kaboom - expansion of the crab nebula

Hi,

Came across a couple of images of the crab nebula, taken with a similar filter (I need to research that more), but 40 years apart, 1951 (POSS I) and 1991 (POSS II).

I used a morphing program to simulate the expansion of the nebula over this time. While both images are allegedly of the same are and size the stars on the left do move, exagerrating the expansion on that side. You can also make out what I assume is the proper motion of a star in the top right corner.

www.irishastronomy.org/user_resources/fi...1097987164-crab2.swf 700kb. Sorry thats the smallest format i could do it in.

Next to work out the expansion rate.

Cheers,
~Al

p.s. I anyone knows of a good (preferably free) morphing program please let me know. I'm using shareware at the moment, but all only allow a morph of 2 images.

Why does that star move and all the others don't? surely if it was motion of a star then all the others would be moving? could it be something else?

Also, in the lower left of the image there is a long streak coming from a star?

Why does that star move and all the others don't? surely if it was motion of a star then all the others would be moving? could it be something else?

Also, in the lower left of the image there is a long streak coming from a star?

i think most of them are moving a small amount, if you look in the bottom left it seems more pronounced as you can see one star pass another. maybe the one in the top right is in the local neightbourhood whereas the others are farther away.
stephen.

Very cool "picture" Al!

Its pretty neat actually! To see the difference over time.

1 thing I would comment on that swiff movie is that all the stars seem to move in/out of allignment from the center of the picture. Seems to indicate that while the Crab Nebula has expanded over time, the second picture had a slightly larger magnification than the earlier picture - thus pronouncing the expansion that bit extra.

A cool set of pictures that sticks in my memory is of the star V838 in Monoceros. Hubble caught a few pictures of it showing how its light echo expanded over a period of just a few months in 2002!

V838 Monoceros

Its pretty amazing to see something so big expand so fast in such a short space of time!


Seanie.

Very cool stuff there Al !