<p>You should wonder if the astronomer has taken account of perspective.</p>
<p>A circular orbit, seen in perspective will appear to be an elliptical orbit, and if the brighter component is sufficiently more massive, it will appear to be at the centre of the ellipse. In this case Kepler's laws are not broken.</p>
<p>But if the astronomer has accounted for perspective, and the orbit is truly elliptical, then the two stars will move in ellipises around a common barycentre at a focus, and if the bright component is sufficiently more massive then it will be nearly static at a focus of the orbit of the less massive star. It would break Kepler's first law if the massive star was stationary at the centre of the elliptical orbit of the less massive star.</p>

CC BY-SA 4.0
2021-09-16T06:32:44.977Z
2021-09-16T06:32:44.977Z
James K
<p>I'm trying to solve this task:</p>
<blockquote>
<p>Observing a visual binary star with a highly elongated elliptical orbit for a long time, the astronomer noticed that the bright component lies in the center of the ellipse, and not in its focus.  Does it follow from this that Kepler's first law is violated?</p>
</blockquote>
<p>Is it possible and if it is then why?</p>

CC BY-SA 4.0
2021-09-16T06:59:07.467Z
This may be helpful: https://astronomy.stackexchange.com/a/43350/16685
PM 2Ring
<orbit><binary-star>
What if a component of a binary star lies in the center of it's orbit and not in the focus?
ALiCe P.
# What if a component of a binary star lies in the center of it's orbit and not in the focus?

(Asked by: username_0 on 2021-09-16)

I'm trying to solve this task:

> Observing a visual binary star with a highly elongated elliptical orbit for a long time, the astronomer noticed that the bright component lies in the center of the ellipse, and not in its focus. Does it follow from this that Kepler's first law is violated?

Is it possible and if it is then why?

**Tags:** orbit, binary-star

> **Comments:**
> **username_1**: This may be helpful: https://astronomy.stackexchange.com/a/43350/16685  

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## 1 answers

### Answer by username_2 on 2021-09-16. Score: 3 | Accepted answer

You should wonder if the astronomer has taken account of perspective.

A circular orbit, seen in perspective will appear to be an elliptical orbit, and if the brighter component is sufficiently more massive, it will appear to be at the centre of the ellipse. In this case Kepler's laws are not broken.

But if the astronomer has accounted for perspective, and the orbit is truly elliptical, then the two stars will move in ellipises around a common barycentre at a focus, and if the bright component is sufficiently more massive then it will be nearly static at a focus of the orbit of the less massive star. It would break Kepler's first law if the massive star was stationary at the centre of the elliptical orbit of the less massive star.


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