Last updateMon, 24 Aug 2020 12pm


30 Jan 2020
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In the western evening sky, Mercury reaches one of its highest positions at dusk for 2020. In the predawn darkness of Feb. 18, the moon covers and uncovers Mars. Meanwhile, all three bright outer planets—bright Jupiter, with Mars to its upper right, and Saturn to its lower left—are gradually coming together in the southeast before dawn, until their rare, once-in-20-years compact gathering in late March! You won’t fail to notice brilliant Venus well up in the west-southwest to west at dusk. Mercury makes an appearance to its lower right. Mercury shines at magnitude -1 on Feb. 1, fading to magnitude 0 on Feb. 13, and magnitude +1 by Feb. 17; it then dims rapidly and drops into bright twilight within a few days. Mercury lingers 24 degrees from Venus Feb. 4-11. The revolution of the planets around the sun is counterclockwise, as viewed from above the northern side of the…
25 Dec 2019
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Venus climbs higher above the setting sun week by week, and late in January sets more than three hours after sunset. Mercury, after passing the far side of the sun on Jan. 10, emerges into the west-southwest evening twilight sky to the lower right of Venus by the last week of month. Mars, very slowly brightening, appears in the southeast morning sky. Jupiter emerges into the southeast morning sky to the lower left of Mars by mid-January, followed by Saturn in early February. By modeling the solar system on orbit charts, or—here’s a weird party idea—asking friends to act out the motions of the planets, you can see why, when an outer planet such as Mars, Jupiter or Saturn is behind the sun, it is transitioning from the evening sky to the morning sky; and why, when either inner planet, Mercury or Venus, is behind the sun, it is transitioning…
28 Nov 2019
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Venus becomes ever more prominent in the evening, while Jupiter, and then Saturn, sink into the southwest twilight glow in December. Mars, slowly brightening, appears in the southeast morning sky, with bright Mercury below it in the first half of the month. Do not miss Venus and Saturn within 5 degrees Dec. 7-14 (see right), with their closest pairing 1.8 degrees apart on Dec. 10; and the spectacular Venus-moon conjunction on Dec. 28. Three planets span 18 degrees in the southwest at dusk in early December. On Dec. 1, find Venus, magnitude -3.9, with Jupiter, magnitude -1.8, just 8 degrees to the lower right, and Saturn, magnitude +0.6, 11 degrees to Venus’ upper left. Venus is now on the far side of its orbit, with its light taking 12 minutes to reach us, compared to the sun’s eight minutes. Light reflected from Jupiter and Saturn takes 51 and 90 minutes,…