Space

Question 1

what does 1AU equal?

Answer 1

1.5x10^11m

Distance between ear tbh and sun

Question 2

What does 1 light year equal?

Answer 2

9.5x10^15m

Distance light travels in a year

Question 3

What is the net work done when an object moves vertically (with or against gravity)?

Answer 3

0

Question 4

What is the centripetal force required to keep a satellite in a circular orbit supplied by?

Answer 4

the gravitational force

Question 5

Difference between Vp and Ep

Answer 5

Vp is a property of the gravitational field

Ep is a property of the object in the field

Question 6

Sentence describing mads and curviture

Answer 6

mass tells spacetime how to curve and the curvature of spacetime tells mass how to move

Question 7

Does time pass slower or faster the stronger the gravitational field is

Answer 7

(the deeper you are into a gravitational well) the slower time will pass

Question 8

world lines (space-time diagram)

Answer 8

person at rest through time: vertical line

An object with constant velocity: straight diagonal line (not touching y axis)

An accelerating object: log graph (not touching y axis)

Question 9

Light’s worldlines

Answer 9

space-time diagram
2 lines crossing at (0,0)

-top region: tells us everything in their observable future
-bottom region: tells us everything in their observable past
-other two side regions are forbidden

Since nothing can travel faster than light, all moving objects are bound into the region between the axes and the worldlines

Question 10

What happens at the event horizon of a black hole?

Answer 10

time appears to be frozen

Question 11

The birth of a star

Answer 11

Stars are born in giant clouds of cold gas (mainly H2) called nebulae

Gravity pills the clouds if gas together, increasing mass and slowly increasing the density, pressure and temperature

Eventually, the temperature become so large that H2 fuses into He via the proton-proton chain, releasing energy in the process

Question 12

The death of a star

Answer 12

When all the helium and hydrogen has been used up, the star’s core will contract due to gravity (gravity exceeds thermal pressure->diameter increases)

In a star like the Sun, the core shrinks and will become hot enough for the He in the core to begin fusion

The madd of a star determines its lifetime and its eventual fage

Every star star ultimately becomes a white dwarf, a neutron star, or a black hole

Question 13

Why will the sun not be a black hole?

Answer 13

its radius is larger than its schwarzchild radius

Question 14

When does the sun leave its main sequence?

Answer 14

When hydrogen fusion stols

Question 15

Properties of stars

Answer 15

As mass, luminosity, temperature and radius decrease, lifetime increases

relationships are not linear

Question 16

What does the luminosity of a star depend on?

Answer 16

radius and temperature

Question 17

Proton-proton chain

Answer 17

1
proton+proton->Hydrogen-2 nucleus+positron+neutrino

(2 protons combine to form 1 deuterium nucleus. One of the protons becomes a neutron and in doing so releases a positron (anti-electron) and neutrino. This reaction occurs twice.) (hydrogen-2 nucleus=deuterium nucleus)

2
deuterium nucleus+proton->helium-3 nucleus+gamma photon

(each deuterium nucleus undergoes fusion with another proton to produce 1 helium-3 nucleus. A gamma photon is emitted in the process. This reaction occurs twice)

3
helium-3 nucleus->helium-4 nucleus+2 protons

(2 helium-3 nucleus fuse to produce one helium-4 nucleus. 2 protons are released.)

Overall
6 protons->helium-4 nucleus+2 protons+2 positrons+2 neutrinos+2 gamma photons

Question 18

Hertzsprung-Russel diagrams

Answer 18

luminosity-surface temperature

surface temperature increases towards (0,0) with decreasing peak wavelength

-supergiants
-giants
-main sequence
-white dwarfs

moves anti-clockwise from main sequence

Question 19

Main sequence stars

Answer 19

when stars are fusing together H2 and He, it is in a gravitational equilibrium. These stars are stable.

Question 20

Main sequence summary

Answer 20

-Fuse H into He via the proton-proton chain while on main squence

-remain in gravitational equilibrium where the gravitational pull inwards is balanced by the thermal pressure outwards

-When H fusion stops, the star collapses inwards due to gravity. This increasing pressure and temperature kickstarting He fusion into elements like C and O

-The thermal pressure outwards is now greater and so the star’s outer layers expand to become red giants or red supergiants