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Earth of Jet Propulsion Laboratory (JPL) and Goddard Space Flight Center (GSFC) from 2008
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Three Years of Saturn
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Three Years of Saturn |
| Explanation |
Using an image recorded just last month as a base, this composite illustration tracks the motion of bright Saturn [ http://antwrp.gsfc.nasa.gov/apod/ap070406.html ] as it wanders through planet Earth's night sky [ http://soc.jpl.nasa.gov/viewing.cfm ]. Starting at the upper right, Saturn's position is shown about every two weeks beginning in August 2005 and projected through September 2008. Over the three year period, Saturn actually appears to reverse its general eastward (leftward) drift, tracing out three flattened curves. The periodic backwards or retrograde motion [ http://antwrp.gsfc.nasa.gov/apod/ap060422.html ] with respect to the background stars is a reflection of the motion of the Earth itself. Retrograde motion [ http://www.lasalle.edu/~smithsc/Astronomy/ retrograd.html ] can be seen each time Earth overtakes and laps planets orbiting farther from the Sun, the Earth moving more rapidly through its own closer-in [ http://csep10.phys.utk.edu/astr161/lect/retrograde/ copernican.html ] orbit. The Beehive [ http://antwrp.gsfc.nasa.gov/apod/ap060128.html ] star cluster in Cancer lies near the track at the upper right. Stars along the "backward question mark" at the head of Leo [ http://stardate.org/nightsky/constellations/leo.html ] are in the left half of the frame. Saturn's position this month [ http://skytonight.com/observing/home/April_podcast.html ] is near the right hand limit of the middle curve. Click on the picture to download and view the gif animation. |
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Mars in View
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Mars in View |
| Explanation |
Very good telescopic views of Mars [ http://mars.jpl.nasa.gov/allabout/nightsky/ viewing-tips-2007.html ] can be expected in the coming weeks as the Red Planet [ http://www.uapress.arizona.edu/onlinebks/mars/contents.htm ] nears opposition on December 24th. Of course [ http://antwrp.gsfc.nasa.gov/apod/ap060422.html ], opposition means opposite the Sun in planet Earth's sky - an arrangement [ http://mars.jpl.nasa.gov/allabout/nightsky/nightsky03.html ] that occurs every 26 months for Mars. Because of Mars' [ http://nssdc.gsfc.nasa.gov/planetary/factsheet/marsfact.html ] more elliptical orbit, the actual date of closest approach to Earth will be December 18, when Mars will be within about 88 million kilometers of our fair planet. Situated in the constellation Gemini and rising after evening twilight, the bright, ruddy disk of Mars will reach nearly 16 arcseconds [ http://coolcosmos.ipac.caltech.edu/cosmic_classroom/ cosmic_reference/angular.html ] in diameter (about 1/100th the diameter of the Full Moon). In this already exceptional image taken on November 18, north is down and surface markings around the sprawling, dark, albedo feature Syrtis Major [ http://photojournal.jpl.nasa.gov/catalog/PIA01592 ] are remarkably clear. The image was recorded with a video camera and filters on a 1 meter telescope at Pic Du Midi [ http://en.wikipedia.org/wiki/Pic_du_Midi_de_Bigorre ], a mountain top observatory in the French Pyrenees. NASA launched the Phoenix [ http://phoenix.lpl.arizona.edu/mission.php ] lander to Mars in August, scheduled to arrive in May 2008. |
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Messenger Launch
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Messenger Launch |
| Explanation |
Streaking [ http://www.jhuapl.edu/newscenter/pressreleases/2004/ 040803.htm ] into the early morning sky on August 3rd, a Delta II rocket [ http://www.boeing.com/defense-space/space/delta/delta2/ delta2.htm ] launches NASA's Messenger spacecraft [ http://messenger.jhuapl.edu/index.html ] on an interplanetary voyage to Mercury [ http://www.nineplanets.org/mercury.html ]. Scheduled to become the first probe to orbit Mercury, Messenger will begin by looping through [ http://messenger.jhuapl.edu/the_mission/ mission_design.html ] the inner Solar System in a series of close flybys of planet Earth and Venus. The flybys are designed as trajectory changing gravity assist [ http://www2.jpl.nasa.gov/basics/grav/primer.html ] encounters to ultimately achieve the goal of orbiting Mercury in 2011. Prior to entering orbit, Messenger will also flyby Mercury in 2008 and 2009 as the first spacecraft to visit the Solar System's innermost planet since Mariner 10 [ http://antwrp.gsfc.nasa.gov/apod/ap011124.html ] in the mid 1970s. This dramatic view [ http://www.geocities.com/ovpathfinder/ MESSENGER.html ] of the Messenger launch was recorded from a pier in Jetty Park at the north end of Cocoa Beach about 2.5 miles from the Cape Canaveral [ http://www.astronautix.com/sites/capveral.htm ] launch site. So what's that erratic blue streak on the right? It's the reflection from a camera blurred in the time exposure. |
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