Class 7 Stellar Evolution

explain the notion of a specific instance that occurs to white dwarfs

white dwarfs aren’t always left alone, sometimes they have a companion star which it steals mass from

what is a nova

when white dwarf takes mass from companion and the matter forms external layer which ignites and shines

• gentle explosion of hydrogen gas on surface of white dwarf

does a nova damage star

no, it can repeat

what is a supernova Ia

mass excessive which means dwarf can’t support mass and turns into a supernova type 1a

result of supernova 1a

no remnant

what defines a massive star

mass greater than 8 solar masses

when does a massive star originate

begins on main sequence as blue star

what path does a massive star follow

same path as low mass however at a faster pace but end result different

• after hydrogen fusion it begins to burn through other elements and stops at iron

as the shells of fusion around core increase

thermal pressure increases and overpowers gravity in outer layers causing expansion and then cooling where it becomes a red giant (shifts right)

fun facts of red super giant

iron core diameter of earth

300-1000x diameter sun

explain the iron problem

the iron core of supergiants is difficult as fusion of iron doesn’t make energy (you keep making iron!)

what is at result of iron problem

if fusion stops then gravity will overcome pressure and smash together electrons/protons to form neutrons

how does a supernova type 2 occur

the neutron core soon collapses so that inward falling material bounces off, recoil sends star flying into space

how fast supernova type 2

seconds which causes the biggest explosion in the entire universe (light from supernova is brighter than entire galaxy)

how do we know that a supernova type 2 occurred before we did?

causes elements until iron (stars), release of energy so great greater than iron created

cores of neutron star and black hole

neutron star: 1.4-3 of sun core

blackhole 3+

sizes of end state of stars

white dwarf: earth

neutron star: big city (10km)

black hole: city blocks (10+)

WHITE DWARFS

1. remnants of

2. how are they supported: electron degenerate pressure

3. composition of core

1. remnants of low mass stars

2. supported by electron degenerate pressure where they are tightly packed yet electrons repulsed

3. carbon core, but not hot enough to fuse

END OF LIFE WHITE DWARF

1. what happens to the core

2. supported by

3. size of

4. star ____

1. core becomes so dense it cannot contract or heat

2. degenerate electron pressre

3. earth

4. cools

what is a neutron star and how does it come?

left over from high mass supernova (1.4-3), pressure merges protons and electrons to form neutrons throughout the object

what happens to a neutron core of <3m

stop collapsing and held up neutron degeneracy pressure

size of neutron size

spin period

density

piece of neuron star the size of sugar cube

1. dense and small

2. 0:03-4sec

3. 10^11kg/cm³

4. 100 b pounds

how do blackholes go thru neutron phase

the collapsing core goes through the neutron star stage but it is unstable and stinks to become blackhole due to insufficiency of degeneracy pressure

black hole

black

hole

black: neither emits or radiates light

hole: nothing cab escape

1915 blackhole

Einstein’s Theory of Gravity predicted the possibility
of black holes, but no one believed they actually
existed!

1967 blackhole

Term “Black Hole” coined

1970 blackhole

Convincing evidence that black holes are real
Today: NASA space telescopes have discovered evidence for
black holes throughout the universe

how is space curved

mass causes space to curve and that curve allows for objects to move. for instance, the earth orbits the curved space of the sun

when is gravity stronger

when you cram mass into small volume, as mass increases so does gravitational pull

define blackhole

dense region of space where space curves due to large mass, little volume, so gravity becomes so strong that nothing can escape

explain center of blackhole

infinite density, zero volume called a singularity (smaller than atom)

what is blackhole singularity surrounded by

surrounded by event horizon where light can’t escape

distance between singularity and event horizon

Schwarzschild
radius (RSch)

what occurs to have a large SCh R

larger mass = larger radius

what happens when object crosses radius or event horizon

can never escape (point no return)

what is centre Milky Way

sagittarius where a supermassive blackhole exists 3x sun named saggitarus a

how to detect blackhole

x rays given off by material as it falls inwards towards blackhole

HDE226868

gases from super giant are captured into accretion disk of blackhole and as these gases spiral they heat by friction and hot enough x rays

stages of falling in

tidal forces, time dilation, redshift

explain tidal forces

body stretched along length by tidal forces due to the part that is closer to be pulled more strongly

time dilation

person watching: infinity amount of time to cross horizon and time stay still but in your reference frame then the clock is normal

red shift

any object moving in has stretched wavelength (redshift)

astronaut falling

sending signal every second, but that means the stretching of space time and the time between signals gets stretched so his signals are farther (red shift)

why does our astronaut look red

any light reflecting gets redshifted so he look redder and then signals go into blackhole and we can’t see

when are blackholes dangerous

if something gets too close, objects far away have no effect for instance if sun was replaced blackhole everything would remain same in orbit except dark and colder

wormhole

blackholes connect to universe that is parallel via a bridge called a wormhole (wormholes collapse as soon as formed)

birth of the solar system 4.6B years ago

1. collapse of interstellar gas (solar nebula)

2. cloud flattened

3. young sun shines and disk has planets forming due to random collision

how did collisions dominate early solar system

1. clump of interstellar gas collapse

2. formed protoplanetary disk (planets form from disk)

