Astronomy Exam III Study Guide

Vocabulary practice flashcards based on the Astronomy Exam III Study Guide covering planetary science, historical astronomers, solar features, spectroscopy, and stellar characteristics.

Voyager 1

A robotic space probe launched by NASA on September 5, 1977, designed to explore the outer Solar System and interstellar space.

Voyager 2

The space probe that visited Uranus (only).

William Herschel

An astronomer (1738–1822) who, with the assistance of his sister, discovered the planet Uranus using a unique telescope.

Clyde Tombaugh

An American astronomer (1906–1997) best known for discovering the dwarf planet Pluto.

Christiaan Huygens

A 17th-century Dutch astronomer, mathematician, and physicist (1629–1695) who made foundational contributions to observational astronomy and the Scientific Revolution.

Edmund Hally

An astronomer (1656–1742) who suggested that comets behave and follow rules in the same manner as other objects orbiting the Sun.

Wilhelm Wien

A physicist (1864–1928) who experimented with light sources and spectroscopes, formulating Wien's Law regarding blackbody temperature and wavelength.

Wien's Law

A physical law stating that the wavelength becomes shorter when the black body becomes shorter, and the amount of energy emitted becomes greater as the black body becomes hotter.

Samuel Heinrich Schwabe

A German pharmacist and amateur astronomer (1789–1875) who discovered the periodic cycle of sunspots.

Hipparchus

The earliest known astronomer to classify stars not only by their sky positions but also by how bright they appeared.

Jupiter

The first gas giant, characterized by the fastest rotation period of any planet, composed of 88% hydrogen and 11% helium, and entirely liquid with no solid surface.

Great Red Spot

A long-lived storm on Jupiter that changes in size and color while remaining at a constant latitude, dredging material from deep within the planet.

Saturn

The sixth planet from the Sun and the second-largest planet in the Solar System, classified as a low-density gas giant.

Uranus

The 7th planet from the Sun; a gas planet with an icy core, an atmosphere of hydrogen and helium, a speculated diamond layer, and an obliquity of $90^\circ$, earning it the title 'Planet on its side.'

Neptune

A planet discovered in 1846 sharing similar mass and size with Uranus, featuring atmospheric clouds and the Great Dark Spot.

Great Dark Spot

A massive, spinning anticyclonic storm system located in the southern atmosphere of Neptune.

Galilean Satellites

Moons of Jupiter that orbit within its equatorial plane, forming a flattened disk analogous to a miniature Solar System.

Callisto

One of Jupiter's Galilean moons, possessing a density of $1.85\,\text{g/cm}^3$.

Ganymede

The largest moon orbiting Jupiter, characterized by a density of $1.94\,\text{g/cm}^3$.

Europa

A moon of Jupiter with a density of $2.99\,\text{g/cm}^3$; it is the only Galilean moon not larger than Earth's Moon.

Io

A moon of Jupiter with a density of $3.53\,\text{g/cm}^3$.

Titan

The largest natural satellite of Saturn and the second-largest moon in the Solar System.

Triton

The largest natural satellite of Neptune and the only large moon in the Solar System featuring a retrograde orbit.

Pluto

A dwarf planet situated in the Kuiper Belt among icy and rocky bodies beyond Neptune's orbit.

Oort Bloud

A theoretical, vast spherical shell containing billions to trillions of icy planetesimals and comets surrounding the outer edges of the Solar System.

Kuiper Belt

A circumstellar disc beyond Neptune believed to be the reservoir from which short-period comets originate.

Pleiades

A prominent open star cluster and asterism situated between 440 and 444 light-years away in the constellation Taurus.

Sirius

The brightest star in Earth's night sky, possessing an apparent magnitude of $-1.46$.

Hydrogen

The simplest and most abundant chemical element in the universe, constituting roughly 75% of normal matter and fueling stellar lifecycles.

Helium

The second-lightest and second-most abundant element in the universe, comprising roughly 24% of its elemental mass.

Jovian Planet

A low-density, hydrogen-rich planetary body located beyond the Solar System's frost line.

Metallic Hydrogen

A highly electrically conductive state of hydrogen formed under immense pressure, naturally present inside Jupiter and Saturn.

Zone

A distinct, belt-like, or concentric atmospheric or spatial region defined by specific physical properties and conditions.

Belt

A dark, alternating atmospheric band on a gas giant, or a torus-shaped region hosting a concentration of small celestial bodies.

Ammonia

A volatile hydride molecule ($\text{NH}_3$) made of one nitrogen and three hydrogen atoms, functioning as a chemical tracer in planetary atmospheres.

Barge

Transient, dark atmospheric openings on Jupiter that expose deeper, brown layers, interpreted as storm features.

White Oval

Tall, storm-related ammonia cloud columns rising above Jupiter's brown cloud decks without visible openings.

