Astronomy Flashcards

1
Q

Does gravity change when you go to other planets and moons

A

Yes

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2
Q

What is the equation for weight

A

Weight = mass x gravity

W = mg

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3
Q

What does gravitational force cause these objects to do:
1. Planets in the solar system
2. The moon and artificial satellites
3. Comets in the solar system

A
  1. Orbit the sun
  2. Orbit the earth
  3. Orbit the sun
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4
Q

What is the equation for orbital speed

A

Orbital speed = (2 x pi x orbital radius)/time

(2 pi r)/t

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5
Q

How does the orbit of a comet differ from the orbit of a moon or planet

A

Comets orbit in an elliptical path but moons and planets orbit in a circle

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6
Q

What is a satellite

A

Something that orbits a larger object in space. Can be natural e.g. moons or man made e.g. telecommunication satellites

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7
Q

What galaxy is the solar system in

A

The milky way

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8
Q

What is the definition of a galaxy

A

A large collection of billions of stars

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9
Q

What is the definition of the universe

A

A large collection of billions of galaxies

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10
Q

What is the definition of the universe

A

A large collection of billions of galaxies

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11
Q

What is orbital period

A

The time taken for an object to complete one full orbit

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12
Q

When calculating the orbital radius of the moon, must you include the radius of the earth

A

Yes - measure from the centre of the earth

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13
Q

What is the time period of the earth orbiting the sun

A

365.25 days

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14
Q

How long does it take for the earth to rotate on its axis

A

24 hours

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15
Q

How long does it take for the moon to orbit the sun

A

One month as an approximation but its actually 27 days

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16
Q

What is the Doppler effect

A

The apparent change in frequency of a wave due to the relative motion between the source and observer

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17
Q

What is a redshift

A

The measured wavelength is longer than the emitted wavelength - the object is moving away from the

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18
Q

What is a blueshift

A

The measured wavelength is shorter than the emitted wavelength - the object is moving towards us

19
Q

What are the equations for the wavelengths of light and sound (4 parts)

A

(Observed wavelength - emitted wavelength)/emitted wavelength = change in wavelength/ emitted wavelength = Z (red shift constant) = V/C where c is the speed of light

20
Q

What is CMB

A

Cosmic microwave background radiation - after the Big Bang, the radiation emitted cooled as it spread out. A radiotélescope can detect this constant hum of microwaves.

21
Q

What is the temperature of the universe

A

2.3K (but it is slowly going down)

22
Q

What is hubble’s law

A

The velocity of a galaxy is directly proportional to the distance from earth (straight line graph with gradient of 69.8)

V = H(constant of 69.8)d

23
Q

How is a red shift shown on a spectra of light

A

As the lines shift towards the red direction of the spectrum

24
Q

What is a nebula and what stage is it

A

First stage - clouds of dust and gas

25
Q

What does a nebula become and what is it

A

A protostar - the dust and gas collapse in due to gravity, meaning that the GPE is converted to KE, which increases core temperature. With high enough temperature and pressure, hydrogen fusion occurs, therefore forming a star

26
Q

What happens after a nebula to an average star

A

It becomes a main sequence star - like the sun. Hydrogen is fusing to Helium, releasing energy, causing the star to heat up.

27
Q

What is hydrostatic equilibrium

A

When the outwards pressure from the temperature equals the inwards pressure from gravity

28
Q

What happens to an average size main sequence star

A

After running out of hydrogen, it becomes a red giant. The star starts collapsing, so higher elements e.g. helium can fuse.

29
Q

What happens to an average size red giant

A

Eventually when too much iron has been fused in the core, the star collapses and explodes. This outer explosion of dust forms around the white dwarf core, making it a planetary nebula

30
Q

What happens to

31
Q

What happens to a planetary nebula

A

The gas around the white dwarf core eventually disperses, leaving behind a white dwarf

32
Q

What happens to a white dwarf

A

It cools and becomes a black dwarf (the universe isn’t old enough for this to have happened yet though)

33
Q

What happens to a massive star after the nebula stage

A

It becomes a main sequence star

34
Q

What happens to a massive main sequence star

A

It becomes a red super giant

35
Q

What happens to a red super giant

A

It becomes a supernova - an extremely powerful and bright explosion

36
Q

What happens to the most massive supernovas

A

It becomes a black hole

37
Q

What happens to the normal sized supernovas

A

It becomes a neutron star - a star made of neutrons which ejects powerful jets of matter

38
Q

Is a planetary nebula for massive or normal stars

39
Q

Which is for massive and which is for normal: planetary nebula, supernova

A

Normal - PN
Massive - supernova

40
Q

What reaction type fuels a star

A

Fusion - two nuclei coming together to form a high mass nucleus

41
Q

What conditions do fusion reactions require and why

A

Very high temperature and pressure, to overrule the electrostatic repulsive force

42
Q

When does a star become classed ‘dead’

A

When it stops fusing hydrogen