A Green Flash from the Sun
4.06.2014

Many think it is just a myth. Others think it is true but its cause isn't known. Adventurers pride themselves on having seen it. It's a green flash from the Sun. The truth is the green flash does exist and its cause is well understood.

APOD: 2023 December 12 Б Aurora and Milky Way over Norway
12.12.2023

What are these two giant arches across the sky? Perhaps the more familiar one, on the left, is the central band of our Milky Way Galaxy. This grand disk of stars and nebulas here appears to encircle much of the southern sky.

Spiral Meteor through the Heart Nebula
5.09.2016

What is this meteor doing? Dynamically, the unusually short and asymmetric train may indicate that the sand-sized grain at the center of the glow is momentarily spinning as it ablates, causing its path to be slightly spiral.

Night Glows
18.04.2017

What glows in the night? This night, several unusual glows were evident -- some near, but some far. The foreground surf glimmers blue with the light of bioluminescent plankton. Next out, Earth's atmosphere dims the horizon and provides a few opaque clouds. Further out, the planet Venus glows bright near the image center.

Moonrise Through Mauna Keas Shadow
5.12.2010

How can the Moon rise through a mountain? It cannot -- what was photographed here is a moonrise through the shadow of a large volcano. The volcano is Mauna Kea, Hawai'i, USA, a frequent spot for spectacular photographs since it is arguably the premier observing location on planet Earth.

Compton Reentry
3.06.2000

Nine years ago the massive Compton Gamma Ray Observatory, the second of NASA's space-based great observatories, was deployed in low earth orbit. Lofted above the protective atmosphere, Compton's instruments could explore the extreme high-energy Universe in gamma rays -- photons with 100,000 times or more the energy of visible light.

Quadrantid Meteors through Orion
20.01.2020

Why are these meteor trails nearly parallel? Because they were all shed by the same space rock and so can be traced back to the same direction on the sky: the radiant of the Quadrantid Meteor Shower.

Colorful Aurora over Iceland
6.03.2017

You don't always see a scene this beautiful when you hike to an ancient volcano -- you have to be lucky. When the astrophotographer realized that aurora were visible two-weeks ago, he made a night-time run for the top of the caldera to see if he could capture them also reflected in the central lake.

Strawberry to Honey Moonrise
25.06.2016

Near the horizon the Full Moon often seems to loom large, swollen in appearance by the famous Moon illusion. But timelapse images demonstrate that the Moon's apparent size doesn't really change as it climbs toward the zenith. Its color does, though.

Orion's Horsehead Nebula
2.10.1996

The Horsehead Nebula is arguably the most famous nebula on the sky. It is visible as the black indentation to the red emission nebula seen just to the right of center of the above photograph. The bright star near the center is located in the belt of the familiar constellation of Orion.