October 12, 2020 - Delicate Dance of Shadows
Delicate Dance of Shadows Every six months the Earth’s axis of rotation is neither pointing toward the Sun nor away from it. At these times of equinox, or equal night, the Sun appears directly overhead at the equator at local noon, and days and nights there are exactly 12 hours long. Because Saturn takes much longer to orbit the Sun, an equinox there occurs about every 15 years, but when it does, it sets the stage for a memorable play of light and dark as the shadows cast by Saturn’s moons fall directly on the planet’s rings. In April 2009, four months before Saturn’s equinox, the Cassini spacecraft captured this rare image. The shadow of its moon Tethys falls across the A ring and Cassini Division in this view, which looks toward the unilluminated side of the rings from about 50° above the ringplane.
Image credit: NASA / JPL / Space Science Institute
Weekly Calendar
October 12 - 18, 2020
Holidays - Sky Events - Space History
Monday 12
Thanksgiving Day (Canada)
Columbus Day
1964: Voskhod 1 launched, first three-person space flight
1977: Shuttle Enterprise’s first glide test without aerodynamic tailcone
2008: ISS Expedition 18 crew launched
Tuesday 13
Mars at opposition
Venus 4° south of Moon
1773: Charles Messier observes M-51
1933: British Interplanetary Society founded
1968: Apollo 7 first live TV broadcast from space
2004: ISS Expedition 10 crew launched
Wednesday 14
Mercury stationary
1947: World’s first supersonic flight
1957: USAF announces X-20 Dyna-Soar project
1983: Venera 16 arrives in orbit around Venus
Thursday 15
1829: Asaph Hall born
1997: Cassini-Huygens launched
2003: Shenzhou 5 launched, Yang Liwei becomes first Chinese astronaut
Friday 16
New Moon 3:31 PM ET
Moon at perigee
Saturday 17
Mercury 7° south of Moon
1956: Mae Jemison born
2016: Shenzhou-11 launched
Sunday 18
1967: Venera 4 makes first direct studies of Venus’s atmosphere
1989: STS-34 Atlantis launched
1993: STS-58 Columbia launched
2003: ISS Expedition 8 crew launched