On Tuesday morning a thin crescent moon appears low in the southeastern sky before sunrise near the bright planet Saturn.

Saturn, the ringed planet, resides in the zodiacal constellation Virgo, where it has been for more than two years. It usually takes Saturn two years to move from one zodiacal constellation into the next. The moon takes two days to move through one constellation.

On Wednesday morning the moon will have advanced farther eastward and will appear in the zodiacal constellation Libra.

Saturn is creeping toward Libra and will be in that constellation later this month.

Venus, the brightest planet in the eastern sky, is close to the horizon and quite brilliant.

Jupiter is well into the western sky at that hour of the morning. But most of us have been watching Jupiter as it rises in the east after sunset. By 10 p.m. Jupiter is the dominant celestial object in the east. By midnight it is almost overhead.

Jupiter moves a lot faster than Saturn through the night sky. It is half the distance from the Sun as Saturn. Jupiter is in the zodiacal constellation Taurus and will be there only one year.

For purposes of comparison, the Earth moves through a zodiacal constellation each month. It takes one year for the Earth to complete its orbit. It takes Jupiter 12 years to complete the same task. It takes Saturn 29 years to make one trip around the sun.