The Rhythm of the Spheres

Reading the Night Sky

Wandering in Astronomy

The night sky is the oldest pattern of man, and every culture reads it differently. The stars above keep silent time, moving to a rhythm we are just now beginning to understand. Astronomy is where math, science, art, music, and words meet in a wondrous collision. In this section of our site, learn the basics of astronomy: from how a star chart is made, to projections and art that map the night sky, to how an astrolabe works just like it did thousands of years ago. Watch the North Star shift across centuries, explore how one sky has been mapped by many traditions, read what happened on this day in space, and see tonight’s moon for your location.

Map the Stars

The math behind star charts, with a projection explorer and a working astrolabe.

The Moving Sky

How the sky shifts across centuries, with a precession clock you can run.

The Traditions

One sky reads many ways, with a same-sky overlay of the world’s constellations.

This Day in the Stars

The sky’s events, discoveries, and lore tied to today’s date.

The Moon Tonight

Its phase and face, drawn live for where you’re standing.

✦  Astronomy Picture of the Day  ✦

Six Moons of Saturn

April 14, 2012
© Rafael Defavari
How many moons does Saturn have? So far 62 have been discovered, the smallest only a fraction of a kilometer across. Six of its largest satellites can be seen here, though, in a sharp Saturnian family portrait taken on March 9. Larger than Earth's Moon and even slightly larger than Mercury, Titan has a diameter of 5,150 kilometers and starts the line-up at the lower left. Continuing to the right across the frame are Mimas, Tethys, [Saturn], Enceladus, Dione, and Rhea at far right. Saturn's first known natural satellite, Titan was discovered in 1655 by Dutch astronomer Christiaan Huygens, while most recently the satellite provisionally designated S/2009 S1 was found by the Cassini Imaging Science Team in 2009. Tonight, Saturn reaches opposition in planet Earth's sky, offering the best telescopic views of the ringed planet and moons.

Customized Star Charts Coming 1st Quarter 2027

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✦  EarthSky  ·  Astronomy.com  ·  Phys.org  ✦
Astronomy Sep 27, 2026

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