Astronomy Test 1 Part 1 Flashcards

Questions and Answers

The point in the sky directly above your head at any given time is called the ___

zenith

The celestial sphere turns once around each day because ______.

the planet is rotating

The south celestial pole and the north celestial pole lie in the sky directly above the _____.

Earth's axis

Halfway between the celestial poles lies the _____.

celestial equator Signup and view all the answers

In the Northern Hemisphere, the altitude (height in degrees above the horizon) of the North Star is always roughly equal to the ____.

latitude of the observer Signup and view all the answers

The star that is currently closest to the North Celestial Pole is ______.

Polaris Signup and view all the answers

As seen from the continental United States, the Big and Little Dipper _____.

are in the north circumpolar zone throughout the year Signup and view all the answers

Where on Earth do stars always circle the zenith (and never rise and set)?

the north pole Signup and view all the answers

From horizon to opposite horizon, the sky takes up how much angular distance?

180 degrees Signup and view all the answers

The Sun's apparent path around the celestial sphere is called _____.

ecliptic Signup and view all the answers

If the Earth goes around the Sun, why is the ecliptic not lined up with the celestial equator?

Because the Earth is tilted on an axis Signup and view all the answers

Every celestial object appears to go around the Earth once a day. In addition to this motion, which celestial object has the fastest apparent motion in the sky?

The Moon Signup and view all the answers

The strip of the sky through which the Sun, Moon, and bright planets appear to move in the course of a year is called ____.

the zodiac Signup and view all the answers

The 88 sectors into which astronomers today divide the celestial sphere (the whole sky) are called ______.

constellations Signup and view all the answers

Which ancient Greek thinker suggested (long before Copernicus) that the Earth is moving around the Sun?

Aristarchus of Samos Signup and view all the answers

How did Eratosthenes measure the size of the Earth?

by measuring the height of the Sun in the sky on the same day in two cities at different latitudes Signup and view all the answers

When a planet temporarily moves westward in the sky over the course of several weeks or months (instead of eastward, as it typically does), we call it _____.

retrograde motion Signup and view all the answers

The slow tipping of the Earth's axis in a circle with a period of about 26,000 years is called_______.

precession Signup and view all the answers

The great astronomer of ancient times who summarized and improved a system of circles upon circles to explain the complicated motions of the planets (and published the system in a book now called The Almagest) is: ______.

Ptolemy Signup and view all the answers

In Ptolemy's system, how did the planets explain the retrograde motion of planets like Jupiter?

the planets moved on a small circle whose center in turn circled a point near the Earth Signup and view all the answers

Study Notes

Celestial Concepts

The zenith is the point directly above an observer's head in the sky.
The celestial sphere rotates daily due to Earth's rotation.
North and south celestial poles align with Earth's axis.
The celestial equator lies halfway between the celestial poles.

Observational Astronomy

In the Northern Hemisphere, the altitude of the North Star (Polaris) equals the latitude of the observer.
Big and Little Dipper constellations are circumpolar in the northern sky throughout the year.
At the North Pole, stars circle the zenith, never rising or setting.

Angular Measurements

The sky from horizon to horizon spans an angular distance of 180 degrees.
The ecliptic is the Sun's apparent path across the celestial sphere.

Celestial Mechanics

The ecliptic does not align with the celestial equator due to Earth's axial tilt.
The Moon exhibits the fastest apparent motion among celestial objects, completing its journey across the sky daily.
The zodiac is the band of the sky where the Sun, Moon, and bright planets appear to move annually.

Constellation and Historical Figures

The celestial sphere is divided into 88 constellations by astronomers.
Aristarchus of Samos proposed the heliocentric model long before Copernicus.
Eratosthenes calculated Earth's circumference by comparing the Sun's angle at two different latitudes.

Motion Dynamics

Retrograde motion refers to a planet's apparent westward movement over weeks or months.
Precession is the gradual change in Earth's axial tilt that occurs over approximately 26,000 years.

Ancient Astronomical Systems

Ptolemy enhanced a geocentric model that utilized circular orbits to explain planet movements and retrograde motion.
In Ptolemy’s system, planets are thought to move along small circles (epicycles) while circling near Earth.

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Description

Test your knowledge of key astronomy terms and concepts with these flashcards. Each card presents a fundamental idea related to celestial mechanics and the structure of the sky. Ideal for students preparing for an astronomy exam or anyone interested in the field.