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 7, 1998
See Explanation.  Clicking on the picture will download 
 the highest resolution version available.

COBE Hotspots: The Oldest Structures Known
Credit: DMR, COBE, NASA, Two-Year Sky Map

Explanation: Above is a microwave image of the entire sky. The plane of our galaxy runs horizontally through the center. This historic all-sky map is based on the first two years of data from NASA's COsmic Background Explorer (COBE) satellite. After computer processing to remove contributions from nearby objects and the effects of the earth's motion, the map shows temperature variations in the early Universe as red "spots". These spots are the oldest, most distant structures known. As our Universe expanded and cooled, conglomerations of mass formed. The COBE images confirm that only a million years after the big-bang - which occurred roughly 15 billion years ago - parts of the universe were visibly hotter than other parts. By studying the size and distribution of the spots found with COBE and future missions, astronomers hope to learn what matter and processes caused the spots to form - and hence determine the composition, density, and future of our Universe.

Tomorrow's picture: M1: Filaments of the Crab Nebula

< 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.