Astronomy 101

Question 1

Define ecliptic

Answer 1

The celestial sphere representing the sun’s apparent path.

Question 2

Celestial equator

Answer 2

The projection into space of earth’s equator.

Question 3

Define celestial poles

Answer 3

The point on the celestial sphere directly above either of the earth’s geographical poles, around which the stars and planets appear to rotate. The north celestial pole is currently within one degree of the star Polaris.

Question 4

Zenith

Answer 4

The point directly above you.

Question 5

Meridian

Answer 5

The line that passes through both the zenith and the celestial poles.

Question 6

Zodiac

Answer 6

An imaginary belt in the heavens that includes the apparent paths of most of the planets and is divided into 12 star signs.

Question 7

Phases of the moon

Answer 7

New moon, waxing crescent, first quarter, waxing gibbous, full moon, waning gibbous, third quarter, waning crescent.

Question 8

Summer solstice

Answer 8

June 21

Question 9

Winter solstice

Answer 9

December 21

Question 10

Equinoxes

Answer 10

September 21st and March 21st

Question 11

Altitude

Answer 11

How high up in the sky an object lies. Measured from the horizon at 0 and runs from -90 (nadir) to +90 (zenith).

Question 12

Azimuth

Answer 12

How far around the sky an object lies. Measured from 0 (due North.)

Question 13

Declination

Answer 13

The “latitude” on the celestial sphere. 0 at the celestial equator. 90 for the North/South Celestial Poles.

Question 14

Right Ascension

Answer 14

The “longitude” on the celestial sphere. 0 hours at March equinox. Measured as “Hours-Minutes” eastward.

Question 15

Why does Earth have seasons?

Answer 15

Earth has seasons because it’s axis is tilted. In the equinoxes the sun shines equally on both hemispheres. On solstices it shines on one hemisphere more than the other, because of the tilt.

Question 16

Geocentric model

Answer 16

Earth is center of the universe. Planets revolve around the earth. Stars are set into a giant unmoving sphere.
-Ptolemy adds epicycles to explain retrograde motion.

Question 17

Heliocentric model

Answer 17

Aristarchus places sun at the center of the universe.
Planets including Earth revolve around the Sun.

Question 18

Two main types of eclipse

Answer 18

Solar eclipse, lunar eclipse.

Question 19

What is the significance of Ptolemy to astronomy?

Answer 19

Ptolemy adds epicycles to the geocentric model.

Question 20

Moon’s position in solar eclipse

Answer 20

Between earth and sun, with shadow over the earth.

Question 21

Moon’s position in lunar eclipse.

Answer 21

Earth is between the sun and the moon, with earth’s shadow over the moon.

Question 22

Why does retrograde motion happen

Answer 22

Because earth is overtaking planets in their orbit.

Question 23

What were the beliefs of Copernicus?

Answer 23

Believed increasing complexity was not a sign of a good theory.
Made the shift to the heliocentric model of the universe.

Question 24

Key concepts of Copernicus’ Heliocentric system

Answer 24

1. Earth is just one of the planets.
2. The daily motion of the sun and stars is the result of earth turning on its axis.
3. The sun lies at the center of the solar system.
4. All planets orbit in the same direction.
5. The orbits are circles and move at a constant speed.

Question 25

What was Tycho Brahe known for?

Answer 25

His eyesight and accurate naked eye observations of the stars.

Question 26

What was Tycho Brahe known for?

Answer 26

His eyesight and accurate naked eye observations of the stars.

Question 27

What event did Tycho observe that helped him disprove the ancient Greeks?

Answer 27

In 1577 he observed a comet that led him to theorize that it and presumably all comets existed far above the atmosphere and deep into the solar system. Additionally, he observed a supernova breaking the dogma that the heavens were perfect and immutable.

Question 28

Kepler’s first law of planetary motion

Answer 28

The orbit of each planet around the sun is an ellipse with the Sun at one focus.

Question 29

Kepler’s second law

Answer 29

As a planet moves around its orbit, it sweeps out equal areas in equal times. This means a planet travels faster when it is nearer the Sun and slower when it is farther from the Sun.

Question 30

Kepler’s third law

Answer 30

The period p of an object’s orbit is linearly related to its average orbital distance R. p squared is directly related to R cubed. The closer to the sun the faster the orbit.

Question 31

What was the evidence Galileo used to disprove the Greeks?

Answer 31

Moons of Jupiter did not orbit the Earth. Ptolemy’s model could not explain the phases of Venus.

Question 32

Newton’s first law

Answer 32

An object moves at constant velocity unless a net force acts to change its velocity or direction.

Question 33

Newton’s second law

Answer 33

If a net force is present on an object, there must be a net acceleration of that object.

Question 34

Newton’s third law

Answer 34

For every force, there is always an equal and opposite reaction force.

Question 35

What are the types of spectra?

Answer 35

Emission, absorption, continuous.

Question 36

What is the relationship between energy and frequency in a wave?

Answer 36

The higher the frequency, the more energy the wave carries.

Question 37

Properties of Continuous Spectra/ what do hotter objects do?

Answer 37

1. Hotter objects emit more light at all frequencies 2. Hotter objects emit photons with higher average energy.

Question 38

Emission line spectra

Answer 38

A thin or low density gas cloud emits light only at specific wavelengths that depend on its composition and temperature, producing a spectrum with bright emission lines.

Question 39

Continuous spectra

Answer 39

A cloud of gas can absorb light of specific wavelengths, leaving dark absorption lines.

Question 40

Absorption spectra- what does the electron do?

Answer 40

Electron absorbs a photon, resulting in an increase of electron energy and an outward transition.

Question 41

The electromagnetic spectrum Long to short wavelength

Answer 41

Radio, microwave, infrared, visible, ultraviolet, x-Ray, gama ray.

Question 42

What is the relationship between wavelength, frequency, and speed of a wave?

Answer 42

Speed is equal to frequency times wavelength.

Question 43

What is a blackbody?

Answer 43

A blackbody is an object that re radiates exactly as much energy as it absorbs.

Question 44

What do black body curves do?

Answer 44

Blackbody curves give wavelengths of maximum radiation.

Question 45

Wien’s law

Answer 45

For black body sources a higher temperature means a shorter wavelength.