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I know that Sirius A and B orbit each other. I'd like to ask how large is their relative apparent motion in arc seconds, seen from Earth?

uhoh
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pol0
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1 Answers1

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From Sirius A to Sirius B on the sky is around 3 arcsec on average.

The separation between Sirius A and Sirius B actually varies from 3 to 11 arcseconds b/c of their orbital motion over a long period of time (Here).

I believe you're referring to that. There's a lot of information (and even some graphs and diagrams) here: Here. The information on that website is sort of vague, but I think it'll be helpful in visualization.

Hope that helps!

MystaryPi
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  • not the separation between the two, the movement of Sirius A only – pol0 Oct 17 '18 at 00:40
  • Sirius B has a wider orbit – pol0 Oct 17 '18 at 00:40
  • looking at the link you included, http://www.as.utexas.edu/white_dwarfs/wkshp_05/SiriusAB.pdf, it looks like Sirius A has an orbit of 12 arc seconds in total, is that correct? – pol0 Oct 17 '18 at 01:22
  • It looks like so. I think this source is slightly outdated, so I'm not putting too much reliance on it. – MystaryPi Oct 17 '18 at 02:21
  • I read it wrong actually, it only goes to -0.5, so around 6.5 arc seconds. – pol0 Oct 17 '18 at 02:23
  • Wait... Ha ha looks like I made the same mistake too. The graph goes down to -0.5, so it ranges to 6.5 arcsec. I was looking at the scale and thought that since it goes from -6 to +6 arcseconds, it has a range of 12 arcsec... – MystaryPi Oct 17 '18 at 02:25