Hot Gas and Dark Matter
4.04.1999

Is the gravity of the galaxies seen in this image high enough to contain the glowing hot gas? Superposed on an optical picture of a group of galaxies is an image taken in X-ray light.

APOD: 2025 July 1 Б Eye Sky a Dragon
1.07.2025

What do you see when you look into this sky? In the center, in the dark, do you see a night sky filled with stars? Do you see a sunset to the left? Clouds all around? Do you see the central band of our Milky Way Galaxy running down the middle?

Io: Moon Over Jupiter
20.04.2001

How big is the Jovian moon Io? The most volcanic body in the Solar System, Io (usually pronounced "EYE-oh") is 3,600 kilometers in diameter, about the size of planet Earth's single large natural satellite.

NGC 2787: A Barred Lenticular Galaxy
8.04.2002

Lenticular galaxies aren't supposed to be photogenic. Like spiral galaxies, they contain a disk, but like elliptical galaxies, they are usually short on dust, gas, and pretty spiral arms. Lenticulars are relatively little studied, possibly because of their seemingly benign nature. Famous galaxies historically classified as lenticular include M84, M85, and M86.

Saturn: Dirty Rings and a Clean Moon
6.06.2005

Eating surface ice from Enceladus might be healthier than eating ice from Saturn's rings -- it certainly appears cleaner. From their apparent densities and reflectance properties, both the rings of Saturn and its shiniest moon, Enceladus, are thought to be composed predominantly of water ice.

Spiral Galaxy NGC 2403 from Subaru
5.07.2006

Sprawling spiral arms dotted with bright red emission nebulas highlight this new and detailed image of nearby spiral galaxy NGC 2403. Also visible in the photogenic spiral galaxy are blue open clusters, dark dust lanes, and a bright but relatively small central nucleus.

The Dark Doodad Nebula
8.12.2008

What is that strange dark ribbon on the sky? When observing the great globular cluster NGC 4372, observers frequently take note of a strange dark streak nearly three degrees in length running near it. Unnamed, the streak, actually a long molecular cloud, has become known as the Dark Doodad Nebula.

Black Sun and Inverted Starfield
19.02.2017

Does this strange dark ball look somehow familiar? If so, that might be because it is our Sun. In the featured image from 2012, a detailed solar view was captured originally in a very specific color of red light, then rendered in black and white, and then color inverted.

Space Shuttle Rising
15.04.2018

What's that rising from the clouds? The space shuttle. Sometimes, if you look out the window of an airplane at just the right time and place, you see something unusual -- in this case a space shuttle launching to orbit.

A Partial Solar Eclipse Sequence Reflected
27.12.2019

What's happened to the Sun? Yesterday, if you were in the right place at the right time, you could see the Sun rise partially eclipsed by the Moon. The unusual sight was captured...