Twenty Full Moons
3.01.2007

In celebration of tonight's Full Moon, the first of 2007, consider this grid of twenty Full Moons. From upper left to lower right, the images represent every lunation from May 2005 through December 2006.

A Sun Pillar Over Ontario
18.08.2011

What is that on the horizon? No, it's not an alien starship battling distant Earthlings, but rather a sun pillar. When driving across Ontario, Canada in early June, the photographer was surprised to encounter such an "eerie and beautiful" vista, and immediately took pictures.

Warped Spiral Galaxy ESO 510 13
7.06.2003

How did spiral galaxy ESO 510-13 get bent out of shape? The disks of many spirals are thin and flat, but not solid. Spiral disks are loose conglomerations of billions of stars and diffuse gas all gravitationally orbiting a galaxy center.

Comet Hale-Bopp Develops a Tail
12.02.1997

Comet Hale-Bopp has quite a tail to tell already. This remarkable comet was first discovered in 1995, even before Comet Hyakutake. Since then, this erupting snowball continues to fall into our inner Solar System and is starting to put on quite a show.

Jupiter Season, Hawaiian Sky
2.06.2018

Volcanic activity on the Big Island of Hawaii has increased since this Hawaiian night skyscape was recorded earlier this year. Recent vents and lava flows are about 30 kilometers to the east, the direction...

Mars and the Pleiades Beyond Vinegar Hill
6.04.2021

Is this just a lonely tree on an empty hill? To start, perhaps, but look beyond. There, a busy universe may wait to be discovered. First, physically, to the left of the tree, is the planet Mars.

APOD: 2024 December 23 Б Christmas Tree Aurora
23.12.2024

It was December and the sky lit up like a Christmas tree. Shimmering, the vivid green, blue, and purple auroral colors that formed the tree-like apparition were caused by high atmospheric oxygen and nitrogen reacting to a burst of incoming electrons.

Leonids Over Korean Observatory
12.12.2001

There were two peaks to this year's Leonid Meteor Shower. The first peak was best seen during the early morning hours of November 18 in North America, while the second peak, almost twice the intensity of the first, occurred eight hours later and was best seen from Asia.

The Lyman Alpha Forest
26.01.2003

We live in a forest. Strewn throughout the universe are "trees" of hydrogen gas that absorb light from distant objects. These gas clouds leave numerous absorption lines in a distant quasar's spectra, together called the Lyman-alpha forest.

Perseid Meteors and the Milky Way
15.08.2005

Where will the next Perseid meteor appear? Sky enthusiasts who trekked outside for the Perseid meteor shower that peaked over the past few days typically had this question on their mind. The above movie, where the time-line has been digitally altered, captures part of that very mystery.