planet to reach another when it sailed around Venus. Look for Mars 12 degrees above the Moon. Thursday night, the crescent Moon will be about 8 degrees to the left of Mars, and below the Pleiades star cluster. The Moon reaches perigee, its closest point to Earth during this lunar cycle, on Thursday at 8:32 a.m., at the distance of 266,088 miles. Jupiter rises at 8:01 p.m. in Virgo. Saturn rises at 1:45 a.m. in the constellation Ophiuchus.

Comet 41P/Tuttle-Giacobini-Kresak is below the Big Dipper’s outermost top star of its bowl. Look for this comet 2 degrees below magnitude 2.0 star, Dubhe. Comet 41P/Tuttle-Giacobini-Kresak is currently at 7th magnitude, and can be seen with binoculars or a small telescope. On March 30th in 239 BC, Chinese astronomers were the first to chronicle the passage of Halley’s Comet. It wasn’t until 1705 that English astronomer Edmond Halley predicted the comet’s 75 year orbit and its return.

Arcturus, “the Spring star”, rises in the constellation Bootesafter 8 pm. At a magnitude of -0.05, Arcturus is the brightest star in the northern celestial hemisphere. Arcturus, along with Spica and Denebola, form the asterism known as the Spring Triangle. Arcturus, or Alpha Bootis, is a red giant star, 36.7 light-years from our Sun. It is estimated to be about 7.1 billion years old, and about 0.2 times its diameter. The globular cluster, M3, can be found 10 degrees above Arcturus.

Wednesday night, there will be an extremely bright International Space Station pass over our region. This -3.9 magnitude ISS pass will emerge from the southwest at 8:15 p.m., and head toward the northeast. The ISS will pass through the constellations Orion, and Gemini, and pass by the Big Dipper, before disappearing into Earth’s shadow in Bootes.

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