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
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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

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.)

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

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