Archive for August 12, 2014

08/12/2014 – Ephemeris – Comet Swift-Tuttle progenitor of the Perseid meteors

August 12, 2014 Comments off

Ephemeris for Tuesday, August 12th.  The sun rises at 6:41.  It’ll be up for 14 hours and 11 minutes, setting at 8:52.   The moon, 2 days past full, will rise at 9:50 this evening.

The Perseid meteor shower will reach its peak later this evening.  The moon will still interfere with all but the brightest meteors.  The meteors are caused by bits of sand grain to pea sized rubble given off by Comet Swift-Tuttle on past runs through the inner solar system.  As comets go Comet Swift-Tuttle is large, with a nucleus of some 16 miles  (26 km) in diameter.  Comet Halley’s nucleus is half that and Churyumov–Gerasimenko’s nucleus that ESA’s Rosetta spacecraft is now orbiting is half Halley’s.  Despite the wear and tear that a comet’s nucleus must endure when coming close to the Sun, the distribution of debris to give us a pretty even annual meteor shower means the comet has been near its present orbit for a very long time.
Times are for the Traverse City/Interlochen area of Michigan.  They may be different for your location.


Comet Swift-Tuttle orbit

Orbit of Comet 109P/Swift-Tuttle. Blue line is the comet’s orbit, coming from above. Credit NASA / JPL / Applet by Osamu Ajiki (AstroArts), and further modified by Ron Baalke (JPL)

Link to the animation from which the above image was taken and other information on Comet Swift-Tuttle go to;cad=1