Eris: More Massive than Pluto
19.06.2007

Eris, a dwarf planet currently orbiting the Sun at about twice Pluto's distance, has been measured to have about 27 percent more mass than Pluto. The mass was calculated by timing the orbit of Eris' moon Dysnomia.

The Known Universe
19.01.2010

What would it look like to travel across the known universe? To help humanity visualize this, the American Museum of Natural History has produced a modern movie featuring many visual highlights of such a trip.

Comet Catalina Emerges
6.12.2015

Comet Catalina is ready for its close-up. The giant snowball from the outer Solar System, known formally as C/2013 US10 (Catalina), rounded the Sun last month and is now headed for its closest approach to Earth in January.

The View Toward M101
20.01.2016

Sweeping through northern skies, Comet Catalina (C/2013 US10) made its closest approach on January 17, passing about 6 light-minutes from our fair planet. Dust and ion tails clearly separated in this Earth-based view, the comet is also posed for a Messier moment, near the line-of-sight to M101, grand spiral galaxy in Ursa Major.

International Space Station Transits Saturn
21.01.2016

From low Earth orbit to the outer Solar System, this remarkable video frame composite follows the International Space Station's transit of Saturn. On January 15, the well-timed capture from a site near Dulmen, Germany required telescope and camera to be positioned along the predicted transit centerline, a path only 40 meters wide.

Milky Way over the Pinnacles in Australia
10.10.2020

What strange world is this? Earth. In the foreground of the featured image are the Pinnacles, unusual rock spires in Nambung National Park in Western Australia. Made of ancient sea shells (limestone), how these human-sized picturesque spires formed remains unknown.

Fireball over Lake Louise
11.10.2021

What makes a meteor a fireball? First of all, everyone agrees that a fireball is an exceptionally bright meteor. Past that, the International Astronomical Union defines a fireball as a meteor brighter than apparent magnitude -4, which corresponds (roughly) to being brighter than any planet -- as well as bright enough to cast a human-noticeable shadow.

APOD: 2024 July 17 Б Villarrica Volcano Against the Sky
16.07.2024

When Vulcan, the Roman god of fire, swings his blacksmith's hammer, the sky is lit on fire. A recent eruption of Chile's Villarrica volcano shows the delicate interplay between this fire -- actually...

Periodic Comet Swift Tuttle
7.08.2024

A Halley-type comet with an orbital period of about 133 years, Comet 109P/Swift-Tuttle is recognized as the parent of the annual Perseid Meteor Shower. The comet's last visit to the inner Solar System was in 1992.

APOD: 2025 January 15 Б Wolf Moon Engulfs Mars
14.01.2025

Does the Moon ever engulf Mars? Yes, but only in the sense that it moves in front, which happens on rare occasions. This happened just yesterday, though, as seen from some locations in North America and western Africa.