Question 11

For a long time, astronomers assumed that the planets in our solar system formed in their current positions and stayed there. This static model, however, struggles to explain a glaring anomaly observed in the wider galaxy: the high prevalence of 'Super-Earths' orbiting close to their stars. These planets, larger than Earth but smaller than Neptune, are common elsewhere but entirely missing from our own system. To account for this, researchers have proposed the 'Grand Tack' hypothesis. It suggests that the early solar system was far more chaotic than previously thought. In this scenario, a young Jupiter migrated inward toward the Sun, disrupting the orbits of early planetary building blocks and effectively clearing the inner solar system of material. This movement would have prevented the formation of Super-Earths. Crucially, the subsequent formation of Saturn created a gravitational resonance that pulled Jupiter back out to its current location. This retreat left behind a depleted band of debris from which the smaller, terrestrial planets-Mercury, Venus, Earth, and Mars-eventually coalesced. Essentially, Jupiter's chaotic journey may be the primary reason our solar system has its unique architecture.