Naked-eye Astronomy

Question 1

What causes light pollution?

Answer 1

skyglow

Question 2

What defines seeing conditions?

Answer 2

stillness of stars

The most ‘still’ stars have an Antoniadi scale value of V and the least still have a value of I.

Question 3

How can professional telescopes track changes in the atmosphere that affect seeing conditions?

Answer 3

A laser!

The laser is removed from the image in real time.

Question 4

How does weather affect observations?

Answer 4

Weather affects the sky’s transparency.

Question 5

Why is the sky blue?

Answer 5

Rayleigh scattering

Blue light has a longer wavelength so it is scattered in the atmosphere.

Question 6

How can you find Polaris in the night sky?

Answer 6

The two ‘pointer’ stats of the Plough point to Polaris.

Question 7

How can you find Arcturus in the night sky?

Answer 7

The handle of the Plough ‘arcs’ towards Arcturus.

Question 8

How can I find Sirius in the night sky?

Answer 8

Orion’s belt points down and to the left to Sirius.

Question 9

How can I find Aldebaran in the night sky?

Answer 9

Orion’s belt points up and to the right towards Aldebaran.

Question 10

How can Polaris be used to find information about your location on Earth?

Answer 10

Polaris’ altitude is equal to the observer’s latitude.

The direction of Polaris in the night sky is due North.

Question 11

How can you find the Andromeda galaxy in the night sky?

Answer 11

Up and to the left of the top left corner of the square of Pegasus

Question 12

How are meteor showers named?

Answer 12

The constellation that the radiant appears to lie in. e.g: The Perseids, The Lyrids etc…

Question 13

What points does an observer’s meridian lie on?

Answer 13

NCP, SCP, Zenith, Nadir, (direction of due North)

Question 14

Which direction to stars culminate in the Northern Hemisphere?

Answer 14

due South

(due North in the Southern hemisphere)

Question 15

What are cardinal points?

Answer 15

North, South, East and West.

Question 16

Where is a star when it culminates?

Answer 16

On the meridian.

Facing South if in the Northern hemisphere and North if in the Southern hemisphere.

Question 17

What is a circumpolar star?

Answer 17

One that never sets below the horizon.

Question 18

How do you know if a star is circumpolar?

Answer 18

A star is circumpolar if it’s declination is greater than the observer’s co-latitude.

Question 19

How can you find a star’s altitude when it is at upper transit / culminating?

Answer 19

altitude = latitude + co-declination

Question 20

How can you find a star’s altitude at lower transit?

Answer 20

altitude = latitude - co-declination

Question 21

What is Polaris’ azimuth?

Answer 21

0°

Question 22

How are rilles formed?

Answer 22

Collapse of lava tubes under the Moon’s surface

Question 23

How are ‘wrinkle ridges’ formed on the Moon?

Answer 23

They form when the basalt cools.

Question 24

Which was more recently formed: maria or highlands?

Answer 24

Maria

They are formed by lava flowing into a large impact crater, which creates a darker, smoother surface.

Question 25

How long is a sidereal month?

Answer 25

27.3 days

(must know to 1 d.p.)

Question 26

How long is a synodic month?

Answer 26

29.5 days

(must know to 1 d.p.)

Question 27

How are ray systems formed?

Answer 27

Streaks of ‘ejecta’ are thrown out during formation of an impact crater.

e.g: Tycho crater has a visible ray system

Question 28

Why can we sometimes see the part of the Moon not illuminated by the Sun?

Answer 28

Earth shine (light reflected from the Earth)

Question 29

What causes the Earth’s shape to be an oblate spheroid?

Answer 29

Centrifugal force during rotation

Question 30

Identify 3 methods of safely observing the Sun.

Answer 30

Pinhole camera

Telescopic projection

H-alpha filter

Question 31

Name the regions of the sun from inside out.

Answer 31

Core, radiative zone, convective zone, photosphere, chromosphere, corona, heliosphere.

Question 32

Where does fusion occur during the main sequence?

Answer 32

The core

Question 33

Where does fusion occur in a red giant?

Answer 33

A shell surrounding the core

Question 34

What causes solar flares / sunspots?

Answer 34

The Sun’s magnetic field ‘penetrates’ the surface. In the case of solar flares, this can cause material to be ejected.

Question 35

What effects of solar wind can be seen on Earth?

Answer 35

Aurorae, formation of comets’ tails, geomagnetic storms.

Question 36

How can sunspot data be used to find the mean rotational period of the Sun?

Answer 36

rotational period / change in time

=

360 / change in longitude

Question 37

Temperatures of the Umbra and Penumbra of sunspots:

Answer 37

3,800K at Umbra
5,600K at Penumbra

Question 38

What is solar wind?

Answer 38

An outflow of charged particles: protons and electrons.

Question 39

What protects us from solar wind?