3. center collaspes for sun

4. 50-100m years

within the disk surrounding protosun

grains collide and clump into planetesimals

two categories of planets

1. small rocky planets (terrestrial)

mercury, venus, mars, earth

2. gas giants

jupiter saturn uranus and neptune

as the sun rotates axis how long it take to rotate once

27 days

what are terrestrial planets made of

rock and metal

weight terrestrial

heavy

size terrestrial

small

rings and moon teresstial

no rings and few moons if any

MERCURY

1. size, heat, composition

2. relative size

3. atmosphere

4. temperature

5. moons

1. small, hot, rocky

2. 1/3 of earth

3. no atmosphere so it is heavily cratered

4. 430 to -180

5. no moon

1. VENUS

   • size

   • brightness

   • moons

   • atmosphere

   • temperature

1. earths twin in size

2. brightest object sky

3. no moons

4. carbon dioxide so greenhouse effect

5. hot (480)

venus surface

The surface of Venus is completely
hidden beneath permanent cloud cover

habitable zone

earth in it meaning not too hot or cold so water liquid

asteroids composed of

carbon, iron, rock

what is asteroid belt

group
of rocks that appear to have
never joined to make a
planet

why is Jupiter fault asteroid belt

Jupiter’s
large gravity re-
directs many of
these Asteroids that come to earth

(few asteroids cross earth)

when small asteroid enter earth what happens

it burns
up as it encounters air friction at tremendous speeds

shooting star, what is it

rock that has entered the Earth’s
atmosphere. Air friction causes the rock to heat up so
much it begins to burn across the sky

define crater

Hole/impression in the ground
caused by an asteroid hitting Earth.

(largest in Mexico 65m years ago)

mercury and moon cratered

No atmosphere to
cause asteroids to
burn up – they
always reach the
surface

how long it take moon to rotate earth

29 days

(takes us 3 days tp travel moon)

moon’s surface is covered in

dust and
rocky debris from meteor impacts.
It has no water or atmosphere

moon reflects light

from the
sun onto the earth’s surface

how did we get our moon

According to one theory, 4.5 billion years ago a
Mars size asteroid or rock hit the Earth at such a
high speed that it tore a chunk of Earth away,
creating another large rock close to the Earth

Does the moon always appear the same? _______
2. What causes the moon to look differently night to
night? i.e.) Why does the moon go through phases?

Moon appears
different over the
course of one month
due to its orbit
around the Earth
We (from Earth)
only see certain
parts of the moon lit
up by the Sun at
different times

why do we have seasons

earths axis tilted.

Since the Earth is tilted, the Sun penetrates the
Earth differently in various parts

explain distribution of heat

1. When the Sun is high in the sky during the day, the number of
   daylight hours is greater and the amount of direct sunlight received is greater. This results in Summer.

2. When the Sun is low in the sky during the day, the number of daylight hours is less and the amount of direct sunlight received is less. This
   results in Winter.

   
   

why do we have seasons

earths axis is tilted and the sun penetrates the earth differently

MARS

1. size

2. color

3. temperature

4. atmosphere

5. gravity

6. moons

1. smaller than earth

2. rusty red soil

3. -10 to -120

4. mostly CO2

5. 1/3 of earth gravity

6. 2 moons (Phobos and deimos)

mars canyon

Valles Marineris size of the US

rovers

opportunity —- curiosity —— perseverance ——

why do we want to live on mars

• survive asteriods

• population

• tecnology

• run out resources on earth

characteristics of jovian gas planets

Enormous
• Made mostly of Hydrogen
and Helium
• Far from Sun
• Separated by large
distances
• Have ring systems
• Have many moons
Outer (Jovian) Gas Planets

JUPITER

1. size

2. moons

3. rings

4. gravity

5. red spot

1. largest

2. 95 moons

3. faint rings

4. 2.5 gravity

5. giant hurricane

name Jupiters greatest moons

io, europa, Ganymede, Callisto

SATURN

1. ring system

2. what are the rings

3. density

4. moons

1. extensive ring system

2. rings are orbiting rocks

3. less dense than water (float)

4. 274 moons

URANUS

1. angle

2. moons

3. rings

1. 98

2. 27

3. faint, narrow

NEPTUNE

1. size

2. rings

3. moons

1. smallest gas giant

2. faint

3. 13

how did the gas giants form

when sun formed it swept away lighter elements leaving the heavier ones close to it and then the solar lights lack of energy allowed them to condense into gas giants

what are the planetesimals that formed outer solar system

they are composed of hydrogen composed (some helium)

what causes different planets to form

temperature and density for instance hotter centre planets = rocky, farther out beyond frostline are cooler and gas

define planet

A “planet” is a celestial body that
1) is in orbit around the Sun,
2) has sufficient mass to have enough
gravity to pull itself into a round shape
3) has cleared the neighbourhood around its
orbit.

why Pluto not planet

crosses neptune

what is dwarf planer

A dwarf planet is
a) an object in orbit around the Sun
b) massive enough to have its own gravity pull
itself into a round (or nearly round) shape.
c) orbits in a zone that has other objects in it.

pluto moon

charon

what is an extrasolar planet or exoplanet

planet beyond our solar system orbiting a star other than our sun

method 1 depicting exoplanet: direct observation

image the planet similar to stars, however planets are so much smaller and observable in reflected light spectrum they are fainter and harder to see

method 2: transit method

the passage of the planet causes decrease of light intensity in front of star

method 3: doppler

in a stellar system, both planet and star revolve around a centre of mass and even if the planet is not visible the star can be observed to rotate the mass

radial velocity tec (doppler wobble)

granted star + planet orbit centre of mass, as the star moves towards the observer (blue shifted) and away is red shifted

newton gravity

if gravity causes apple to fall, what holds moon

why do astronauts float

they’re not fall enough tp escape earths gravity and experience weightlessness (falling around earth im orbit) js require speed

how many sattteltes orbit earth

how long iss take to orbit

2k

1.5 hours

what is a vomit comet

training how to continuously fall

(explain procedure)