Astronomy - Planets and The Solar System

Kepler’s 1st Law

The Law of Ellipses; solar objects orbit around the sun in an elliptical shape, not a perfect circle.

Kepler’s 2nd Law

The Law of Equal Areas; a planet moves faster when closer to the sun and slower when farther away.

Kepler’s 3rd Law

The Law of Harmonies; the square of a planet’s orbital period (p) is equal to the cube of the length of the semi-major axis of its orbit (a). $p^2 = a^3$.

Newton’s 1st Law

The Law of Inertia; an object at rest stays at rest, an object in motion stays in motion unless acted upon by an external force.

Newton’s 2nd Law

The Law of Force and Acceleration; the acceleration of an object is directly proportional to the force acting on it and inversely proportional to its mass. $F = m \times a$.

Newton’s 3rd Law

The Law of Action and Reaction; for every action, there is an equal and opposite reaction.

Newton’s Law of Gravitation

Describes how planets move in ellipses due to the force of gravity, which is a universal attraction among all bodies. The formula is $F_{gravity} = G \frac{(M_1 M_2)}{R^2}$.

Momentum

A measure of how much motion an object has, calculated as the product of mass and velocity. $Momentum = mass \times velocity$.

Angular Momentum

The measure of the rotation of a body around a fixed point, calculated as a product of mass, velocity, and distance from that point.

Conservation of Momentum

In an isolated system, the total momentum remains constant if no external forces are acting on it.

Mass Distribution in the Solar System

The sun accounts for 99.85% of the mass in our solar system, exerting the largest gravitational force.

Geological Activity

Determined by a planet's internal heat and size; involves processes like volcanism and earthquakes.

Dating Planets

Methods include counting impact craters to estimate surface age and radioactive dating of rocks to gauge age.

Radioactive Decay

The process where an unstable atomic nucleus loses energy to become a more stable form through emission of radiation.

Half-life

The time it takes for half of a given sample of a radioactive material to decay.

Formation of the Solar System

Formed approximately 4.5 billion years ago from a giant, spinning cloud of dust called a solar nebula.

Giant Planets

Large planets with gaseous compositions, including Jupiter and Saturn.

Terrestrial Planets

Smaller, rocky planets including Mercury, Venus, Earth, and Mars.