Many people know Venus as the brightest of all the planets. And many
know Mars as the red planet. What many don't know is that these two planets often put on
a fascinating show in our sky due to their rapid and unexpected motions.
At the start of 2015, Mars was ahead -- left -- of Venus in our western sky in early evening. Venus, as the
faster of the two, caught up and passed Mars in February as the photo above shows. Venus will continue
to pull ahead for months.
But near the end of June something very strange will happen: Venus will abruptly reverse directions and
go back to Mars, do a loop around it and then pull ahead again. Weird!
Here's a video of the motions of Venus and Mars in our sky for 2015. Also watch the sun. When a planet is
close to the left side of the sun, look for it shortly after sunset. When a planet is close to the right side,
look for it shortly before sunrise. The month label closest to the sun shows when to look.
Can planets really do this -- change directions and do loops? Not quite! It is actually all an illusion caused
by the fact that Earth is moving too. Venus appears to move backwards when it approaches and passes
Earth while they both orbit the sun --laps-- us on the inside track so to speak. This is known as
apparent retrograde motion and all the planets appear do this in turn -- Venus just happens to do it
more quickly than the other planets (except for Mercury).