Astronomy Chapter 1 Flashcards

Universe and Astronomy

• Universe encompasses all space, time, matter, and energy.
• Astronomy focuses on celestial phenomena beyond Earth’s atmosphere.

Measurements and Definitions

• A light-year equals approximately 10 trillion kilometers, representing the distance light travels in one year at 300,000 km/s.
• The scientific method involves continuous testing and modification of scientific laws.

Theories and Models

• A theory is a framework for explaining observations and predicting real-world outcomes.
• Theoretical models mathematically explain physical processes and make testable predictions.

Celestial Mechanics

• Constellations are recognizable star patterns in the night sky, grouped by human perception.
• The celestial sphere is an imaginary construct where celestial bodies appear attached.

Earth’s Movements

• Rotation refers to an object's spinning around an axis, like Earth on its axis.
• Revolution is the orbital motion around another body, such as Earth around the Sun.

Time Measurement

• A solar day is the time from one overhead Sun position to the next.
• A sidereal day measures the interval between successive appearances of a star.

Celestial Geography

• The celestial equator is Earth's equator projected onto the celestial sphere.
• The celestial poles are projections of Earth's poles onto the celestial sphere.

Seasonal Changes

• Seasons arise from Earth's axial tilt relative to its orbital plane.
• The summer solstice occurs around June 21, marking the Sun’s highest point north of the celestial equator.
• The winter solstice occurs around December 21, marking the Sun’s lowest point south of the celestial equator.

Equinoxes

• The vernal equinox occurs around March 21, when the Sun crosses the celestial equator moving north.
• The autumnal equinox occurs around September 21, when the Sun crosses southward.

Orbital and Astronomical Periods

• A tropical year lasts from one vernal equinox to the next.
• A sidereal year is the time for constellations to return to their original positions in the sky.

Physical Phenomena

• Precession refers to the slow change in the rotation axis direction due to external gravitational influences.
• The phase of the Moon varies as its sunlit face appears from Earth during its orbit.

Lunar and Solar Eclipses

• Eclipses occur when one celestial body passes in front of another, blocking light.
• A lunar eclipse happens when the Moon passes through Earth's shadow, while a solar eclipse occurs when the new Moon blocks sunlight from reaching Earth.
• Total eclipses completely obscure a celestial body, while partial eclipses block only part of it.

Measurement Techniques

• Triangulation uses geometry to determine distance via angles from separate locations.
• The cosmic distance scale employs various indirect methods for measuring cosmic distances.
• Baseline refers to the distance between two observation points used in triangulation; larger baselines improve measurement accuracy.
• Parallax gives an apparent motion perspective of an object as the observer’s viewpoint changes.

Study the key terms of astronomy with these flashcards from Chapter 1. Each card provides definitions for important concepts such as 'universe,' 'astronomy,' and 'light-year.' Perfect for reinforcing your understanding of the universe and its components.