MR. SYMEONIDES’ EARTH SCIENCE
Chapters 26 and 27 notes, Studying Space and The Planets of the Solar System
Standards Covered:
1 a-d, f Covering the formation of the solar system, the differences and similarities of its
planets, the changes to the Earth as it cooled and changed, the solar system’s place in the
universe.
2b, d Most of the Universe we can see is made of billions of galaxies and the billions of
stars and planets they contain, and galaxies are made of stars of many different types that
live very different lives.
8 b,c and 4d On the evolution of our atmosphere and how it is different from that of the
other planets.
Take Notes
So, how do we know what we think we know about how the Earth formed?
Mostly we learned what we know from two sources, studying the Earth and the other
planets of our Solar system, and using different kinds of telescopes to study stars, nebulas,
galaxies and planets and looking to see how they are formed and behave.
Chapter 26, page 659- STUDYING SPACE
The Universe.
For our purposes, everything that exists is the Universe. Most astrophysicists
(who are WAY smarter than me) say that the universe we live in started with The Big Bang
about 14 billion years ago. No one knows for sure what came before that though there are
a lot of hypotheses.
Since the Big Bang the universe has been growing and expanding, with galaxies
moving away from each other and spreading out. Some parts of the universe are mostly
empty, others, like the region in Figure 2 on page 660 are packed with galaxies.
Some typical galaxy shapes.
There are many others
This is a drawing of OUR galaxy, the Milky Way.
As you can see, it is a Spiral Arm
Galaxy. Our sun is in-between the
arms where the stars are packed
close together and so we don’t have
a lot of bright stars in the sky.
When you see the stripe of the Milky
Way galaxy in the night sky, you are
looking towards the center of the
galaxy and seeing that our galaxy is
pretty flat.
We don’t know how many stars are
in the Milky way but about 200
billion is the guess I see most often
How Do We Study Space?
Light and the electromagnetic spectrum.
THE SPEED OF LIGHT. Light travels at a speed of 186,000 miles per SECOND.
Multiply that by 360 and you see that light can travel
670 million miles per hour
Or 1 light year = 6 Trillion miles
The closest star to Earth is Sol, our sun is 8 light minutes away
The next closest star to us is Proxima Centauri and is 4.4 light years away
Review of the electromagnetic spectrum
This shows all of the
different kinds of
electromagnetic energy that
travels through space.
As you can see, light that is
visible to our eyes is right in
the middle. Very high
energy radiation like X rays
and Ultraviolet rays are at
the left, with very short
wavelengths. Low energy
long wavelength radiation is to the right and includes the radio waves that are captured by
telescopes to study objects too far away to see with regular telescopes.
But the visible part of the spectrum can be the most useful in the study of stars and
planets.
These are absorption spectra for stars of different types and different temperatures.
By looking at the dark lines in these absorption spectra, one can tell what stars are made
of, because the patterns of lines show what the star is made of or what materials the light
is passing through.
Notice that the cooler stars have more different elements in them. This is because as the
stars run out of the lighter fuels, they cool down. Gravity pulls the star into a tighter,
denser space, and heavier elements begin to combine. If the star was big enough this will
eventually cause the star to explode as a Nova or Supernova.
We will leave the rest of the chapter for later.
We will start on chapter 27, page 684
Take out 2 pieces of paper and put your name and period number on each.
Title the first paper “ Chapter 27 Vocabulary and Notes”
Title the second paper “Chapter 27 Questions”
I’ll give you an A-F grade on the Vocabulary and Notes,
and a points grade for the Questions.
Chapter 27.1 The Formation of the Solar System
Section 1 The Nebular Hypothesis
This is a nebula. Most of outer space is
empty with nearly no matter in it. If you
were to take a tube a foot across that went
from here to the Sun, there would be less
than a teaspoon of atoms in it.
Nebula are regions of space where a dying
star has blown off its outer layers, with only
a small hot white dwarf star left near the
middle. The space around the dwarf star
has a lot of dust and gas molecules in it,
these were the material in the outer layers
of the star. Though there billions of nebula
in space, the one that our Solar System
formed from is called the solar nebula, after
the name of our sun – Sol.
You have 10 minutes to do the following
Read pages 685-687
On your Definitions and notes page, define the following:
Nebula, Solar Nebula, Nuclear Fusion, Planetessimals and
Protoplanets, Gas Giants
About 5 billion years ago, a star exploded near where our solar system is now. It left behind all of
the chemical elements that the star had been made of, the
gasses, the dust and the atoms of metals. This material
was the solar nebula, the nebula that our solar system
formed from. Most of the matter in this nebula was near
its center and the center started pulling other material
towards it, through magnetic attractions and by gravity.
This caused the whole nebula to start spinning and to
flatten into a disk as shown in figure (a)
Eventually the center of the nebula became dense
enough and hot enough for the sun to begin burning,
through the fusion of Hydrogen into Helium. It pulled all of
the matter near it into the sun so that today 99% of all the
material in the solar system is in Sol, our star. (b and c)
As the solar nebula continued to spin, the matter
left over started to pull together through gravity to form
chunks of rock, metal and gasses. The bigger these chunks
got, the stronger their gravity. They started to attract each
other, adding their material together. We call the biggest
chunks planetessimals – tiny planets. As the
planetessimals continued orbiting the sun, they added
together through collisions, cleaning up their orbits and
getting larger. (b and c)
The largest of these objects are called protoplanets (proto
meaning early or before). The protoplanets were the
beginnings of the planets we have now. (d) They were
finished after their gravity pulled all of the material in their
orbits to them (e).
Terrestrial vs. Gas Giant Planets
The terrestrial planets are the 4 closest to the sun - Mercury, Venus, Earth and Mars. They formed
in the part of the solar nebula that had more heavy elements (for metals and the minerals in rocks). Also
they formed in the hotter part of the solar nebula, nearer the sun. Since molecules move faster when they
are hot, the lighter gas molecules were moving fast enough to escape the gravity of the terrestrial planets.
This means that they have thinner atmospheres with very little hydrogen or helium.
The typical terrestrial planet has an iron and nickel core that
makes up at least a quarter of its diameter. This core can be solid, liquid
or both. Outside of the core is a thick layer of rock. This rock can be
either solid or soft, like silly putty. Which a planet will have depends on
both the size of the planet and where it is. Larger planets lose heat more
slowly and keep this soft layer of rock (the mantle) longer. The surface of
a terrestrial planet is solid. It may have many craters. The atmosphere of
a terrestrial planet is thin, only 10’s of miles thick at the most, and made
of the heavier gasses such as Nitrogen, Oxygen, Ozone, and Carbon
Dioxide.
The gas giants are the four outside of the asteroid belt- Jupiter, Saturn, Uranus and Neptune.
These planets formed in the cooler part of the solar nebula where there were fewer heavy elements and
much more of the lighter elements. Because these planets were also more massive, their stronger gravity
was able to keep more of their hydrogen, helium and other light gases. Some of the gas giants have many
satellites, or moons, orbiting them. Jupiter and Saturn have more than 60 each. All of the gas giants also
have rings of ice and dust orbiting them, but only those of Saturn are truly spectacular.
Gas giants have very small metal or rocky cores, since most of these materials stayed near the
center of the solar nebula as the solar system formed. Then there is a thick layer of liquid or frozen gasses.
This would be the planet’s surface. The atmosphere of gas giants is hundreds of miles thick and is over
90% hydrogen and helium. These planets are closer in composition to the sun than to the terrestrial
planets, but they are not big enough to start fusion explosions and light up like the sun.