Retrograde Mars
11.05.2008

Why would Mars appear to move backwards? Most of the time, the apparent motion of Mars in Earth's sky is in one direction, slow but steady in front of the far distant stars. About every two years, however, the Earth passes Mars as they orbit around the Sun.

APOD: 2024 May 15 Б AR 3664 at the Suns Edge
15.05.2024

What did the monster active region that created the recent auroras look like when at the Sun's edge? There, AR 3664 better showed its 3D structure. Pictured, a large multi-pronged solar prominence...

APOD: 2025 October 5 Б A Long Storm System on Saturn
5.10.2025

It was one of the largest and longest lived storms ever recorded in our Solar System. First seen in late 2010, the featured cloud formation in the northern hemisphere of Saturn started larger than the Earth and soon spread completely around the planet.

Gamma Ray Sky Map
23.06.1995

What if you could "see" gamma rays? This computer processed image represents a map of the entire sky at photon energies above 100 million electron Volts. These gamma-ray photons are more than 40 million times more energetic than visible light photons and are blocked from the Earth's surface by the atmosphere.

Moons and Bright Mars
1.08.2003

In this serene view, the moons of Earth along with the bright planet Mars shine above the city of Turku near the southwestern tip of Finland. Of course Earth's large natural satellite, the Moon, at a distance of 400,000 kilometers, is by far the brightest object in this sky.

APOD: 2023 July 30 Б Spiral Aurora over Icelandic Divide
30.07.2023

Admire the beauty but fear the beast. The beauty is the aurora overhead, here taking the form of a great green spiral, seen between picturesque clouds with the bright Moon to the side and stars in the background.

Aurora Australis and the International Space Station
13.09.2024

This snapshot from the International Space Station was taken on August 11 while orbiting about 430 kilometers above the Indian Ocean, Southern Hemisphere, planet Earth. The spectacular view looks south and east, down toward the planet's horizon and through red and green curtains of aurora australis.

Moon Meets Mercury
9.05.2008

On Tuesday, May 6, while standing on planet Earth and sweeping your binoculars along the western horizon just after sunset, you might have encountered this arresting skyscape. The view features a slender crescent Moon and bright planet Mercury separated on the sky by only about 2 degrees.

Sakurajima Volcano with Lightning
11.03.2013

Why does a volcanic eruption sometimes create lightning? Pictured above, the Sakurajima volcano in southern Japan was caught erupting in early January. Magma bubbles so hot they glow shoot away as liquid rock bursts through the Earth's surface from below.

Springtime Comet Fever
20.03.1997

Today marks the Vernal Equinox, the first day of Spring for planet Earth's northern hemisphere. Despite recent attempts by other spectacular and dramatic celestial events to take center stage, Comet Hale-Bopp remains the most popular object in the sky (according to APOD access logs!) and is likely to make this spring memorable for many.