physics - space Flashcards

1
Q

What is in our solar system?

A
  • The Sun (a star)
    ● Eight planets (Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune)
    ● Dwarf planets (Pluto)
    ● Natural Satellites (Moons)
    ● The asteroid belt (this exists between Mars and Jupiter)
    ● Comets are frozen rocks that move around the Sun in often very elliptical orbits
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2
Q

Where is our solar system?

A
  • Milky Way galaxy, a collection of around 100 billion stars.
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3
Q

How was our Sun formed?

A
  • 4.5 billion years ago
  • a cloud of gas and dust (a nebula) was pulled together by gravitational attraction.
  • particles in the cloud got faster and collided more. The gas warmed up and eventually became hot enough to glow. This was a protostar.
  • the protostar gets more dense, more collisions take place and it gets hotter. Eventually the cloud gets hot enough for hydrogen atoms to fuse, forming helium. We call a star in this state a main sequence star.
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4
Q

Why does the Sun remain in the main sequence stage?

A
  • the gravitational attraction still pulling on the gas is balanced by the outward force of the radiation from the nuclear fusion in the core.
  • forces are in equilibrium.
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5
Q

Why do we have uranium?

A

Uranium and other such heavy elements naturally present on Earth can only be formed in a supernova explosion so the Sun must have formed from the remnants of a supernova.

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6
Q

What is going to happen to our Sun eventually?

A
  • When a star starts to run out of hydrogen to fuse, its core collapses and the outer layers swell, cool down and the star will become a red giant.
  • Here, helium and other light elements in the core fuse to form heavier elements.
  • When there are no more light elements in the core, fusion stops and no more radiation is released.
  • The star collapses, becoming a white dwarf
  • Such stars eventually fade out becoming black dwarfs.
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7
Q

What would happen eventually if our Sun was much bigger?

A
  • Stars much bigger than ours become red supergiants then they collapse.
  • more mass the collapse is more violent and a supernova explosion occurs.
  • explosion compresses the core into a neutron star.
  • If the original star was massive enough, it becomes a black hole instead of a neutron star.
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8
Q

How do we decide if something is a planet, moon or satellite?

A
  • A planet orbits a star, enough gravity to make it spherical and sweeps out its own orbital path of other smaller objects.
  • A moon orbits a planet.
  • A satellite is something that orbits something else.
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9
Q

What provides the force that allows planets and satellites (natural and artificial) to maintain their circular orbit?

A

Gravity. It is an example of a centripetal force because it is acting towards the centre of a circle.

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10
Q

Describe a circular orbit.

A
  • An object orbits another at a constant speed. Its direction is constantly changing so its velocity is changing
  • Therefore we say the object is accelerating towards the centre of the circle. The acceleration is a change of velocity per second.
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11
Q

What happens to the orbit of an object if its speed changes?

A

If an object in orbit slows down, it will fall into a lower orbit, if it gets to slow it will crash to the surface
- If an object in orbit speeds up, it will move to a higher orbit, if to fast it will fly off to space
- At the correct speed an object will orbit at a constant height and speed.

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12
Q

What is red-shift?

A

Light waves are stretched out if a star or galaxy is moving away from an observer. The wavelength of the light increases.This is called red-shift because the light is shifted towards the longer wavelength - red end of the visible spectrum.

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13
Q

What is red-shift evidence for?

A

universe is expanding

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14
Q

What does the Big Bang theory suggest?

A

The universe is expanding and originated as a very small and extremely hot and dense region.

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15
Q

What other evidence is there for the Big Bang theory?

A

scientists discovered microwaves coming from every direction in space, there must have been a massively
energetic event in one place to still have evidence of it today. This radiation was called the Cosmic Microwave Background Radiation

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16
Q

Were there any other theories for the origin of the universe?

A

The Steady State theory suggested that the universe was expanding, but it had always been there and matter was created into the spaces that the universe expanded into.

17
Q

What will happen to our universe?

A

1)[If the universe is less dense than a certain amount] Expand forever, the stars will gradually die out and the universe will cool (Big Yawn)

2) [If the universe is more dense than a certain amount] Stop expanding and collapse (Big Crunch)