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  ✦

Colorful Aurora over Icelandic Waterfall

August 27, 2026
© Victor Lima Text: Cecilia Chirenti (NASA GSFC, UMCP, CRESST II)
What a sight to behold, when a night sky became filled with colors that appeared to rain over the Skógafoss waterfall in Iceland. This image was taken in a single 5 second exposure by the photographer in April 2025. Seeing an aurora is on many people's bucket lists. But it is not easy. It requires high solar activity, dark and clear skies, and usually a viewing location at high latitude. That makes the northern lights more easily seen than the corresponding southern lights, simply because there is less landmass in the Southern Hemisphere, especially around the Antarctic Circle. Auroras are caused by charged particles from the solar wind that are captured by the Earth's magnetosphere and guided by the magnetic field to a region close to one of the poles, where they collide with gas particles in the atmosphere. Different colors indicate interactions with different gases at different altitudes, like oxygen (red and green) and nitrogen (blue and pink). APOD's main NASA site is moving : From apod.nasa.gov to science.nasa.gov/apod

Customized Star Charts Coming 1st Quarter 2027

We respect your privacy. Unsubscribe at any time.

✦  EarthSky  ·  Astronomy.com  ·  Phys.org  ✦
Observing Sep 14, 2026

The Sky Today on Monday, September 14: Connect four

Looking for a sky event this week? Check out our full Sky This Week column.  September 13: Venus, the Moon, and Spica The Moon passes 0.5° due north of Venus at 7 A.M. EDT. In the e…

Read
Astronomy Sep 13, 2026

Astronomers unmask a supernova impostor

A distant star has captured astronomers' attention over the past decade, teasing them with indications that it will soon explode as a supernova. But new research shows that something else entirely …

Read
Astronomy Sep 13, 2026

Gravitational-wave analysis narrows the search for black hole impostors

Black holes are regions of spacetime where gravity is so strong that nothing, not even light, can escape. When two black holes orbit each other and merge, they produce gravitational waves (i.e., ri…

Read
Robotic Spaceflight Sep 13, 2026

Sept. 13, 1994: Ulysses at the Sun’s south pole

A joint NASA-ESA mission, the Ulysses solar probe launched Oct. 6, 1990, from the Space Shuttle Discovery. The mission was tasked with studying the solar wind, mapping the heliosphere, and becoming…

Read
Astronomy Essentials Sep 13, 2026

Venus brightest in the evening sky this week

See Venus brightest in the evening sky this week, with greatest brilliancy coming around September 18, 2026. Look west after sunset.

Read
Astronomy Essentials Sep 13, 2026

Visible planets and night sky guide for September

Visible planets and night sky guide: Venus reaches its brightest in the sky this week. Look west this evening to see the crescent moon near brilliant Venus.

Read
Astronomy Sep 13, 2026

Researchers pinpoint key early-universe measurement with record precision

An international team, including researchers from the University of Minnesota Twin Cities, has reached a major milestone in "precision cosmology" by measuring the amount of helium created in the un…

Read
Space Sep 13, 2026

Alien tech on the moon? Scientists propose search for microscopic debris

Could there be alien tech on the moon? Scientists propose a new search for microscopic particles shed by alien technology.

Read
Observing Sep 13, 2026

The Sky Today on Sunday, September 13: Venus, the Moon, and Spica

Looking for a sky event this week? Check out our full Sky This Week column.  September 12: Dione skims Saturn’s pole Blazing at magnitude –4.8, Venus is nearing its greatest illu…

Read