A highly stylized rendition of our solar system. Image Credit: NASA
QUESTION: How is a solar system such as ours created?
ANSWER: A solar system is created when a rotating cloud of gas and dust in space start to coalesce – they are pulled together and towards the center of the gas/dust cloud by their gravitational attraction to each other.
As they condense, the particles collide faster and more often, which causes the gas and dust to heat up. The gas and dust at the center collapses to form the central star of the solar system; the heat generated by the colliding particles starts nuclear fusion in its core.
If there was enough angular momentum in the system at the very beginning, then not all of the dust and gas will go into the central star – the rest will remain in a flattened disk around the star. The planets form from this disk of rotating material as it clumps together because of gravity.
NOTES:
- Dust: This is NOT the type of dust one finds around the house (which is typically fine bits of fabric, dirt, and dead skin cells). Rather, irregularly shaped grains of carbon and/or silicates measuring a fraction of a micron across which are found between the stars. Dust is most evident by its absorption, causing large dark patches in regions of our Milky Way Galaxy and dark bands across other galaxies.
- Gravity: A mutual physical force attracting two bodies.
- Fusion: The process in which atomic nuclei collide so fast that they stick together and emit a large amount of energy. In the center of most stars, hydrogen fuses into helium. The energy emitted by fusion supports the star’s enormous mass from collapsing in on itself, and causes the star to glow.
- Angular momentum: A quantity obtained by multiplying the mass of an orbiting body by its velocity and the radius of its orbit. According to the conservation laws of physics, the angular momentum of any orbiting body must remain constant at all points in the orbit, i.e., it cannot be created or destroyed. If the orbit is elliptical the radius will vary. Since the mass is constant, the velocity changes. Thus planets in elliptical orbits travel faster at perihelion and more slowly at aphelion. A spinning body also possesses spin angular momentum.
- J. Allie Hajian for “Ask an Astrophysicist”
