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.

โœฆ  Astronomy Picture of the Day  โœฆ

Arp 93: A Cosmic Embrace

August 16, 2023
Credit: Mike Selby , Observatorio El Sauce
See this entry on NASA's APOD โ†’
Locked in a cosmic embrace , two large galaxies are merging at the center of this sharp telescopic field of view. The interacting system cataloged as Arp 93 is some 200 million light-years distant toward the constellation Aquarius in planet Earth's sky. Individually the galaxies are identified as NGC 7285 (right) and NGC 7284. Their bright cores are still separated by about 20,000 light-years or so, but a massive tidal stream , a result of their ongoing gravitational interaction, extends over 200,000 light-years toward the bottom of the frame. Interacting galaxies do look peculiar , but are now understood to be common in the Universe. In fact, closer to home, the large spiral Andromeda Galaxy is known to be approaching the Milky Way. Arp 93 may well present an analog of their distant future cosmic embrace .

Notable submissions to APOD: Perseids Meteor Shower 2023

Customized Star Charts Coming 1st Quarter 2027

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โœฆ  EarthSky  ยท  Astronomy.com  ยท  Phys.org  โœฆ
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