dougettinger wrote: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.
[quote="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.[/quote]
Well...first off, the solar wind mass loss is only (2–3) × 10[sup]−14[/sup] 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[sup]-10[/sup] % increase in Jupiter's orbital radius Saturn's orbital radius must decrease by about 2.45 x 10[sup]-10[/sup] %. 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.