Alpha Centauri Data Anomalies - ignore this post
Please ignore this post. I should delete it but there were comments.
Binary stars do not move by Kepler's third law. Our Moon and Earth are a binary and do not conform.
The only useful item below is the mistake with Proxima Centauri axis. That error caused a misdirection to look at other data - which is my mistake.
Please ignore the rest ****
Wikipedia provides data for Alpha Centauri and the numbers might be wrong.
Alpha Centauri is the closest star system and so it is the 3rd brightest in the sky.
This 'star' is actually a binary of 2 similar stars in a tight orbit, so it is often called Alpha Centauri AB.
There is a third dimmer star, called Proxima Centauri, in orbit around Alpha Centauri AB.
There are recent claims a second exoplanet has been detected near Proxima Centauri. This claim remains under debate.That debate is not part of this topic.
The following data from Wikipedia are analyzed below.
The relationships of axis and period seem wrong when comparing just to our solar system.
Alpha Centauri AB orbit:
Alpha Centauri A distance: 4.37 ly
Alpha Centauri B distance: 4.37 ly
semi-major axis: 17.57 arc-seconds
period: 79.91 yr
A separation of that angle at that distance is 23.5409 AU.
From another reference: distance is about 23 AU for a period of about 80 years.
Proxima Centauri orbit:
semi-major axis: 8700 AU
period: 547 yr
The first exoplanet is named Proxima Centauri b.
semi-major axis: 0.0485 AU
period: 11.186 days
On 01/22/2020, Forbes had an article titled "Astronomers Announce Proxima Centauri's Second Planet, And It's Perfect For Direct Imaging"
This artile had orbit data for Proxima Centauri c.
semi-major axis: 1.5 AU
period: 5 years
Analysis of the above 4 orbits ...
For comparison: P=period, A= axis.
Mercury P=88d, A= 0.387AU; Mars P=1.88y A=1.52AU; Uranus P=84y A=19.2AU; Eris P=557y A=67.7AU
Note: AB period is similar to Uranus; Prox C period is similar to Eris; Proxima Cent b axis is closer than Mercury; Prox Cent c axis = Mars
When applying Kepler's 3rd law of planetary motion with its relation between Period and Axis (P^2/A^3) the following are values when in conformance:
AB period for the A is 110.3 yr not 80
AB radius for the P is 18.55 AU not 23
Prox Cent period for the A =8700 is 811,482 yr (almost 1My) not 547
Note if 8700 AU is a mistake for 87 then:
Prox Cent period for the A=87 is 811.482 yr not 547
Prox Cent radius for the P is 66.88 AU not 8700
Prx Cent b period for the A is 3.9 days not 11.19 days
Prx Cent b radius for the P is 0.3129 AU not 0.049 AU
Prx Cent c period for the A is 1.837 y not 5 yr
Prx Cent c radius for the P is 2.924 AU not 1.5 AU
Because all are different than expected by Kepler's 3rd law it is impossible to know if any published values are valid.
One could expect measurements would be verified by a simple check like this.
Proxima Centauri axis is an obvious mistake. 8700 AU = 0.138 ly.
Someone should notice 87 AU is more likely than 8700AU!
No other web site has orbit data for this system.
Alpha Centauri is the closest star system so its numbers should be correct.
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