Moden Astronomy Terms

Question 1

What is a heliocentric model?

Answer 1

A sun centered astronomical model.

Pg. 31

Question 2

What is the magnitude system?

Answer 2

A system that describes the brightness of stars.

Pr. 33

Question 3

Who is the first astronomer to use the magnitude system?

Answer 3

Hipparchus (190 - 120 BC)

Pg. 33

Question 4

Where did Claudius Ptolemaeus work?

Answer 4

Alexandria, Egypt during the mid second century AD

Pg. 34

Question 5

From an observer on the surface of the Earth, how would a prograde vs. retrograde orbit appear in the night sky?

Answer 5

Prograde = Eastward progressing
Retrograde = Westward progressing

Pg. 34

Question 6

The constraint of “uniform circular motion” can be traced to which Greek astronomers?

Answer 6

Pythagoras and Plato

Pg. 35

Question 7

What is the littoral meaning of that work “eccentric.”

Answer 7

Away from the center.

Pg. 35

Question 8

What does the term “parallax” refer to?

Answer 8

The shift in apparent position of an object when see from two different locations.

Pg. 37

Question 9

Define “geocentric” paralax.

Answer 9

The shift in apparent position of a relatively nearby object such as the moon or a planet, when seen from two different points on the Earth’s surface.

Pg. 37

Question 10

What is a synonym for geocentric parallax?

Answer 10

Durinal parallax.

Pg. 37

Question 11

What is heliocentric parallax?

Answer 11

The shift in apparent position of a relatively nearby star when seen from two different points on the Earth’s orbit.

Pg. 37

Question 12

What is a synonym for heliocentric parallax?

Answer 12

Annual parallax.

Pg. 37

Question 13

What was the first scientist since antiquity to advance a heliocentric model of the solar system?

Answer 13

Nicholas Copernicus

Pg. 38

Question 14

What is an “inferior planet?”

Answer 14

A planet with an orbit smaller than the Earth’s orbit around the sun.

Pg. 40

Question 15

What is a “superior planet?”

Answer 15

A planet with an orbit larger than Earth’s.

Pg. 40

Question 16

Define “Opposition.”

Answer 16

This occurs when the Earth lies between the Sun and a superior planet under study.

Notes: The angle is 180 degrees. See Fig. 2.8 on Pg. 41.

Pg. 40

Question 17

Define “Conjunction.”

Answer 17

Conjunction occurs when the Sun lies between the Earth and the superior planet or the standard angle between the Earth and the object is zero degrees.

Notes: See Fig. 2.8 on Pg. 41.

Pg. 40

Question 18

Define “Quadrature.”

Answer 18

Quadrature occurs when the Sun and the superior planet are 90 degrees apart as seen from the Earth.

Notes: See Fig. 2.8 on Pg. 41.

Pg. 40

Question 19

What is Inferior conjunction?

Answer 19

An Inferior conjunction occurs when the inferior planet lies between the Earth and the sun.

Pg. 41

Question 20

What is a Superior conjunction?

Answer 20

A superior conjunctions occurs when the Sun lies between the Eartha and the inferior planet.

Pg. 41

Question 21

What is “Elongation?”

Answer 21

When a planet is not in conjunction, it is separated from the Sun on the celestial sphere by an angle known as the planets’ elongation.

Pg. 41

Question 22

How is the synodic period measured?

Answer 22

By measuring the time elapsed between successive conjunctions.

Pg. 41

Question 23

What is a planet’s “sidereal period?”

Answer 23

The time it takes the planet to complete one full circuit of the sky relative to the fixed stars.

Pg. 41 & 42

Question 24

True or False

The synodic period of a planet is longer than its sidereal period.

Answer 24

True

Pg. 42

Question 25

What is the AU unit?

Answer 25

The astronomical unit. It is defined as the average distance between the Earth and the sun. Pg. 44

Question 26

State Occam's Razor.

Answer 26

The simplest description of nature is most likely to be most nearly correct. Pg. 47

Question 27

What are the four Galilean satellites orbiting Jupiter?

Answer 27

Io, Europa, Ganymede, and Callisto. Pg. 48

Question 28

What is Kepler's first law of planetary motion?

Answer 28

Planets travel on elliptical orbits with the sun at one focus. Pg. 50

Question 29

The longest distance along an ellipse (which passes through both foci) is called the _____.

Answer 29

Major axis. Pg. 50

Question 30

The semi-major axis of an ellipse can be described by ______.

Answer 30

1/2 of the major axis. Pg. 50

Question 31

Geometrically, how could one describe an ellipse?

Answer 31

An ellipse is the focus of points for which the sum of the distances to the foci is constant. Pg. 50

Question 32

What is the eccentricity of an ellipse?

Answer 32

The distance between the foci divided by the length of the major axis. Pg. 50

Question 33

Which planet has the largest eccentricity? What is its value?

Answer 33

Mercury 0.21 Pg. 51

Question 34

What is Kepler's second law of planetary motion?

Answer 34

A line drawn from the Sun to a planet sweeps out equal areas in equal time intervals. Pg. 51

Question 35

Kepler's second law implies that planets move most rapidly at ________, and least rapidly at _______.

Answer 35

Perihelion. Aphelion. Pg. 51

Question 36

Kepler's second law is a consequence of __________.

Answer 36

Conservation of angular momentum. Pg. 51

Question 37

What is Kepler's third law of planetary motion?

Answer 37

The squares of the sidereal orbital periods of the planets are proportional to the cubes of the semi major axis of their obits. Pg. 51

Question 38

Describe the aberration of starlight.

Answer 38

The aberration of starlight is an effect that causes the apparent positions of the starts on the celestial sphere to be deflected in the direction of the observers motion. Pg. 58

Question 39

What is the definition of an arcsecond?

Answer 39

1/3600 of a degree. Ref: Wikipedia

Question 40

What is the definition of a parsec?

Answer 40

The distance at which a star has a parallax of exactly 1''. Pg. 59

Question 41

True or False | The number of AU in one parsec is equal to the number of arseconds in one radian.

Answer 41

True Pg. 59

Question 42

How many AU are in one parsec?

Answer 42

206265 Pg. 59

Question 43

What is the nearest start to the sun?

Answer 43

Proxima Centauri Pg. 59