Astronomy unit test (better one)

Asteroid

A rocky object, mostly found in the asteroid belt between Mars and Jupiter.

Comet

A small icy object from the outer solar system with a tail when near the Sun.

Astronomical Unit (AU)

Average distance from Earth to the Sun (~93 million miles or 150 million km).

Revolution

One complete orbit around another body (Earth's revolution = 1 year).

Rotation

One complete spin on an axis (Earth's rotation = 1 day).

Terrestrial Planet

Rocky planets: Mercury, Venus, Earth, and Mars.

Galilean Moon

The four largest moons of Jupiter discovered by Galileo (Io, Europa, Ganymede, Callisto).

Gas Giant

Large planets made mostly of gas: Jupiter, Saturn, Uranus, Neptune.

Dwarf Planet

A body orbiting the Sun, like a planet but not dominant in its orbit because its too close to another planet (e.g., Pluto).

Spectroscope

Tool that breaks light into a spectrum to analyze composition.

Telescope

Tool to observe distant objects in space by collecting light.

Light-Year

Distance light travels in one year (~6 trillion miles).

Apparent Magnitude

How bright a star appears from Earth.

Absolute Magnitude

The true brightness of a star at a standard distance.

Luminosity

Total energy output of a star per second.

Nuclear Fusion

Process powering stars; hydrogen atoms fuse into helium.

Star

A ball of gas undergoing nuclear fusion.

Radiative Zone

Layer of a star where energy moves outward as radiation.

Convection Zone

Layer where hot plasma rises and cooler plasma sinks.

Photosphere

The visible surface of the Sun.

Chromosphere

A reddish layer above the photosphere.

Corona

The Sun's outer atmosphere; visible during eclipses.

Hertzsprung-Russell Diagram (H-R Diagram)

Graph showing relationship between star brightness and temperature.

Main Sequence Star

A stable star in the middle of its life (like our Sun).

Nebula

A cloud of gas and dust; birthplace of stars.

White Dwarf

The remains of a low-mass star after it sheds its outer layers.

Supernova

Massive explosion marking the death of a large star.

Neutron Star

Extremely dense remnant of a supernova.

Black Hole

A region of space with gravity so strong not even light can escape.

Galaxy

A massive system of stars, gas, dust, and dark matter.

Dark Matter

Invisible matter that affects gravity but doesn't emit light.

Parallax

Apparent shift in position of a nearby star due to Earth's orbit; used to measure distance.

Inner planets

Small, rocky, solid surfaces, closer to the Sun, fewer moons, no rings.

Outer planets

Large, made of gas or ice, have rings and many moons, far from the Sun.

Kuiper Belt

Region beyond the asteroid belt, home to Pluto.

Oort Cloud

Farthest region of the solar system.

Astronomical Units (AU)

Unit of measurement used inside the solar system.

Light-years (ly)

Unit of measurement used outside the solar system.

Parsecs

Another unit of measurement used outside the solar system.

Constellations

Patterns used to map the night sky.

H-R Diagram usage

Compares temperature (x-axis) and luminosity/brightness (y-axis) of stars.

Types of galaxies

Spiral, Elliptical, and Irregular.