Chapter 2 HW Questions

(a) Several constellations are shown in more than one season. Which observation is true? (b) What best explains the pattern described in the previous question?

(a) Constellations move in a westward direction from one season to the next. (b) Earth's position moves eastward from one season to the next.

(a) The minimum / maximum temperatures for any location are reached on the solstices. (b) Which factor does not contribute to the low temperatures in Antarctica?

(a) False (b) For most of the year, it is farther from the Sun.

(a) Use the figure below to rank the following objects from brightest to dimmest: Polaris, full moon, Sirius, Venus. (b) Rank the following objects in the figure from dimmest to brightest: Sun, Polaris, Venus, Sirius. (c) Use the figure to rank the magnitude differences between the following pairs of objects (or magnitudes) from the biggest difference to the smallest difference: Sun/full moon, Venus/Sirius, Venus/Polaris, naked eye limit/Hubble space telescope limit.

(a) Full moon, Venus, Sirius, Polaris (b) Polaris, Sirius, Venus, Sun (c) Naked eye/Hubble, Sun/Full moon, Venus/Polaris, Venus/Sirius

(a) If the Earth's tilt were 13.5 degrees instead of 23.5 degrees, the path of the Sun would be: (b) Just as the Sun sets, the shadows are: (c) Cooler days in winter are due to:

(a) Not as far north in summer nor as far south in winter. (b) Always the same length BUT pointed to a different compass point according to the season. (c) Both of these answers : Fewer hours of sunlight Less direct Sunlight, therefore less heating

(a) For Northern Hemisphere observers, at what compass point does each object reach its highest altitude, or distance from the horizon? (b) The stars seem to move across the sky together, maintaining their positions relative to one another. Why? (c) For an observer at the North Pole, what would the star trails look like?

(a) South (b) All the stars are so far from Earth that we cannot perceive their individual motions. (c) A dome of concentric circles, that appears as straight horizontal lines at the horizon.

From your knowledge of star names and constellations, which of the following stars in each pair is the brighter? Explain your answers. (a) Alpha Ursae Majoris; Epsilon Ursae Majoris (b) Epsilon Scorpii; Alpha Pegasi (c) Alpha Telescopii; Alpha Orionis

(a) The Greek letter designation suggests Alpha Ursae Majoris is brighter because alpha comes before epsilon in the Greek alphabet. (b) The relative brightness cannot be determined from their names alone because the Greek letter designation only provides information about the relative brightness of stars in the same constellation. (c) The relative brightness cannot be determined from their names alone because the Greek letter designation only provides information about the relative brightness of stars in the same constellation.

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

+2.8

How did the magnitude system originate in a classification of stars by brightness?

-6 -1st -6th -negative -inverse

In what ways is the celestial sphere a scientific model?

-It describes what we see as the sky appears to turn above us. -It enables us to predict correctly the future positions of the stars and the planets at various times of the night and throughout the year.

What are two reasons why winter days are colder than summer days?

-The length of time that the sun is above the horizon is noticeably shorter during the winter than during the summer. -During the winter, light from the sun hits Earth at a more oblique angle than it does during the summer.

Why does the number of circumpolar constellations depend on the latitude of the observer?

As an observer moves away from the equator, towards the north or south pole, there are more constellations that the rotation of the earth does not ever block from his or her view throughout one full rotation.

At what location on Earth is an observer that has the South Celestial Pole directly overhead?

At Earth's South Pole (90 degrees South Latitude)

Why is the amount of solar heating less on a clear day in January at northern latitudes than on a clear day in July?

Both the sun is above the horizon for less than 12 hours in January in the north and at low sun angles, the received sunlight is spread over a larger surface area.

Based on this figure, in what constellation is the sun on July 1 each year?

Gemini (across the line)

Why does the sun move relative to the stars as observed from Earth?

It is due to Earth revolving around the sun

What does the word apparent mean in apparent visual magnitude?

It means that the magnitude describes how bright the star appears to us, observing from Earth.

What does the word visual mean in apparent visual magnitude?

It means that the magnitude includes only light that is visible to the human eye.

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. (Star B appears brighter than star A, however it may not be emitting more light.)

The stamp below shows the constellation Orion. Explain why this looks odd to residents of the Northern Hemisphere.

Orion appears upside down compared to how it looks in the Northern Hemisphere.

When it is autumn in Asia, what season is it in Antarctica?

Spring

How does the Greek-letter designation of a star give you clues both to its location and its brightness?

The constellation name describes the star's location in the sky and the Greek letter indicates its brightness relative to the other stars in the constellation. The brighter stars have Greek letters nearer the beginning of the Greek alphabet.

How do the seasons in Earth's southern hemisphere differ from those in the northern hemisphere?

The seasons are reversed. The season during which the sun is highest in the sky at noon in the southern hemisphere occurs when the sun is lowest in the sky at noon in the northern hemisphere.

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.

In the constellation Orion, we receive more light from the star Rigel (β) than we do from the star Betelgeuse (α). Why does this figure have the alpha and beta designations as shown?

This is one exception to the way in which brightness has been assigned in this system.

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

all of the above (North Celestial Pole and South Celestial Pole Vernal Equinox and Autumnal Equinox Summer Solstice and Winter Solstice both North Celestial Pole and South Celestial Pole and Vernal Equinox and Autumnal Equinox all of the above)

The Milankovitch hypothesis proposes that the ice ages on Earth are due to long-term changes in the amount of seasonal solar heating brought about by which of the following?

all of the above (changes in the shape of Earth's orbit. precession of Earth's rotational axis. changes in the tilt angle of Earth's rotational axis. both changes in the shape of Earth's orbit and precession of Earth's rotational axis)

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)

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

beta Lyrae

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

earth's rotation on its axis

The five naked-eye planets and three telescopic planets that wander among the stars in the sky are always near which of the following?

ecliptic

Where would you go on Earth if you wanted to be able to see both the north celestial pole and the south celestial pole at the same time?

equator

When you observe a star on the celestial equator for a period of a few hours, you notice which of the following?

moves from east to west relative to the horizon

If you could see the sun and stars during the daytime for several weeks, you would notice that the sun does which of the following?

moves slowly eastward relative to the stars

If the tilt of Earth's axis were to change from 23.5 degrees to 0 degrees, what celestial circles would coincide for all observers?

the Celestial Equator and the Ecliptic