STS 1: First Shuttle Launch
12.04.2001

On April 12, 1981, twenty years ago today, the Space Shuttle Columbia became the first shuttle to orbit the Earth. In this gorgeous time exposure, flood lights play on the Columbia and service structures (left) as it rests atop Complex 39's Pad A at Kennedy Space Center in preparation for first launch.

The Farthest Explosion Yet Measured
19.10.2000

It happened so far away that common human distance measures are inadequate to describe it. Furthermore, astronomers do not even claim to know exactly what happened. What is known is that satellites across our Solar System reported on 2000 January 31 a tremendous explosion of gamma rays had occurred towards some previously uninteresting direction.

Mars: Just The Facts
27.06.1997

Mars, the freeze-dried planet, orbits 137 million miles from the Sun or at about 1.5 times the Earth-Sun distance. It has two diminutive moons, towering extinct volcanos, an immense canyon system, a thin atmosphere...

A Telescopic View of Erupting Comet Holmes
28.10.2007

What's happened to Comet Holmes? A normally docile comet discovered over 100 years ago, Comet 17P/Holmes suddenly became nearly one million times brighter last week, possibly over just a few hours. In astronomical...

Stickney Crater
6.11.2009

Stickney Crater, the largest crater on the martian moon Phobos, is named for Chloe Angeline Stickney Hall, mathematician and wife of astronomer Asaph Hall. Asaph Hall discovered both the Red Planet's moons in 1877.

The W in Cassiopeia
17.03.2016

A familiar, zigzag, W pattern in northern constellation Cassiopeia is traced by five bright stars in this colorful and broad mosaic. Stretching about 15 degrees across rich starfields, the celestial scene includes dark clouds, bright nebulae, and star clusters along the Milky Way. In yellow-orange hues Cassiopeia's alpha star Shedar is a standout though.

The Tarantula Nebula
15.11.2017

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...

The Long Gas Tail of Spiral Galaxy D100
27.01.2019

Why is there long red streak attached to this galaxy? The streak is made mostly of glowing hydrogen that has been systematically stripped away as the galaxy moved through the ambient hot gas in a cluster of galaxies. Specifically, the galaxy is spiral galaxy D100, and cluster is the Coma Cluster of galaxies.

Julius Caesar and Leap Days
28.02.2020

In 46 BC Julius Caesar reformed the calendar system. Based on advice by astronomer Sosigenes of Alexandria, the Julian calendar included one leap day every four years to account for the fact that an Earth year is slightly more than 365 days long.

APOD: 2023 July 5 Б A Map of the Observable Universe
4.07.2023

What if you could see out to the edge of the observable universe? You would see galaxies, galaxies, galaxies, and then, well, quasars, which are the bright centers of distant galaxies. To expand understanding...