Colliding Supernova Remnants
2.10.1997

When a massive star exhausts its nuclear fuel it explodes. This stellar detonation, a supernova, propels vast amounts of starstuff outwards, initially at millions of miles per hour. For another 100,000 years...

Comet Hale-Bopp and the Dumbbell Nebula
20.02.1997

Comet Hale-Bopp is now slowly moving across the morning sky. During its trip to our inner Solar System, the comet passes in front of several notable objects. Here Comet Hale-Bopp was photographed on February 11th superposed nearly in front of the picturesque Dumbbell Nebula, visible on the upper right.

The Heart and Soul Nebulas
14.09.2008

Is the heart and soul of our Galaxy located in Cassiopeia? Possibly not, but that is where two bright emission nebulas nicknamed Heart and Soul can be found. The Heart Nebula, officially dubbed IC 1805 and visible in the above zoomable view on the right, has a shape reminiscent of a classical heart symbol.

A Roll Cloud Over Uruguay
5.01.2010

What kind of cloud is this? A roll cloud. These rare long clouds may form near advancing cold fronts. In particular, a downdraft from an advancing storm front can cause moist warm air to rise, cool below its dew point, and so form a cloud.

Saturns Hyperion: A Moon with Odd Craters
27.02.2011

What lies at the bottom of Hyperion's strange craters? Nobody's sure. To help find out, the robot Cassini spacecraft now orbiting Saturn swooped past the sponge-textured moon in 2005 and 2010 and took images of unprecedented detail.

A Huge Solar Filament Erupts
15.12.2010

Click the arrow and watch an unusually long filament explode out from the Sun. The filament had been seen hovering over the Sun's surface for over a week before it erupted earlier this month.

GOES 16: Moon over Planet Earth
26.01.2017

Launched last November 19 from Cape Canaveral Air Force Station, the satellite now known as GOES-16 can now observe planet Earth from a geostationary orbit 22,300 miles above the equator. Its Advanced Baseline Imager captured this contrasting view of Earth and a gibbous Moon on January 15.

APOD: 2026 January 26 Б NGC 55: A Galaxy of Nebulas
26.01.2026

Can you see nebulas in other galaxies? Yes, some nebulas shine brightly enough -- if you know how to look. Clouds of hydrogen and oxygen emit light at very specific colors, and by isolating them, astronomers and astrophotographers can reveal structures that would otherwise be too faint to notice.

A Day in the Life of a Human Sundial
12.08.2017

Have you ever wanted to be a gnomon? Of course, a gnomon is the tall part of a sundial that casts a shadow. The gnomon's shadow moves as the Sun moves across the sky, indicating time by the shadow's position on the dial face.

APOD: 2026 April 21 Б Three Sky Arches over Snowy Alps
21.04.2026

Why are there three arches across the sky instead of two? Last month, after being dropped off by a helicopter at a high mountain peak in the Alps near the Swiss Italian border, an adventurous astrophotographer expected two arches of our Milky Way galaxy to be visible during the night.