Astronomy

Astronomy

Study of space, celestial bodies, and the universe beyond Earth’s atmosphere

Observational Astronomy

Study of celestial objects through observation using telescopes and instruments

Theoretical Astronomy

Uses mathematics, physics, and models to explain space phenomena

Astrophysics

Study of physical properties and behaviors of celestial bodies

Cosmology

Study of the origin, evolution, and structure of the universe

Big Bang Theory

Most accepted theory explaining the origin of the universe; states that the universe began about 13.8 billion years ago from a hot, dense singularity and continues to expand

13.8 billion years

How long ago did the universe begin according to the Big Bang Theory

Singularity

Extremely hot and dense point from which the universe began

Inflation

Rapid expansion of the universe immediately after the Big Bang

Edwin Hubble

Astronomer who discovered that galaxies are moving away from each other

Hubble’s Law

The farther a galaxy is, the faster it moves away

Redshift

Shift of light toward red wavelengths, showing that galaxies are moving away from Earth

Cosmic Microwave Background Radiation (CMB)

Weak radiation found throughout space, considered leftover heat from the Big Bang

Steady State Theory

Theory suggesting the universe has always existed and continuously creates matter

Oscillating Universe Theory

Theory suggesting the universe repeatedly expands and contracts

Stars

Massive glowing sphere of hot gases (mostly hydrogen and helium) that produces energy through nuclear fusion

Nuclear Fusion

Process where hydrogen atoms combine to form helium, releasing heat and light

Brightness

Amount of light a star emits

Color

Characteristic of a star indicating temperature

Red Star

Coolest type of star

Yellow Star

Medium-temperature star

Blue Star

Hottest type of star

Dwarf

Small-sized star

Giant

Large-sized star

Supergiant

Extremely large star

Nebula

Cloud of gas and dust; birthplace of stars

Protostar

Early stage of star formation

Main Sequence Star

Stable stage of a star where hydrogen fusion occurs

Red Giant

Stage of small/medium stars after main sequence

Planetary Nebula

Expanding shell of gas ejected by a dying small/medium star

White Dwarf

Dense remnant of a small/medium star

Black Dwarf

Theoretical final stage of a cooled white dwarf

Red Supergiant

Late stage of a massive star

Supernova

Explosive death of a massive star

Neutron Star

Extremely dense remnant left after some supernovas

Black Hole

Region in space where gravity is so strong that nothing can escape

Event Horizon

Boundary around a black hole where escape becomes impossible

Stellar Black Hole

Black hole formed from dying massive stars

Supermassive Black Hole

Massive black hole found at centers of galaxies

Intermediate Black Hole

Black hole between stellar and supermassive sizes

Galaxy

Huge collection of stars, gas, dust, and dark matter held together by gravity

Spiral Galaxy

Galaxy with rotating arms

Elliptical Galaxy

Oval-shaped galaxy containing older stars

Irregular Galaxy

Galaxy with no clear shape

Milky Way

Galaxy containing our solar system

Solar System

System made up of the Sun and all objects orbiting it

Mercury

First planet from the Sun

Venus

Second planet from the Sun

Earth

Third planet from the Sun

Mars

Fourth planet from the Sun

Jupiter

Fifth planet from the Sun

Saturn

Sixth planet from the Sun

Uranus

Seventh planet from the Sun

Neptune

Eighth planet from the Sun

Dwarf Planet

Celestial body orbiting the Sun but not classified as a full planet

Rotation

Spinning of a body on its axis

24 hours

Earth’s Rotation Period

Revolution

Movement of a body around another body

365.25 days

Earth’s Revolution Period

Seasons

Caused by Earth’s revolution and axial tilt

Comets

Small icy object orbiting the Sun made of ice, dust, and rock

Nucleus

Solid center of a comet

Coma

Cloud surrounding a comet’s nucleus

Tail

Trail of gas and dust extending from a comet

Asteroid

Rocky object orbiting the Sun

Asteroid Belt

Region between Mars and Jupiter where most asteroids are found

Meteoroid

Small rock in space

Meteor

Rock burning in Earth’s atmosphere; also called a shooting star

Meteorite

Rock that reaches Earth’s surface

Moon Phases

Different appearances of the Moon caused by changing positions of Earth, Moon, and Sun

New Moon

Moon is not visible from Earth

Waxing Crescent

Less than half illuminated and increasing

First Quarter

Half of the Moon is illuminated

Waxing Gibbus

More than half illuminated and increasing

Full Moon

Entire visible side of the Moon is illuminated

Waning Gibbous

More than half illuminated and decreasing

Third Quarter

Half of the Moon is illuminated while decreasing

Waning Crescent

Less than half illuminated and decreasing

Moon Cycle

Complete cycle of Moon phases

Eclipse

Occurs when one celestial body moves into the shadow of another

Solar Eclipse

Occurs when the Moon moves between Earth and the Sun, blocking sunlight

Total Solar Eclipse

Moon completely blocks the Sun

Partial Solar Eclipse

Moon blocks only part of the Sun

Annual Solar Eclipse

Moon appears smaller than the Sun, creating a ring of light

Lunar Eclipse

Occurs when Earth moves between the Sun and Moon, blocking sunlight from reaching the Moon

Total Lunar Eclipse

Entire Moon passes through Earth’s shadow

Partial Lunar Eclipse

Only part of the Moon enters Earth’s shadow

Penumbral Lunar Eclipse

Moon passes through Earth’s outer shadow, causing slight dimming