Answer 39

Earth’s magnetosphere

Question 40

Differences between solar maxima and minima:

Answer 40

solar maximum: many sunspots, high space weather, sunspots with high latitude

solar minimum: fewer sunspots, low solar weather, sunspots with lower latitude

Question 41

Where is an annular solar eclipse visible from Earth?

Answer 41

Antumbra

Question 42

Why are solar eclipses only briefly visible?

Answer 42

The Moon orbits the Earth, causing the Umbra to move across the surface of the Earth.

The size of the Umbra on the Earth’s surface is also quite small.

Question 43

What is the inclination of the Moon’s orbit?

Answer 43

5.1°

Question 44

Why is Jupiter’s moon Io geologically active?

Answer 44

Tidal forces created by the other Moons of Jupiter (Galilean moons) cause internal warming in Io.

Question 45

How many high tides occur a day? (24hrs)

Answer 45

2

Question 46

What phases of the Moon do Neap tides occur?

Answer 46

First and third quarter (half moon, 50% illuminated)

Question 47

What is the Equation of Time?

Answer 47

EoT = AST - MST

(apparent solar time minus mean solar time)

Question 48

What makes a good shadow stick?

Answer 48

vertical, reasonably thin, on a flat horizontal surface

Question 49

What can a shadow stick be used for?

Answer 49

Finding the time of local noon and finding longitude.

Question 50

What is the shape created by a graph of the Sun’s declination against the Equation of Time called?

Answer 50

Analemma

it looks like a bottom-heavy figure-of-eight

Question 51

What is the Local Mean Solar Time of Greenwich known as?

Answer 51

Greenwich Mean Time (GMT)

Question 52

What was the method used before the invention of the marine chronometer?

Answer 52

The lunar distance method

The angular distance between the Moon and certain bright stars is compared with a table of values (a nautical almanac)

Question 53

Who invented the first marine chronometer?

Answer 53

John Harrison

Question 54

Why was an understanding of astronomy useful in ancient civilisation?

Answer 54

The heliacal rising of a star (when a non-circumpolar star becomes visible in the night sky) could be used to predict events, significant times of year, or for religious association.

An example of this is the heliacal rising of Sirius, used to predict the flooding of the Nile in Ancient Egypt.

Question 55

How many years does it take for the Earth to make one precession?

Answer 55

26,000 years

Question 56

What phenomena disproved the geocentric model of the solar system?

Answer 56

Retrograde motion of planets, e.g: Mars

Question 57

Ptolemy introduced the ‘Ptolemaic model’ to solve the problem of retrograde motion. Describe the Ptolemaic model.

Answer 57

Planets move on epicycles which themselves move on an orbit around the Earth known as the deferent. (All orbits are perfectly circular)

He also moved the Earth away from the common centre of rotation.

Question 58

When does superior conjunction occur?

Answer 58

When a planet is the ‘opposite side’ of the Sun from the Earth.

Any planet other than Earth can exist in superior conjunction to Earth, including inferior planets.

Question 59

When does inferior conjunction occur?

Answer 59

When a planet lies ‘between’ the Earth and Sun.

Only inferior planets can exist in inferior conjunction to the Earth.

Question 60

When is a planet at greatest elongation?

Answer 60

When an inferior planet is observed as far away from the Sun as possible.

The Earth is at a 90° angle to the other planet relative to the Sun.

Question 61

What is transit?

Answer 61

When an object passes ‘in front’ of another object without fully obscuring it.

This could be a planet, e.g: Transit of Venus.

Question 62

What is occultation?

Answer 62

When a celestial object fully obscured another object.

Question 63

Who introduced the idea of Heliocentrism?

Answer 63

Aristarchus of Samos first presented the heliocentric model, however Copernicus published his ideas later and is also credited with the idea.

Question 64

How can the gravitational force between to objects be calculated?

Answer 64

(mass of first object x mass of other object x a constant) / distance squared

This is the inverse square law

Question 65

What is Kepler’s first law of planetary motion?

Answer 65

A planet orbits the Sun in an elliptical orbit with the Sun at one of its foci.

Question 66

What is Kepler’s second law of planetary motion?

Answer 66

The imaginary line joining a planet and the Sun sweeps equal areas of space during equal time intervals as the planet orbits.

(The planet does not have constant speed in its orbit.)

Question 67

What is Kepler’s third law of planetary motion? (in words)

Answer 67

The square of a planet’s orbiting period is directly proportional to the cube of the semi-major axis of its orbit.

(semi-major axis = mean orbiting distance)

Question 68

What is Kepler’s third law of planetary motion? (as a formula)

Answer 68

T² / r³ = a constant

or

T² ∝ r³

Question 69

What does the constant in Kepler’s third law depend on?

Answer 69

The constant in Kepler’s third law is inversely proportional to the mass of the central body.