Astronomy Vocabulary Terms PDF

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This is a comprehensive list of the most important terms (as well as a few names) that are crucial to know for the course....

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ASTRONOMY VOCABULARY TERMS ●

Asterisms- lines drawn of constellations that make “stick figures” (88 constellations)

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Circumpolar Star- a star that never dips below the horizon along its path in the sky

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Seasonal Star- stars that dip below the horizon along their path in the sky

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Ecliptic- a star’s annual path relative to the background stars

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Constellations of the Zodiac- constellations covered annually by the sun’s ecliptic

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Models- used to aid understanding, make predictions, and simplify complex phenomena

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Heliocentric- model assuming the sun at the center of the solar system

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Geocentric- model assuming the Earth at the center of the solar system

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Theory- a model and a statement of the law’s relative truth

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Law- a theory repeatedly confirmed by experiments

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Aristotle- claimed that the Earth was spherical

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Eratosthenes- first person to measure the Earth/ calculate its size using relative positions of the Sun on the same day in different years

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Aristarchus- first measured the size of the moon relative to the Earth using Earth’s shadow on the moon

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Pythagorean Model- Model claiming the universe to be geocentric, surrounded by a pythagorean sphere

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Pythagorean Sphere- conceptual celestial sphere surrounding Earth “painted” with stars

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Immutable- unchanging

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Wandering Stars- first description of planets (derived from the greek word ‘planetes’, meaning ‘wanderers’

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Copernicus- theorized a model that demoted Earth to ‘just a planet’

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Eudoxes of Cnides- student of Plato that devised a multisphere model that Aristotle used for his model

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Epicycle- small circular motion a planet makes in its orbit around Earth (used to explain retrograde motion

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Celestial Mechanics- study of motions of objects in the heavens

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Isaac Newton- combined terrestrial and celestial laws of mechanics with gravity

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Kepler’s 1st Law- The Sun is at the center of the solar system

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Kepler’s 2nd Law- Planets orbit the sun in an elliptical motion. As they are closer to the Sun, they move faster in their orbit so that an imaginary line drawn between the planet and the Sun covers the area between at the same rate

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Kepler’s 3rd Law- The length of a planet’s year is proportional to the size of its orbit. (distance = period^2 / mass)

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3 Components to measure radiation- collect & focus light, sort radiation by wavelength, detect & record data

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OBAFGKM- classification order of stellar radiation

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Apparent Brightness- how bright a star appears to us on Earth

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Luminosity- how much light a star gives off (the Sun has a luminosity of 1)

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Hertzsprung-Russel (HR) Diagram- a chart/graph plotting stars by luminosity, temperature, and color

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Types of Galaxies- Barred, Spiral, Barred Spiral, Elliptical, & Irregular

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Types of Star Clusters- Globular and open (globular contain far more than open and all stars are same age and contain same materials

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Pleiades- Star cluster that the subaru logo is composed of

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Hubble’s Constant- estimated constant for measuring how old the universe is based on recessional velocity (the larger Hubble’s constant is, the younger the universe is)

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Laniakea- the supercluster in which our milky way galaxy resides

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Layers of the Sun- (internal to external) core, radiation zone, convection zone, photosphere, chromosphere, corona

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Coronal loops- filamentary structure traces in the Sun’s magnetic field...