Astronomy Exam 1 - Ch. 2

The apparent visual magnitudes of four stars are listed below. Of these four stars, which one appears dimmest in the sky?

+2.8

Which magnitude star is brightest?

-1

The magnitude system is the astronomer's scale of the brightness of stars and other objects. Based on the magnitude system, select all of the correct statements from the following list.

-If two stars' brightnesses are separated by one magnitude, the brighter star is about 2.5 times brighter than the dimmer one. -A star must be brighter than sixth magnitude to be seen with the unaided eye. -An object of magnitude -2 is very bright.

The motion of the planets observed from Earth is due to their orbits around the sun; some closer than Earth's, some farther away. Based on the motions of the planets, select all of the correct statements from the following list.

-Planets closer to the sun than Earth can be seen only in the early evening or early morning. -Some planets are too faint to be seen with the naked eye. -The planets are observed to move approximately along the ecliptic.

It is useful to model the sky as a celestial sphere that rotates around Earth from east to west once per day. Based on the motion of the sky, select all of the correct statements from the following list.

-The apparent rotation of the sphere is caused by Earth's rotation -The celestial sphere is still useful even though it is no longer accepted as physical reality. -The celestial equator is a line in the sky directly above Earth's equator. -Precession is literally a wobbling of Earth's rotational axis.

Because Earth orbits the sun once per year, the sun appears to move through the sky once per year on a path we call the ecliptic. Based on the cycles of the sun, select all of the correct statements from the following list.

-The constellations that lie along the ecliptic are those of the zodiac. -The ecliptic's tilt is caused by the tilt of Earth's rotational axis. -In the summer the sun is above the horizon longer than in the winter. -In the summer the sun is higher in the sky than in the winter.

Every star is part of a constellation and is assigned a Greek letter within the constellation. Many stars still bear ancient Arabic names. Based on how astronomers refer to stars, select all of the correct statements from the following list.

-The star in a constellation is usually brighter than the B star. -All stars are part of some constellation. -A star with an ancient Arabic name is probably relatively bright.

The precession of Earth's rotational axis causes the location of the _________ to change.

-north celestial pole and south celestial pole -vernal equinox and autumnal equinox -summer solstice and winter solstice -north and south celestial poles and vernal and autumnal equinoxes

What is responsible for the observed motion of a star along the celestial equator?

Earth's rotation on its axis

What is true about the celestial sphere?

It was once believed to represent reality.

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.

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.

Use the figure above to find which of the following lists of objects is dimmest to brightest (from left to right):

Polaris, Sirius, Venus, full moon

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

Imagine that Earth did not turn on its axis. What would be true?

The day would be the same length as a year.

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.

Why does the rotational axis of Earth precess?

The sun and moon pull on Earth's equatorial bulge.

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.

Which statement below most accurately describes modern constellations?

They are 88 well-defined regions on the celestial sphere.

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.

What is true about astronomers?

They use the celestial sphere, a scientific model, to explain motions of the stars.

A star with an ancient Arabic name is which of the following?

a relatively bright star

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)

At what location on Earth is an observer that has the south celestial pole directly overhead?

at Earth's south pole (90° south latitude)

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

What is the most likely Greek letter name of the second brightest star in the constellation Lyra?

beta Lyrae

A star's Greek letter designation tells you which of the following?

its relative brightness within its constellation

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