NanoSail D2
1.01.2026

In 2011, on January 20, NASA's NanoSail-D2 unfurled a very thin and very reflective 10 square meter sail becoming the first solar sail spacecraft in low Earth orbit. Often considered the stuff...

Announcing Comet Machholz
12.12.2004

A comet discovered only this summer is brightening quickly and already visible to the unaided eye. Comet C/2004 Q2 (Machholz) is currently best visible in Earth's Southern Hemisphere where some observers report it brighter than magnitude 5. The comet is moving rapidly to northern skies and should continue to brighten until early January.

NGC 4676: When Mice Collide
26.04.2009

These two mighty galaxies are pulling each other apart. Known as "The Mice" because they have such long tails, each spiral galaxy has likely already passed through the other. They will probably collide again and again until they coalesce.

A Dust Jet from the Surface of Comet 67P
5.11.2017

Where do comet tails come from? There are no obvious places on the nuclei of comets from which the jets that create comet tails emanate. Last year, though, ESA's Rosetta spacecraft not only imaged a jet emerging from Comet 67P/Churyumov-Gerasimenko, but flew right through it.

APOD: 2023 November 26 Б A Dust Jet from the Surface of Comet 67P
25.11.2023

Where do comet tails come from? There are no obvious places on the nuclei of comets from which the jets that create comet tails emanate. In 2016, though, ESA's Rosetta spacecraft not only imaged a jet emerging from Comet 67P/Churyumov-Gerasimenko, but flew right through it.

APOD: 2026 June 8 Б Comet R3 PanSTARRS Through Time
7.06.2026

What happens to a comet as it leaves our inner Solar System? Now, the arrival of a comet into the inner Solar System is typically heralded with great fanfare and high hopes that the comet will become bright and photogenic.

APOD: 2026 May 15 Б R3 PanSTARRS: An Orion Comet
14.05.2026

Comet R3 PanSTARRS might be best remembered as an Orion comet. A key reason is because Comet C/2025 R3 (PanSTARRS) was near its most spectacular -- in terms of tail visibility -- when passing in front of the iconic constellation.

Cometary Globule CG4
5.03.2015

The faint and somehow menacing cometary globule CG4 reaches through the center of this deep southern skyscape. About 1,300 light-years from Earth toward the constellation Puppis, its head is about 1.5 light-years in diameter and its tail about 8 light-years long.

NGC 4676: When Mice Collide
12.06.2004

These two mighty galaxies are pulling each other apart. Known as "The Mice" because they have such long tails, each spiral galaxy has likely already passed through the other. They will probably collide again and again until they coalesce.

Solar Sail
26.05.2000

Nearly 400 years ago astronomer Johannes Kepler observed comet tails blown by a solar breeze and suggested that vessels might likewise navigate through space using appropriately fashioned sails. It is now widely recognized that...