Stars, Galaxies and The Universe
Science

The brightness of a star as seen from a distance of 10 parsecs
Absolute magnitude
The brightness of a star as seen from a distance of 10 parsecs. Absolute magnitude. Absolute magnitude is a measure of how bright a star or celestial object appears from a standard distance of 10 parsecs about 32.6 light years.

States that the universe began with a huge explosion 13.8 billion years ago
Big bang theory
States that the universe began with a huge explosion 13.8 billion years ago. Big Bang Theory. The Big Bang Theory explains that the universe started from an extremely hot and dense point and has been expanding ever since.

A dense core composed mainly of neutrons, left behind after a supernova explosion
Neutron star
A dense core composed mainly of neutrons, left behind after a supernova explosion. Neutron star. A neutron star is an incredibly dense and compact object formed from the remnants of a massive star after it explodes in a supernova.

The process by which hydrogen atoms join together to form helium, inside the sun
Nuclear fusion in the sun
The process by which hydrogen atoms join together to form helium, inside the sun nuclear fusion in the sun. Nuclear fusion in the sun is the reaction that powers the sun, fusing hydrogen atoms into helium and releasing energy.

The apparent change in position of an object when viewed from different places
Parallax
The apparent change in position of an object when viewed from different places. Parallax. In simple terms, parallax is the way an object's position seems to change when you look at it from different locations, which is often used in astronomy to measure distances to stars.

The hot dense core of a star left behind when its outer layers have escaped into space
White dwarf
The hot dense core of a star left behind when its outer layers have escaped into space. White dwarf. A white dwarf is a small, dense star that forms when a star like our Sun uses up its nuclear fuel and sheds its outer layers.