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Flashcards in Chapter 2 Deck (31)
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1
Q

Heliocentric

A

sun-centered model for the universe

2
Q

Magnitude System

A

system devised by Hipparchus for describing brightness of stars

3
Q

Prograde motion

A

eastward motion

4
Q

Geocentric

A

Earth centered model for the universe

5
Q

Epicycle

A

the circle path a planet travels around

6
Q

Deferent

A

the larger circle which the epicycle moves at a constant speed around

7
Q

Parallax

A

the shift in apparent position of an object when seen from two different locations

8
Q

geocentric parallax

A

the shift in apparent position of a relatively nearby object

9
Q

Heliocentric parallax

A

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

10
Q

Inferior Planets

A

those with orbits smaller than the Earth’s orbit (Mercury, Venus)

11
Q

Superior Planets

A

those with orbits larger than the Earth’s orbit.

12
Q

Opposition

A

occurs when the Earth lies between the Sun and the superior planet. The Sun and planet are 180 degrees apart

13
Q

Conjunction

A

occurs when the Sun and the superior planet are 0 degrees apart as seen from the Earth

14
Q

Quadrature

A

occurs when the Sun and the superior planet are 90 degrees apart as seen from the Earth, can be either eastern or western

15
Q

Inferior conjunction

A

occurs when the inferior planet lies between the Earth and the Sun

16
Q

Superior conjunction

A

occurs when the Sun lies between the Earth and the inferior planet

17
Q

elongation

A

the angle in which the planet is separated from the Sun on the celestial sphere

18
Q

Synodic period

A

time interval which can be found by measuring the time elapsed between either successive superior conjunctions or successive inferior conjunctions

19
Q

Sidereal period

A

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

20
Q

Greatest elongation

A

the maximum angular separation between the planet and Sun as seen from the Earth

21
Q

Astronomical Unit

A

average distance from the Earth to the Sun

22
Q

Kepler’s first law

A

Planets travel on elliptical orbits with the Sun at one focus

23
Q

major axis

A

the longest distance across the ellipse

24
Q

minor axis

A

the shortest distance across the ellipse

25
Q

eccentricity

A

the distance between the foci divided by the length of the major axis, if the foci coincide then the ellipse is a circle, e = 0

26
Q

Kepler’s second law

A

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

27
Q

perihelion

A

the point on a planets orbit closest to the Sun, (moves rapidly)

28
Q

aphelion

A

the point farthest from the Sun, (least rapidly)

29
Q

Kepler’s third law

A

The squares of the sidereal orbital periods of the planets are proportional to the cubes of the semi-major axis of their orbits.

30
Q

aberration of starlight

A

an effect that causes the apparent positions of stars on the celestial sphere to be deflected in the direction of the observer’s motion.

31
Q

parsec

A

the distance at which a star has a parallax of exactly 1 arcsecond