Astronomy Revision

Question 1

What is meant by apparent magnitude?

Answer 1

Apparent magnitude is how bright a star appears to be to the naked eye.

Question 2

What is meant by absolute magnitude?

Answer 2

Absolute magnitude is how bright a star would be if it was 10 parsecs away from Earth.

Question 3

What is the equation for absolute magnitude?

Answer 3

M = m + 5 - (5 log d)

Question 4

What does d stand for in the equation for absolute magnitude?

Answer 4

d = Distance modulus formula

Question 5

What are the 7 stellar types?

Answer 5

O B A F G K M

Question 6

What is meant by luminosity?

Answer 6

Luminosity is the total energy output of the star per second.

Question 7

What stellar type is our Sun?

Answer 7

G2

Question 8

What are all the electromagnetic radiation in the electromagnetic spectrum in order from lowest to highest frequency?

Answer 8

Radio waves
Microwaves
Infrared
Visible light
UV
X-rays
Gamma rays

Question 9

Where are the red and white dwarfs on the main sequence?

Answer 9

White dwarfs are located in the bottom left (type A), whereas the red dwarfs are located in the bottom right (type M).

Question 10

What is the rearranged equation of absolute magnitude?

Answer 10

m = M - 5 + 5 log d

Question 11

What happens to a star if it has a core mass that surpasses the Chandrasekhar limit?

Answer 11

A main sequence star turns into a red supergiant over time, and then transforms into a supernova.

Question 12

What happens to a supernova if it’s original core mass was less than 3 solar masses?

Answer 12

The supernova would become a neutron star (supported by neutron degeneracy pressure) - a star that doesn’t have a spectral type.

Question 13

What happens to a supernova if it’s original core mass was more than 3 solar masses?

Answer 13

The supernova would then become a black hole.

Question 14

Where on the HR diagram is electron radiation found?

Answer 14

Where the white dwarfs reside - the bottom left .

Question 15

Where on the HR diagram is radiation pressure found?

Answer 15

Anywhere on the main sequence.

Question 16

What is the main sequence?

Answer 16

A stable stage in the life cycle of a star where nuclear fusion occurs, fusing hydrogen nuclei into helium nuclei. There is a balance between the outwards radiation and the force of gravity pulling inwards.

Question 17

What is a nebula?

Answer 17

Large clouds of gas (mainly hydrogen) and dust.

Question 18

Types of nebulae?

Answer 18

Emission nebulae

Reflection nebulae

Planetary nebulae

Dark nebulae

Supernova remnants

Question 19

The first stage of the proton-proton chain?

Answer 19

1 1 2 0 + 0
H + H —–> H + e + v
1 1 1 1 0

Proton + proton —> Deuterium + positron + neutrino

Question 20

The second stage in the proton-proton chain?

Answer 20

2 1 3
H + H —> He + Y
1 1 2

Deuterium + Proton —> Helium - 3 + gamma ray photon

(- means hyphen, not minus)

Question 21

The third stage in the proton-proton chain?

Answer 21

3 3 4 1 1
He + He —> He + H + H
2 2 2 1 1

Helium - 3 + Helium - 3 —> Helium - 4 + 2 protons

Question 22

What does 1 AU represent (2 points)?

Answer 22

The AVERAGE distance from the Earth to the Sun = 1.5 x 10^8km

Question 23

How long is a light year in km?

Answer 23

9.5 x 10^12km

Question 24

How long is a parsec in light years?

Answer 24

3.1 x 10^13km = 3.26 l.y.

Question 25

How long is a sidereal day of Earth?

Answer 25

23 hours 56 minutes and 4 seconds

Question 26

How long is a synodic day of Earth?

Answer 26

24 hours

Question 27

What is the equation of time?

Answer 27

EOT = AST - MST

Equation of time = Apparent solar time - Mean solar time

Question 28

Rearranged equation for MST (Mean Solar Time)?

Answer 28

MST = AST - EOT

Question 29

What’s the temperature of the umbra and penumbra of a sunspot?

Answer 29

Umbra = 4000K

Penumbra = 5600K

Question 30

What two factors are needed in order to measure the distance (approximately) from Cepheid Variable stars to the Earth?

Answer 30

Luminosity and apparent magnitude