Space Physics Flashcards
What is a light year?
The distance light travels in a year.
What is the universe?
All that can be observed in the cosmos: all of space and time. It is mostly empty space.
What is a galaxy?
A group of billions of stars held together by gravitational attraction.
What is a nebula?
A large cloud of gas and dust.
What is a solar system system?
A star orbited by planets and other bodies.
What is our solar system called?
The Milky way.
What is a star?
A massive body that gives off light (and other EM radiation) due to the fusion of hydrogen.
What is a planet?
A mostly spherical body in orbit around a star. It has cleared its orbit.
What is a dwarf planet?
A mostly spherical body in orbit around a star. It has not cleared its orbit.
What is a moon?
A rocky, or gaseous, body in orbit around a planet.
Celestial objects in size order? (largest to smallest)
-Universe
-Galaxy
-Nebula
-Solar system
-Star
-Planet
-Dwarf planet
-Moon
(-Comets)
(-Asteroids)
Why haven’t dwarf planets cleared their orbits?
They aren’t big enough.
What are the arm like things on a galaxy called?
Spiral arms.
A star orbits the centre of its home galaxy in the same way as what?
Planets in the solar system orbit the star. .
What is the old model called with the Earth as the centre of the universe?
The geocentric model
What is the new model called with the sun as the centre of the universe?
The heliocentric model (as the sun is made mostly of the element helium).
Why was the model of the universe changed?
Because the heliocentric model fit evidence on orbital pathways and the gravitational force of the sun. (it must pull earth in as it’s bigger).
Where is the asteroid belt located?
Between Mars and Jupiter
What is the difference between asteroids and comets?
Asteroids are made mostly of rock and metal, and are found in the asteroid belt.
On the other hand, comets are made mostly of ice and dust, and are found orbiting the sun elliptically (often to the outskirts of our solar system).
Mercury, Venus, Earth and Mars are ____ _____ planets.
_____ can be melted here.
rock-based
water
Jupiter, Saturn, Uranus, and Venus are ___ _____ planets, or ‘___ ______’.
Water is ______ here.
gas based
gas giants
frozen
What are Saturn’s rings made of?
Dust and debris.
Name the hottest planet.
Venus.
What does the colour of celestial bodies tell you?
-What elements they’re made of (think flame tests!)
-Their temperature
What is the difference between an artificial and natural satellite.
Artificial satellites are man-made, or ‘synthetic’, whereas natural satellites are formed naturally.
How can natural satellites be formed?
-From a nebula
-From old star material
Name the things in our solar system (The Milky Way)
-One star (the Sun)
-Eight planets
-Dwarf planets
-Natural satellites, including the moons that orbit the planets
How was the Sun formed?
From a cloud of dust and gas (nebula) pulled together by gravitational attraction.
Newton’s 1st law?
“An object travelling at a certain velocity will continue to travel at that velocity unless acted upon by a resultant force.”
What allows planets and satellites to maintain their circular orbits?
The force of gravity.
Orbit
The curved path of a celestial body about a larger body due to mutual gravitational attraction.
Do stars produce their own light?
YES! - through fusion reactions.
How are planets, moons, and artificial satellites similar?
They do not produce their own light/are not luminous.
They can be seem because they reflect star light.
Origin of stars, planets, and moons?
-All natural
-Stars are formed from a nebula, whereas planets and moons are formed from old star material
Origin of artificial satellites?
Synthetic/man-made
Relative mass of a star?
Very large.
Relative mass of a planet?
Large
Relative mass of a moon?
Small
Relative mass of an artificial satellite?
Negligible/very small
Orbit of a star?
Around the centre of its home galaxy.
Orbit of a planet?
Around a parent star.
Orbit of a moon?
Around a planet.
Orbit of an artificial satellite?
Around a larger body e.g. Earth.
When labelling diagrams, don’t get confused by sizes!!!
Look at what’s orbiting what/shape.
