(A) Topic 13 wrongs

Question 1

Describe the system used to differentiate the apparent magnitude between stars.

Answer 1

A bright star would have an apparent magnitude of 1, whereas a faint star would have a magnitude of 6.

Question 2

What are the four factors magnitude depends on?

Answer 2

• total energy radiated by the star
• distance to the star
• the amount of interstellar gas and dust that reflects and absorbs light
• amount of light absorbed +scattered by the Earth’s atmosphere

Question 3

What equipment is used to detect the spectrum of a star?

Answer 3

Spectometer

Question 4

What does the spectrum tell us about the star?

Answer 4

Helps us identify the chemical elements present, the temperature of the star, and whether the star is moving toward or away from us in its line of sight (radial velocity)

Question 5

What are absorption and emission lines?

Answer 5

Absorption: show what atoms are absorbing light - are dark
Emission: shows which atoms are emitting light

Question 6

How can we tell a star’s radial velocity using the spectrum?

Answer 6

The radial velocity of a star can be measured by measuring the distance between certain spectral lines - we can tell its wavelength and by how much it shows redshift or blueshift

Question 7

What is an HR diagram?

Answer 7

Graph in which the absolute magnitudes of stars are plotted against their spectral class

Question 8

What are the main components of the HR diagram?

Answer 8

• magnitude
• spectral class
• the shape of the main sequence
• position of giants and super giants
• position of the sun
• position of white dwarfs

Question 9

How is an HR diagram used to determine distances to stars?

Answer 9

Calculate the luminosity of the star and use the apparent brightness to work out its distance

Question 10

What are arcminutes and arcseconds?

Answer 10

arcminute = 1/60 of a degree
arcsecond = 1/60 of an arcminute

Question 11

Describe how scientists can use heliocentric parallax to establish distances to nearby stars.

Answer 11

Measure the distance to nearby stars by measuring how they appear to move against distant stars. For example, measure the star in one month, then again in six months when the Earth is on the other side of the sun

Question 12

What is a light curve?

Answer 12

Graph that displays how bright an object is over a period of time

Question 13

Define short period stars

Answer 13

Eclipsing binaries, cepheids or pulsating stars change magnitude over several days or weeks

Question 14

Define long period stars

Answer 14

Giant stars with periods between 100-1000 days

Question 15

Define eclipsing binary stars

Answer 15

Consists of a bright primary star and a dimmer second star. Large drop = secondary star blocks first and vice versa

Question 16

Define cepheid variable stars

Answer 16

Class of giant yellow stars that expand and contract regularly

Question 17

Define nova

Answer 17

A star that suddenly increases its output tremendously then fades away to its former obscurity in a few months or years

Question 18

Define supernova

Answer 18

The explosion of a star

Question 19

What is the equation used for star trail calculations?

Answer 19

angle of arc/ 360 = time exposure/24 hours

Question 20

Name three benefits and drawbacks of the Earth’s atmosphere.

Answer 20

pros: - oxygen allows humans + animals to breath
- protect us from harmful radiation
- makes temperature and climate consistent
cons: - clouds regularly obscure good astronomical viewing
- refracts light which means less accurate position and clarity of star viewing
- pollution obscures observations

Question 21

Why does the location of observatories matter? Name 3 factors which affect it.

Answer 21

• light pollution
• less atmosphere
• good dry weather with less clouds

Question 22

Give a simple explanation of how radio telescopes work.

Answer 22

Large concave dish reflects radio waves to a focus, where an ariel converts radio waves into electrical signals that can be stored + processed

Question 23

What can cause interference between the telescopes?

Answer 23

• telecommunications
• emergency services communications
• air traffic control
• television and FM/AM signals

Question 24

Why are infrared telescopes located in high and dry locations?

Answer 24

Water vapour absorbs IR light, so high and dry conditions are ideal

Question 25

What discoveries can be attributed to infrared telescopes?

Answer 25

• protostars
• dust and molecular clouds
• hotspots on the moon

Question 26

Name three advantages and disadvantages of space telescopes.

Answer 26

pros:
- clearer observations (no distortions)
- wider wavelengths of the EM spectrum
- no limitations in terms of day and nighttime

cons:
- expensive
- difficult maintenance
- limitations with the Hubble Space Telescope : not being able to photograph some things due to light sensitivity

Question 27

What does ultraviolet observation allow us to study?

Answer 27

Chemical make up and temperature of stars

Question 28

What kind of objects produce X-rays?

Answer 28

Hotter objects outside of the visual band of the EM spectrum

Question 29

What are Gamma-ray bursts?

Answer 29

Powerful explosions observed in distant galaxies - brightest EM events in the universe

Question 30

What is X-ray used to observe?

Answer 30

Effects of fast-moving particles under a strong gravitational force that surround a black hole - an accretion disc

Question 31

How does a telescope alter the appearance of binary stars and double stars?

Answer 31

They’re viewed as multiple stars

Question 32

How does a telescope alter the appearance of open clusters?

Answer 32

Numerous individual stars can be seen

Question 33

How does a telescope alter the appearance of globular clusters?

Answer 33

Detailed numerous stars can be seen

Question 34

How does a telescope alter the appearance of nebulae?

Answer 34

More detailed shape + more obvious colours

Question 35

How does a telescope alter the appearance of galaxies?

Answer 35

Brighter and more detailed view