APOD: 2023 December 5 Б Energetic Particle Strikes the Earth
5.12.2023

It was one of the most energetic particles ever known to strike the Earth -- but where did it come from? Dubbed Amaterasu after the Shinto sun goddess, this particle, as do all cosmic rays...

Flying over the Earth at Night II
12.03.2018

What would it be like to orbit the Earth? The International Space Station (ISS) does this every 90 minutes, and sometimes the astronauts on board take image sequences that are made into videos. The featured time-lapse video shows many visual spectacles of the dark Earth below.

Aurora and Fireball Over Norway
5.10.2012

What's happening behind that mountain? A convergence of variable sky spectacles. One night in mid-September near TromsЬ, Norway, high red aurora could be seen shimmering through lower green aurora in a way that created a striking and somewhat unusual violet glow.

The Horsehead Nebula
6.10.2019

The Horsehead Nebula is one of the most famous nebulae on the sky. It is visible as the dark indentation to the red emission nebula in the center of the above photograph. The horse-head feature is dark because it is really an opaque dust cloud that lies in front of the bright red emission nebula.

A Sonic Boom
19.08.2007

Is this what a sonic boom looks like? When an airplane travels at a speed faster than sound, density waves of sound emitted by the plane cannot precede the plane, and so accumulate in a cone behind the plane.

Mountains of Titan
14.12.2006

Peering through the thick, hazy atmosphere of Saturn's largest moon, an infrared camera onboard the Cassini spacecraft recorded this view of the tallest mountains ever seen on Titan. Captured during a flyby...

Meteors, Comet, and Big Dipper over La Palma
23.04.2019

Meteor showers are caused by streams of solid particles, dust size and larger, moving as a group through space. In most cases, the orbits of these meteor streams can be identified with dust expelled from a comet.

Sunrise by Season
21.12.2005

Does the Sun always rise in the same direction? No. As the seasons change, the direction toward the rising Sun will change, too. The Sun will always rise and set furthest to the south during the day of Winter Solstice, and furthest to the north during Summer Solstice.

Orion's Horsehead Nebula
25.10.1997

The Horsehead Nebula is one of the most famous nebulae on the sky. It is visible as the black indentation to the red emission nebula seen just to the right of center of the above photograph. The bright star near the center is located in the belt of the familiar constellation of Orion.

A Horizon with Blue and Red
5.12.2017

What's happening on the horizon? The horizon itself, past a spinach field in Guatemala, shows not only trees but a large volcano: the VolcАn de Fuego (Volcano of Fire). The red glow at the top of the volcano is hot lava.