Explain what happens at the start of any star’s life cycle.
Dust and gas drawn together by gravity causes fusion reactions.
What do fusion reactions in stars lead to?
An equilibrium between the gravitational collapse of the star and the expansion of the star due to fusion energy.
(this is why it doesn’t collapse or explode)
Explain how, for circular orbits, the force of gravity can lead to changing velocity but unchanged speed.
The mass of Earth exerts a gravitational pull on the moon
This acts perpendicular to its motion/instantaneous velocity
This causes the moon to change direction, which means a change in its velocity
The moon is therefore accelerating as a = △v ÷ t
Speed us a scalar so remains constant.
Explain how, for a stable orbit, the radius must change if the speed changes.
If the speed increases, the radius must decrease & vice versa.
This is to maintain the balance between the gravitational force and the instantaneous velocity.
Describe the relationship between orbital speed and distance from the sun.
The further from the sun (so the lager the radius of an orbit), the slower the orbital speed.
Why does orbital speed increase closer to the sun?
The force of gravity is stronger, so the speed at which the planet must travel to maintain a stable orbit is high.
(the forces must balance)
What is centripetal force?
A force that keeps an object moving in a curved path.
It is directed towards the center of the object’s circular path.
What provides the centripetal force needed to keep planets and all types of satellite in orbit?
Gravitational attraction/pull
What keeps an orbit stable?
The forces of inertia and gravity need to balance :
Gravitational force pulls the object towards the center, while the object’s inertia tries to keep it moving in a straight line.
When these are balanced, the object follows a curved path around the central body, creating a stable orbit.
Inertia
The tendency of objects to continue in their state of rest or of uniform motion .
(its tendency to move in a straight line, at a constant speed, if no forces acted on it).
How do we calculate the orbital speed of a planet?
2 x π x (mean radius of orbit)
divided by
periodic time (s)
How do we calculate the distance travelled by a planet (m)?
2 x π x (mean radius of orbit)
(as the circumference is the distance travelled in one orbit).
Periodic time
The amount of time it takes for an object to complete one full cycle of motion
Briefly explain why planets accelerate.
Acceleration changes because velocity changes. Velocity changes due to a directional change.
What is the life cycle of a star determined by?
The size of the star.
Describe the first three stages in the life cycle of ANY star
Nebula - matter is far apar and slowly being pulled together by the force of gravity.
Protostar - The force of gravity has caused enough matter to attract to form a star.
Main Sequence Star - Nuclear fusion occurs.
Describe the difference between a protostar and a main sequence star.
No fusion occurs in a protostar, but fusion occurs in a main sequence star.
A protostar is cooler than a main sequence star.
Describe the fourth stage in the life cycle of a star the same size as the sun.
Red giant - Hydrogen runs out in the core so no more fusion occurs. The main sequence star collapses but then balloons out into a larger body (a Red Giant).
Why does a main sequence star collapse?
Hydrogen runs out in the core so no more fusion occurs.
So, there is no radiational pressure to balance the force of gravity and the star collapses.
Why does a collapsed main sequence star balloon back out?
Particles are closer together so collide more and start doing other fusion e.g. helium into carbon and oxygen.
Eventually there’s enough radiational pressure to balance the force of gravity so the matter pushes out into a Red Giant.
Describe the fifth stage in the life cycle of a star the same size as the sun.
White Dwarf - Helium runs out in to core so no fusion occurs.
So, there is no radiational pressure to balance the force of gravity and the star collapses.
The outer layers of matter rebound of a hot white core (‘A white dwarf’) into space.
Describe the sixth stage in the life cycle of a star the same size as the sun.
Black dwarf - A white dwarf eventually cools, dimming into a dark lump of mass.
Does fusion occur in white dwarfs?
NO!
Why are red dwarfs red?
The have a cool outer surface due to a large surface area.
(however the core is hot because of the synthesis of larger elements).
Why are white dwarfs white?
Because they are very hot!
