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.

February 8, 1999
See Explanation.  Clicking on the picture will download 
 the highest resolution version available.

The Solar Wind Emerges
Credit: D. Hassler (SRI) et al., SOHO, ESA /NASA

Explanation: Winds of fast particles blow out from the Sun, but why? Astronomers came a step closer to answering this question recently by making detailed observations of the high-speed wind source with the space-borne Solar and Heliospheric Observatory (SOHO). Images like those shown above isolate regions of inflowing gas, shown in red, and outflowing gas, shown in blue. Particles such as electrons and protons flow out at speeds near 3 million kilometers per hour. This wind will typically enter one of the Sun's coronal holes before flowing out into the Solar System. Analysis indicates that the high-speed wind escapes at the edges of large convection cells, drawn in black. SOHO has recently been revived to run without the use of any orienting gyroscopes.

Tomorrow's picture: Supernova Star-field

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

Authors & editors: Robert Nemiroff (MTU) & Jerry Bonnell (USRA)
NASA Technical Rep.: Jay Norris. Specific rights apply.
A service of: LHEA at NASA/ GSFC
& Michigan Tech. U.