Dolphin Head Nebula (M.J. Post)

Celestial hemisphere: Southern · Constellation: Canis Major (CMa) · Contains: 16 CMa) · The star Udra (ο1 CMa

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Dolphin Head Nebula

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Dolphin Head Nebula

This target is a bit more accessible from Dark Sky New Mexico than more northerly locations. I gathered 3.5 hours each H and O data using an 11" RASA scope. Here's the HOO result at half frame (~1.7 x 1 deg). I may add RGB stars at a later date. This image is NOT correctly oriented, but the Head is more obvious to me this way. Rotate 90 deg CW for correct orientation (north up, east to left). This object has a Sharpless designation (SH2-308) but there is not much organized hydrogen emission here. I suppose Stewart Sharpless was using an H-alpha filter on the Palomar scope in 1953 and may not not have been aware of the Dolphin Head in OIII. The Dolphin Head is about 4500 l.y. from Earth and 60 l.y. in diameter.

The Head surrounds a massive pre-supernova Wolf-Rayet star that ejected the oxygen gas we see 70,000 years ago when it was forming, and that is now ionizing it with strong UV output. Solar winds from this star are pushing outward at about 3.8 million mph! The W-R star is NOT the bright star near the periphery of the nebula, but instead the next brightest star more centrally located.
I was pleased to "discover" the planetary nebula PN G234.9-9.7 just below the neck of the Dolphin Head.

New Mexico Imagers

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Astrometry.net job	6839446
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