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New Findings Could Dash Hopes for Past Oceans on Mars
In article ,
Eric Crew writes: Only a minority of planetary nebulae are like small rings or disks - brightly glowing shells of gas, as C E R Bruce discovered many years ago. Most are more like small galaxies with spiral shapes and arms - generally two or four. Could you post the names of a few examples of PN that look "like small galaxies with spiral shapes and arms?" -- Steve Willner Phone 617-495-7123 Cambridge, MA 02138 USA (Please email your reply if you want to be sure I see it; include a valid Reply-To address to receive an acknowledgement. Commercial email may be sent to your ISP.) |
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In sci.astro Steve Willner wrote:
In article , Eric Crew writes: Only a minority of planetary nebulae are like small rings or disks - brightly glowing shells of gas, as C E R Bruce discovered many years ago. Most are more like small galaxies with spiral shapes and arms - generally two or four. Could you post the names of a few examples of PN that look "like small galaxies with spiral shapes and arms?" Have a look at NGC 4361 - I'm pretty sure that's the one that a Famous Astronomer mistook for a Virgo-cluster galaxy in a classification assignment based on Crossley plates, about 20 years ago. Pretty convincingly like a Seyfert galaxy, even - bright, very pointlike nucleus and dim spiral features. These are much less tightly wraped than the features in NGC 6543 (from the famous Hubble images). Bill Keel |
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In article ,
"William C. Keel" writes: Have a look at NGC 4361 - I'm pretty sure that's the one that a Famous Astronomer mistook for a Virgo-cluster galaxy in a classification assignment based on Crossley plates, about 20 years ago. There's a nice picture at http://crux.astr.ua.edu/goodies/misc...s/ngc4361h.gif although the caption gives a somewhat different slant on the story. Of course both could be true: Famous Astronomer gets fooled, then sees how many students fall into the same trap. A color image at http://www.3towers.com/ngcB.htm shows that the gas is brightest in the green [O III] lines. Pretty convincingly like a Seyfert galaxy, even - bright, very pointlike nucleus and dim spiral features. These are much less tightly wraped than the features in NGC 6543 (from the famous Hubble images). Based on the image, it looks like the bulk of the gas is in the (apparently) spherically symmetric shell, but I see what you mean about the spiral features. Very nice! -- Steve Willner Phone 617-495-7123 Cambridge, MA 02138 USA (Please email your reply if you want to be sure I see it; include a valid Reply-To address to receive an acknowledgement. Commercial email may be sent to your ISP.) |
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In sci.astro Steve Willner wrote:
In article , "William C. Keel" writes: Have a look at NGC 4361 - I'm pretty sure that's the one that a Famous Astronomer mistook for a Virgo-cluster galaxy in a classification assignment based on Crossley plates, about 20 years ago. There's a nice picture at http://crux.astr.ua.edu/goodies/misc...s/ngc4361h.gif although the caption gives a somewhat different slant on the story. Of course both could be true: Famous Astronomer gets fooled, then sees how many students fall into the same trap. They should be the same story, if one notices where the picture is from... Bill Keel |
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In sci.astro Steve Willner wrote:
In article , "William C. Keel" writes: Have a look at NGC 4361 - I'm pretty sure that's the one that a Famous Astronomer mistook for a Virgo-cluster galaxy in a classification assignment based on Crossley plates, about 20 years ago. There's a nice picture at http://crux.astr.ua.edu/goodies/misc...s/ngc4361h.gif although the caption gives a somewhat different slant on the story. Of course both could be true: Famous Astronomer gets fooled, then sees how many students fall into the same trap. They should be the same story, if one notices where the picture is from... Bill Keel |
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