M20 - Trifid Nebula
Messier 20 or M20 (also designated NGC 6514) is a nebula and star cluster in the constellation Sagittarius. It has an apparent visual magnitude of 9 and its angular diameter is 28 arc-minutes. M20 lies at an estimated distance of 5200 light years. The Equinox 2000 coordinates are RA= 18h 02.6m, Dec= -23° 02´ which makes M20 best seen during the summer. The Messier Summer Star Chart shows the position of all Messier objects visible during that season. As one of the more famous objects in the Messier Catalog, it is commonly known as the Trifid Nebula.
The image above shows the uncropped view of M20 through the Takahashi E-180 Astrograph (North is to right). A 3x enlargement of this image appears to the right.
This nebula and star cluster were discovered by Messier in 1764 although he failed to detect the nebulosity. The Trifi Nebula is remarkable for the three-lobed appearance of its hydrogen emission nebula as well the nearby blue reflection nebula. According to Kharchenko et al. (2005), the distance of M20 is 2660 light years and its diameter is 15 light years. It contains >120 stars and its estimated age is 0.3-0.4 million years.
Messier's Description of M20
June 5, 1764
`Cluster of stars, a little above the Ecliptic, between the bow of Sagittarius and the right foot of Ophiuchus. Reviewed on March 22, 1781.' [see also description of M21]
- Object: M20
- Other Names: NGC 6514, Trifid Nebula
- Object Type: nebula and star cluster
- Object Data: Apparent Magnitude = 9, Angular Size = 28 arc-minutes
- Object Position (Equinox 2000): RA= 18h 02.6m, Dec= -23° 02´, Constellation = Sagittarius
- Date/Time: 2011 Aug 02 at 06:33 UTC
- Location: Bifrost Astronomical Observatory, Portal, AZ
- Mount: Astro-Physics 1200GTO
- Telescope: Takahashi Epsilon 180 Hyperbolic Astrograph
- Camera: Canon EOS 550D (Rebel T2i) (modified with a Baader UV/IR filter)
- Field of View: 1.70° x 2.56° at 1.7 arc-sec/pixel (web version: 10.0 arc-sec/pixel)
- Exposure: 4 x 300s, f/2.8, ISO 800
- File Name: M20-01w.jpg
- Processing (Adobe Camera Raw): Graduated Filter, Vignetting Correction, Noise Reduction, White Balance, Curves
- Processing (Photoshop CS5): Average Images, Curves, Noise Reduction
- Original Image Size: 3454 × 5179 pixels (17.9 MP); 11.5" x 17.3" @ 300 dpi
- Rights: Copyright 2011 by Fred Espenak. All Rights Reserved. See: Image Licensing.