Picture of the Universe

[rov1200]

Those wonderful pictures of the Universe taken by the space camera are marvellous. Would it be possible to take different whole pictures separated by a time period to show how much the universe is expanding?

[squarebear]

I would imagine this time frame would have to be many years to notice any difference.

[jake-the-peg]

No because the Universe's expansion appears to be away from every point and the distances are such that as a percentage it's quite small

You can over a period of time see certain stars move it's called their "proper motion"

The most remarkable is "Barnards star" it's actually plotted on star maps as a small line with years on it it's so fast

http://en.wikipedia.org/wiki/Barnard%27s_Star

here's an animation of it's moving position

http://en.wikipedia.o.../File:Barnard2005.gif

[rov1200]

Nothing to do with proving Hubble's Law then?

http://en.wikipedia.org/wiki/Hubble's_law

[mibn2cweus]

Hubble's law is derived largely on the corresponding relationship between red-shift and established distances. At distances where red-shifts display an obvious trend, slow, long term changes in apparent size which would confirm a similar motion are inconclusive if at all discernable.

[beso]

Incidentally, distances of relatively nearby stars are established by parallex using the extremes of the Earth's orbit around the Sun.

The common unit is the parsec. If I remember correctly it is the distance where an object's apparent location relative to the background stars moves by one second of arc during the orbit of the Earth. Astronomers generally talk in kiloparsecs.

However this system only works for nearby (astronomically speaking) objects. Most of the distance data for Hubble's constant is derived from the relative brightness of a particular type of supernova which is known to be very consistent in absolute brightness.