The Universe

all existing matter and space considered as a whole; the cosmos. Has been constantly expanding since the big bang 13 billion years ago.

The observable universe is the ball shaped part of the universe that contains all matter that can be seen or detected from earth

a group of stars forming a recognizable pattern that is traditionally named after its apparent form or identified with a mythological figure.

a system of millions or billions of stars, together with gas and dust, held together by gravitational attraction of a black hole

The solar system is made up of the sun and the 8 planet that orbit it

a celestial body moving in an elliptical orbit round a star.

a unit of distance equal to 3.26156 light years

the brightness of an object relative to earth

A star is a luminous celestial body made up of hot gases, primarily hydrogen and helium, undergoing nuclear fusion to produce energy and light.

A light year is the distance light would travel in a year

the brightness of an object at a distance from earth of 10 parsecs

3.0 x 10^8 m/sec

The milky way galaxy is large collection of gas, dust and billions of stars and their systems

Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune

The Hertzsprung-Russell (HR) diagram is a chart that plots stars by their brightness and temperature, showing how they change and evolve over time.

Stellar evolution is the process by which a star changes over time, from its formation to its death

Nuclear fusion is the process where two light atomic nuclei combine to form a heavier nucleus, releasing energy

A supernova is a massive explosion that occurs at the end of a star’s life cycle, resulting from core collapse in a supergiant star

A planetary nebula is a glowing shell of gas and dust ejected from a dying star, surrounding the remaining hot core after it has shed its outer layers.

A white dwarf is a small, dense remnant of a star that has exhausted its nuclear fuel and shed its outer layers, no longer undergoing fusion.

A neutron star is an extremely dense remnant of a supernova explosion, composed mostly of neutrons and having a strong gravitational field.

A black hole is a region of spacetime with gravitational pull so strong that nothing, not even light, can escape from it, formed from the collapse of a massive star.

Luminosity is the total amount of energy emitted by a star per unit time, often expressed in watts or as a multiple of the Sun’s brightness.

The main sequence is a continuous band of stars on the HR diagram where stars spend most of their life, fusing hydrogen into helium in their cores.