Astronomy and Physics Quiz

The Solar System

• Our Solar System is located in the Milky Way galaxy, along with billions of other stars.

• The Sun is the largest object in our Solar System.

• The Sun's gravity keeps planets, dwarf planets, asteroids, and comets in orbit around it.

• Planets orbit the Sun at different distances.

• Earlier models placed Earth at the center of the Solar System (geocentric), but the current model (heliocentric) shows the Sun at the center, with Earth and other planets orbiting it.

• Planets have different properties and conditions. Temperature generally decreases as the distance from the Sun increases. Time taken to orbit the Sun also increases with distance.

• For an object to be considered a planet, its gravity must be strong enough to make it spherical and clear its orbital path of other objects.

Moons

• Moons are natural satellites that orbit planets.

• Our Moon is Earth's only natural satellite.

• Many planets have moons, some with many.

Dwarf Planets

• Pluto is a dwarf planet.

• Dwarf planets do not have enough gravity to clear the neighbourhood of other objects in their orbit.

Asteroids

• Asteroids are smaller objects orbiting the Sun.

• They are mostly made of metals and rocky material.

• Many asteroids orbit between Mars and Jupiter, in a region called the asteroid belt.

• Some asteroids are also found beyond Neptune, in the Kuiper Belt.

Comets

• Comets are made of ice, dust, and rocky materials.

• They have highly elliptical orbits around the Sun.

• As comets approach the Sun, they vaporise, creating a visible tail.

Gravity

• All objects have gravity.

• Larger objects have stronger gravitational pulls.

• The amount of gravitational pull can be measured in Newtons (N).

• Earth's average gravitational pull is approximately 10 N/kg.

• On Earth, your weight is calculated as mass x gravity.

• Your weight on the Moon would be different because the Moon's gravitational pull is different.

Orbits

• Gravity is essential for maintaining orbits of planets, moons, and artificial satellites.

• Circular orbits require objects to travel at a specific speed.

• Objects in smaller orbits travel faster than those in larger orbits.

• The force acting on objects in circular motion is centripetal force.

Types of Orbits

• Geostationary Orbits: These orbits stay over the same point on Earth, and useful for weather forecasting and communication satellites. They orbit at a distance of 36,000 km above the equator.

• Medium Earth Orbits: These orbits are at a distance of approximately 20,000 km and are useful for GPS satellites.

• Low Earth Orbits: These orbits are closest to Earth, at a distance of 200-2,000 km. They are used for many scientific and Earth observation missions.

How Stars are Formed

• Stars form from massive clouds of gas and dust called nebulae.

• Gravity pulls dust and gas particles together, causing it to heat up and eventually fuse hydrogen in the core to create helium which produces energy to balance the core.

Stages of a Star's Life Cycle

• Nebula
• Protostar
• Main sequence star
• Red giant star
• White dwarf
• Black dwarf (for smaller stars)
• Red Supergiant
• Supernova
• Neutron star or Black hole (for larger stars)

Redshift and the Expansion of The Universe

• Distant galaxies' light appears redder due to the stretching of wavelengths of light due to the expansion of space.

• The further a galaxy is, the faster it moves away from us based on the amount of redshift.

• This suggests that the Universe is expanding.

• The Big Bang theory proposes the Universe originated from a very small, hot, and dense point that expanded over time.

• Evidence like cosmic microwave background radiation (CMBR) supports the theory.