Formation and evolution of the Solar System owe its substantially lower mass simply to having formed a few million years after Jupiter, when there was less gas available to consume. T Tauri stars like the young Sun have far stronger stellar winds than more stable, older stars. Uranus and Neptune are thought to have formed after Jupiter and Saturn did, when the strong solar wind had blown away much of the disc material. As a result, those planets accumulated little hydrogen and helium—not more than each. Uranus and Neptune are sometimes referred to as failed cores. The main problem with formation theories for these planets is the
Solar eclipses on Jupiter the variations were caused by the varying distance between Earth and Jupiter as the two planets moved in their orbits around the Sun. Spacecraft can be used to observe the solar eclipses on Jupiter; these include "Pioneer 10" and "Pioneer 11" (1973 and 1974), "Voyager 1" and "Voyager 2" (1979), "Galileo" orbiter (1995–2003), "Cassini–Huygens" (2000) and "New Horizons" (2007) observed the transits of their moons and its shadows. The mean angular diameter of the Sun as viewed from Jupiter is 372 arc-seconds, or 6' 12" (about that of the Sun as viewed from Earth), varying slightly from 381" at perihelion