Identify this Phenomenon
13.09.2004

What caused this ring of colors? At the time of this writing, MIT Physics Professor Walter Lewin had yet to find someone who can give the correct explanation. Not students. Not colleagues. Not APOD editors. He wonders how the astute readers of APOD will do. Can you match wits with Professor Lewin?

A Strange Streak Imaged in Australia
6.12.2004

Meteor experts don't think it's a meteor. Atmospheric scientists don't think it's lightning. The photographer insists that the streak and flash on the above image has not been created digitally. So what is it? Nobody is sure.

Leonid Meteors in 2002
18.11.2002

All during today, APOD will be posting the best images of the Leonid Meteor Shower as seen by the wide-angle digital cameras perched around the world as part of the Night Sky Live (NSL) Project. The main APOD site will be updated several times with topical information and new images.

The Gegenschein
25.12.2006

If you look carefully enough, you can even see the glow of the Sun in the opposite direction. At night this glow is known as the gegenschein (German for "counter glow"), and can be seen as a faint glow in an extremely dark sky. The gegenschein is sunlight back-scattered off small interplanetary dust particles.

Lunation
5.02.2012

Our Moon's appearance changes nightly. This time-lapse sequence shows what our Moon looks like during a lunation, a complete lunar cycle. As the Moon orbits the Earth, the half illuminated by the Sun first becomes increasingly visible, then decreasingly visible. The Moon always keeps the same face toward the Earth.

Upgrading the International Space Station
24.12.2006

The International Space Station (ISS) will be the largest human-made object ever to orbit the Earth. The station is so large that it could not be launched all at once -- it is being built piecemeal with large sections added continually by flights of the Space Shuttle.

Comet NEAT Approaches the Sun
9.02.2003

A comet may likely become visible to the unaided eye over the next few days above the horizon where the Sun has just set. Comet NEAT (C/ 2002 V1), discovered last November, has brightened dramatically as it approached the Sun.

Dumbbell Nebula Close Up from Hubble
10.02.2003

What causes unusual knots of gas and dust in planetary nebulas? Seen previously in the Ring Nebula, the Helix Nebula, and the Eskimo Nebula, the knots' existence was not predicted previously and still not well understood.

A Year of New Perspectives
27.12.1999

Fittingly, 1999 saw a decade of astronomical discoveries to an end with portents of things to come - embodied in new spacecraft, telescopes, and perspectives to explore the distant Universe across the electromagnetic spectrum. X-ray astronomy in particular will likely flourish in coming

I Brought You the Moon
31.03.2018

I love you so much that I brought you the Moon. Please take it before this tree becomes more interested. Also the Moon is heavier than I thought. And I foolishly picked it up by the hot side by mistake. But it is for you and, well, the others reading this APOD.