Sun-Jupiter Barycentre Sits 46,000 Km Beyond Solar Surface

Q: If the Sun isn't exactly at the center of our solar system, what invisible point is Earth actually orbiting?

Earth is most precisely orbiting the solar system’s barycentre — the moving center of mass of the entire Sun-planet system — though for most practical purposes it is still accurate to say Earth orbits the Sun. That barycentre is an invisible point set by the combined masses and positions of the Sun and all the planets. Because the Sun contains about 99.8 percent of the solar system’s mass, the barycentre usually stays very close to the Sun, often inside it. But it is not fixed at the Sun’s exact center, and it shifts over time as the planets move. Jupiter is the biggest reason the barycentre can be offset. Its large mass and wide orbit are enough to pull the Sun into a small wobble around a shared center of mass. Saturn and the other planets add smaller shifts. So Earth is not circling a perfectly motionless Sun, but moving in the Sun’s gravitational field while the whole system responds to this changing balance point. In a simpler two-body picture, Earth and the Sun also have their own shared barycentre, but that point lies deep inside the Sun because Earth is much less massive than Jupiter. For everyday astronomy, heliocentric models remain extremely useful. But the more exact answer is that Earth moves around the Sun while both Earth and the Sun, along with the rest of the planets, orbit the solar system’s shifting barycentre.

1 articles · Updated · spacedaily.com · Aug 10

About 742,000 km from the Sun’s centre, the Sun-Jupiter barycentre lies roughly 46,000 km beyond the Sun’s visible surface, meaning neither body circles a perfectly fixed Sun-centre.
Jupiter’s pull is strong enough because it carries about 318 Earth masses and orbits at an average distance of 778 million km, shifting the shared centre of mass outside the photosphere.
The 46,000-km figure comes from combining JPL gravitational parameters with the IAU’s 695,700-km nominal solar radius; it is an average, not a fixed geometry, because Jupiter’s orbit is elliptical and other planets also tug the Sun.
That small solar wobble matters beyond terminology: the same barycentre physics underpins the radial-velocity method astronomers use to detect exoplanets from repeated Doppler shifts in starlight.