Astronomy From An F-18
28.01.2000

In an era of blossoming ground and space-based observatories, astronomers are also pushing the envelope with airborne instrumentation - successfully capturing an asteroid occultation from a high performance jet aircraft. This blinking animation represents...

Small Worlds Ceres and Vesta
22.06.2007

Ceres and Vesta are, respectively, only around 950 kilometers and 530 kilometers in diameter - about the size of Texas and Arizona. But they are two of the largest of over 100,000 minor bodies orbiting in the main asteroid belt between Mars and Jupiter.

Planetary Nebula Mz3: The Ant Nebula
26.04.2015

Why isn't this ant a big sphere? Planetary nebula Mz3 is being cast off by a star similar to our Sun that is, surely, round. Why then would the gas that is streaming away create an ant-shaped nebula that is distinctly not round?

The Lunar X
10.12.2016

The striking X appearing in this lunarscape is easily visible in binoculars or a small telescope. Yet, not too many have seen it. The catch is this lunar X is fleeting, only apparent in the hours before the Moon's first quarter phase.

NGC 3621: Far Beyond the Local Group
24.02.2017

Far beyond the local group of galaxies lies NGC 3621, some 22 million light-years away. Found in the multi-headed southern constellation Hydra, the winding spiral arms of this gorgeous island universe are loaded with luminous blue star clusters, pinkish starforming regions, and dark dust lanes.

M13: The Great Globular Cluster in Hercules
19.03.2020

In 1716, English astronomer Edmond Halley noted, "This is but a little Patch, but it shews itself to the naked Eye, when the Sky is serene and the Moon absent." Of course...

Saturn and Six Moons
6.07.2021

How many moons does Saturn have? So far 82 have been confirmed, the smallest being only a fraction of a kilometer across. Six of its largest satellites can be seen here in a composite...

APOD: 2025 August 14 Б M13: The Great Globular Cluster in Hercules
14.08.2025

In 1716, English astronomer Edmond Halley noted, "This is but a little Patch, but it shews itself to the naked Eye, when the Sky is serene and the Moon absent." Of course...

Simulated Supergiant Star
22.12.2000

Looking for that perfect holiday gift for an astronomer? Consider this "star in a box". Of course, the box is actually a computational box consisting of a three dimensional grid of points, and the star is a virtual one whose physical properties and internal dynamics are numerically simulated at the points on the grid.

Andromeda Island Universe
8.09.2000

How far can you see? The most distant object easily visible to the unaided eye is M31, the great Andromeda Galaxy some two million light-years away. Without a telescope, even this immense spiral galaxy appears as an unremarkable, faint, nebulous cloud in the constellation Andromeda