Astronomy Picture of the Day
Posted By admin On April 28, 2011 @ 7:39 am In Photo Essays | Comments Disabled
An ingenious and creative 10 second exposure from a swinging camera recorded these gyrating trails of the celestial pairing. Can you tell which trail belongs to the star and which to the planet?
Scintillating
Image Credit & Copyright [1]: Juergen Michelberger [2]
Explanation: On June 4, 2010 Regulus, alpha star of the constellation Leo, and wandering planet Mars were at about the same apparent brightness, separated on the sky [3] by 1.5 degrees. An ingenious and creative 10 second exposure from a swinging camera [4] recorded these gyrating trails of the celestial pairing. Can you tell which trail belongs to the star and which to the planet? Hint: atmospheric turbulence causes the image of the star to scintillate [5] or vary in brightness and color more readily than the planet. The scintillation is more pronounced because the star is effectively a point source of light seen as a narrow bundle of light rays. Rapidly changingrefraction [6] due to turbulence along the line of sight affects [7] different colors of light by different amounts and generally produces a twinkling effect for stars [8]. But Mars is much closer than the distant stars and an extended source of light. Though tiny, its disk is seen as a bundle of light rays that is substantially broader compared to a star’s and so, on average, less affected by small scale turbulence [9]. The result is the varied, rainbow like trail for Regulus (left) and the steadier, consistently reddish trail for Mars.
Visit the NASA/JPL website to view more Astronomy Pictures of the Day [10]
Article printed from Recorder Online: http://www.berthoudrecorder.com
URL to article: http://www.berthoudrecorder.com/2011/04/28/astronomy-picture-of-the-day-64/
URLs in this post:
[1] Copyright: http://apod.nasa.gov/apod/lib/about_apod.html#srapply
[2] Juergen Michelberger: http://www.jmichelberger.de/
[3] separated on the sky: http://apod.nasa.gov/apod/ap100610.html
[4] a swinging camera: http://apod.nasa.gov/apod/image/1104/CamerapendularMichelbergerX.jpg
[5] star to scintillate: http://www.astrophys-assist.com/educate/starry/starrynight.htm
[6] refraction: http://www.physicsclassroom.com/class/refrn/u14l4a.cfm
[7] line of sight affects: http://www.scientificamerican.com/article.cfm?id=why-do-stars-twinkle
[8] twinkling effect for stars: http://adsabs.harvard.edu/abs/1952IrAJ....2....5E
[9] turbulence: http://www.islandnet.com/~see/weather/elements/twinkle.htm
[10] Astronomy Pictures of the Day: http://antwrp.gsfc.nasa.gov/apod/
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