Astronomy Picture of the Day

Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.

2006 July 10
See Explanation.  Clicking on the picture will download
 the highest resolution version available.

Dark Sun Sizzling
Credit: TRACE Project, Stanford-Lockheed Institute for Space Research, NASA

Explanation: Is this our Sun? Yes. Even on a normal day, our Sun is sizzling ball of seething hot gas. Unpredictably, regions of strong and tangled magnetic fields arise, causing sunspots and bright active regions. The Sun's surface bubbles as hot hydrogen gas streams along looping magnetic fields. These active regions channel gas along magnetic loops, usually falling back but sometimes escaping into the solar corona or out into space as the solar wind. Pictured above is our Sun in three colors of ultraviolet light. Since only active regions emit significant amounts of energetic ultraviolet light, most of the Sun appears dark. The colorful portions glow spectacularly, pinpointing the Sun's hottest and most violent regions. Although the Sun is constantly changing, the rate of visible light it emits has been relatively stable over the past five billion years, allowing life to emerge on Earth.

Tomorrow's picture: saturn sideways

< | Archive | Index | Search | Calendar | Glossary | Education | About APOD | Discuss | >

Authors & editors: Robert Nemiroff (MTU) & Jerry Bonnell (USRA)
NASA Web Site Statements, Warnings, and Disclaimers
NASA Official: Jay Norris. Specific rights apply.
A service of: EUD at NASA / GSFC
& Michigan Tech. U.