P16 Space Flashcards
What are comets?
• What shape are their orbits?
Frozen rocks.
• Elliptical shape (ovalish)
What’s a meteor?
Small bits of rock that burn up when they enter the earth’s atmosphere. (Shooting star)
How did the sun form?
By clouds of dust and gas pulled together by gravitational attraction.
What temperature is the ‘habitable’ zone?
What does it mean?
1-100 degrees C
Liquid water can exist there.
What are stars formed from?
Gas and dust.
What is a protostar?
Is a concentration of gas and dust that becomes hot enough to cause nuclear fusion.
How does a protostar form?
- Particles of dust and gas are pulled together by their own gravitational attraction - particles speed up.
- Clouds merge
How does a star form?
- Protostar
- As it becomes denser the particles speed up more and the temp increases - energy transfer from GP energy to thermal.
- If becomes hot enough, nuclei of the hydrogen atoms fuse together forming helium nuclei. Energy released.
Why is the sun stable?
Because the gravitational forces acting inwards balance the force of nuclear fusion in the core acting outwards.
Why is energy released inside a star?
Because of nuclear fusion.
When does a star become unstable? (Stats smaller then the sun or the same size)
What is the star now called?
It runs out of hydrogen nuclei. Reaches the end of its main-sequence stage it’s core collapses and it starts to swell.
A red giant.
How are heavier elements formed? (Nuclei larger than iron nuclei)
In the core of a red giant, helium and other light elements fuse.
What happens to stars much bigger than the sun after they finish their main-sequence stage?
- They swell out and become red supergiants.
- They collapse
- in collapse, the matter surrounding the stars core compresses the core more and more, the compression suddenly reversed in a supernova
- the explosion compresses the core into a neutron star.
- If enough mass it turns into a black hole.
Stages of a star the same size or smaller then the sun?
Protostar ~ main-sequence star ~ red giant ~ white dwarf ~ black dwarf
Stages of a star much more massive than the sun?
Protostar ~ main-sequence star ~ red supergiant ~ supernova ~ neutron star (or black hole if enough mass)
An example of a:
- Natural satellite
- Artificial satellite
- the moon
- a satellite
What shape is the earth’s orbit?
Circular.
What keeps a planet moving along its orbit?
The force of gravity between a planet and the sun
What keeps a satellite moving along its orbit?
The force of gravity between a satellite and the earth.
As a body in a circular orbit moves around its orbit…?
3 points
- The magnitude of velocity DOES NOT change. (Speed)
- The direction of its velocity DOES change
- It experiences an acceleration towards the centre of the circle
What is the red-shift?
Is the shift to longer wavelengths (lower frequencies) of the light from the galaxy because it is moving away.
The faster the galaxy is moving away…
The greater it’s red-shift
What is a galaxy?
A enormous collection of stars that stay together because of the force of gravity between them.
The universe is…
expanding.
Evidence for the Big Bang?
Cosmic microwave background radiation (CMBR) can only be explained by the Big Bang. Red-shift
What is the Big Bang theory?
That the universe began with a sudden unexplained explosion, and space, matter and time were created by it.
Name given to the change in pitch of the sound of moving objects?
the Doppler effect
Galaxy moving towards the Earth = …… shift
blue
When does star finish main sequence phase?
when it runs out of fuel (hydrogen nuclei)
Why cant heavier elements such as zinc form in sun’s core?
not hot or dense enough - too much energy required
D. Black hole?
an area in space where the gravitational force is so great that not even light can escape it
D. Light year?
the distance that light from an object can travel in one Earth year
Force of gravity on a planet from the sun is an example of what force?
centripetal (acts towards the centre of a circle)
Direction of motion of any planet in a circular orbit is….
at right angles to the direction of the force of gravity onit
Why does a planet in a circular orbit experience acceleration towards the centre of a circle?
because the resultant force on it acts towards the centre of the circle
Satellites too close to the Earth….
gradually loose speed due to atmospheric drag and gradually spiral downwards until hits the Earths surface
Stable orbit?
moves around the Earths surface at a constant height
Why does velocity of a planet on a circular orbit change but its speed doesn’t?
force is at 90 degrees to direction of motion so no work is done by the force so kinetic energy and speed don’t change
Further a satellite is from the Earth or a planet….(2)
- less particular speed is needed for it to remain in a circular orbit - force of gravity is weaker so doesn’t need to travel as fast
- longer the orbiting body takes to move around orbit once
D. Geostationary?
orbit where the object remains above 1 point on the earths surface constantly
Neutron star?
extremely dense object made of only neutrons
Missing mass in the universe =
?
dark matter - cant be seen
presence means that average density of universe is much greater then if it wasn’t there
If density of universe is less then a particular amount, it will…. forever
expand - Big yawn
If density of universe is more then a particular amount, it will….
stop expanding and go in reverse - Big crunch
Steady State theory?
galaxies being pushed apart caused by matter entering universe through white holes
