Sky's Up July-September 2017 - Page 32

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Phenomena related to eclipses
About 13 times a century for Mercury and in pairs eight years apart separated by more than a century for Venus , we see these planets transit the Sun ’ s disk . The silhouette of the planet passes across the disk of the Sun , taking a few hours to make the full crossing . Mercury ’ s silhouette is tiny , invisible without a telescope . The silhouette of Venus is large enough that with a safe solar filter you can see it without a telescope ; with a telescope Venus is a small but distinct disk . Asteroids and comets can also transit . Halley ’ s Comet was predicted to transit the Sun in 1910 but the passage was not visible in telescopes . This told astronomers that the solid nucleus of the comet was small . Earth satellites also transit the Sun ( and Moon ) on occasion . The pass takes about 1 second . The distinctive shape of the International Space Station can be seen and imaged . Sometimes spacecraft see the Moon crossing the Sun ’ s disk . It ’ s sometimes not obvious whether to call the event an annular eclipse or a transit . We call an event when a larger body passes in front of a smaller body in the sky an occultation . If we were consistent using definitions of astronomical phenomena , a total solar eclipse would be called a total occultation of the Sun . Only events during which we see the shadow of one object fall projected on another object would be called an eclipse ( like an eclipse , total or partial , of the Moon when it passes through Earth ’ s shadow ). But in common usage , an occultation refers to ( usually ) night time events such as the Moon passing in front of ( occulting ) a star or asteroid or planet . There are also occasions when an asteroid or planet occults a star . See the discussion of Jupiter in Sidebar Two for more information .
COURTESY OF Steve Edberg
COURTESY OF Steve Edberg Venus is much larger than the sunspots visible on the Sun ’ s disk to its right .
COURTESY OF NASA / Bill Ingalls Above , this composite image made from five frames shows the International Space Station , with a crew of nine onboard , in silhouette as it transits the Sun at roughly five miles per second on Sept . 6 , 2015 . Left , in this view , the Moon is partially occulting Saturn . At most locations for viewing this event , Saturn eventually disappeared completely behind the Moon and reappeared an hour or less later . From this site , the Moon never completely covered Saturn and spent about five minutes sliding by , partially covering the planet . Notice that Saturn is covered by a narrow piece of the night side of the Moon , not by the mountains illuminated by Sun in the foreground .
Sky ’ s Up 17
kentucky event spotlight The Moon’s shadow begins its race across a narrow portion of southwest Kentucky at 1:22 p.m. CDT and is out by 1:30 p.m. CDT. Eclipse chasers and residents in this swath of lucky real estate should remain alert to cloud conditions because statistically the chance for overcast skies in the afternoons is slightly elevated. Paducah is among the first communities that will take in the stunning sight of the blackened Sun. There, totality will begin at 1:22 p.m. CDT and last 2 minutes and 21 seconds. The McCracken County Public Library will host a public observing event with free solar viewing glasses. Also in Paducah, West COURTESY OF Michael Zeiler, www.GreatAmericanEclipse.com Kentucky Community and Technical Kentucky cities on the centerline of the path of totality: College will hold Night at Noon — a Adairville • Dycusburg • Eddyville • Elkton • Fredonia • Hopkinsville • Princeton • Salem public viewing event emceed by astronaut Terry Wilcutt. The most talked about location in Kentucky is the point of greatest eclipse near Hopkinsville. Greatest eclipse is the instant when the axis of the Moon’s shadow cone passes closest to Earth’s center. Here, the time in totality will be within a tenth of a second of the greatest duration time in Illinois. Listed as the location of an official NASA viewing site, the Hopkinsville community will offer a host of eclipse-related events, including a special Eclipse Con event on the Saturday and Sunday before the big day. For information on festivities in the area, click here. Bowling Green, which is one of the larger cities on this segment of the path is very close to the northeastern edge, so viewers there will have less than 1 minute of totality. The abbreviated time hasn’t dampen the anticipation. In fact, Western Kentucky University has canceled all classes before 4 p.m. that day to provide eclipse programming for their students, faculty and staff as well as thousands of K-12 students who will visit the campus that day for a special viewing event. Greatamericaneclipse.com estimates that between 63,000 and 253,000 people will travel to the path of totality in Kentucky for the eclipse. 32 Sky ’ s Up Eclipse 2017 at Vol State Volunteer State Community College in Gallatin, Tenn., is celebrating the city’s 2 minutes and 40 seconds of totality by holding a free eclipse viewing event. Totality does not being until 1:27 p.m. CDT, but activities and presentations will be held in various buildings around the college’s campus from 9 a.m. to 1 p.m. The observing area will be on the library lawn, and attendees are encouraged to bring their own blankets and chairs for seating. Free safe solar viewing glasses will be available while supplies last. A presenter will be on hand to narrate the progression of the eclipse. Although the event is free, those who plan on viewing at this location are asked to register so that organizers can prepare. For more information or to register for the event, click here. tennessee Totality in Tennessee begins at 1:25 p.m. CDT as the Moon’s shadow races in from Kentucky, crosses into a new time zone and exits around 2:36 p.m. EDT. One of the first communities to fall under the spell of the umbra is Clarksville, which will experience 2 minutes and 18 seconds of totality. Clarksville’s Austin Peay State University will offer a variety of eclipse-related programs as well as a general viewing event in the campus’ football stadium. The $5 parking fee includes two pairs of safe solar viewing glasses. As totality is wrapping up in Clarskville, the big show is just beginning in Nashville. For nearly 2 minutes, hundreds of thousands of Nashvillians and visiting eclipse chasers will bear witness to totality as the Moon’s shadow overtakes the Sun over Music City beginning at 1:27 p.m. CDT. Since Nashville takes up a large chunk of real estate on the path of totality, duration times will vary throughout parts of the city so you may want to consult х͔́Ѽ͔)ȁ͕٥иȁɔɵѥٕ)9͡٥Ёѡéѡ)ݕͥєݡՑ́䁕͔履и)܁ɔ͕́չȁѡܰ͡ԁ)Ѐ́ѡЁ9͡٥Ѽѥ)ݡ́ѡѕɱ!ɔԁɥ(ȁѕ͕́́ѽх丁Q͕)䁽٥ݥѥ́ȁёȁѡ̰ͥ)Ս́=]MIٕȁ9ѥMхє)AɬɕЁM5չх́9ѥAɬɥ͕́)ȁѡѡ)յɇéɹ)ѡɽ՝Q͕)Qѥɔݕѕɸ)ѡɬ)ݡɅݱ́ɽ)ѡɑȁݕ)Q͕9Ѡ) ɽ́)ѡ齹ѽх)AՉ٥ݥٕ)ɔݥѡ)ѡɬȁɔ)ɵѥ)ɔ) =UIQMd=5iȰܹɕɥ͔)M䃊d)U)Q͕ѥ́)ѡѕɱ)ѡѠѽх)ѥɑ٥)5ͽ٥Mф)Mɥ (