915
Lectures Watched
Since January 1, 2014
Hundreds of free, self-paced university courses available:
my recommendations here
Peruse my collection of 275
influential people of the past.
View My Class Notes via:
Receive My Class Notes via E-Mail:

VIEW ARCHIVE


Contact Me via E-Mail:
edward [at] tanguay.info
Notes on video lecture:
The Origin of Solar Systems
Choose from these words to fill the blanks below:
irregular, disc, capture, condrules, helium, Horsehead, collapse, Orion, dynamic, inclusions, Eagle, bubble, star, accretion, winds, cease, invisible, terrestrial, forming, CAI, scattered, rotate, enormous, runaway, sizes, tentacle, Moon, interstellar, plane, silicate, molecular, discs, simulations, light, ice, photoevaporation, hopeless, Mars
while solar systems are based on hydrogen and             , they also also likely to include all the elements of the period table
many generations of dying stars have injected freshly synthesized matter into                          space
how can this widely                    matter be used to form dense solar systems for planets
if the matter was evenly distributed throughout the universe, this would be a                  task
fortunately, due to the force of gravity, matter is concentrated in galaxies such as our own Milky Way galaxy
within the galaxies, most of the matter is concentrated in                    clouds
these are                  clouds, even when we observe them from as far away as the Earth
yet because they are also very faint, they also remain almost                    to the naked eye
the            constellation which lies close to the terrestrial equator
the three bright stars are known as Orion's belt
if we zoom in and increase the brightness, the underlying cloud becomes visible
                   Nebula
Orion Nebula
this is a star-               region
we cannot observe how our own solar system formed, but observing places like this, we can deduce how solar systems form in general
the size of molecular clouds can be measured in units of            years
molecular clouds look passive but they are highly               
stellar            push the gas around at speeds up to several hundred km/s
even at these speeds, it would take a millions years to traverse the width of these clouds
we use computer                        to fast-forward this process
can run the simulation for two million years
newborn stars light up within the cloud as the simulation runs
but we need to compress it by many orders of magnitude to form a solar system
sometimes gas gets compressed to a point that gravity is stronger than the gas pressure
the result is a                collapse resulting in star formation
a famous example of star formation is seen in the Hubble image of the            Nebula
intense stellar winds have created a              in the cloud
the stellar winds not only push the gas further and further away from the star through a process known as                                 
it also compresses the gas to point where a gravitational                  is triggered
this is exactly what we need to form a new         
once a dense core is formed, it's gravity field will start to grow as attracts more and more gas and thus further increases a gravity field, which is called                   
each of these                 -like structures contains a new star at the tip
eventually the gas will clear around the new star, accretion will           , and the star will begin its life as an independent object
as the gas collapses toward the growing star, it will              faster and faster, much like water running out of a bathtub
the accretion prevents all of the gas from accreting directly to the star
instead, a rotating disc of gas and dust is formed around the young star
it is from these            that planets are formed
this explains why all of the planets in our solar system orbit in the same            around the sun
early solar systems
matter from the cloud is falling in toward the         
most of the mass is drifting inwards toward the star
concentrated toward the mid-plane, we find solids of different           
near the start, milimeter-size particles known as       's condense out of the gas
Calcium/Aluminum-rich                     
calcium and aluminum condense at very high temperatures
meteorites have CAIs, e.g. white,                    inclusions in a rock
further away from the star we find                  spheres known as chondrules
the disc is composed of dust and gas
near the center there are no        crystals, further out there are ice crystals
as a result, outer planets grow faster and bigger
the gas in the disc was only present for a few million years
the outer planets beyond the frost line grew big enough to                gas from the disc while it was still there
became gas giants
inside the frost line, smaller rocky or                        planets formed, e.g. Mercury, Venus, Earth and Mars
accretion of the planets
a protoplanetary core
accretes dust,                    and CAIs
in the last stages of accretion there were only a few large planetary formations
one of the last of these later formations which accreted to the Earth was probably         -sized
resulted in a collision of cataclysmic proportions
the presence of our          was likely a consequence of this event

Vocabulary:

chondrule, n. From the Ancient Greek χόνδρος, or grain, chondrules are round grains found in chondrites, which themselves are stony, non-metallic meteorites that have not been modified due to melting or differentiation of the parent body. Chondrules form as molten or partially molten droplets in space before being accreted to their parent asteroids. Because chondrites represent one of the oldest solid materials within the Solar System and are believed to be the building blocks of the planetary system, it follows that an understanding of the formation of chondrules is important to understand the initial development of the planetary system.  "Further out in the disc which is moving in a swirling motion around the star, we find millimeter to submillimeter-size silicate spheres known as chondrules, which seem to chrystillize from freely mobile molten droplets."

Spelling Corrections:

tenticaltentacle
meteroritesmeteorites

Ideas and Concepts:

Star, solar system, and planet formation via this afternoon's Origins of the Universe course:

"A famous example of star formation is seen in the Hubble image of the Eagle Nebula. Stars begin in this way as very small, mere particles in vast clouds of dust and gas which remain cold and monotonous for millions of years.

Then everything get stirred up when something speeds through. This disturbance might be a streaking comet or the shockwave from a distant supernova. As the resulting force moves though the cloud, particles collide and begin to form clumps. Individually, a clump attains more mass and therefore a stronger gravitational pull, attracting even more particles from the surrounding cloud.

As more matter falls into the largest clump, its center grows denser and hotter. Over the course of a million years, the clump grows into a small, dense body called a protostar, and continues to draw in even more gas and grows even hotter.

When the protostar becomes hot enough, its hydrogen atoms begin to fuse, producing helium and an outflow of energy in the process, an atomic reaction called nuclear fusion. However, the outward push of its fusion energy is still weaker than the inward pull of gravity at this point in the star's life.

Material continues to flow into the protostar, providing increased mass and heat. Finally, after millions of years, some of these struggling stars reach the tipping point. If enough mass collapses into the protostar, a bipolar flow occurs. Two massive gas jets erupt from the protostar and blast the remaining gas and dust clear away from its fiery surface.

At this point, the young star stabilizes and reaches the point where its output exceeds its intake. The outward pressure from hydrogen fusion now counteracts gravity's inward pull. It is now a main sequence star begins its life as an independent object.

The remaining gas and dust around the new star begins again to be attracted by the star's more stabilized gravitational pull, this time the gas, dust and particles begin moving in toward the star in rotating fashion, faster and faster, the smaller particles merging with the larger particles through their gravitational pull, which begins the process of planet formation."
Examining the Agpalilik Meteorite
Nuclear Synthesis: The Origins of Elements in Our Solar System
The Origin of Solar Systems