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Lecture

AST101H1 Lecture Notes - Kuiper Belt, Oort Cloud, Solar Wind


Department
Astronomy & Astrophysics
Course Code
AST101H1
Professor
Michael Reid

Page:
of 2
AST101
ASTEROIDS, COMETS, MOONS
Asteroids
Rocky and metal some have icy mantle (eg ceres)
Circular orbit
Some have carbonaceous (carbon molecules) chondrite (primitive
asteroids) from differentiation and melting of planetesimals in beginning
of solar system
Total mass is about 4% of our moon (very tiny and insignificant)
Can find them in asteroid belt (between mars and jupiter)
But can also find them in other parts of solar system (Orbiting Jupiter called
Trojan) special because they will never collide with jupiter because the
orbital period of jupiter is same of trojan asteroids) gravitational attraction
is completely balanced and they’ll never collide with each other
Important because they can hit up
o Eg. YU55 (happened nov 8 of this year) and if it hit us it would cause
gigantic impact was 400m in diameter
o If an asteroid is bout 100 m or bigger, we should be concerned about
it 400m is HUGE
o Just a 100m one destroyed a whole forest even though never hit earth
Comets
Icy and have tails
In Kuiper belt and oort cloud
Elliptical orbit
As it gets close to sun, suns radiation spews out the vapor (tail); solar wind
hits on the coma and it squeezes out the vaporized material and forms the
tail
o Through solar radiation and solar wind
Has 2 tails- dust tail and plasma tail
o Different materials have different velocities the velocity is what
determines degree of deflection, why you can see two distinct tails
o Why are tails directed away from sun? Because of relative velocity
A typical shooting star (fallen asteroid) has a size closest to what? A pebble
Meteor showers
Strings of shooting stars
Leftover debris from comets occurrence of them is periodic
Moons of Jupiter
Active because of tidal heating and resonance
Gravitational pull that causes a bulge which stretches the moon (friction)
which causes heat and that’s called tidal heating and why moons are active
Accretion of rings around jovian planets: because of gravity (in beginning of
solar system) jovian planets are massive enough to have its own disk
o Roche lobe: the radius at which if asteroid or object goes inside the
roche lobe, it will break up
o Self gravity vs. tide (competition between the two)
o One theory for rings around jovian planets
The sun
The core: power source of the sun (nuclear fusion)
Radiation zone on top of that emits energy by photons (light)
On top of that is convection zone another heat transport mechanism-
circles where hotter material rises and then cools and then falls back down
Then there’s photosphere (surface of sun- what we see)
Then there’s chromosphere cool layer of atmosphere (on top of hot stuff
which is absorption lines on spectra)
Outer layer is corona hot layer of atmosphere (why it stays hot is through
magnetic activity- magnetic reconnection)
o Extremely low density if you put your hand in corona it will freeze
Proton-proton chain
4 protons that collide (through nuclear reaction) to form 1 helium
in this process u have neutrino coming out and positron and gamma ray
(energy)
E= mc^2 (energy, mass, speed of light)
Energy of 4 protons = 1 helium = E (E 4 p > E hE)
How do we know whats going on in the interior of the sun?
By studying vibrations on the surface of the sun
By building computer models that use the laws of physics to make
predictions
By observing neutrinos generated in the suns core