Mars in the Loop
30.05.2025

This composite of images spaced a weather-permitting 5 to 9 days apart, from 2024 September 19 (top right) through 2025 May 18 (bottom left), faithfully traces ruddy-colored Mars as it makes a clockwise loop through the constellations Gemini and Cancer in planet Earth's night sky.

Sunspots and Solar Active Regions
1.08.2002

July was a good month for sunspots ... really big sunspots. In fact, the full disk and inset pictures above show three large groups of spots, photographed only a few days ago on July 28. Together the sunspots span a region about thirty times the diameter of planet Earth.

Lunar Prospects
18.09.1998

Launched on January 6th, NASA's Lunar Prospector spacecraft has been exploring the Moon with instruments designed to sense global properties while orbiting pole-to-pole, 63 miles above the lunar surface. Now over half...

Recurrent Nova RS Ophiuci
24.02.2006

This pretty star field in the constellation Ophiucus is centered on a star not often seen - RS Ophiuci. In fact, early last week RS Oph suddenly became visible to the naked eye for the first time since 1985.

Spacecrafts Streak Over Colorado
14.03.2011

Have you ever seen a "star" drifting slowly overhead, but not known what it was? Sometimes even pointing it out to friends or family will only lead to a shrug. What you are seeing...

Mars in the Loop
9.08.2012

This composite of images spaced some 5 to 7 days apart from late October 2011 (top right) through early July 2012 (bottom left), traces the retrograde motion of ruddy-colored Mars through planet Earth's night sky.

The Tarantula Nebula
26.02.2016

The Tarantula Nebula is more than a thousand light-years in diameter, a giant star forming region within nearby satellite galaxy the Large Magellanic Cloud, about 180 thousand light-years away. The largest, most violent star...

APOD: 2023 September 6 Б HESS Telescopes Explore the High Energy Sky
6.09.2023

They may look like modern mechanical dinosaurs, but they are enormous swiveling eyes that watch the sky. The High Energy Stereoscopic System (H.E.S.S.) Observatory is composed of four 12-meter reflecting-mirror telescopes surrounding a larger telescope housing a 28-meter mirror.

Gamma Ray Moon
17.04.1999

What if you could see gamma rays (photons with more than 40 million times the energy of visible light)? If you could, the Moon would appear brighter than the Sun! This startling notion...

Unexplained Dimmings in KIC 8462852
13.06.2016

Why does star KIC 8462852 keep wavering? Nobody knows. A star somewhat similar to our Sun, KIC 8462852 was one of many distant stars being monitored by NASA's robotic Kepler satellite to see if it had planets.