A photograph of the Crab Nebula did create a "wow" moment in my head, but I
only got to see it as I was finishing up my PhD long after having decided on
a science career.
I have two "astromurals" purchased from Edmond Scientific Company back in
1968 (and designated by them as C-1 and C-2). C-1 shows the Crab Nebula as
photographed by the Hale (200") telescope with a 4 hour exposure. C-2 shows
the Veil Nebula as photographed by the Schmidt (48") telescope. Both
pictures were taken by William C. Miller and measure, approximately, 2' x
3'. I liked these pictures so much that they were given to me as a
graduation present by my brother who also made two very nice wood frames for
them. Later on I kept them in my office at work (after my wife finally
tired of displaying them in our home family room - too many questions by
quests). It would be interesting to measure the expansion rate of the Crab
Nebula from the time of the astromural picture (not sure of the precise
year, but on, or before, 1968), but not sure if this is feasible with
pictures in such different formats. Also, although state of the art at the
time, the resolution of the astromural picture is so much poorer than either
of the modern pictures below that it would be very difficult to compare
similar features even if reduced to the same format. The literature which
came with the Crab Nebula astromural says that the expansion rate was about
70 million miles per day. The Veil Nebula literature says that the initial
gas velocity was about 5000 miles per second 50,000 years ago, appears to be
slowing down, and the Veil Nebula will probably fade from site in another
25,000 years. No word on when the Crab Nebula will fade from site!
Don
Dr. Donald G. Polvani
Retired
Adjunct Faculty, Physics
Anne Arundel Community College
Arnold, MD 21012
-----Original Message-----
From: Phys-l [mailto:phys-l-bounces@phys-l.org] On Behalf Of Bill Nettles
Sent: Tuesday, August 06, 2013 12:49 PM
To: Phys-L@Phys-L.org
Subject: [Phys-L] Crab Nebula expansion
For those who can fit it into the busy semester, here's something that might
create one of the "wow" moments in some student's head and they decide they
want to "do" science. It compares a 20th century photo with a 2012 photo.
Notice the stars are fixed, but the gas tendrils in the Crab aren't. Given
the diameter of the Crab, some eager students could give an estimate of the
speed of the gas (with uncertainties, of course!). http://vimeo.com/71117055
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