It's where the sun resides on the March equinox, used to define the sky's prime meridian. Tonight's moon and planets can help you visualize this point on our sky's dome.
Beginning on January 29, 2017, watch as the waxing crescent moon sweeps past Venus and then Mars on the sky's dome. You'll find them all in the west at nightfall.
The parade of 5 bright planets visible in Earth's sky tonight will conclude with the moon and Mercury rising as darkness ebbs into dawn Wednesday morning.
Given clear skies, it should be easy to use the waning crescent moon to locate the star Antares and planet Saturn before dawn’s first light on January 23.
The moon is sweeping past Jupiter now, but - if you know where to look - you can find all 5 bright planets on these January 2017 nights. Charts and info here.
On January 19, 2017, Mercury will be at greatest elongation. That means it's now nearly at its farthest from the sun on our sky's dome for this morning apparition. Watch for it!
Bruce McClure served as lead writer for EarthSky's popular Tonight pages from 2004 to 2021, when he opted for a much-deserved retirement. He's a sundial aficionado, whose love for the heavens has taken him to Lake Titicaca in Bolivia and sailing in the North Atlantic, where he earned his celestial navigation certificate through the School of Ocean Sailing and Navigation. He also wrote and hosted public astronomy programs and planetarium programs in and around his home in upstate New York.