Re: Estimation of the age of the milky way.
- From: "Mike Dworetsky" <platinum198@xxxxxxxxxxxxxxxxxxxx>
- Date: Mon, 24 Nov 2008 07:56:29 -0000
"Timberwoof" <timberwoof.spam@xxxxxxxxxxxxxxxxxxxxx> wrote in message
news:timberwoof.spam-B85CF5.13075123112008@xxxxxxxxxxxxxxxxxxxxxxxxxxx
...
The parallax of a star is caused by its apparent change in position in
the sky as the Earth moves about the sun during the course of a year. It
does not tell you anything about the sun's movement or the star's
movement around the galaxy.
Just as a side note, the rotation of the galaxy was first determined from
analysis of the proper motions and radial velocities of stars in the disk
within about 500-1000 parsecs of the Sun. (Not from parallaxes.) The
differential rotation could thus be measured, leading via models to the
general rotation.
Jan Oort (of Oort cloud fame) was one of the pioneers of this technique.
--
Mike Dworetsky
(Remove pants sp*mbl*ck to reply)
.
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