Astronomy Flashcards
How are planets’ orbits similar
They have an elliptical orbit and they orbit the sun.
How are planets’ orbits different
They have different orbital radii
How can some moons be faster than others considering the fact that they are orbiting larger planets?
Orbital radii of the 2 moons are different; one moon has a orbit radius larger than the other
Supernova
An explosion where the outer layer of stars is ejected
Black hole
an area of such immense gravity that not even electromagnetic waves such as light can escape from it
How stars produce energy
Nuclear Fusion and there are lots of reactions occurring on stars
What waves do black holes emit
X-rays
Why does a star remain stable
Radiation pressure and gravitational forces are equal
How does a star form (2)
Dust and gas particles are pulled together and clumped by gravitational forces pulling inwards
Differences between a protostar and a main sequence star
Protostar is at a lower temperature because nuclear fusion’s not started
How does the universe contain a large variety of different elements
- Nuclear fusion takes place within stars where hydrogen nuclei fuse to form helium
- Fusion continued and formed larger elements.
- Elements larger and heavier than iron were formed during a supernova
Why is the rate of nuclear fusion in a larger star faster than in a smaller star?
larger stars have a shorter main sequence period hence, they use up the hydrogen at a faster rate and therefore they have a faster rate of nuclear fusion occurring
What is meant by the big bang theory?
Universe started from a point of singularity where all matter was concentrated and an explosion occurred which sent the matter outwards
What does a larger orbital radius of a planet tell you about its speed?
If the planet moves further away from the star, it has to move faster to keep going around it. So, if a planet is far away, it has to go faster than if it is close
Larger the orbital radius of a planet –> The faster it travels
Gravitational field strength is measured in
N/kg
There are billions of galaxies in the
Universe
Why does a telescope travel fastest when it’s closest to the Earth?
- Gravitational forces increase when it’s closer to the Earth
- mass remains constant
- hence, it accelerates
Difference between X-rays and Visible Light?
X-rays have a shorter wavelength compared to Visible Light
X-rays have a higher frequency compared to Visible Light
Why does the distance between 2 planets vary?
They travel at different speeds and have different orbits
There is a vehicle on mars, Why is the speed kept so low?
There is a time delay and also damaged is reduced if there is a collision
Why does a comet travel fastest at that point nearest to the Sun?
The comet is closest to the Sun at that point hence, the gravitational forces are strongest at that point
Why is a 24-hour orbit of a satellite an advantage for communication?
The satellite always appears in the same part of the sky
Describe the evolution of stars of similar mass to the sun
- a cloud of dust and gas particles clump together due to gravitational forces pulling inwards, therefore, forming a protostar
- Nuclear fusion occurs which releases energy and creates outwards pressure hence, a main sequence star is formed which remains stable for long periods of time
- Hydrogen runs out therefore, the star collapses, becoming unstable and then turns into a red giant. Helium fusion begins on the Red Giant. Once the helium fusion stops, the red giant contracts to form a white dwarf
- As the white dwarf cools, the black dwarf forms
Explain what red shift is and how it provides evidence that the universe is expanding (6 marks)
- light from galaxies shifts towards the red end of the spectrum
- wavelength increases as galaxies move further away
- hence, the farther away the galaxy is and the faster it’s moving away, the greater the redshift
- therefore, showing galaxies are moving away
- and that the universe is expanding
Why do astronomers usually give the distance from stars as a number of light years instead of kilometres?
Distance is too great
Describe how careful observation of electromagnetic radiation from distant galaxies and from the whole of space gave evidence supporting Big Bang Theory (6 marks)
- light from galaxies shifts towards the red end of the spectrum
- wavelength increases as galaxies move further away
- hence, the farther away the galaxy is and the faster it’s moving away, the greater the redshift
- therefore, showing galaxies are moving away
- and that the universe is expanding
Describe how the process continues for stars much more massive than the Sun
- After H in main sequence stars runs out, star expands and cools to form a red super giant
- red super giant explodes into a supernova when outwards pressure is too great
- remains are a neutron star
- or a black hole the star was exceptionally massive
“The smaller the planet, the shorter its period of orbit”
Evaluate the statement
Correct = smaller an object’s orbit, the faster the object travels to increase its velocity and smaller planets travel faster
Why do planets nearer to the star take less time to orbit the star?
The planets have a shorter orbital path
What evidence is there to suggest that the Sun was formed form the material produced when an earlier star exploded?
There is presence of nuclei of the heaviest elements
Why might scientists think one theory is wrong?
New evidence can’t be explained by that theory
Define red shift
It’s when the wavelength increases
Why does red-shift provide evidence that the universe is expanding? (2)
- Red shift provides evidence that the distance of galaxies is increasing
- Red shift supports the idea of an expanding universe
Why might scientists be keen to carry out new research if one theory is similar to another?
To find more evidence to support one theory
How might the universe have started?
From an explosion
Explain briefly one piece of evidence which may be used to support that the universe started from an explosion (3 - RS)
- Light from galaxies shifts to the red end of the spectrum
- The further away the galaxies, the greater the redshift
- Therefore indicating galaxies are moving away
What should scientists do when a theory does not appear to be supported by new data? (2)
- Amend the theory
- Check the reliability of data
Why are there telescopes that detect different types of electromagnetic waves to observe the universe?
There are sources emitting different types of electromagnetic waves
Are red giants brighter and hotter than the main sequence?
Red giants are cooler but brighter than the main sequence as it’s more powerful
How is a main sequence star formed from a nebula (3)
- dust and gas particles clump together due to gravitational forces pulling inwards
- Hence, forming the protostar
- Nuclear fusion occurs on protostar to form the main sequence star
How does a main sequence star form a white dwarf
- Main sequence star collapses
- Main sequence star expands to form Red Giants
- Surface temperature of red giant decreases
- Helium fusion occurs
- Once helium fusion stops, red giant condenses into a hot and dense white dwarf
What does nuclear fusion do in terms of energy?
Nuclear Fusion releases energy
Define absolute magnitude
Measurement of the brightness of a star at a standard distance of 10 parsecs
During nuclear fusion and nuclear fission, what energy store of the star increases
- Fusion:
- Energy store that increases: Kinetic
- Fission:
- Energy store that increases: Thermal
Describe the evolution of the universe from the Big Bang until the present day
- Supernova explosion occurred and layer of stars was ejected outwards
- Galaxies moved away
- and the Universe expanded
How is Helium, Carbon and Hydrogen formed in stars and galaxies?
- Stars are mostly made of hydrogen
- Helium and carbon is formed during fusion
