M20 (NGC 6514) "Trifid Nebula"
Mag. - 6.3
Constellation - Sagittarius
Location - R.A. 18:02.3, Dec. -23.02
Size - 30 light years across,
Distance - 6.700 light years [Kepple & Sanner, Night Sky
Observers Guide],
This combination emission and reflection nebula
is a showpiece of the summer Milky Way. M20 can be easily spotted as a
patch of nebulosity and stars with binoculars. The dust lanes which
inspired its name are visible with medium size amateur telescopes of 8 to 10
inch aperture.
M20, also known as the Trifid Nebula, was first observed by Le Gentil in
1747 and was subsequently "rediscovered" by Messier in June
1764. Burnhams Celestial Handbook reports that John Herschel was
probably the first to call M20 the Trifid Nebula and described it as
"consisting of 3 bright and irregularly formed nebulous masses..."
When photographed, M20 is seen to be made up of two separate components, the lower half which contains
the conspicuous dust lanes is an emission nebula which glows with the
characteristic pink of H II emissions. The less conspicuous blue colored reflection nebula
is interstellar dust which reflects light from the bright
stars.
This image was selected as
Astronomy
Picture of the Day for May 26, 2005.
