A Proton Aurora
17.12.2003

What are auroras made out of? Most auroras are caused by the solar wind exciting electrons that are funneled down the Earth's magnetic field. These electrons strike air molecules, liberating other electrons that glow when re-acquired.

A Yukon Aurora
8.10.2001

Last week was another good week for auroras. The story began about two weeks ago when two large Coronal Mass Ejections exploded off the Sun. Waves of elementary particles and ions swept out past the Earth on September 28 and 29, causing many auroras.

Hale-Bopp's Fickle Ion Tail
14.05.1997

What's happening to Comet Hale-Bopp's blue ion tail? The comet's ion tail is fluctuating more rapidly as it passes a region of changing solar wind. As the comet passes from north to south, it crosses the plane of the Sun's equator, where the solar magnetic field changes direction.

Unusual Auroras Over Saturns North Pole
19.11.2008

What's causing this unusual aurora over Saturn? No one is sure. Infrared images by the robotic Cassini spacecraft of the north pole of Saturn have uncovered aurora unlike any other seen previously in our Solar System.

The Earths Magnetic Field
25.11.2002

Why does the Earth have a magnetic field? The electrical conductivity of the molten plasma of the Earth's core should be able to damp the current magnetic field in only thousands of years. Yet our five billion year old Earth clearly causes magnets to point to (defined) north.

APOD: 2026 January 6 Б Jupiters Clouds in High Definition from Juno
6.01.2026

How complex is Jupiter? NASA's Juno mission to Jupiter is finding the Jovian giant to be more complicated than expected. Jupiter's magnetic field has been discovered to be much different from our Earth's simple dipole field, showing several poles embedded in a complicated network more convoluted in the north than the south.

Complex Jupiter
5.06.2018

How complex is Jupiter? NASA's Juno mission to Jupiter is finding the Jovian giant to be more complicated than expected. Jupiter's magnetic field has been discovered to be much different from our Earth's simple dipole field, showing several poles embedded in a complicated network more convoluted in the north than the south.

APOD: 2024 April 2 Б Detailed View of a Solar Eclipse Corona
2.04.2024

Only in the fleeting darkness of a total solar eclipse is the light of the solar corona easily visible. Normally overwhelmed by the bright solar disk, the expansive corona, the sun's outer atmosphere, is an alluring sight.

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: 2023 May 16 Б Total Eclipse: The Big Corona
16.05.2023

Most photographs don't adequately portray the magnificence of the Sun's corona. Seeing the corona first-hand during a total solar eclipse is unparalleled. The human eye can adapt to see coronal features and extent that average cameras usually cannot. Welcome, however, to the digital age.