APOD: 2024 July 9 Б Noctilucent Clouds over Florida
9.07.2024

These clouds are doubly unusual. First, they are rare noctilucent clouds, meaning that they are visible at night -- but only just before sunrise or just after sunset. Second, the source of these noctilucent clouds is actually known.

Iridescent clouds
11.03.2003

Why would clouds appear to be different colors? A relatively rare phenomenon known as iridescent clouds can show unusual colors vividly or a whole spectrum of colors simultaneously. These clouds are formed of small water droplets of nearly uniform size.

Crescents of Titan and Dione
29.03.2005

What would it be like to see a sky with many moons? Such is the sky above Saturn. When appearing close to each other, moons will show a similar phase. A view with...

Zal Patera on Jupiter's Moon Io
7.03.2000

The Galileo orbiter's flyby of Io last November captured an unusual part of Jupiter's volcanic moon. From 26,000 kilometers away, Zal Patera was found to be a cauldron of flowing lava, gaseous vents, and tremendous peaks.

Comet Between Fireworks and Lightning
5.02.2007

Sometimes the sky itself is the best show in town. On January 26, people from Perth, Australia gathered on a local beach to watch a sky light up with delights near and far. Nearby, fireworks exploded as part of Australia Day celebrations. On the far right, lightning from a thunderstorm flashed in the distance.

An Antarctic Total Solar Eclipse
4.05.2008

The Sun, the Moon, Antarctica, and two photographers all lined up in 2003 Antarctica during an unusual total eclipse of the Sun. Even given the extreme location, a group of enthusiastic eclipse chasers ventured near the bottom of the world to experience the surreal momentary disappearance of the Sun behind the Moon.

A Rainbow Pileus Cloud over Zimbabwe
19.02.2014

Yes, but how many dark clouds have a multicolored lining? Pictured, behind this darker cloud, is a pileus iridescent cloud, a group of water droplets that have a uniformly similar size and so together diffract different colors of sunlight by different amounts.

Comet Wirtanen Passes by the Earth
16.12.2018

Today Comet Wirtanen passes by the Earth. The kilometer-sized dirty snowball orbits the Sun every 5.4 years, ranging as far out as Jupiter and as close in as the Earth. Today Comet 46P/Wirtanen passes within only 31 lunar distances to the Earth, the closest approach in 70 years.

APOD: 2024 December 18 Б NGC 660: Polar Ring Galaxy
18.12.2024

What kind of strange galaxy is this? This rare structure is known as a polar ring galaxy, and it seems to have two different rings of stars. In this galaxy, NGC 660, one ring...

GRO J1655 40: Evidence for a Spinning Black Hole
5.09.2010

In the center of a swirling whirlpool of hot gas is likely a beast that has never been seen directly: a black hole. Studies of the bright light emitted by the swirling gas frequently indicate not only that a black hole is present, but also likely attributes.