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What Process Gives the Helix Nebula its Apparent Pole-On-View Structure?

-- Richard | November 27, 2020

Question:

Astronomy Picture of the Day says this about NGC 7293: “The Helix Nebula is one of brightest and closest examples of a planetary nebula, a gas cloud created at the end of the life of a Sun-like star. The outer gasses of the star expelled into space appear from our vantage point as if we are looking down a helix.” And they are right. It does look like the star exploded in every direction, except towards earth. My guess is that we are facing one of the poles of the star and the rotation of the star imparted enough motion to the ejected material to open a hole in the nebula. Is that correct? Or is there another process at work that I’m not aware of?

Thanks!

-- Richard

Answer:

You are right in that the properties of the ejected material from the star and the fact that the star is surrounded by dense gas resulted in a bipolar lobe structure with holes at its poles. Our view of the star is toward one of those poles where the outflow from the star was able to more freely expand, leading to what appears to be a “hole” in the helical structure.

-- Jeff Mangum

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