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31 Oct 2019

November Astronomy: Don't Miss the Transit of Mercury Across the Face of the Sun—Because You'll Have a 30-Year Wait to See It Again

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The sky’s highlights in November include Mars and Spica forming a colorful pair before dawn on Nov. 10. Mercury crosses the sun Nov. 11 to join Spica and Mars a week later. Venus and Jupiter form a brilliant pair at dusk Nov. 23-24. The moon passes three bright evening planets Nov. 27-29.

Our evening twilight chart for November shows Venus higher each evening at the same stage of twilight, while Jupiter and Saturn, dragged westward along with the starry background, appear lower. The Abrams Planetarium Sky Calendar highlights the resulting spectacular gatherings of Nov. 24, Nov. 28 and Dec. 10 involving these planets.

Planets at dusk: Begin looking low in the southwest about a half-hour after sunset to catch the two brightest planets, Venus (magnitude -3.9), and Jupiter (-1.9, only one-sixth as bright). They are 20 degrees apart on Nov. 4; 10 degrees apart on Nov. 14; and within 5 degrees, fitting within a binocular field, Nov. 19-28. Don’t miss this spectacular pair at its closest, 1.5 degrees apart, on Nov. 23 and 24.

Saturn, of magnitude +0.6, one-tenth as bright as Jupiter, is 22 degrees to the upper left of Jupiter on Nov. 1; 19 degrees to the upper left of the Venus-Jupiter pair on Nov. 24; and 12 degrees to the upper left of Venus on Nov. 30. Venus will pass 1.8 degrees from Saturn on Dec. 10; by then, Jupiter will be almost gone.

The first, young crescent moon of a new cycle appears within 6 degrees to the lower right of Jupiter on Nov. 27. Don’t miss the crescent moon within 3 degrees to the upper left of Venus on Thanksgiving, Nov. 28, and even closer to Saturn on the next evening.

Mornings: About one hour before sunrise, enjoy dim red Mars (magnitude +1.8) and blue Spica (+1.0), low in the east-southeast within a five-degree binocular field Nov. 4-16. They’ll appear closest on Nov. 10, as Mars passes 2.8 degrees north (to the upper left) of Spica. The next two Mars-Spica pairings, in 2021 and 2023, will be lost in the glare of the sun. Their next visible pairing after this one: They’ll be 2.2 degrees apart on Sept. 13, 2025.

Mercury transits across the face of the sun on Nov. 11. The disk of Mercury is tiny, only 10 arcseconds across, little more than 1/200th of the sun’s diameter. Use a telescope magnifying 50x to 100x with a solar filter securely installed over its front end, or use equipment to project an image of the sun on a white screen or paper 1-2 feet from the eyepiece. Mercury will appear as a tiny black dot already near the center of the solar disk at 7:20 a.m., just more than an hour after sunrise in the Coachella Valley. The leading edge of Mercury’s disk reaches the edge of the sun near 10:03 a.m.; egress from the solar disk is complete 1.7 minutes later. The next transit of Mercury visible in U.S. won’t be until May 7, 2049, so you might want to catch this one!

In the days after the transit, Mercury rises before sunrise, but is in a thin crescent phase, too faint to be seen for several mornings. Mercury brightens quickly, reaching magnitude +0.7 by Nov. 19, within 12 degrees to the lower left of Mars, and -0.1 by Nov. 22, within 10 degrees to the lower left of Mars. Once Mercury emerges from the solar glare, follow the striking lineup of Spica, Mars and Mercury. Watch the waning, old crescent moon slide downward past Spica, Mars and Mercury, in order, Nov. 23-25, while Mercury pauses 9.5 degrees to Mars’ lower left. On Nov. 28, only 17 days after its transit, Mercury shines at magnitude -0.6 and stands at greatest elongation, 20 degrees from the sun.

The morning twilight chart for November below shows Spica and Mars getting higher daily, while Mercury ascends to its highest position before month’s end. The panel of Sky Calendar illustrations also shows Mars passing Jupiter and Saturn in late March 2020, after the giant planets have emerged from behind the sun to join Mars in the morning sky. For a summary of planetary visibility in 2019-20, visit www.abramsplanetarium.org/msta.

Check the website of the Astronomical Society of the Desert at www.astrorx.org and come to our free evening star parties offered monthly at two locations. Our primary, more-accessible venue is the Visitor Center of the Santa Rosa and San Jacinto Mountains National Monument (on Highway 74, within 4 miles south of Highway 111 in Palm Desert). Our next session there will be on Saturday, Nov. 2, from 6-9 p.m. Sawmill Trailhead, our high-altitude site (elevation 4,000 feet), will next host sessions on Saturday, Nov. 23, starting at dusk. At various locations, some members will host observing sessions for special events, including the transit of Mercury and gatherings of planets. These might be announced on short notice, so periodically check the link to Impromptu Star Party Dates. You can also pre-register for one of the stargazing parties offered several times each month at the Rancho Mirage Library Observatory by visiting www.ranchomiragelibrary.org/observatory.html. Click on Stargazing Parties, then sign up for their eNewsletter to receive registration information.

Wishing you clear skies!

Robert C. Victor was a staff astronomer at Abrams Planetarium at Michigan State University. He is now retired and enjoys providing sky watching opportunities for a variety of groups in the Coachella Valley. Robert D. Miller did graduate work in planetarium science and later astronomy and computer science at Michigan State University and remains active in research and public outreach in astronomy.

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