Chapter 2 Flashcards
Where are the remaining 48 ancient constellations that we still recognize today located?
at mid and northern celestial latitudes
Which statement below most accurately describes modern constellations?
They are 88 well-defined regions on the celestial sphere.
What is the most likely Greek letter name of the second brightest star in the constellation Lyra?
beta Lyrae
The apparent visual magnitudes of four stars are listed below. Of these four stars, which one appears dimmest in the sky?
+2.8
Which pair of apparent visual magnitudes listed below indicates that we receive about 16 times as much visible light from star W than we do from star X?
mv of star W = 2, and mv of star X = 5
The apparent visual magnitude of star A is 2 and the apparent visual magnitude of star B is 1. Based on this information which statement below must be true?
Light output and distance cannot be determined from a star’s apparent visual magnitude alone.
If the apparent visual magnitude of the sun is –26.5 and that of the full moon is –12.5, what is the light flux ratio of sunlight to full moonlight received by Earth?
400,000
Notice in this figure that the magnitude scale is “awkward” in that the smaller, or more negative, magnitude number corresponds to a brighter star. Why does this scale have this “awkward” direction?
The system was originally set up as a set of classes with first class as the brightest.
When you observe a star on the celestial equator for a period of a few hours, you notice which of the following?
The star moves from east to west relative to the horizon.
What is responsible for the observed motion of a star along the celestial equator?
Earth’s rotation on its axis
At what location on Earth is an observer that has the south celestial pole directly overhead?
at Earth’s south pole (90° south latitude)
At what location on Earth is an observer that has the Celestial Equator pass through the point directly overhead?
at Earth’s equator (0° latitude)
If the tilt of Earth’s axis were to change from 23.4° to 0°, what celestial circles would coincide for all observers?
the celestial equator and the ecliptic
Why does the rotational axis of Earth precess?
The sun and moon pull on Earth’s equatorial bulge.
The precession of Earth’s rotational axis causes the location of the _________ to change.
All of these choices are correct.
In this figure it is apparent that the radius of the precession circle is 23.5°. At what latitude on Earth is the entire precession path currently above the horizon?
at all locations north of 23.5° north latitude
Which of the following is true for most modern constellations?
They are located in the southern sky because the southern regions of the world were explored more recently.
A star’s Greek letter designation tells you which of the following?
its relative brightness within its constellation
A star with an ancient Arabic name is which of the following?
a relatively bright star
Based on how stars are named, which star is probably brightest?
a Ursae Majoris
Based on how stars are named, which star is probably dimmest?
E Ursae Majoris
Based on how stars are named, which star is probably brightest?
a Pegasus
Based on how stars are named, which star is probably dimmest?
E Scorpii
Which magnitude star is brightest?
–1
How many times brighter is a magnitude 1 star than a magnitude 2 star?
2.5 times brighter
What is true about stars we say to be on the celestial sphere?
They are all different distances away.
What is true about the celestial sphere?
It was once believed to represent reality.
What is true about astronomers?
They use the celestial sphere, a scientific model, to explain motions of the stars.
Imagine that Earth did not turn on its axis.
What would be true about the ecliptic?
It would still be defined and could be seen from all points on Earth, but only when they faced the sun.
Imagine that Earth did not turn on its axis.
What would be true?
The day would be the same length as the year.
Which list shows the repeating astronomical cycles or events from the shortest to the longest duration (from left to right):
rotation of the Earth; orbital motion of Earth about the sun; precession of Earth’s axis of rotation
Magnitude System I. Star A has an apparent visual magnitude of 2.5; Star B, 5.5; and Star C, 9.5. Which is brightest?
Star A
Magnitude System II. Star A has an apparent visual magnitude of 2.5; Star B, 5.5; and Star C, 9.5. Which are visible to the unaided eye?
Star A, Star B
