Astronomy: Chapter 2

Question 1

Describe the coordinate system of the celestial sphere.

Answer 1

• Used to locate object, aim telescopes, and study the relationship of night sky to ancient culture.
• an imaginary spear of a large radius surrounding Earth.
• has Northern and Southern celestial poles, in which the sky appears to rotate westward.
• if the earth did not rotate, we would not be able to find the celestial pole and equator because the poles and equators are located where the sky appears to rotate.

Question 2

What is a constellation and how is it different from a star cluster?

Answer 2

Constellation: one of the stellar patterns identified by name, usually of mythological gods, people, animals, or objects. Also, the region of the sky containing that star pattern.

Star Cluster: stars that are bunched together.

Question 3

Hipparchus method of measuring the brightness of stars.

Answer 3

• Hipparchus came up with a method to determine the brightness of a star. He used a “magnitude scale”
• Magnitude scale: the brightest stars were ranked as 1 and the dimmer stars were ranked as 6. Some stars are so bright they have extended them to negative numbers. it has also been extended for fainter stars.

Question 4

What does a Foucault Pendulum demonstrate? How does it work? where does it work best? worst?

Answer 4

Demonstrates the earths rotation on its axis.

Question 5

Precession

Answer 5

• The slow change in orientation of the Earth’s axis of rotation. One cycle takes nearly 26,000 years.
• a spinning top precesses in a slow circular motion around the perpendicular to the floor because its weight tends to make it fall over.
• earth precesses around the perpendicular to its orbit because the gravity of the sun and moon tend to twist it “upright”
• Precession causes the north celestial pole to drift among the stars

Question 6

Why is it cold in the winter and hot in the summer?

Answer 6

• This is due to the tilt of earth on its axis.
• Summer Solstice: Earth’s northen hemisphere is inclined toward the sun, and sunlight shines almost straight down at northern latitudes.
• winter solstice: Earth’s northern hemisphere is inclined away from the sun, and sunlight strikes the ground at an angle and spreads out.

Question 7

Solar Day vs Sidereal Day

Answer 7

A solar day takes 24 hours, but a sidereal day takes 23 hours and 56 minutes because it takes 4 minutes to realize the rotation of the earth.

in the time it takes the earth to spin, the sun has moved about 1 degree in its journey around the earth. so a solar day (on average) 4 minutes longer than a sidereal day.

Question 8

Do people from other cultures on Earth see the same stars, constellations, and asterisms that you see?

Answer 8

no

Question 9

If earth did not rotate, could we define the celestial pole and celestial equator?

Answer 9

No, the poles and equator are located where the sky appears to rotate.

Question 10

Name and sketch the eight phases of the moon in order, beginning with the new moon.

Answer 10

New Moon, Waxing Crecent, First quarter, Waxing Gibbous, Full moon, Waning Gibbous, Third Quarter, Waning Crecent.

Question 11

How does the moon keep the same face toward the earth? doesn’t it rotate?

Answer 11

Because the same side of the moon faces Earth, and both Earth and the moon rotate together.

Question 12

Solar Eclipse

Answer 12

• Total Eclipse of the sun
• During a solar eclipse, the moon is between the earth and the sun.
• the moon blocks our view of the sun.

Question 13

Lunar Eclipse

Answer 13

• Total eclipse of the moon.
• the earth is between the sun and the moon.
  the full moon darkens as the moon moves through the shadows of the earth.

Question 14

Why can you never see a full moon overhead at sunset?

Answer 14

A full moon always rises at sunset and a full moon is always overhead at midnight.