Celestial hemisphere:  Southern  ·  Constellation: Canis Major (CMa)  ·  Contains:  16 omi01 CMa  ·  The star ο1CMa
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Sh2-308 - 2021, Gary Imm
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Sh2-308 - 2021

Getting plate-solving status, please wait...
Sh2-308 - 2021, Gary Imm
Powered byPixInsight

Sh2-308 - 2021

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Description

This object is a Wolf-Rayet emission nebula located 3000 light years away in the constellation of Canis Major at a declination of -24 degrees. Its nature is a bit different than the classic planetary nebula, though most people call it a planetary nebula anyway. The nebula spans 45 arc-minutes in our apparent view and is 40 light years in diameter.

The nebula is being blown out by fast winds from a hot huge 6.8 magnitude Wolf-Rayet star (HD 50896), the bright blue star near the center of the nebula. Wolf-Rayet stars have over 20 times the mass of our Sun and are thought to be in a brief, pre-supernova phase. The gas in this nebula is primarily oxygen gas, which not only forms the object but permeates the background sky of the image.

Although the nebula is roughly spherical, it is elongated along an axis that runs from bottom left to top right of the image. This is likely due to bi-polar gas expulsion from the opposite stellar poles.

My favorite part of this object, aside from the overall shape, is how the oxygen nebula is slightly larger in diameter than the hydrogen nebula. This is seen in the image where the white nebula surfaces at top and bottom right sit slightly inside the cyan oxygen surface.

The bright 3.9 magnitude red supergiant star is Omicron Canis Majoris (HD 50877). The distance estimates to it are uncertain, so it is not clear whether this star is in front of or behind the nebula. This cool (4000 K) star is about 8 times as massive as our Sun, 280 times its diameter, and shines with 16,000 times its luminosity.

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