Astronomy and Scientific Investigation Unit Vocabulary Field Guide

Vocabulary flashcards covering key terms and concepts from the Astronomy and Scientific Investigation Unit Vocabulary Field Guide.

Reasoning

The scientific principle that links evidence to a claim.

Light-year

The distance light travels in one year.

Electromagnetic spectrum

The full range of electromagnetic radiation.

Wavelength

The distance between corresponding points on successive waves.

Frequency

The number of wave cycles passing a point per second.

Spectrum

Radiation separated and arranged by wavelength.

Spectral line

A distinctive bright or dark feature at a specific wavelength.

Absorption spectrum

A continuous spectrum crossed by dark lines.

Doppler effect

A wavelength change caused by relative motion.

Redshift

A shift toward longer wavelengths from a receding source.

Blueshift

A shift toward shorter wavelengths from an approaching source.

Hubble's law

The relationship between galaxy distance and recession speed.

Big Bang theory

The current scientific explanation for the origin and expansion of the universe.

Hot, dense state

The early condition of the universe described by the model.

Expansion

An increase in large-scale distance as space changes over time.

Cosmic microwave background

Cooled radiation remaining from the early universe.

Hydrogen

The most abundant element formed shortly after the Big Bang.

Helium

A light element whose abundance supports model predictions.

Abundance

The relative amount of a substance that is observed.

Galaxy

A gravitationally bound collection of billions of stars, gas, and dust.

Spiral galaxy

A galaxy with a disk, central bulge, and spiral arms.

Elliptical galaxy

A smooth, rounded or oval galaxy without clear arms.

Irregular galaxy

A galaxy without a regular spiral or elliptical shape.

Gravity

The attractive force that organizes matter across cosmic scales.

Galaxy cluster

A gravitationally bound group of galaxies.

Merger

The joining and reshaping of galaxies through interaction.

Gravitational interaction

A mutual pull that changes the motion or structure of objects.

Milky Way

The spiral galaxy that contains the solar system.

Star system

One star and the objects gravitationally bound to it.

H-R diagram

A graph relating stellar luminosity to surface temperature.

Luminosity

The total energy a star emits per unit time.

Absolute magnitude

A measure of intrinsic stellar brightness at a standard distance.

Apparent brightness

How bright a star appears from Earth.

Surface temperature

The temperature of a star's visible outer layer.

Main sequence

The band of stars fusing hydrogen in their cores.

Giant

A large, luminous star above the main sequence.

Supergiant

An extremely large and luminous evolved star.

White dwarf

A hot, dim stellar remnant with a small radius.

Stellar mass

The amount of matter in a star and a major driver of evolution.

Nebula

A cloud of gas and dust from which stars may form.

Protostar

A collapsing young object before stable hydrogen fusion begins.

Fusion

The combining of light nuclei that releases energy.

Red giant

An expanded, luminous stage of a lower-mass star.

Supernova

The explosive death of a massive star.

Neutron star

An extremely dense remnant made mostly of neutrons.

Black hole

A compact remnant whose gravity prevents light from escaping.

Solar nebular theory

The current explanation for formation of the Sun and planetary system from a nebula.

Protoplanetary disk

A rotating disk of gas and dust around a young star.

Accretion

Growth by collisions and sticking of smaller particles.

Planetesimal

A small solid body that can grow into a planet.

Terrestrial planet

A small inner planet made mainly of rock and metal.

Gas giant

A large planet dominated by hydrogen and helium, such as Jupiter.

Ice giant

A large planet rich in water, ammonia, and methane materials.

Asteroid

A mostly rocky remnant or collision fragment orbiting the Sun.

Comet

A volatile-rich body that follows a typically elongated orbit.