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.

January 19, 1998
See Explanation.  Clicking on the picture will download 
 the highest resolution version available.

The Hubble 5 Planetary Nebula
Credit: B. Balick (U. Washington) et al., WFPC2, HST, NASA

Explanation: The Hubble Double Bubble Planetary Nebula is bubbling over with excitement. More mundanely known as Hubble 5, this bipolar planetary nebula is being created by a hot wind of particles streaming away from the central star system. The hot gas expands into the surrounding interstellar medium in a fashion similar to the inflation of hot air balloons. A supersonic shock-wave can form at the boundary, causing newly excited gas there to shine as electrons recombine with resident elements. In the above picture, colors are assigned according to the energy of the recombinant radiation. This star system lies about 2200 light-years from Earth, and likely includes a Sun-like star slowly transforming itself into a white dwarf.

Tomorrow's picture: Arachnoids on Venus

< 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.