Talk:Barycenter (astronomy)

message: "When the two bodies are of similar masses ... the barycenter will be located outside of either of them and both bodies will follow an orbit around it. This is the case for Pluto and Charon, Jupiter and the Sun..."
:I just crunched the numbers, and the barycenter as calculated for just the two objects Sol & Jupiter gets me a barycenter that is about 87% of Sol's diameter (i.e., about 13% of the way inside Sol's outermost layer).  I used the following values: 
::rtot = 7.783x108 km (mean distance between Sol and Jupiter)
::m1 = 1.899×1027 kg (mass of Jupiter)
::m21.9891×1030 kg (mass of Sol).
:This results in Jupiter being 777 557 663.3 km from the barycenter, and Sol being 742 336.7 km from the barycenter.  Is the above-quoted claim incorrect, or is my math misleading due to ignoring the other bodies in the Solar System?
::The barycenter is more than 50% of the diameter of the Sun away from the center, so outside the Sun.--Patrick 12:21, 21 October 2005 (UTC)
thread_title: Comments

message: I think this article should be merged with center of mass. Physically this article gives no new info than center of mass. 193.52.24.125 18:42, 23 October 2005 (UTC)
replies: text: I have just merged the 2. 193.52.24.125 17:46, 24 October 2005 (UTC)
thread_title:  Merge? (2005) 

message: The location of the Earth-Moon Barycenter is based on 1 Plus (the Ratio of the Mass of the Earth divided by the of the mass of the Moon),
and then Multiplied by the Average distance between the two.  That ratio ( to a ridiculous number of digits) is 81.30059122 .
Adding 1 gives ( 1 / 82.30059122 ) X 384,401 km = 4670.695487 km ( also to a ridiculous number of digits ).
Rounding would gives Earth to E-M BC = 4670.7 km and Moon to E-M BC = 379,730.3 km for a total of 384,401 km. 
The number ( 81.30059122 ) is gradually increasing as the Earth gains mass, very slowly, but, faster than the Moon gains mass.
The change in mass, and the change in mass ratio gradually moves the Moon to a higher orbit, and the Earth to a lower orbit
relative to the E-M BC.  The total change is a gross increase of approximately 42.36 mm per year, but the 
net change is only measured at about 38.2 mm per year ( McDonald Observatory, Texas: Lunar Laser Ranging ).
The difference is the net increase in the Radius of the Earth ( 4.16 +/- 0.01 mm per year ).
The change in the distance is about 1 part in 9.0888 Billion, which is 1 part in twice the age of the Earth.
The Radius of the Earth is actually about 6372.4567 Km at the tilt angle of 23.491 degrees.  The 6378 is an Equatorial
Radius of the Earth.  If a planet had uniform density, and was a sphere, ( both are not true of the Earth ), then
the equal force tilt angle would be close to 23 degrees, 19 minutes and 39.3 seconds of tilt relative to the
Force applied by the Sun.  This would be the tilt angle radius that would represent the mass of the Planets, which
in turn would apply to the mass ratio between co-orbiting planets, and thus that ratio of r1 and R2.
A large Mass multiplied by a small radius is equal to a Large radius multiplied by a smaller mass. This determines
both the Mass Ratio, and/or the distance Ratio. In the case of the Earth and Moon it is the same number
( 81.30059122 ). Most would round this to 81.3 which would change the Earth to E-M BC to 4670.72904 KM, which
would still round down to 4670.7 km. 63.225.17.34 (talk) 21:22, 24 February 2016 (UTC)
thread_title:  Barycenter Edits 

message: The first figure in the article is with extremely low resolution, and I suggest to replace it with a better one. 213.8.204.61 (talk) 08:48, 20 April 2016 (UTC)
replies: text: Here's a candidate:   Do you know of a better image? Certes (talk) 10:57, 20 April 2016 (UTC)
thread_title:  The First Figure in the Atricle 

message: To make the data useful and practical, it is necessary to have the date/time of barycentric perihelion, and the rate of apsidal precession. Otherwise it reads like a textbook on theory and it is impossible to visualise the reality of it. Bards (talk) 13:26, 20 August 2016 (UTC)
replies: text: That's a very good remark. Please go ahead and make the data useful and practical. Thank you, Rfassbind – talk  15:38, 20 August 2016 (UTC)
thread_title:  Barycentre perihelions? 

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thread_title:  External links modified 

message: Does the semimajor axis refer to the distance between two orbiting bodies or the distance from a body to the barycenter? According to this article it is the distance from a body to the barycenter (assuming circular orbits). This is inconsistent with other wiki articles. E.g. the Moon article lists both the Earth-Moon average distance and semimajor axis as 384400 km. But according to this article, the Moon's semimajor axis should be 379730km (and the Earth's 4670km). Also wiki lists Jupiter having a semimajor axis of 7.783x108 km rather than 7.776x108 km as suggested by Patrick above. Gigarose (talk) 11:34, 15 April 2017 (UTC)
replies: text: After reviewing information in the Semi-major_and_semi-minor_axes article - particularly the equation for orbital period - I've concluded that 'semi-major axis' refers to the distance between orbiting bodies and not the distance from a body to the barycenter. This article uses the separation distance definition, but also defines it according to the barycenter distance, which might be wrong. Gigarose (talk) 14:01, 19 April 2017 (UTC)
replies: text: The ephemerides of the Moon and planets used by most of the world is described in Explanatory Supplement to the Astronomical Almanac, Chapter 8: Ephemerides of the Sun, Moon, and Planets, 3rd edition, 2013. This is an iterative calculation of this n-body problem. The daily positions of all planets are calculated relative to the barycenter of the Solar System, page 4. However, elliptical dimensions such as their semimajor axis is not specified because ellipses are not used. Instead, their Keplerian elements are curve fitted to the results giving a lower accuracy relative to the center of the Sun (Heliocentric), page 28. The distance from the center of the Sun to the center of Jupiter is specified as 5.20288700 au −0.00011607 au/cty for the mean ecliptic and equinox of J2000 valid for 1850–2050, where au = astronomical unit = 149597870.691 km, and cty is a Julian century of 36525 SI days. Thus at J2000 (2000 January 1 noon Tepm ≅ Barycentric Dynamical Time), the distance from Jupiter to the Sun was 7.78340817 × 108 km. — Preceding unsigned comment added by Joe Kress (talk • contribs) 15:16, 24 April 2017 (UTC)
thread_title: Semi-major axis definition?

message: mass1 / mass2 * distance * .5 = barycenter
distance = distance between the centers of the 2 objects 
mass1    = smaller of the 2 objects
mass2    = larger  of the 2 objects
barycenter= ration of mass between the 2 objects * distance divided ny 2
it doesn't just just looks easier to understand than the formula presented. computers can run it faster  — Preceding unsigned comment added by Jonathan scott james (talk • contribs) 07:45, 31 October 2020 (UTC)
thread_title:  barycenter formula