What is a proposed origin of the Sun according to the material?

• A. The Sun formed from a cloud of gas collapsing spontaneously without external disturbance.
• B. The Sun formed from solid debris aggregating in a calm disk without external impact.
• C. The Sun formed when the galaxy's core collapsed into a star.
• D. A supernova explosion disturbed the dust cloud, forming a solar nebula that led to the Sun.

Answer: (D)

The idea being tested is that the Sun’s birth is tied to the solar nebula model, where a cloud of gas and dust collapses under gravity to form a rotating disk, with the central mass becoming the Sun and the surrounding material forming planets. An external shock, such as a nearby supernova explosion, can provide the disturbance that compresses a diffuse cloud enough to start this collapse. This trigger helps explain why a disk of material surrounds a young star and how planets can form within that disk.

Why this option fits best: a supernova explosion disturbing the dust and gas gives the cloud the push needed to begin collapsing into a solar nebula, aligning with how stars and protoplanetary disks are understood to originate. The resulting solar nebula then leads to the Sun forming at the center with planets accruing from the surrounding material.

Why the other ideas don’t fit as well: forming from gas collapsing spontaneously without an external nudge is less consistent with how star formation is typically triggered in the interstellar medium, where such collapses often rely on some disturbance. Building the Sun from solid debris in a calm disk ignores the gaseous nature of the proto-Sun and the clear role of a disk as the birthplace of planets. The notion of the galaxy’s core collapsing into a star isn’t how individual stars form in galaxies.