Astronomy Celestial Sphere Flashcards

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Questions and Answers

What is a celestial sphere?

Imaginary sphere surrounding Earth to which all objects in the sky were once considered to be attached.

What is a celestial pole?

Projection of Earth's North and South pole onto the celestial sphere.

What is the celestial equator?

The projection of Earth's equator onto the celestial sphere.

What is a celestial meridian?

Line that goes from North and South Celestial pole that passes directly overhead. Signup and view all the answers

What is the ecliptic?

The apparent path of the Sun, relative to the stars on the celestial sphere, over the course of a year. Signup and view all the answers

What is the zodiac?

The 12 constellations on the celestial sphere through which the Sun appears to pass during the course of a year. Signup and view all the answers

What is the vernal equinox?

Date on which the Sun crosses the celestial equator moving northward, occurring on or near March 21st. Signup and view all the answers

What is the autumnal equinox?

Date on which the Sun crosses the celestial equator moving southward, occurring on or near September 21st. Signup and view all the answers

What is a winter solstice?

Point on the ecliptic where the Sun is at its southernmost point below the celestial equator, occurring on or near December 21st. Signup and view all the answers

What is a summer solstice?

Point on the ecliptic where the Sun is at its northernmost point above the celestial equator, occurring on or near June 21st. Signup and view all the answers

What is precession?

The slow change in the direction of the rotation axis of a spinning object, caused by some external gravitational influence. Signup and view all the answers

What are circumpolar stars?

Stars that are always above the horizon. Signup and view all the answers

What is the celestial horizon?

Line that delineates between the half of the celestial sphere we can see and cannot see. Signup and view all the answers

What is right ascension?

Celestial coordinate used to measure longitude on the celestial sphere. Signup and view all the answers

What is declination?

Celestial coordinate used to measure latitude above or below the celestial equator on the celestial sphere. Signup and view all the answers

What does latitude tell us?

It tells how far North or South we are. Signup and view all the answers

What does longitude tell us?

It tells how far East or West we are. Signup and view all the answers

What is a sidereal day?

The time needed between successive risings of a given star. Signup and view all the answers

What is a solar day?

The period of time between the instant when the sun is directly overhead (noon) to the next time it is directly overhead. Signup and view all the answers

What is retrograde motion?

Backward, westward loop traced out by a planet with respect to the fixed stars. Signup and view all the answers

What are inferior planets?

Planets that are closer to the Sun than Earth. Signup and view all the answers

What are superior planets?

Planets that are further away from the Sun than Earth. Signup and view all the answers

What is planetary opposition?

In exact opposite point in the sky at midnight (opposite of noon). Signup and view all the answers

What is a constellation?

A human grouping of stars in the night sky into a recognizable pattern. Signup and view all the answers

What is a lunar phase?

The appearance of the Moon at different points along its orbit. Signup and view all the answers

What does lunar planetary mean?

Works same as phases do, only see a face of Venus. Signup and view all the answers

What is the transit of the Sun?

When Mercury passes in front of the Sun. Signup and view all the answers

Study Notes

Celestial Sphere Concepts

Celestial Sphere: An imaginary sphere surrounding Earth, historically thought to hold all celestial objects.
Celestial Pole: The projection of Earth’s North and South poles onto the celestial sphere.
Celestial Equator: Represents the projection of Earth’s equator on the celestial sphere.
Celestial Meridian: A line extending from the North to South Celestial pole, traversing directly overhead.

Solar and Celestial Events

Ecliptic: Describes the Sun's apparent annual path against the backdrop of stars on the celestial sphere.
Zodiac: Comprises 12 constellations that the Sun appears to traverse throughout the year.
Vernal Equinox: Marks the Sun’s northward crossing of the celestial equator, occurring around March 21.
Autumnal Equinox: Occurs when the Sun crosses the celestial equator moving southward, around September 21.
Winter Solstice: The point where the Sun reaches its southernmost position below the celestial equator, around December 21.
Summer Solstice: The point where the Sun is at its northernmost position above the celestial equator, around June 21.

Astronomical Phenomena

Precession: The gradual shift in the orientation of a spinning object's rotation axis, influenced by gravitational forces.
Circumpolar Stars: Stars that are permanently visible above the horizon throughout the year.
Celestial Horizon: The boundary separating the visible and invisible halves of the celestial sphere.

