Astronomy Picture of the Day

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

October 23, 1995
See Explanation.  Clicking on the picture will download 
 the highest resolution version available.
Gamma-Ray Quasars
Credit: NASA, CGRO, EGRET team.

Explanation: Gamma rays are more than 10,000 times more energetic than visible light. If you could "see" gamma rays, the night sky would seem very different indeed. The bright object in the center of the false color gamma-ray image above is quasar 3C279, a nondescript, faint, starlike object in the visible sky. Yet, in June of 1991 a gamma-ray telescope onboard NASA's orbiting Compton Gamma Ray Observatory unexpectedly discovered that it was one of the brightest objects in the gamma-ray sky. Shortly after this image was recorded the quasar faded from view at gamma-ray energies. Astronomers are still trying to understand what causes these enigmatic objects to flare so violently. Another quasar, 3C273, is faintly visible above and to the right of center.

Tomorrow's picture: A Total Solar Eclipse

| Archive | Glossary | Education | About APOD |
Top 5 logo Best pick logo Cool NASA site logo

Authors & editors: Robert Nemiroff (GMU) & Jerry Bonnell (USRA).
NASA Technical Rep.: Sherri Calvo. Specific rights apply.
A service of: LHEA at NASA/ GSFC