Astronomy Reviewer & Glossary Flashcards

40 QUESTION_AND_ANSWER flashcards covering key astronomy terms from Tarbuck Earth Science notes.

What is the Celestial Sphere?

An imaginary sphere surrounding Earth on which celestial bodies appear projected.

What is Right Ascension (RA)?

A celestial coordinate like longitude, measured eastward from the First Point of Aries.

What is Declination (Dec)?

A celestial coordinate like latitude, measured north/south of the celestial equator.

What are Azimuth and Altitude?

Horizontal coordinates: azimuth is the compass direction, altitude is the angle above the horizon.

What is the Ecliptic?

The apparent annual path of the Sun across the celestial sphere.

What do Equinoxes and Solstices mark?

Seasonal markers; equinox = equal day/night; solstice = Sun at maximum declination.

In Solar System Dynamics, what is Orbit?

Path of a body around another due to gravity.

In Solar System Dynamics, what is Revolution?

The orbital motion of a body around another to define a year around the Sun.

What is Phase?

Illumination pattern of the Moon and planets based on Sun–Earth positions.

What is Eclipse?

When one celestial body moves into another's shadow (lunar or solar).

What is Transit?

A smaller body passes in front of a larger one (e.g., Mercury transit).

What is Retrograde Motion?

Apparent backward motion of planets as Earth overtakes them.

What is Spectrum?

Light separated into wavelengths; reveals composition.

What are Absorption Lines?

Dark spectral lines where cooler gas absorbs light.

What are Emission Lines?

Bright spectral lines from hot gas emission.

What is Spectroscopy?

Technique analyzing spectra to determine properties of objects.

What are Telescopes?

Instruments gathering and focusing light; refractors use lenses, reflectors use mirrors.

What is a Star?

Self-luminous sphere of gas powered by nuclear fusion.

What is Magnitude?

Apparent brightness as seen; Absolute magnitude is intrinsic brightness.

What is Spectral Type?

Classification by temperature/color (O–M sequence).

What is a Luminosity Class?

Classification by brightness (I–V).

What is the H–R Diagram?

Graph of stellar luminosity vs temperature, showing evolution stages.

What is a Nebula?

Gas/dust cloud; may emit or reflect light.

What is a Star Cluster?

Group of stars; open = young, globular = old.

What is a Galaxy?

Massive system of stars, gas, and dust (e.g., Milky Way).

What is the Big Bang Theory?

Universe began from hot, dense state and expanded.

What are Redshift and Blueshift?

Spectral shift indicating motion: red = away, blue = toward.

What does Expansion of the Universe mean?

Observation that galaxies are moving apart.

What is a Light-Year?

Distance light travels in a year (~9.46 trillion km).

What is a Parsec?

Astronomical distance unit, 1 parsec ≈ 3.26 light-years.

From what reference point is Right Ascension measured?

The First Point of Aries.

Which two horizontal coordinates locate objects in the sky?

Azimuth and altitude.

What does an equinox indicate about day length?

Day and night are approximately equal.

What does a solstice indicate about the Sun's position?

Sun at its maximum declination; longest or shortest day.

What is the First Point of Aries used for?

The zero reference for measuring Right Ascension.

What does spectral type O indicate?

Highest temperature with a blue color.

What does spectroscopy allow astronomers to determine?

Composition, temperature, density, and motion of objects from spectra.

What characterizes a globular cluster?

Old, dense cluster of stars.

What characterizes an open cluster?

Young, loosely bound cluster of stars.

What is the difference between apparent magnitude and absolute magnitude?

Apparent is brightness as seen from Earth; absolute is intrinsic brightness at 10 parsecs.