Epsilon Aries STF333

[lunator]

Something a little bit different.

Attached to this post is a document outlining a preliminary apparent orbit for STF 333.

Brian Mason is reviewing this at the moment and I hope he will be able to provide a true orbit for the pair.

I was amazed that there was not and orbit for this pair as they have over 400 measures in 179 years.

This is my first foray into double star orbits but I now really understand relationship between semi-major axis and the orbital period

*WARNING* The file is a bit on the large size 1.16Mb

http://ukastronomers.com/lunator/action/download_files/fileid/13

Cheers

Ian

[blinky]

Just read it, very interesting (the bits I could understand!). What is the diffrence between the seperaton and angle? Or rather I can see how you would measure seperation but how do you measure the angle?

Also I take it from your orbit graph that you have worked out it is an eccentric orbit, how did you come to this conclusion (not that I am in any way doubting you :shock:). Lastly what does Periastron and Aperiastron mean?

[lunator]

Just read it, very interesting (the bits I could understand!). What is the difference between the separation and angle? Or rather I can see how you would measure separation but how do you measure the angle?

Also I take it from your orbit graph that you have worked out it is an eccentric orbit, how did you come to this conclusion (not that I am in any way doubting you :shock:). Lastly what does Periastron and Aperiastron mean?

Hi Craig

The separation is the distance between the 2 stars in arc seconds. (1 arc second = 1/3600 of a degree)

The position angle is the angle of the secondary from the primary and is measured from a line pointing due north and is measured round to East/South/West. So a Star due east is at postion angle 90 degrees.

In this case the secondary is south west of the primary.

To work out the orbit is a bit of trial and error.

The ellipse shows a sharp turn at one end and from this you can draw a preliminary ellipse. From this you can position the foci's and begin to refine the ellipse.

The ellipse that best fitted the observed positions had an eccentricity of 98.5.

Periastron is where the 2 stars are closest together and apastron is where they are furthest apart.

I hope this is clear

Cheers

Ian

[blinky]

Very clear thanks for that, very interesting. Good to see somebody on here that does some research as well as observing/imaging!

[Astroman]

Just to add a bit to Ian's explanation, the separation is measured as they appear on the sky. With enough data on their orbits, and filling in the ellipse, one can end up calculating the masses of the stars involved and the actual distance between them. This can then be calibrated to enable further calculations of temperature, size of each and so on, all of which can be applied to other systems to gain a more complete knowledge of other such orbiting stars.

Lots of fun!

Great work, Ian.

[lunator]

Leatest Update....

Bob Argyle has just returned from observing Southern pairs from South Africa and my STF333 orbit is being reviewed by him and a couple of other experienced astronomers.

I'll keep you all informed of progress.

Cheers

Ian

[Talitha]

That's great Ian, keep us posted!