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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
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?
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.
b) All of the eight major planets orbit in the same direction as the Sun’s spin.
c) All of the eight major planets orbit on a plane perpendicular to the Sun’s axis.
d) Pluto and further objects orbit with very different tilts.
e) The Moon, Earth, Mars and Mercury are covered with craters. Venus and the gas giants are not.
f) The first four planets are small and rocky, while the next four are gas giants.
3) Go to the gravitation simulation at 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?
b) What else do you notice about solar system formation?
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?
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
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
planets habitable? Watch a Sudden Multiplication of Planets ScienceAtNASA
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 What does the universe look most like?
A) a road map
B) tree
C) spider’s web
D) a sponge
6) The universe is full of huge objects at huge distances. How do they compare? Watch Powers of Ten What astronomical sizes are mentioned?
7) Contest: Name an astronomical object that just fits in boxes with sides of 10P m.
Textbook Consolidation: Read pages 385 -391 and answer questions 2, 7, 8, 9