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  ✦

The Unexpected Tails of Asteroid P5

November 12, 2013
What is happening to asteroid P/2013 P5? No one is sure. For reasons unknown, the asteroid is now sporting not one but six discernible tails. The above images were taken two months ago by the orbiting Hubble Space Telescope and show the rapidly changing dust streams. It is not even known when P5 began displaying such unusual tails. Were the main belt asteroid struck by a large meteor, it would be expected to sport a single dust tail. Possible explanations include that light pressure from the Sun is causing the asteroid to rotate increasingly rapidly, which in turn causes pools of previously gravity-bound dust to spin off. Future observations should better indicate how P5 and its dust plumes are evolving and so provide more clues to its nature -- and to how many similar asteroids might exist.

Customized Star Charts Coming 1st Quarter 2027

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✦  EarthSky  ·  Astronomy.com  ·  Phys.org  ✦
Today in the History of Astronomy Sep 20, 2026

Sept. 20, 2016: Spotting a supernova shock breakout

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Astronomy Essentials Sep 20, 2026

Visible planets and night sky guide for September

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The Sky Today on Sunday, September 20: Juno’s movement

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Today in the History of Astronomy Sep 19, 2026

Sept. 19, 1959: A SETI kickstart

On Sept. 19, 1959, the paper “Searching for Interstellar Communications” was published. Printed in the respected scientific journal Nature and written by Cornell University physicists Giuseppe …

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Astronomy Sep 18, 2026

Hubble spots an out-of-sync galaxy

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Astronomy Sep 18, 2026

From the start, the solar system chose fire over ice to build its first bodies

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Astronomy Sep 18, 2026

Time is running out to catch a giant planet's strange orbit

A team of researchers, including those from the University of Tokyo, spotted a rare kind of planet that's unusually hot and eccentric. TOI-1355 b orbits its star, TOI-1355, which is also much hotte…

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