• That dazzling starlike object close to the moon on January 20, 2013 is the giant planet Jupiter.
• Unlike the stars, the moon and Jupiter don't shine by their own light but by reflecting the light of the sun.
• As the moon and Jupiter go westward across the sky tonight, they'll do so for the same reason that the sun goes westward during the day. It's because the

Earth rotates from west-to-east on its axis, causing the sun, moon, planets and stars to appear to move from east to west on a daily basis.
• You'll see the moon closer to Jupiter on the sky's dome tomorrow night. That's because the moon travels about 13o eastward in front of the backdrop stars every day. (For reference, the moon's diameter equals one-half degree.) This change in the moon's position after 24 hours is reflective of the moon's true motion through space.
• Jupiter changes its position in front of the background stars, too. Yet, in contrast to the moon, it does so at a snail's pace and sometimes erratically. Jupiter's true motion is more difficult to make out than that of the moon because Jupiter orbits the sun, not the Earth. Because we view Jupiter from the moving platform of Earth, Jupiter appears to move backwards in its orbit for about four months, though it really does no such thing.
• Planet Jupiter stationary in front of Taurus on January 30
• Believe it or not, Jupiter's orbital speed (13 kilometers/second) is much faster than the moon's (1 km/second). Keep in mind, though, that far-distant Jupiter takes nearly 12 years to circle the sun in its great big orbit. On the other hand, our moon circles the Earth in its tiny orbit in less than four weeks. That's why, as seen from Earth, the nearby moon appears to travel more swiftly than the distant planet Jupiter.
• Look for these two brilliant beauties to couple up together for the next several nights: the waxing gibbous moon and the giant planet Jupiter.
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