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

Globular Star Cluster NGC 6355 from Hubble

January 30, 2023
Credit: ESA / Hubble & NASA , E. Noyola , R. Cohen
See this entry on NASA's APOD โ†’
Globular clusters once ruled the Milky Way . Back in the old days , back when our Galaxy first formed, perhaps thousands of globular clusters roamed our Galaxy . Today, there are less than 200 left . Over the eons, many globular clusters were destroyed by repeated fateful encounters with each other or the Galactic center . Surviving relics are older than any Earth fossil , older than any other structures in our Galaxy , and limit the universe itself in raw age. There are few, if any, young globular clusters left in our Milky Way Galaxy because conditions are not ripe for more to form. The featured image shows a Hubble Space Telescope view of 13-billion year old NGC 6355 , a surviving globular cluster currently passing near the Milky Way's center . Globular cluster stars are concentrated toward the image center and highlighted by bright blue stars. Most other stars in the frame are dimmer, redder, and just coincidently lie near the direction to NGC 6355 .

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โœฆ  EarthSky  ยท  Astronomy.com  ยท  Phys.org  โœฆ
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