Universe

Question 1

Describe a star?

Answer 1

Flaming ball of gas
Core is a nuclear reactor undergoing constant fusion
Constant nature of this reaction is the cause of star’s heat and light emissions and allows planets to have access to UV radiation.

Question 2

What is the life cycle of a star?

Answer 2

Average Star Size: Stellar nebula, protostar, main sequence star, red giant, planetary nebula and white dwarf
Massive Star Size: Stellar nebula, protostar, main sequence star, red supergiant, supernova, neutron star or black hole

Question 3

What criteria must be reached in order for a star to be created?

Answer 3

In a stellar nebula, the gases float around aimlessly until the magic number of 100 atoms per cubic centimetre is reached

Question 4

How is a star created?

Answer 4

The condensing of atoms caused by gravity in a nebula increases the pressure and density, which sequentially increases the temperature. This cycle continues until there is enough hydrogen gathered and condensed to begin the process of nuclear fusion.

Question 5

How does the main sequence stage begin?

Answer 5

When a protostar begins the process of fusing the hydrogen it is made of into helium in its core, the star enters what is known as its Main Sequence.

Question 6

How does the star maintain its stability?

Answer 6

Fusion produces an outward pressure that balances with the inward pressure caused by gravity, stabilizing the star.

Question 7

How is the star classified as a massive or average star?

Answer 7

Depending on exactly how much hydrogen and stellar material has gathered, the star is classified as either an average star or a massive star.

Question 8

How are brown dwarfs made?

Answer 8

Smaller bodies — with less than 0.08 the sun’s mass — cannot reach the stage of nuclear fusion at their core.

Question 9

What is a brown dwarf?

Answer 9

Stars that never ignite.

Question 10

Surface temperature range in main sequence star

Answer 10

2600°C- 44200°C

Question 11

What determines the lifespan of a main sequence star?

Answer 11

How long a main sequence star lives depends on its size

Question 12

Why does the size of the star determine the lifespan of a main sequence star?

Answer 12

A higher-mass star may have more material, but it burns through it faster due to higher core temperatures caused by greater gravitational forces.

Question 13

Lifespan of planetary nebula

Answer 13

Planetary nebula are relatively short-lived, and last just a few tens of thousands of years.

Question 14

Surface temperature of planetary nebula

Answer 14

100,000°C+

Question 15

Describe the planetary nebula stage

Answer 15

Low-massstarsturn into planetary nebulae towards the end of theirred giantphase. At that point the star becomes highly unstable and starts to pulsate. The outer layers are ejected by the resulting stellar winds. As the outer layers drift away from the star, the remaining core shines brightly and is very hot. Theultraviolet radiationpumped out by the white dwarf causes the ejected outer layers to glow - the planetary nebula.
Over time, the enriched material from the planetary nebula is scattered into space and will constitute future stars

Question 16

Cause of white dwarf luminosity

Answer 16

A white dwarf’s faintluminositycomes from theemissionof residualthermal energy; no fusion takes place in a white dwarf.

Question 17

Why does a white dwarf’s temperature decrease?

Answer 17

A white dwarf is very hot when it forms, but because it has no source of energy, it will gradually cool as it radiates its energy away.

Question 18

Surface temperature range of white dwarf

Answer 18

White dwarfeffective surface temperaturesextend from over 150,000K to barely under 4,000K.

Question 19

Do black dwarfs exist? Explain your answer

Answer 19

Because the length of time it takes for a white dwarf to reach this state is calculated to be longer than the current age of the known universe (approximately 13.8billion years),it is thought that no black dwarfs yet exist.

Question 20

How is a black dwarf created?

Answer 20

Over a very long time, a white dwarf will cool and its material will begin to crystallize, starting with the core.

Question 21

Lifespan of a red supergiants

Answer 21

Typically only a few hundred thousand years, maybe up to a million.

Question 22

How is a supernova created?

Answer 22

In the core of the red supergiant, it continues to fuse heavier and heavier elements. This process stops when iron builds up in the core of the star. Iron is the equivalent of ash when it comes to nuclear fusion. The process of fusing iron actually requires more energy than it releases. At this point, many red supergiants will detonate as a supernova.
Or when awhite dwarfis triggered into runawaynuclear fusion.

Question 23

Which two basic mechanisms trigger most supernovae?

Answer 23

The sudden re-ignition ofnuclear fusionin adegenerate starsuch as a white dwarf, or the suddengravitational collapseof a massive star’score.

Question 24

How does the main two causes of the creation of supernovas create supernovas?

Answer 24

Nuclear fusion in a degenerate star is causes the object to raise its temperature to a certain level enough to triggerrunawaynuclear fusion, completely disrupting the star. Possible causes are an accumulation of material from abinary companionthroughaccretion, or astellar merger.
In the massive star case, the core of amassive starmay undergo sudden collapse, releasinggravitational potential energyas a supernova.

Question 25

Radius and mass of neutron stars

Answer 25

Neutron stars have a radius on the order of 10 kilometres and a mass of between 10-25 solar masses.

Question 26

How are neutron stars created?

Answer 26

They result from thesupernovaexplosion of amassive star, combined withgravitational collapse, that compresses the core pastwhite dwarfstar density to that ofatomic nuclei.

Question 27

Surface temperature of neutron stars

Answer 27

600000K

Question 28

Give an example of a neutron’s star density

Answer 28

They are so dense that a normal-sizedmatchboxcontaining neutron-star material would have a weight of approximately 3billiontonnes, the same weight as a 0.5 cubic kilometre chunk of the Earth (a cube with edges of about 800 metres) from Earth’s surface.

Question 29

Size of neutron star magnetic and gravitational field

Answer 29

Theirmagnetic fieldsare between 10^8and 10^15(100millionto 1quadrillion) times stronger than Earth’s magnetic field.

