Astronomy Picture of the Day
    


Curious Cometary Knots in the Helix Nebula
<< Yesterday 13.04.2008 Tomorrow >>
Curious Cometary Knots in the Helix Nebula
Credit & Copyright: C. R. O'Dell and K. Handron (Rice University), NASA
Explanation: What causes unusual knots of gas and dust in planetary nebulas? Seen also in the Ring Nebula, the Dumbbell Nebula and the Eskimo Nebula, the knots' existence was not initially predicted and their origins are still not well understood. Pictured above is a fascinating image of the Helix Nebula by the Hubble Space Telescope showing tremendous detail of its mysterious gaseous knots. The above cometary knots have masses similar to the Earth but have radii typically several times the orbit of Pluto. One hypothesis for the fragmentation and evolution of the knots includes existing gas being driven out by a less dense but highly energetic stellar wind of the central evolving star. The Helix Nebula is the closest example of a planetary nebula created at the end of the life of a Sun-like star. The Helix Nebula, given a technical designation of NGC 7293, lies about 700 light-years away towards the constellation of Aquarius.


January
February
March
April
May
June
July
August
September
October
November
December
 < April 2008  >
Mo Tu We Th Fr Sa Su

123456
78910111213
14151617181920
21222324252627
282930



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: LHEA at NASA / GSFC
& Michigan Tech. U.

Based on Astronomy Picture Of the Day

Publications with keywords: Helix Nebula - HST
Publications with words: Helix Nebula - HST
See also:
All publications on this topic >>