Friday, January 3, 2014

Venus closing in on inferior conjunction

Venus de Milo
Venus (the planet, not the goddess of love) is closing in on inferior conjunction - the point when it lies directly between Earth and the Sun in its orbit.  Inferior conjunction will take place on Sat, 11 Jan 2014 at 05:19 MST (12:19 UT).

Because Venus orbits between the Earth and the Sun, it moves through phases of illumination just like our Moon.  As Venus is now 8 days from inferior conjunction, only a very thin crescent is illuminated.  Below is a stack of 500 frames from an avi file of Venus I captured this afternoon through my TEC 140.  I may have overdone the processing a little as the extreme tips of Venus seem to have been lost, but either way you can appreciate how thin the crescent is.

Currently, Venus is nearly at its largest apparent size, with a diameter of 61.08 arcseconds and is a beacon of light shining at magnitude -4.26, making it far and away the brightest object in the evening sky.  In a nice coincidence of numbers, it is 2.3 light minutes away, and is also 2.3% illuminated.
Of course, Venus' orbit is tilted with respect to Earth's orbit and as a result it will not appear to transit across the face of the Sun as it did in June of 2012. From our vantage point on the Earth, Venus will pass within a 5 degrees of the Sun and will be lost in its glare. Venus will also pass perigee (the time when it is physically closest to the Earth) within a few days of inferior conjunction. It will move to within a distance of 0.27 Astronomical Units (AU) from the Earth, which is approximately six times closer to Earth than at superior conjunction (when Venus is on the far side of the Sun).  If it could be observed, it would measure 62.7 arcseconds in diameter, which is approximately 50% larger than Jupiter, yet it would not be illuminated at all! As Venus moves past inferior conjunction, it will once again become a morning object over the next few weeks.

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