The gravitational field at the neutron star’s surface is about2×10^11(200 billion) times that of Earth’s gravitational field.

Question 30

Why is the gravity in a black hole so strong?

Answer 30

The gravity is so strong because matter has been squeezed into a tiny space.

Question 31

Why are black holes invisible?

Answer 31

Because no light can get out, people can’t see black holes.

Question 32

What feeds a rotating black hole?

Answer 32

Quasar

Question 33

What happens when there isn’t any matter left or the quasar to feed on?

Answer 33

Aquasardims into a normalblack holewhen there is nomatteraround it left to eat.

Question 34

Why is it named the event horizon?

Answer 34

The event horizon is referred to as such because if an event occurs within the boundary, information from that event cannot reach an outside observer, making it impossible to determine whether such an event occurred.

Question 35

Difference of singularity shape in non-rotating and rotating black hole

Answer 35

For a non-rotating black hole, this region takes the shape of a single point and for a rotating black hole, it is smeared out to form aring singularitythat lies in the plane of rotation.

Question 36

What is a Schwarzschild black hole?

Answer 36

A non-rotating and not charged black hole

Question 37

What is a Reissner–Nordström black hole?

Answer 37

A charged black hole

Question 38

Can you avoid the singularity in a black hole?

Answer 38

Observers falling into a Schwarzschild black hole (i.e., non-rotating and not charged) cannot avoid being carried into the singularity once they cross the event horizon whereas in the case of a charged (Reissner–Nordström) or rotating (Kerr) black hole, it is possible to avoid the singularity.

Question 39

What happens when you enter the singularity of a Schwarzschild black hole?

Answer 39

When they reach the singularity, they are crushed to infinite density and their mass is added to the total of the black hole. Before that happens, they will have been torn apart by the growingtidal forcesin a process sometimes referred to asspaghettificationor the “noodle effect”.

Question 40

Describe the Sun

Answer 40

The Sun is a star at the centre of our Solar System. It provides light and heat to everything in the solar system. It is very very big (1 million times bigger than earth). All of the planets orbit (move around) the sun

Question 41

Describe Mercury

Answer 41

Mercury is the planet closest to the Sun. It is small and rocky and turns slowly, so that one side is very hot (400ºC) and the other very cold (-200ºC).

Question 42

Describe Venus

Answer 42

Venus is the second planet from the Sun. It is the hottest planet. It is always covered with acid clouds.

Question 43

Describe radio telescopes

Answer 43

Radio telescope can observe in the radio wave part of the spectrum
Can see through dust and detect elements that light telescope cannot detect
Works day and night
However they are very big

Question 44

Describe The Hubble space telescope

Answer 44

The Hubble space telescope was put into low Earth orbit in 1990 on the Space Shuttle.
It is a reflecting telescope with two mirrors.
The primary curved mirror bounces the light to a secondary mirror, which then reflects the light through a small hole in the first mirror.
The various cameras are behind the mirror – depending on what they want to look at, they move different cameras into place.

Question 45

The Hubble space telescope advantages

Answer 45

Light doesn’t distort its images
Cameras can observe the light due to the atmosphere not blocking ultraviolet or infrared light
Can operate almost 24 hours a day, with no day/night time.
Can hold incredibly steady for long-exposure shots.

Question 46

Hubble telescope disadvantages

Answer 46

Really expensive to build and launch into space
REALLY expensive to fix or upgrade (evident when needing to repair the dodgy mirror it was launched with)
Can’t be huge or it wouldn’t fit on the rocket.
Gets outdated.
There’s some things it can’t look at (e.g. the sun and things close to it)

Question 47

Why is gravity strong?

Answer 47

Even though the force gravity is weak, because there is an innumerable number of atoms and each atom exerts gravity, gravity is strong.

Question 48

Example of gravity weakness

Answer 48

A magnet can pick up a paperclip, and beat gravity.

Question 49

Evidence that proves big bang theory

Answer 49

Red Shift (Hubble’s Law)
Cosmic Background Radiation
Abundance of “Light elements”

Question 50

How does redshift prove the big bang theory?

Answer 50

This was actually the first evidence found that suggested the Big Bang might have happened.
Edwin Hubble looked at lots of galaxies and discovered (using the Doppler effect / red shift) they were almost ALL moving away from the Milky Way (our galaxy)
The only explanation was that they all used to be together once.

Question 51

How does CMBR prove the big bang theory?

Answer 51

If the universe was extremely hot at the beginning, there should still be some remnant of that heat today.
2 Scientists, Penzias and Wilson, found this Cosmic Microwave Background Radiation (CMBR) by accident in 1964.
The universe has had a lot of time to cool, and if the big bang was 13.8 billion years ago, it should have cooled to around 3 degrees Kelvin (around -270°C). Guess what temperature Penzias and Wilson measured?

Question 52

How does the abundance of light elements prove the big bang theory?

Answer 52

When we look at the universe, we can measure 77% Hydrogen, 23% Helium, and about 0.1% Lithium (including all the stuff in stars, gas clouds, etc). Scientists initially had no idea why.
As other scientists did calculations on what the big bang was like, they discovered that when the universe cooled enough to make matter, only certain amounts of certain elements would be made. Guess what those amounts were…

Question 53

What is a Kerr black hole?

Answer 53

A rotating black hole

Question 54

Purpose of naming redshift and blueshift

Answer 54

For visible light, the bluer part of the spectrum has shorter wavelengths, and the redder part of the spectrum has longer wavelengths. Thus, the Doppler effect for light is called a ‘blueshift’ if the light source is coming toward an observer, and a ‘redshift’ if it is moving away.