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...

APOD: 2025 June 3 Б Rainbow Airglow over the Azores
2.06.2025

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.

Thirteen Million Kilometers from Comet Tempel 1
29.06.2005

The Deep Impact spacecraft continues to close on Comet Tempel 1, a comet roughly the size of Manhattan. Early on July 3 (EDT), the Deep Impact spacecraft will separate in to two individual robotic spaceships, one called Flyby and the other called Impactor.

Phi Persei: Double Star
2.10.1999

It's clear who is the biggest star in this binary system. Based on recent results, this artist's vision of the double star Phi Persei, 720 light years away, shows a bright, rapidly rotating massive star surrounded by a disk of gas. A small companion star orbits 100 million miles away.

Target Crater Cabeus
8.10.2009

About 100 kilometers from the Moon's South Pole, 100 kilometer wide crater Cabeus is the target for two LCROSS mission spacecraft on course to impact the Moon tomorrow. The shadowed crater is strongly foreshortened in this mosaic, a representative view of the region for earthbound telescopes.

Along the Western Veil
18.09.2019

Delicate in appearance, these filaments of shocked, glowing gas, are draped across planet Earth's sky toward the constellation of Cygnus. They form the western part of the Veil Nebula. The Veil Nebula itself is a large supernova remnant, an expanding cloud born of the death explosion of a massive star.

The Colors of Comet Hyakutake
28.03.1996

The colors of Comet Hyakutake are caused by the action of sunlight on the dust and gas produced by the warming nucleus. The microscopic dust particles reflect sunlight while the sun's ultraviolet radiation excites and ionizes the gas molecules causing them to glow or fluoresce in a range of visible colors.