Artificial Night Sky Brightness
27.08.2001

Where have all the dim stars gone? From many places on the Earth including major cities, the night sky has been reduced from a fascinating display of hundreds of stars to a diffuse glow through which only a handful of stars are visible.

The Witch Head Nebula
28.12.2003

Double, double toil and trouble; Fire burn, and cauldron bubble -- maybe Macbeth should have consulted the Witch Head Nebula. This suggestively shaped reflection nebula is associated with the bright star Rigel in the constellation Orion.

Red Auroral Corona
14.01.2002

Few auroras show this level of detail. This unusual display of an auroral corona occurred on Earth three days after an unusual solar event -- the fifth most powerful explosion yet recorded on the Sun. An X14-class solar flare on April 15 sent a tremendous Coronal Mass Ejection (CME) into the Solar System.

The Kleinmann Low Nebula
1.03.1999

The most active part of the Orion Nebular Cloud Complex is an area known as the Kleinmann-Low Nebula. There, a cluster of young and forming stars is embedded in a molecular cloud filled with dust.

APOD: 2023 April 17 Б ELVES Lightning over Italy
16.04.2023

What's that red ring in the sky? Lightning. The most commonly seen type of lightning involves flashes of bright white light between clouds. Over the past 50 years, though, other types of upper-atmospheric lightning have been confirmed, including red sprites and blue jets.

Mystery Object Explained
28.09.1999

Explorers often discover the unexpected. Such was the case when the Second Palomar Observatory Sky Survey chanced upon the unusual object circled in the above photograph. The so-called mystery object appeared star-like but displayed colors unlike most stars or quasars.

The Witch Head Nebula
29.10.2015

Double, double toil and trouble; Fire burn, and cauldron bubble .... maybe Macbeth should have consulted the Witch Head Nebula. A suggestively shaped reflection nebula, this cosmic crone is about 800 light-years away though. Its frightening visage seems to glare toward nearby bright star Rigel in Orion, just off the right edge of this frame.

IC 2118: The Witch Head Nebula
26.12.2005

Double, double toil and trouble; Fire burn, and cauldron bubble -- maybe Macbeth should have consulted the Witch Head Nebula. This suggestively shaped reflection nebula is associated with the bright star Rigel in the constellation Orion.

Aurora Slathers up the Sky
28.07.2017

Like salsa verde on your favorite burrito, a green aurora slathers up the sky in this June 25 snapshot from the International Space Station. About 400 kilometers (250 miles) above Earth, the orbiting station is itself within the upper realm of the auroral displays.

Mercurys Sodium Tail
2.05.2022

That's no comet. Below the Pleiades star cluster is actually a planet: Mercury. Long exposures of our Solar System's innermost planet may reveal something unexpected: a tail. Mercury's thin atmosphere contains small amounts of sodium that glow when excited by light from the Sun.