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.

July 23, 1995
See Explanation.  Clicking on the picture will download 
 the highest resolution version available.
M20: The Trifid Nebula
Credit: Hopkins Observatory, Karen Gloria

Explanation: The vivid blue and violet colors present in the Trifid Nebula result from the abundance of young stars there. The light from young massive stars is quite blue and has the ability to remove electrons from surrounding gas. When these electrons re-combine with the gas, radiation rich in blue and violet light is emitted. Some of the nebula's light also results from the reflection of star light off of extremely small carbon specks known as 'dust'. This object is known to astronomers as M20 - the twentieth object on Charles Messier's list of diffuse sky objects. This image was taken with a 6-inch refracting telescope.

For more information on M20 see The Electronic Universe Project's write-up.

Many images of Messier objects can be found in The Electronic Universe Project's The Galaxy Gallery: Messier Objects.

Tomorrow's picture: M31: The Andromeda Galaxy

We keep an archive of Astronomy Pictures of the Day.
Astronomy Picture of the Day is created by Robert Nemiroff and Jerry Bonnell who are solely responsible for its content.