The nebula M20 in Sagittarius, also known as NGC 6514. It is a combined emission and reflection nebula, extending for nearly ½°. The Trifid takes its name from three dark lanes of dust that trisect it. It is centred on the multiple star HN 40, the brightest members of which evidently illuminate it. The Trifid lies 5000 l.y. away.
http://www.eso.org/public/images/eso0930a/http://www.spitzer.caltech.edu/images/1367-ssc2005-02a1-Visible-Light-Pictureof-the-Trifid-Nebula
- Watson, James Dewey (1928– )
- Watson, John Broadus (1878–1958)
- Watson, John Christian (1867–1941)
- Watson, Sir William
- Watson's test
- Watson-Watt, Sir Robert Alexander
- Watsuji Tetsuro (1889–1960)
- watt
- watt-hour
- watt-hour meter
- Watt, James
- Watt, James (1736–1819)
- wattmeter
- watt(symbol: W)
- Waucoban
- wave
- wave analyser
- wave base
- wave-built terrace
- wave clouds
- wave convergence
- wave-cut bench
- wave-cut platform
- wave depression
- wave diffraction