Channel 1 and 2

Question 1

What is stellar structure?

Answer 1

core - radiation zone - convection zone

Question 2

What can we observe from nearby stars?

Answer 2

temperature and brightness

Question 3

What can we observe from binary systems?

Answer 3

mass of a star

Question 4

What does a colour-magnitude diagram measure?

Answer 4

The apparent brightness of stars in two different wavebands e.g B-lue and V-isual
The difference is a measure of colour and surface temperature.

Question 5

What happens to apparent brightness if stars are at the same distance?

Answer 5

It is a measure of intrinsic brightness

Question 6

What is a star cluster?

Answer 6

A group of stars bound together by gravity and formed out of the same material and at the same time

Question 7

What are galactic or open clusters?

Answer 7

they are not well defined
distance to them is not well known
blue stars

Question 8

What are globular clusters?

Answer 8

well defined
distance known reasonably well
crowded
yellow stars

Question 9

What are extragalactic clusters?

Answer 9

distance well known

unresolved

Question 10

How much is 1 mili arcsec?

Answer 10

1/1000 arcsec

Question 11

How much is 1 arcsec?

Answer 11

1/3600 degrees

Question 12

How can the position of a star be measured?

Answer 12

By looking at the declination and right ascension of the star (both in miliarcsecs)

Question 13

What is the parallax of an object used to approximate?

Answer 13

The distance to an object

Question 14

What is the equation for parallax?

Answer 14

D = 1/p
(p = parallax angle observed and D is actual distance measured in parsecs)

Question 15

What is a parsec?

Answer 15

The distance at which an object has a parallax of 1 arcsecond

Question 16

What is luminosity?

Answer 16

The total power integrated over all wavelengths

Question 17

What is flux?

Answer 17

Energy crossed unit area per unit time integrated over all wavelengths arriving at Earth
(Jm-2s-1 or Wm-2)

Question 18

How is the effective temperature of a star measured?

Answer 18

Directly from analysis of stellar spectrum

Question 19

What is the mass luminosity relationship?

Answer 19

L is proportional to M to the power 3.3

Question 20

How much hydrogen does a star which is 10x as massive as the Sun burn?
How quickly does it use up its fuel?

Answer 20

10x as much

as it is 10^3.3 times brighter, 10^3.3/10 = 200 times more quickly

Question 21

What the relationship between time and Mass?

Answer 21

t is proportional to M^-2.3

Question 22

Where do most stars lie on a CMD/HR diagram?

Answer 22

Most stars are on the MS

Question 23

Which characteristics do more massive stars have?

Answer 23

Brighter, bluer and have shorter lives

Question 24

What is the CMD/HR diagram?

Answer 24

The prime medium through which stellar evolution models are compared with observations

Question 25

What do clusters with short lived bright blue stars lack?

Answer 25

They have very few red giants

Question 26

What do clusters with many red giants lack?

Answer 26

They have no short-lived blue MS stars

Question 27

If we look at stellar clusters what do they show us?

Answer 27

Clues to stellar evolution

Question 28

Which assumptions are made about stars in order to study their structure?

Answer 28

STEADY STATE equilibrium and not changing with time SPHERICAL GEOMETRY all variables are function of r only, rotational forces negligible, no magnetic forces INITIAL COMPOSITION IS HOMOGENEOUS

Question 29

What affects the expected lifetime of a star?

Answer 29

Gravitational potential energy (millions of years) Chemical energy (thousands of years) Nuclear fusion of light elements (billions of years)

Question 30

How much mass of a star has conditions that allow nuclear burning?

Answer 30

typically 10% of mass

Question 31

In a fusion reaction of H into He, how much of the mass if converted into energy?

Answer 31

0.7%

Question 32

What is a nuclear timescale?

Answer 32

Nuclear energy available divided by luminosity

Question 33

What is a thermal timescale?

Answer 33

The energy released is due to gravitational contraction | The thermal timescale is then the gravitational potential energy divided by luminosity

Question 34

What happens at several times in evolution?

Answer 34

star pressure-gravity imbalance occurs

Question 35

Which timescale dominates evolution of a star?

Answer 35

Nuclear timescale