A Tale of Comet Holmes
10.11.2007

A beautiful blue ion tail has become visible in deep telescopic images of Comet Holmes. Pointing generally away from the Sun and also planet Earth, the comet's ion tail is seriously foreshortened by our extreme viewing angle.

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.

Earth's Plasmasphere
31.01.2001

Our Earth is surrounded by plasma. The overall shape that this ionized gas plasmasphere takes was discovered last year by NASA's robot IMAGE spacecraft, and shown in the recently released above image in ultraviolet light.

The Witch Head Nebula
27.02.2001

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.

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
29.12.2003

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
15.01.2002

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
2.03.1999

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
17.04.2023

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.