SPACE NEW TEST CORRECT

Astronomical Unit (AU)

An astronomical unit is the distance from Earth to the Sun, about 150 million kilometres, and it is used to measure distances within the Solar System.

Light-Year

A light-year is the distance that light travels in one year, which is about 9.46 trillion kilometres, and it is used to measure distances between stars and galaxies.

Parsec

A parsec is a unit used to measure large distances in space and it is equal to 3.26 light-years, and it is calculated using parallax.

Parallax Formula

The distance to a star in parsecs is calculated using the formula d = 1/p, where p is the parallax angle in arcseconds.

Redshift

Redshift occurs when light from a galaxy shifts toward the red end of the spectrum because the object is moving away from Earth, showing the universe is expanding.

Universe Expansion

The universe is expanding because galaxies are moving away from each other, and this is supported by redshift, the cosmic microwave background, and observations of distant galaxies.

Cosmic Microwave Background (CMB)

The cosmic microwave background is faint radiation left over from the Big Bang that fills the entire universe and has a temperature of about 2.7 Kelvin.

Goldilocks Zone

The Goldilocks Zone is the region around a star where temperatures allow liquid water to exist, which is important for the possibility of life.

Oort Cloud

The Oort Cloud is a distant spherical region surrounding the Solar System that contains icy objects and is believed to be the source of long-period comets.

Orion Arm (Our Location)

The Solar System is located in the Orion Arm of the Milky Way galaxy, about 27,000 light-years from the galactic centre.

Exoplanets

Exoplanets are planets that orbit stars outside our Solar System, and thousands have been discovered using different detection methods.

Transit Method

The transit method detects exoplanets when a planet passes in front of its star, causing a small periodic dip in brightness.

Reflex Motion (Wobble Method)

The reflex motion method detects exoplanets by observing the small wobble of a star caused by the gravitational pull of an orbiting planet.

Doppler Method

The Doppler method detects exoplanets by measuring shifts in a star’s light, where redshift means the star is moving away and blueshift means it is moving toward us.

H-R Diagram

The Hertzsprung-Russell diagram is a graph that shows the relationship between a star’s temperature and brightness and is used to classify stars such as main sequence stars, red giants, and white dwarfs.

Asteroid

An asteroid is a rocky object that orbits the Sun, and most asteroids are found in the asteroid belt between Mars and Jupiter.

Comet

A comet is an icy object made of dust, rock, and frozen gases that develops a tail when it approaches the Sun.

Meteoroid

A meteoroid is a small piece of rock or metal travelling through space before it enters a planet’s atmosphere.

Meteor

A meteor is the streak of light seen when a meteoroid burns up in a planet’s atmosphere.

Meteorite

A meteorite is a meteoroid that survives its passage through the atmosphere and lands on a planet’s surface.

Nebula

A nebula is a large cloud of gas and dust in space where stars are born or where dead stars release material.

Pluto (Why not a planet)

Pluto is not classified as a planet because it has not cleared its orbital neighbourhood of other objects, so it is considered a dwarf planet.