(the intense heat comes from the thermal energy left over from their previous stages as active stars x)
Describe the fourth stage in the life cycle of a star much more massive than the sun.
Red Supergiant - Hydrogen runs out in the core so no more fusion occurs.
The main sequence star collapses but then balloons out into a larger body (a Red SUPERR GIANT)
How much bigger is a star ‘much more massive’ than the sun?
about 10 x
Why do large stars become red Super giants rather than simply red giants?
Because of their greater mass, they become much larger and more luminous.
Describe the fifth stage in the life cycle of a star much more massive than the sun.
Supernova - Helium runs out so the star collapses.
Matter rebounds in a supernova.
Describe the possible sixth stage in the life cycle of a star much more massive than the sun.
A supernova can:
Condense into a neutron star
Collapse into a black hole
What processes produce all of the naturally occurring elements?
Fusion processes in stars.
Explain why a supernova is a likely reason why elements are distributed throughout space.
Supernovas are explosions of massive stars, which likely causes elements to scatter/be distributed around the universe.
Explain where the helium in the sun originated.
The fusion of lighter hydrogen nuclei to form heavier helium nuclei.
Explain where the helium on the Earth originated.
A nebula which made the sun and the planets.
How are elements heavier than iron produced?
In a supernova.
(because there’s excess energy)
Where are elements lighter than iron but slightly heavier than helium produced?
They are fused in red super giants, in shells, with the heaviest elements at the core where it’s hottest. (=layers)
A student argued that in order for the main sequence period of a star’s life, the helium on the star needed to run out.
Explain if they’re correct or not [2]
No.
Hydrogen fusion decreases as hydrogen starts to deplete, NOT HELIUM.
rtfq!
Why are high temperatures needed for the synthesis of large elements?
High temperatures provide the necessary kinetic energy for the nuclei to collide and overcome the repulsion of positive nuclei.
A scientist theorised that some very ancient planets, THE FIRST TO FORM AFTER THE FIRST, SUN-LIKE STARS died, would not be made from many chemical compounds.
Explain why this could be true [3]
The planets would be made from matter left over ONLY from the 1st smaller stars.
No nuclei heavier than iron would be produced meaning less variety in elements and fewer compounds.
Gold is found on Earth.
What does this suggest about Earth’s origin?
-Earth is made from matter left over from supernova explosions
-As these are the events that can synthesise heavy elements like gold
Give the differences between fusion in a red giant and fusion in a main sequence star.
-Fusion in a main sequence star fuses hydrogen to make helium
-red giant fuses helium to make heavier elements up to iron
-The star is cooler on the outside but hotter on the inside
Name some of the many things still not understood about the universe.
-Dark mass
-Dark energy
What does the Big Bang theory suggest?
The universe began from a very small region that was very hot and dense.
This ‘singularity’ exploded, and space started to expand.
What evidence is there that distant galaxies are receding even faster than before?
Observations of supernovae from 1998 onwards.
What is red-shift?
When the wavelengths of light that a star or galaxy moving away from us emit are stretched.
This causes the light to shift towards the red end of the spectrum. This is known as red-shift.
When does red-shift occur?
When the object is moving away from the observer.
Why does red-shift occur?
-The wavelengths of light that a star or galaxy moving away from us emit are stretched
-This means a longer wavelength and a lower frequency (number of waves per second)
-The colour red has the longest wavelength and the lowest frequency
Explain how the change of each galaxy’s speed with distance is evidence of an expanding universe.
-Galaxies appear to move faster the farther away from us they are.
-Which suggests the space between them is stretching
Explain how red-shift provides evidence for the big Bang model
Light from distant galaxies is red-shifted, indication that they’re moving away from us.
Hubble’s law
The expansion can be traced backward in time to when it was smaller and more compact.
What do models help us to understand?
Difficult concepts.
What can be used to model the expansion of the universe?
A balloon and dots.