Right Ascension: A coordinate system for measuring longitude on the celestial sphere.
Declination: A coordinate for measuring latitude above or below the celestial equator.
Latitude: Indicates how far north or south a location is relative to the equator.
Longitude: Indicates how far east or west a location is relative to the prime meridian.

Time Measurement and Motion

Sidereal Day: The duration between successive risings of a specific star, relating to the stars' position.
Solar Day: The time interval from one solar noon to the next, based on the Sun's position in the sky.
Retrograde Motion: The apparent east-to-west movement of a planet against the fixed stars in the night sky.

Planetary Classification

Inferior Planets: Planets that orbit closer to the Sun than Earth does.
Superior Planets: Planets that orbit farther from the Sun than Earth.
Planetary Opposition: A configuration where a planet is positioned opposite the Sun in the sky at midnight.

Astronomical Structures

Constellation: A recognized pattern formed by a group of stars in the night sky, based on human interpretation.
Lunar Phase: The different appearances of the Moon as it orbits Earth.
Lunar Planetary: Similar to lunar phases, this refers to the visibility of Venus, typically as a crescent.

Transits

Transit of the Sun: Occurs when Mercury passes directly in front of the Sun from Earth's perspective.

Celestial Sphere and Components

Celestial Sphere: Imaginary sphere encompassing Earth, where all celestial objects are projected.
Celestial Pole: Earth's North and South poles extended onto the celestial sphere.
Celestial Equator: Projection of Earth's equator onto the celestial sphere, dividing it into northern and southern hemispheres.
Celestial Meridian: Imaginary line connecting the North and South Celestial poles, passing directly overhead.

Key Astronomical Concepts

Ecliptic: The pathway the Sun appears to trace among the stars throughout the year.
Zodiac: A belt of 12 specific constellations through which the Sun travels annually.
Vernal Equinox: Occurs around March 21st when the Sun crosses the celestial equator moving north.
Autumnal Equinox: Occurs around September 21st when the Sun crosses the celestial equator moving south.
Winter Solstice: Around December 21st, the Sun reaches its southernmost point below the celestial equator.
Summer Solstice: Around June 21st, the Sun reaches its northernmost point above the celestial equator.

Celestial Mechanics

Precession: Gradual shift in the orientation of the rotation axis of a spinning object due to gravitational forces.
Circumpolar Stars: Stars that are always visible in the night sky and never set below the horizon.
Celestial Horizon: Imaginary line distinguishing the visible celestial dome from the unseen hemisphere.

Celestial Coordinates

Right Ascension: Longitude-like celestial coordinate, measuring the east-west position on the celestial sphere.
Declination: Latitude-like celestial coordinate, measuring how far an object is above or below the celestial equator.

Earth-Based Coordinates

Latitude: Measures North-South position on Earth.
Longitude: Measures East-West position on Earth.

Time Measurement

Sidereal Day: Time taken for a star to return to the same position in the sky; relates to the stars.
Solar Day: Period between two successive solar noons where the Sun is directly overhead.

Planetary Movements

Retrograde Motion: Apparent backward movement of a planet against the backdrop of fixed stars.
Inferior Planets: Planets that orbit closer to the Sun than Earth; example includes Mercury and Venus.
Superior Planets: Planets that are located further from the Sun than Earth; examples include Mars, Jupiter, Saturn.

Additional Concepts

Planetary Opposition: Configuration when a planet is directly opposite the Sun in the sky at midnight.
Constellation: Recognizable patterns formed by grouping stars in the night sky.
Lunar Phase: Changing appearance of the Moon as it orbits Earth, resulting from its position relative to the Sun.
Lunar Planetary: Refers to Venus as seen in its phases, appearing only as a crescent.
Transit of the Sun: Occurs when Mercury passes directly between Earth and the Sun, appearing as a small dot moving across the Sun.

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Description

Test your knowledge on key terms related to the celestial sphere in astronomy. This study guide covers essential concepts such as the celestial pole, equator, and meridian. Perfect for students looking to deepen their understanding of the night sky and celestial mechanics.