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chornedsnorkack
2009-Mar-17, 02:25 PM
Does anyone know the current position, orbital inclination, eccentricity, apsides and period of Keid A relative to Keid BC?

tusenfem
2009-Mar-17, 03:18 PM
google is your friend
this is what wiki has to say (http://en.wikipedia.org/wiki/40_Eridani)

grant hutchison
2009-Mar-17, 03:43 PM
Does anyone know the current position, orbital inclination, eccentricity, apsides and period of Keid A relative to Keid BC?Probably not. I actively sought a published orbital solution a few years ago, and couldn't find one.
The killer is the 400AU separation between A and the BC pair, which implies a big, slow orbit. Astrometry and Doppler just aren't going to pin that down well enough for a solution.

Grant Hutchison

chornedsnorkack
2009-Mar-17, 09:10 PM
Probably not. I actively sought a published orbital solution a few years ago, and couldn't find one.
The killer is the 400AU separation between A and the BC pair, which implies a big, slow orbit. Astrometry and Doppler just aren't going to pin that down well enough for a solution.

How is the separation knowable in the absence of an orbit?

grant hutchison
2009-Mar-17, 09:26 PM
How is the separation knowable in the absence of an orbit?The components A and BC have a measurable angular separation and known parallaxes. The rest is trigonometry.

Grant Hutchison

chornedsnorkack
2009-Mar-17, 09:53 PM
The components A and BC have a measurable angular separation and known parallaxes. The rest is trigonometry.

Is the parallax measurement really so precise? What was the uncertainty in the distance to Keid components in 1974, and what is it now?

grant hutchison
2009-Mar-17, 10:19 PM
Is the parallax measurement really so precise? What was the uncertainty in the distance to Keid components in 1974, and what is it now?400AU is the minimum, plane-of-sky separation. Any difference in the distances for A and BC components simply makes their mutual orbit larger, the likely period longer, the likely velocities smaller, and the problem of defining an orbit correspondingly greater.

And I'm sure you can follow Wikipedia links as well as the rest of us can.

Grant Hutchison

chornedsnorkack
2009-Mar-17, 10:37 PM
400AU is the minimum, plane-of-sky separation. Any difference in the distances for A and BC components simply makes their mutual orbit larger, the likely period longer, the likely velocities smaller, and the problem of defining an orbit correspondingly greater.

Precisely. What is observational upper bound on their separation?

Proxima Centauri to Alpha Centauri distance still has an uncertainty of 700 a. u.!

grant hutchison
2009-Mar-17, 10:54 PM
Precisely.Yes indeed, precisely. So we agree on why there's no orbital solution. :lol:

Grant Hutchison

chornedsnorkack
2009-Mar-18, 09:30 AM
Yes indeed, precisely. So we agree on why there's no orbital solution. :lol:

Has any peculiar acceleration been observed?