Methane

The simplest hydrocarbon molecule ($\text{CH}_4$), consisting of a central carbon atom bonded to four hydrogen atoms.

Sulfur

An alpha-process element synthesized within massive stars during explosive oxygen burning.

Spokes

Transient, radial streaks of dust and ice particles visible across Saturn's broad B ring.

Short Period Comet

A comet orbiting in the plane of the ecliptic in a counter-clockwise direction with high eccentricity and an orbital period listed as $P > 200\text{ years}$.

Long Period Comet

A comet with an orbital eccentricity near $1$, random orbital inclinations, and periods spanning thousands or millions of years.

Nucleus (of a comet)

The solid, frozen core located at the center of a comet.

Coma

The expansive gaseous envelope that forms around a comet's nucleus as solar heating causes ices to sublimate.

Tail

An elongated feature of a comet up to an astronomical unit in length, categorized into dust tails (which shed along the orbit and cause meteor showers) and gas tails.

Proto-Solar Nebula

The flattened, rotating cloud of gas and microscopic dust from which the Solar System originated approximately $4.6\text{ billion years ago}$.

Solar Wind

A stream of charged particles released by the Sun capable of applying radiation pressure throughout the Solar System.

Planetesimal

A primordial body formed through accretion of dust and rock whose mutual collisions built the planets.

Exoplanet

A planet orbiting a star other than our Sun.

Dispersion

The phenomenon where electromagnetic propagation speeds vary with frequency or wavelength across a medium, spreading signal arrival times.

Spectrosphere

The observational method of dispersing electromagnetic radiation into component wavelengths to analyze celestial objects.

Continuous Spectrum

An unbroken rainbow of radiation across all wavelengths emitted without absorption gaps or localized emission spikes.

Absorption Spectrum

A continuous radiation spectrum interrupted by dark lines caused by intermediate gas absorbing specific photon wavelengths.

Emission Spectrum

Discrete bright spectral lines produced when electrons in an excited gas transition to lower energy levels.

Core (of a star)

The dense, superheated central region where high pressure and temperature sustain energy generation via nuclear fusion.

Photosphere

The visible surface and lowest atmospheric layer of a star that emits its light and heat into space.

Sunspot

A cooler, darker region on the solar photosphere created by intense magnetic fields suppressing convective heat transfer.

Sunspot Cycle

An approximately 11-year cycle regulating the abundance, distribution, and activity of sunspots.

Chromosphere

The lower-to-middle solar atmospheric layer positioned between the photosphere and the transition zone below the corona.

Corona

The extremely hot, tenuous outermost layer of a star's atmosphere, shaped by stellar magnetic field lines.

Prominence

A large loop or arch of dense, cooler plasma suspended above the solar surface by magnetic fields.

Trigonometric Parallax

The geometric method of measuring distance using the apparent shift of a star against background stars when viewed from two different orbital locations.

Parallax Formula

The mathematical relation determining stellar distance: $r = \frac{N}{p}$ or $r\,(\text{pc}) = \frac{1}{p}$.

Parsec

A unit of distance derived from 'parallax second,' equivalent to $3.26\,\text{light-years}$.

Light-Year

The distance traversed by light in one Julian year, equal to $1 \times 10^{13}\,\text{km}$.

Binary Star

A system of two or more gravitationally bound stars orbiting a shared center of mass in close physical proximity.

Open Star Cluster

A grouping of stars loosely bound together in space.

Inverse-Square Law

A mathematical relationship governing observed radiation intensity, expressed as $I \propto \frac{1}{r^2}$, where brightness diminishes with the square of the distance.

Luminosity

The absolute intrinsic energy or light output generated at the source of a star, remaining invariant with distance.

Apparent Magnitude ($m$)

The observed brightness of a celestial object as seen from Earth ('out the window').

Absolute Magnitude ($M$)

The true brightness a celestial object would exhibit if placed at a standardized distance from the observer.

Physical Structure of Jupiter

An oblate sphere composed primarily of fluids, representing the largest and most massive planet in the Solar System, with only Saturn possessing a lower density.

Hydrogen in Jovian Planets

The predominant constituent of giant planets, which can exist in gaseous, liquid, or (in the case of Jupiter and Saturn) metallic states.

Third Class of Planetary Bodies

A category exemplified by the Galilean satellites, Pluto, and Saturn's ring particles, consisting of objects composed largely of medium-density ice.

Surface Indicators of Geologic Activity

Observable surface characteristics—specifically crater density, texture, and terrain variety—that reveal the extent and history of geologic processes experienced by a planet or moon.

Comets

Icy celestial bodies that travel along highly eccentric orbits around the Sun, developing a gaseous coma and tail as their frozen nuclei are heated upon approaching the Sun.