Space

Question 1

What is a black body?

Answer 1

A body of matter that absorbs all radiation that lands on it and it can be considered to be the perfect emitter

Question 2

What does the narrowest peak represent on a black body diagram of emitted light?

Answer 2

Most radiation is emitted at this wavelength

Question 3

As temperature of a black body increases, what happens to the peak wavelength of radiation emitted?

Answer 3

The peak shifts to the left ( lower wavelength )

Question 4

What wavelength do really cold objects emit radiation at?

Answer 4

Really high wavelength like radiowaves

Question 5

What type of light do everyday temperature black body’s emit?

Answer 5

Infrared light

Question 6

Do stars behave like black bodies?

Answer 6

Yes because they emit a continuous spectrum of radiation

Question 7

What’s Weins law (black bodies)

Answer 7

For each temperature, there a peak in the radiation curve called the peake wavelength

Question 8

Define luminosity

Answer 8

Energy radiated by an object per second (in Watts)

Question 9

What’s the relationship between luminosity and temperature or surface area?

Answer 9

Directly proportional to both

Question 10

What is a protostar?

Answer 10

Clouds of dust and gas that clump together under gravity

Question 11

Describe the Hertzsprung-Russell diagram.

Answer 11

Y-axis is luminosity
X-axis is temperature (goes from high to low)
Dwarfs bottom, main sequence middle diagonal, giants high right, super giant very top

Question 12

Whats a problem with trigonometric parallax?

Answer 12

It’s only applicable to close stars, as when the distance increases the angle become too small to measure.

Question 13

What is 1° in minutes of arc?

Answer 13

60’

Question 14

What is a parsec?

Answer 14

The distance the star needs to be for the angle to be 1 second of arc

Question 15

What are standard candles

Answer 15

Objects which have a known luminosity

Question 16

How old is the universe roughly

Answer 16

13.8 billion years

Question 17

What does a high pitch of sound mean

Answer 17

The sound has a higher frequency

Question 18

What does a louder noise mean?

Answer 18

Large amplitude

Question 19

How do we know the universe is expanding.

Answer 19

By measuring the redshift of galaxies, astronomers can determine the speed at which they are moving away from us.

Question 20

Describe the characteristics of a main sequence star.

Answer 20

Constantly converting hydrogen to ugh fusion and maintaining a constant luminosity

Question 21

Describe how to find the distance of nearby stars.

Answer 21

Use trigonometric parallax go find the angle against the background that a star moves by in 6 months. Use this to find the distance .

Question 22

Why do large stars have greater luminosity

Answer 22

Surface temperature and area is the greatest. Most massive stars experience high gravitational force. Therefore, high temperature and density in the core. So rate of fusion is greatest.

Question 23

Explain the conditions required to bring about and maintain nuclear fusion in stars.

Answer 23

• High temperature needed
• nuclei all have positive charge leading to a large repulsive force between nuclei
• at high temps nuclei have KE sufficient to overcome repulsion
• nuclei must get close enough to fuse
• required high density
• collision rate must be high enough to sustain fusion

Question 24

Why do astronomers have difficulty in making accurate measurements to galaxies or measuring the critical density of the universe?

Answer 24

There’s a large uncertainty in bubbles constant because dark matter creates uncertainty of the values of mass and density.

Question 25

What is dark matter roughly?

Answer 25

Matter that doesn’t interact with electromagnetic force

Question 26

What is critical density?

Answer 26

The density of mass of the universe that means gravity is just strong enough to stop the expansion.

Question 27

Explain why radiation received from the earliest stars formed in the universe is in the radio wavelength region of the electromagnetic spectrum.

Answer 27

• The radiation has to travel many light years to reach us
• Light gets red shifted to the radio wavelength
• The Universe is expanding so wavelength has been stretched

Question 28

What can be said about a star that is very bright, easily visible and has a orange-red colour?

Answer 28

• It is a red giant
• Very high luminosity (bright)
• Large mass and volume as it is visible
• Not a very hot star because of the orange red colour
• Heavier elements undergo fusion on the staf