Starship Asterisk*

In 1919, Michelson and Pease used an interferometer on the 100-inch Mt. Wilson telescope to measure the diameter of the star alpha Orionis (Betelgeuse). See for example
http://planetquest.jpl.nasa.gov/technol ... helson.cfm

I do not understand how this device actually enabled the measurement of the star's diameter. I would appreciate a more detailed explanation.

I had mostly forgotten all about this, it was part of my undergrad work, but not covered in much detail. For an introduction to the theory try

http://www.eso.org/projects/vlti/genera ... interf.pdf

this describes the technique and how it is used at ESOs VLT observatory.

Or for the original there is the original paper by Michelson at

http://articles.adsabs.harvard.edu/cgi- ... etype=.pdf

The basic theory is that you collect the light from two telescopes of known separation and then intefere the light like in youngs slit experiments. This gives you interference patterns, (light and dark bands) the size and shape of the interference patterns depends on the size of the object being viewed and the separation between the telescopes. So change the separation of the telescopes a few times and you can work out the diamter of the source. Obviously its a bit more complicated, but I think that is the rough version.

here is a cite that shows the Betelgeuse diameter in comparison to Earth's orbit and Jupiter's orbit.
http://domeofthesky.com/clicks/betelgeuse.html
Orin

astro_uk wrote:... for the original there is the original paper by Michelson at

http://articles.adsabs.harvard.edu/cgi- ... etype=.pdf

For complete articles, how current is the ADS database? I have often wanted recent copies of ApJ articles but did not know where to find them -- until now!

Hi RJ

ADS is essentially totally complete for papers between now and about 1990 or something like that. They are scanning old journals as well, I dont know how far along they are thouhg, but most of the classics have been done already, like the Michelson ones.

A word of caution though, ADS lists modern papers as soon as they are published but if you dont have a subscription to the particular journal they are in you wont be able to download them. This lasts a year or two after a paper has been printed. In these cases its better just to go the astro-ph and get the pre-print version.

http://arxiv.org/archive/astro-ph

Any decent scientist shouldnt publish papers on astro-ph before they have been peer reviewed and accepted by a journal. So the published and astro-ph versions should be identical.