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Day 9) Cosmic Hierarchy 9.5, 9.6
Name __________________
1) How did the solar system form? The solar nebula theory says that the Sun and planets formed from a
swirling cloud of gas and dust that was pulled together by gravity.
a) As the cloud becomes smaller the material will orbit
A) faster
B) slower
C) in random directions
A) The movement of the particles is mostly random but there will be a net spin sin some direction. This
will become more evident as the mass pulls in, in the same way that a figure skater spins faster when the
arms are pulled in. Demonstrate this with the rotating platform.
b) Almost all of the material will get pulled into the center. However, some of the material will be able
to orbit in a disc around it. What conditions must be right for material to orbit?
They must be moving at the right speed, direction and radius as seen with My Solar System and the fabric.
The material in the disc will clump into a few orbiting objects. When the temperature at the centre gets high
enough, fusion starts and produces a strong solar wind which will blow away the gases and dust.
2) Do the following observations provide support for the solar nebula theory? Explain.
a) The mass of the Sun contains 99.8% of the mass of the solar system.
Yes. “Almost all of the material ...”
b) All of the eight major planets orbit in the same direction as the Sun’s spin.
Yes. All formed from same swirling nebula.
c) All of the eight major planets orbit on a plane perpendicular to the Sun’s axis.
Yes. “Some of the materials will be able to orbit in a disc”
d) Pluto and further objects orbit with very different tilts.
No. But these may have been captured later or bumped out of position.
e) The Moon, Earth, Mars and Mercury are covered with craters. Venus and the gas giants are not.
Yes. These planets show how the planets build up with collisions. The planets with large atmospheres
will cause the falling mass to burn up. Gas giants won’t form craters- they are too soft.
f) The first four planets are small and rocky, while the next four are gas giants.
Yes. The solar wind is much stronger near the Sun and blew away most of the gases of these planets.
3) Go to the gravitation simulation at http://www3.sympatico.ca/michael.enns/. At the far right choose
Random and then press Load Preset and then run. This provides a thousand random masses, with
random motion that obey the laws of physics for gravity and circular motion.
a) How well does it match the solar nebula theory? The masses clump through collisions until there are
just a few bodies, they all orbit in the same direction,
b) What else do you notice about solar system formation?
Most of the systems appear to be double-stars. It turns out that most systems are binary.
4) The Sun is just one star. If the solar nebula theory is correct, each other star should have planets.
a) Until 1992 there was no evidence for exoplanets. Why?
They were too hard to detect. Consider how dim our planets look compared to the Sun and then consider
how dim the stars look compared to the Sun.
b) By 2013, about a thousand exoplanets had been found, but over 95% of these planets are the size of
our gas giants or even bigger and they were very close to their star. Why? Watch Minute Physics
How to Find an Exoplanet https://www.youtube.com/watch?t=29&v=AnX7ExBjrHw
It is not because our solar system is unusual. Only the biggest planets in close orbit could make their star
wobble enough or dim enough when transitting to be seen. We are only seeing the easy to detect planets.
c) The Kepler space observatory was launched in 2009 to look for exoplanets. From 2013-16 it
discovered another thousand planets and half these were smaller than our gas giants. Are any of the
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planets habitable? Watch a Sudden Multiplication of Planets ScienceAtNASA
https://www.youtube.com/watch?v=B4hHt3bxaGQ
Kepler could find smaller planets that are not right next to the star, because it avoids the blurring from
the atmosphere. The video is news was from 2014. It is perhaps a cousin, not a twin of the Earth. More
news is coming in all the time and most stars are expected to have planetary systems.
5) Just as dust and gas collapses to form solar systems, larger bodies of material collapse to form larger
structures. Galaxies, like our Milky Way contain millions to hundreds of billions of stars. Open
clusters contain hundreds or thousands of young stars. They are found in the disc of the Milky Way.
Globular clusters contain thousands or millions of old stars and are found in a sphere around the centre
of the Milky Way. Our galaxy and over 50 nearby galaxies are clumped in the Local Group of galaxies.
The local group forms part of the Local (formally Virgo) Supercluster. Superclusters group to form
the largest structures in the universe. Watch the simulation found here
http://cosmicweb.uchicago.edu/filaments.html. What does the universe look most like?
A) a road map
B) tree
C) spider’s web
D) a sponge
D) A road map and a spider’s web are only 2-D. A tree has a direction of branching- mostly away from
downward. The structure looks random, with holes – most like a sponge.
6) The universe is full of huge objects at huge distances. How do they compare? Watch Powers of Ten
https://www.youtube.com/watch?v=0fKBhvDjuy0 What astronomical sizes are mentioned?
Note: The video and exercise below show what object fits inside a box of a given dimension. The power of
ten for the box needs to be bigger than the power of ten size of the object written in scientific notation. For
example, the Earth has a radius of 6.38 x 106 m and therefore a diameter of 1.276 x 107 m. The smallest box
that it will fit in has sides that are 108 m. The video shows the Earth fitting in a box at 7, but it really can’t.
The movie also shows; Moon’s orbit 9, Earth’s orbit 11, Uranus’s orbit 12, Pluto’s orbit 13, Constellations
15, light-year 16, Milky Way almost 21 but 22, Virgo Cluster 23?, Note, the underlined items are not
physical objects but orbits. Students need to find objects for all the sizes except 8 and 22.
7) Contest: Find an astronomical object that just fits in boxes with sides of 10P m.
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Have them first work with notes and textbook. Then allow access to internet.
 A Question of Scale http://www.wordwizz.com/pwrsof10.htm an applet that lets you zoom in and
out and includes lots of information at each scale.
 The Scale of the Universe http://htwins.net/scale/ This lets you slide in and out and quickly find the
answers to the scavenger hunt. You may need to stop the hunt if they find this!
 The Known Universe by AMNH. Good for satellite orbits and biggest distances.
https://www.youtube.com/watch?t=28&v=17jymDn0W6U
 Cosmic Voyage https://www.youtube.com/watch?t=40&v=bhofN1xX6u0
Possible Project: Make a Powers of Ten poster for the object that you are assigned using the given template.
Assign one object to each student. These can be posted for an impressive display.
Textbook Consolidation: Read pages 385 -391 and answer questions 2, 7, 8, 9
Power of Ten Assignments (31 objects, if more are needed add some more planets)
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International Space Station
4
Halley’s Comet core
5
neutron star
5
Cygnus X-1
6
Ceres
7
Pluto
7
Moon
8
Earth
8
White Dwarf
9
Jupiter
10 Sun
11 Sagittarius A*
11 Arcturus
12 Betelgeuse
12 asteroid belt
13 largest star
14 Kuiper belt
15 Sting ray nebula
16 Oort Cloud
16 thickness of Milky Way disk
17 Crab nebula
18 Orion nebula
19 Globular cluster
20 Black hole jets
21 Magellanic clouds
21 bulge of Milky Way
22 Milky Way
21 Andromeda
23 Local group
25 Local Super Cluster
26 Visible Universe
The box below represents 10 m by 10m. The object below is
_________________________. It is shown at the same scale.
Some interesting facts: