A Sun Pillar in Red and Violet
6.11.2001

Sometimes the unknown is beautiful. In 2000 February near Lake Tahoe, Nevada, two amateur photographers noticed an unusual red column of light rise mysteriously from a setting sun. During the next few minutes, they were able to capture the pillar and a photogenic sunset on film.

Uranus' Moon Miranda
23.12.1995

NASA's robot spacecraft Voyager 2 passed the planet Uranus and its moons in 1986. While the cloud tops of Uranus proved to be rather featureless, the surface of Miranda, the innermost of Uranus' large moons, showed several interesting features.

Saturns Rings in Natural Color
23.07.2004

What colors are Saturn's rings? Recent images from the Cassini spacecraft now orbiting Saturn confirm that different rings have slightly different colors. The above image shows their sometimes-subtle differences in brightness and color. The rings reflect sunlight and so, even if they were perfectly reflecting, would appear the color of the Sun.

A Sun Pillar in Red and Violet
4.02.2006

Sometimes the unknown is beautiful. In 2000 February near Lake Tahoe, Nevada, two amateur photographers noticed an unusual red column of light rise mysteriously from a setting sun. During the next few minutes, they were able to capture the pillar and a photogenic sunset on film.

Plane Contrail and Sun Halo
3.04.2017

What's happened to the sky? Several common features of the daytime sky are interacting in uncommon ways. First, well behind the silhouetted hills, is the typically bright Sun. In front...

Pluto: The Frozen Planet
18.08.1995

The Hubble Space Telescope imaged Pluto and its moon Charon in 1994. Pluto is usually the most distant planet from the Sun but because of its elliptic orbit Pluto crossed inside of Neptune's orbit in 1979 and will cross back out again in 1999.

Noctilucent Clouds over Paris
11.07.2022

It's northern noctilucent cloud season. Composed of small ice crystals forming only during specific conditions in the upper atmosphere, noctilucent clouds may become visible at sunset during late summer when illuminated by sunlight from below. Noctilucent clouds are the highest clouds known and now established to be polar mesospheric clouds observed from the ground.

Callisto Enhanced
12.05.1998

Callisto is half rock and half ice. This moon of Jupiter is approximately the size of the planet Mercury, making it the third largest moon in the Solar System, after Ganymede and Titan. Callisto...

A Blue Moon Halo over Antarctica
10.08.2015

Have you ever seen a halo around the Moon? Such 22 degree rings around the Moon -- caused by ice crystals falling in the Earth's atmosphere -- are somewhat rare. OK, but have you ever seen a blue moon?

APOD: 2023 February 12 Б Mammatus Clouds over Nebraska
11.02.2023

When do cloud bottoms appear like bubbles? Normally, cloud bottoms are flat. This is because moist warm air that rises and cools will condense into water droplets at a specific temperature, which usually corresponds to a very specific height. As water droplets grow, an opaque cloud forms.