M15: Dense Globular Star Cluster
4.08.2000

Life might get dull at the core of M15 but the sky would always be bright with stars! In fact, only 40,000 light-years away in the constellation Pegasus, M15 is one of the most densely packed globular star clusters in our Milky Way Galaxy.

Flying Over the Columbia Hills of Mars
19.05.2008

What it would be like to fly over Mars? Combining terrain data from the orbiting Mars Global Surveyor spacecraft (now dormant) with information about the robotic Spirit rover currently rolling across Mars has resulted in a digital movie that shows what a flight over the Columbia Hills might look like.

Sharpless 249 and the Jellyfish Nebula
7.03.2019

Normally faint and elusive, the Jellyfish Nebula is caught in this alluring telescopic field of view. The entire scene is a two panel mosaic constructed using narrowband image data, with emission from sulfur, hydrogen and oxygen atoms shown in red, green and blue hues.

In, Through, and Beyond Saturn's Rings
4.04.2021

Four moons are visible on the featured image -- can you find them all? First -- and farthest in the background -- is Titan, the largest moon of Saturn and one of the larger moons in the Solar System. The dark feature across the top of this perpetually cloudy world is the north polar hood.

Abell 1795: A Galaxy Cluster s Cooling Flow
8.12.2000

Throughout the Universe, galaxies tend to swarm in groups ranging from just a handful of members to casts of thousands. Astronomers have realized since the early 1970s that the larger swarms, immense clusters of galaxies millions of light-years across, are immersed within tenuous clouds of hot gas which glow strongly in x-rays.

Simulation: Two Black Holes Merge
14.04.2019

Sit back and watch two black holes merge. Inspired by the first direct detection of gravitational waves in 2015, this simulation video plays in slow motion but would take about one third of a second if run in real time.

APOD: 2025 June 3 Б Rainbow Airglow over the Azores
3.06.2025

Why would the sky glow like a giant repeating rainbow? Airglow. Now, air glows all of the time, but it is usually hard to see. A disturbance however -- like an approaching storm -- may cause noticeable rippling in the Earth's atmosphere.

Young Star Clusters in an Old Galaxy
4.07.2002

Elliptical galaxy NGC 4365 is old, probably about 12 billion years old. Like most elliptical galaxies, this galaxy was thought to be full of old stars too, its burst of star forming activity having long since ended.

Bright Stars, Dim Galaxy
14.10.1996

These two clusters of bright, newly formed stars surrounded by a glowing nebula lie 10 million light years away in the dim, irregular galaxy cataloged as NGC 2366. The Hubble Space Telescope image shows...

Galaxy Einstein Ring
20.04.2016

Can one galaxy hide behind another? Not in the case of SDP.81. Here the foreground galaxy, shown in blue in an image taken by the Hubble Space Telescope, acts like a huge gravitational...