[BAA 00515] Favourable Appulse/Opposition of Jupiter and Uranus

[Rick]

BAA electronic bulletin No. 00515 -- http://www.britastro.org/
Bulletin transmitted on Sun Sep 19 11:32:24 BST 2010
(c) 2010 British Astronomical Association

Observers may be interested to know that during the last few days the planets Jupiter and Uranus have been passing close to each other in the constellation of Pisces as seen from the Earth and are currently separated by an angular distance of less than 50 arcminutes with Uranus approximately north of Jupiter as seen in the sky.

What makes this special is that both planets reach opposition on the same day, September 21 and furthermore, Jupiter's opposition is a particularly favourable one in that the planet is the closest and brightest since 1963.
Details are as follows:

Sep 20 20:20 UT  Uranus closest to Earth (19.0881644 AU)
Sep 20 21:20 UT  Jupiter closest to Earth (3.9539288 AU)
Sep 21 11:40 UT  Jupiter at opposition (V = -2.94)
Sep 21 17:00 UT  Uranus at opposition (V = 5.73)

Positions and magnitudes were derived from JPL HORIZONS.

Observers should note that when at opposition the nearly full Moon will be about 20 degrees to the west of the planets and so the better views should be obtained tonight (19/20th) and tomorrow might (20/21st).  Using a low-power eyepiece, visual observers should be able to easily see both planets in the same field of view.  When closest, the disk of Jupiter will be some 49.86 arcsec in diameter (equatorial) as compared to Uranus which appears a mere 3.69 arcsec across and nearly 3,000 times fainter.  Look out for the unusual bluish-green colour of Uranus largely caused by the presence of methane in its atmosphere.

Richard Miles