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Physics 🧲 > Astronomy > Flashcards

Astronomy Flashcards

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1
Q

What does The Big Bang Theory state about the universe?

A
  • That it started as a tiny particle about 13.8 billion years ago
  • It expanded from this point in space
  • It is still expanding today
  • Same amount of matter, none created or destroyed
  • Density of matter decreases over time
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2
Q

What does the Steady State Theory state about the universe?

A
  • It has always existed
  • It is still expanding
  • New matter is continuously created as it expands
  • Density of matter stays constant over time
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3
Q

How does Redshift suggest that the universe is expanding?

A
  • When objects that emit light are moving away from us, the light they emit is red shifted
  • This means the wavelengths from them when detected back on Earth will be ‘stretched’
  • The spectral lines will be shifted to the red end of the spectrum
  • The faster the galaxy is travelling away from us, the more these lines will be shifted to the red end of the spectrum
  • As the furthest galaxies show more red shift than those nearer to us, the universe must be expanding
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4
Q

How does cosmic microwave background radiation support The Big Bang Theory?

A
  • CMB comes from all directions in space and has a temperature of about -270°C
  • CNB is the remains of the thermal energy from the Big Bang, spread thinly across the whole universe
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5
Q

What is the Doppler effect?

A

When a wave source is moving relative to an observer there is a change in the observed frequency and wavelength of the waves

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6
Q

How can the speed of the Galaxy be determined from the absorption lines in its spectrum?

A
  • Absorption lines in the spectra of the light from the galaxy can be compared with the corresponding absorption lines of a stationary source
  • The difference in the position/wavelength/frequency can be used to calculate the speed of the galaxy
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7
Q

What is the order of the eight planets from the Sun?

A

Mercury
Venus
Earth
Mars
Jupiter
Saturn
Uranus
Neptune

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8
Q

What is an exoplanet?

A

A planet outside of our solar system

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9
Q

What was the geocentric model?

A
  • Ptolemy, Greek astronomer
  • Earth was the centre of the universe
  • Planets also moved in little circles as they moved around earth
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10
Q

What was the heliocentric model?

A
  • Copernicus
  • Earth and six planets went around the Sun
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11
Q

What are some examples of natural satellites?

A
  • Planets
  • Moons
  • Comets
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12
Q

What are some examples of artificial satellites?

A
  • Satellites in geostationary orbit - used for GPS
  • Satellites in low polar orbits - used for weather monitoring, military, spying, and earth observation purposes
  • Satellites sent from Earth to orbit and monitor the Sun 
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13
Q

What are the stages of the life-cycle of a low mass star?

A
  • Nebula
  • Protostar
  • Main sequence star
  • Red giant star
  • White dwarf
  • Black dwarf
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14
Q

What are the stages of the life-cycle of high mass stars?

A
  • Nebula
  • Protostar
  • Main sequence star
  • Red supergiant star
  • Supernova
  • Neutron star/black hole
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15
Q

What is a nebula?

A

A cloud of dust and hydrogen gas

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16
Q

How is protostar formed?

A
  • Gravity pulls the nebula together
  • As the dust and gas contracts, the nebula gets hotter as work is being done on it
  • When it is hot enough, the hydrogen nuclei fuse together to make helium
  • The fusion process releases energy which keeps the core of the star hot
17
Q

Why is a main sequence star stable?

A

The inward force of gravity is balanced by the outward force of thermal expansion

18
Q

How is a red giant star formed?

A

When most of the hydrogen gas has been used up by fusion, larger nuclei begin to form and it will expand

19
Q

How is a white dwarf formed?

A

All nuclear fusion stops and the star collapses

20
Q

What causes a supernova?

A
  • Larger stars continue making nuclear reactions, getting hotter and expanding until they explode
  • This releases hot gas into space
21
Q

How are neutron stars and black holes formed?

A
  • If the remains of a supernova are less than 4x the mass of the Sun, gravity pulls it together to form a small dense star (neutron star)
  • Larger stars collapse completely and vanish as light cannot escape its gravity

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