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Astrophysics > Moden Astronomy Terms > Flashcards

Moden Astronomy Terms Flashcards

1
Q

What is a heliocentric model?

A

A sun centered astronomical model.

Pg. 31

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2
Q

What is the magnitude system?

A

A system that describes the brightness of stars.

Pr. 33

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3
Q

Who is the first astronomer to use the magnitude system?

A

Hipparchus (190 - 120 BC)

Pg. 33

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4
Q

Where did Claudius Ptolemaeus work?

A

Alexandria, Egypt during the mid second century AD

Pg. 34

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5
Q

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

A 
Prograde = Eastward progressing
Retrograde = Westward progressing

Pg. 34

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6
Q

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

A

Pythagoras and Plato

Pg. 35

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7
Q

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

A

Away from the center.

Pg. 35

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8
Q

What does the term “parallax” refer to?

A

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

Pg. 37

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9
Q

Define “geocentric” paralax.

A

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

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10
Q

What is a synonym for geocentric parallax?

A

Durinal parallax.

Pg. 37

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11
Q

What is heliocentric parallax?

A

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

Pg. 37

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12
Q

What is a synonym for heliocentric parallax?

A

Annual parallax.

Pg. 37

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13
Q

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

A

Nicholas Copernicus

Pg. 38

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14
Q

What is an “inferior planet?”

A

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

Pg. 40

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15
Q

What is a “superior planet?”

A

A planet with an orbit larger than Earth’s.

Pg. 40

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16
Q

Define “Opposition.”

A

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

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17
Q

Define “Conjunction.”

A

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

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18
Q

Define “Quadrature.”

A

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

19
Q

What is Inferior conjunction?

A

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

Pg. 41

20
Q

What is a Superior conjunction?

A

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

Pg. 41

21
Q

What is “Elongation?”

A

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

22
Q

How is the synodic period measured?

A

By measuring the time elapsed between successive conjunctions.

Pg. 41

23
Q

What is a planet’s “sidereal period?”

A

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

Pg. 41 & 42

24
Q

True or False

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

A

True

Pg. 42

25
Q

What is the AU unit?

A

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

Pg. 44

26
Q

State Occam’s Razor.

A

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

Pg. 47

27
Q

What are the four Galilean satellites orbiting Jupiter?

A

Io, Europa, Ganymede, and Callisto.

Pg. 48

28
Q

What is Kepler’s first law of planetary motion?

A

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

Pg. 50

29
Q

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

A

Major axis.

Pg. 50

30
Q

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

A

1/2 of the major axis.

Pg. 50

31
Q

Geometrically, how could one describe an ellipse?

A

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

Pg. 50

32
Q

What is the eccentricity of an ellipse?

A

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

Pg. 50

33
Q

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

A

Mercury
0.21

Pg. 51

34
Q

What is Kepler’s second law of planetary motion?

A

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

Pg. 51

35
Q

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

A

Perihelion.
Aphelion.

Pg. 51

36
Q

Kepler’s second law is a consequence of __________.

A

Conservation of angular momentum.

Pg. 51

37
Q

What is Kepler’s third law of planetary motion?

A

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

38
Q

Describe the aberration of starlight.

A

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

39
Q

What is the definition of an arcsecond?

A

1/3600 of a degree.

Ref: Wikipedia

40
Q

What is the definition of a parsec?

A

The distance at which a star has a parallax of exactly 1’’.

Pg. 59

41
Q

True or False

The number of AU in one parsec is equal to the number of arseconds in one radian.

A

True

Pg. 59

42
Q

How many AU are in one parsec?

A

206265

Pg. 59

43
Q

What is the nearest start to the sun?

A

Proxima Centauri

Pg. 59

Astrophysics (18 decks)

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