In the leading theory of solar system formation, the planets
(a) were ejected from the Sun following a close encounter with another star;
(b) formed from the same flattened, swirling gas cloud that formed the Sun;
(c) are much younger than the Sun;
(d) are much older than the Sun.
The correct answer and explanation is :
The correct answer is (b) formed from the same flattened, swirling gas cloud that formed the Sun.
The leading theory of solar system formation is known as the nebular hypothesis. According to this theory, the Sun and the planets formed from a giant cloud of gas and dust called a solar nebula. This nebula consisted primarily of hydrogen and helium, with heavier elements and compounds scattered throughout. About 4.6 billion years ago, this cloud began to collapse under its own gravity, likely triggered by an external event such as the shockwave from a nearby supernova.
As the cloud collapsed, it started to spin faster due to the conservation of angular momentum. The material within the nebula flattened into a rotating disk, with most of the mass being concentrated in the center, where the Sun eventually formed. In the cooler outer regions of this rotating disk, small particles of dust and ice collided and stuck together, gradually forming larger bodies. These bodies, called planetesimals, continued to collide and merge over time, eventually forming the planets.
This process explains why the planets are composed of the same elements and compounds as the Sun, and why they all orbit the Sun in the same plane and in the same direction. The planets were not ejected from the Sun, nor are they significantly older or younger than the Sun. The Sun and the planets formed together from the same material at the same time, although the Sun’s formation was faster, as it condensed first at the center of the nebula.
The idea that planets could have formed from a swirling, flattened cloud of gas and dust is supported by observations of other star-forming regions in our galaxy, where similar disks are seen around young stars, providing strong evidence for this theory of solar system formation.