S - balloon expands = dots get further apart = represents galaxies moving apart
W - dots only on surface of balloon; galaxies are throughout the universe
W - There is a limit to how far the balloon can expand before it bursts
Why do scientists believe in the big bang theory?
Its predictions are supported by observations.
When did the big bang start?
13.8 billion years ago.
The observed red _____ provides ________ that space itself (the universe) is _________ and supports the ___ ____ theory.
shift
evidence
expanding
big bang
What is meant by the ‘visible spectrum’?
The part of the EM spectrum that can be detected by the eye.
What happens in an atom when EM energy is absorbed?
Electrons can move up energy levels.
Write out the order of the colours in the visible spectrum - from shortest to longest wavelength
Violet, Indigo, Blue, Green, Yellow, Orange, Red.
Name a colour of visible light with a higher frequency than blue.
Indigo/Violet
RED
-long wavelength
-low energy
-low frequency
VIOLET
-short wavelength
-high energy
-high frequency
What is the appearance of an emission spectrum?
A black background with individual bright coloured lines.
What is the appearance of an absorption spectrum?
A continuous spectrum background (rainbow!) with individual black lines where colours have been absorbed.
What causes the black lines on an absorption spectra?
Electrons gain energy in the form of visible light.
The EM wavelengths do not reach the eye.
Different chemicals absorb different…
…wavelengths of EM radiation.
What causes the coloured lines on an emission spectra?
Electrons lose energy in the form of EM radiation and drop down energy levels.
The EM radiation lost can be in the form of visible light waves, allowing us to see colour.
What does the colour of visible light emitted by an atom (when electrons lose energy & drop levels) depend on?
The energy difference between shells:
Larger: photons with higher energy and shorter wavelengths are emitted(towards the blue/violet end of the spectrum).
Smaller: photons with lower energy and longer wavelengths are emitted (towards the red end of the spectrum).
Why do different elements have different distances between shells/ different ‘energy levels’
Different numbers of protons.
What is meant by the ‘Doppler effect’?
A change in the frequency of light, sound, or other waves as the observer and source move relative to each other.
When they move towards each other, the frequency increases (blue-shift for light, higher pitch for sound).
When they move away from each other, the frequency decreases (red-shift for light, lower pitch for sound).
nenawww
Describe what would happen to the pitch of a sound as the source of the sound approached you.
It would get higher.
Describe what would happen to the pitch of a sound as the source of the sound moved away from you.
It would get lower.
Which direction do the lines move for red shift?
To the left (red end, lower frequency)
Hubble’s Law states that…
… the farther away a galaxy is, the faster it is moving away from us.
This relationship between distance and velocity provides evidence that the universe is expanding.
How would we draw a graph to represent Hubble’s law?
X-axis: distance (millions of light yrs)
Y-axis: recessional velocity
The relationship is directly proportional = straight line through origin.
How do we calculate the recessional velocity of a galaxy?
△λ ÷ λo = velocity ÷ speed of light in a vacuum
△λ ÷ λo meaning
change in wavelength ÷ original wavelength
Speed of light in a vacuum?
300 000 000 m/s
What does the Big bang theory suggest about the origin of the universe?
All matter in the universe occupied a tiny space, which was extremely dense and hot.
This ‘singularity’ exploded, so space started to expand.
What is Cosmic Microwave background radiation? (CMBR)
Energy left over from the Big Bang that has been redshifted to the microwave region of the EM spectrum from visible and infrared.
How old is the universe?
13 billion years
When did the universe become transparent?
380 000 yrs after the big bang, when the universe became cool enough.
This is when early light redshifted to a wavelength of 10 -2 (microwave)
What type of instrument detected CMBR in the 1960s?
Antenna
Why could light (EM radiation) not travel through a he early universe?
The early universe was opaque so light couldn’t travel across it.
What was dark energy proposed to explain?
The acceleration of the expansion of the universe at great distances.
What was dark matter proposed to explain?
Observed galaxy rotation speeds not matching the current theory.
