Is Jupiter's orbital radius increasing?

[dougettinger]

I read recently that a change in the radius of Jupiter's orbit has been measured over a period of time. And this radius increase cannot be justified by the calculated loss of the Sun's mass. Does this measurement still hold ? I find it hard to believe that scientists have had enough span of time with the most current measuring instruments to detect with adequate accuracy any sizable difference in Jupiter's radius.

Doug Ettinger
Pittsburgh, PA

[Chris Peterson]

I read recently that a change in the radius of Jupiter's orbit has been measured over a period of time.

Reference?

[dougettinger]

I thought perhaps that this was common knowledge. Yes, you are right. Give me some time to produce this reference.

Doug Ettinger

[The Code]

I read recently that a change in the radius of Jupiter's orbit has been measured over a period of time. And this radius increase cannot be justified by the calculated loss of the Sun's mass.

Quote
''The elliptical orbit of Jupiter is inclined 1.31° compared to the Earth. Because of an eccentricity of 0.048, the distance from Jupiter and the Sun varies by 75 million km between perihelion and aphelion, or the nearest and most distant points of the planet along the orbital path respectively''.

http://en.wikipedia.org/wiki/Jupiter#Orbit_and_rotation

I'm Interested to here if there's more to this.

[Chris Peterson]

''The elliptical orbit of Jupiter is inclined 1.31° compared to the Earth. Because of an eccentricity of 0.048, the distance from Jupiter and the Sun varies by 75 million km between perihelion and aphelion, or the nearest and most distant points of the planet along the orbital path respectively''.

Of course, this is true for every body with an eccentricity greater than zero. I assume that Doug's reference to the radius changing was actually intended to suggest that the semi-major axis was changing.

[dougettinger]

I am referring to the overall average orbital radius of Jupiter; i.e. the elliptical dimensions of the orbit are increasing due to the slow loss of the Sun's mass.

Doug Ettinger ( I am still searching for this reference.)

[Chris Peterson]

I am referring to the overall average orbital radius of Jupiter; i.e. the elliptical dimensions of the orbit are increasing due to the slow loss of the Sun's mass.

But to be clear, a body in an elliptical orbit doesn't have an orbital radius. In orbital dynamics, the term that describes the size of the ellipse, and which is analogous to radius, is semi-major axis. That and the eccentricity fully describe the shape of the orbit (other terms are required to completely characterize the orbit in time and space, however).

[dougettinger]

All what you say is true. I use one reference book that lists perihelion, aphelion, mean distances from the Sun. I presume my reference simply talked about the mean distance. Of couse, I know any measured orbital distance needs to be related to the orbit in time and space.

Doug Ettinger
Pittsburgh, PA

[dougettinger]

I read recently that a change in the radius of Jupiter's orbit has been measured over a period of time. And this radius increase cannot be justified by the calculated loss of the Sun's mass.

Quote
''The elliptical orbit of Jupiter is inclined 1.31° compared to the Earth. Because of an eccentricity of 0.048, the distance from Jupiter and the Sun varies by 75 million km between perihelion and aphelion, or the nearest and most distant points of the planet along the orbital path respectively''.

http://en.wikipedia.org/wiki/Jupiter#Orbit_and_rotation

I'm Interested to here if there's more to this.

I did a serious reference search for this article, probably a magazine, but could not find it. I would be very pleased if anyone knows about this experiment that was performed by NASA. Radio waves were sent back to Earth from a Jupiter space probe(s) at two large intervals of time. It was determined by measuring the signals elapsed times that Jupiter's orbit was enlarging faster than what could be accounted for by the continual lost of the Sun's mass due to solar eruptions and winds.


If you know how I could search for such a reference please let me know. Thanks.


Doug Ettinger
Pittsburgh, PA

[Chris Peterson]

I did a serious reference search for this article, probably a magazine, but could not find it. I would be very pleased if anyone knows about this experiment that was performed by NASA. Radio waves were sent back to Earth from a Jupiter space probe(s) at two large intervals of time. It was determined by measuring the signals elapsed times that Jupiter's orbit was enlarging faster than what could be accounted for by the continual lost of the Sun's mass due to solar eruptions and winds.

If you know how I could search for such a reference please let me know. Thanks.

I've not seen any reference to this. However, none of the planets in the Solar System are in completely stable orbits- all have changed position over billions of years due to perturbations from one another. Furthermore, you might reasonably expect the radius (or semimajor axis) of Jupiter's solar orbit to increase over time, as tidal forces slow its rotation and the conservation of angular momentum requires a larger orbit. Whether this amount is large enough to measure over a relatively short period I don't know, however.

[neufer]

I read recently that a change in the radius of Jupiter's orbit has been measured over a period of time. And this radius increase cannot be justified by the calculated loss of the Sun's mass. Does this measurement still hold ? I find it hard to believe that scientists have had enough span of time with the most current measuring instruments to detect with adequate accuracy any sizable difference in Jupiter's radius.

Well...first off, the solar wind mass loss is only (2–3) × 10⁻¹⁴ solar masses per year so a Jupiter orbital radius increase from such can only be on the order of an unmeasurable ~2 cm/year. The direct interaction of Jupiter with the solar wind & solar magnetic field (and with comets) is probably more significant than that (though not by a whole lot).

If the radius of Jupiter's orbit were to have a measurably change with time then so should the radius of Saturn since Jupiter & Saturn embody almost all of the solar system's conserved angular momentum. Jupiter has 2.45 times the angular momentum of Saturn so for every 1 x 10^-10 % increase in Jupiter's orbital radius Saturn's orbital radius must decrease by about 2.45 x 10^-10 %. So if Jupiter's orbital radius were to increase by 100m then Saturn's orbital radius must decrease by ~450m. With Cassini orbiting Saturn it would be much easier to detect a 450m Saturn radius change than a 100m Jupiter radius change.

[dougettinger]

Thanks, Art. I probably mis-understood the article. The mass loss of 2-3 x 10(-10) resulting in 2 cm/year or orbital change resolves my search.

Doug Ettinger
Pittsburgh, PA