Transit of Mercury November 8, 2006 path today Transit start: 2:12pm Sunset: 5:00pm Transit end: 5:10pm Mercury will look perfectly round and about the same size as a small sunspot. Last transit on May 7, 2003 end Mercury will appear to be 1/194 of the Sun’s diameter. YOU CANNOT SEE IT WITH YOUR NAKED EYE! True ratio of Mercury’s and Sun’s diameter: 1/286. path today start Image copyright Dominique Dierick Distance from Us Diameter Sun 1 AU 1.4 x 109 m (93,000,000 mi) (860,000 mi) Mercury 0.69 AU (today) 4.9 x 106 m (64,000,000 mi) (3000 mi) Earth You’re standing 1.3 x 107 m on it! (8000 mi) Close-up of 2003 transit Websites of interest www.transitofvenus.org/mercury.htm www.exploratorium.edu/transit/ sohowww.nascom.nasa.gov/ Image by Royal Swedish Academy of Sciences

Image by NASA/JPL/Northwestern U. Mercury Facts Mercury is the closest planet to the Sun. Rotation period: 59 d Atmosphere: none Average day temp: 710 K (820o F) Average night temp: 80 K (-320o F) Orbital period: 88 days Ave. dist. from Sun: 0.39 AU (36,000,000 mi) Mercury’s orbit is the most elliptical of all the planets. Today, Mercury is near perihelion, which means it is closest to the Sun. But, that makes it farther from us! Image by Mariner 10, NASA Transit Facts Close-up of Mercury’s surface, seen by Mariner 10. It is completely covered by craters. Transits of Mercury only occur when the Sun, Mercury, and the Earth are precisely lined up. Since Mercury’s orbit is tilted slightly, these alignments happen rarely. Transits of Mercury occur approximately 13 times per century. Next transit: May 9, 2016. Last transit: May 7, 2003. www.astro.umd.edu/openhouse Image by NASA/JPL/Northwestern U.