Download Astronomy Solar System 1

Astronomy
The study of the universe beyond the
Earth’s atmosphere
What is Astronomy
Astronomy is the study of the
Universe, the stars, planets
and all other objects in
space.
How are Distances
Measured in Space?
• Astronomical Unit (AU) is the
distance from the Earth to the
Sun.
1 AU = ~86,000,000 miles
• Light Year (LY) is the distance
that light travels in one year.
1 LY = ~6 trillion miles
What is a Galaxy?
• Galaxy = a large group of stars,
(billions), gas and dust held together
by gravity.
Three Types of Galaxies
Elliptical Galaxy
Spiral Galaxy
Irregular Galaxy
Elliptical Galaxies
• Elliptical galaxies = are groups of
stars that appear to be shaped like
an ellipse (football)
Irregular Galaxies
• Irregular galaxies = are groups of stars
that appear to be together but have no
regular shape.
• The Large and Small Megelanic Clouds are
examples of irregular galaxies.
Irregular Galaxy
Spiral Galaxies
• Spiral galaxies = are groups of stars that
appear to have a dense concentration of
stars in the center and arms that are
made of stars and dust.
• Ex: Milky Way and Andromeda Galaxies
Barred Spiral Galaxy
– A “Barred” Spiral galaxy looks similar to
a spiral galaxy with a “bar” of stars
through the center and the arms extend
outward from the ends of the “bar”.
Milky Way Galaxy
• Our Sun is just one of billions of
stars in the Milky Way Galaxy.
• The Milky Way Galaxy is thought
to be 100,000 LY in diameter
and 15,000 LY thick.
Clusters
• As stars are grouped into
galaxies, galaxies are grouped
into clusters.
• Our cluster is called the “Local
Group”
So Where in the Universe Are We?
• The astronomical address for
Earth would be:
– Earth is the 3rd planet in the solar
system of the star called the Sun,
which is in the Milky Way Galaxy,
of the Local Group of galaxies in
the Universe.
What is our Sun?
• Our Sun is an average star of
yellow-orange classification.
Layers of the Sun
• The sun is
composed of
several
layers.
–
–
–
–
–
–
Core
Radiative zone
Convective zone
Corona
Photosphere
Chromosphere
The Core
• The core of the Sun is the place
where fusion of atoms is taking
place.
– Fusion generates temperatures of
10,000,000 oC
– Our sun is fusing hydrogen atoms
into helium
The Corona
• Corona = the outer layer
of the sun. This is the
gradual boundary
between the sun and
space. This is what we
see during an eclipse.
The Photosphere
• Photosphere = the layer
of the sun that is
incredibly bright and the
source of much of the
light we see on earth.
The Chromosphere
• Chromosphere = is an
active layer of the sun
that is where the
magnificent displays of
prominence and flares
take place.
Prominence / Solar Flares
• Prominence / Flares are bright
spots on the sun formed as gas
particles shoot outward from
the sun.
– These affect the magnetic fields
on earth (radio, television,
communications).
– These also cause the Northern
Lights or “Aurora Borealis”.
Aurora Borealis – “Northern Lights”
Northern Lights
Sunspots
• Sunspot = a dark, cooler spot on
the surface of the sun.
• The sunspot cycle is a pattern
of high sunspot activity and
lower activity .
~11 year cycle for our Sun
• The dark central portion is
called the umbra 4,300 0K
What is the Solar System?
• The Solar
System is: the
Sun, the eight
planets and
their natural
satellites, the
asteroids, the
comets and the
meteoroids.
Formation of the
Solar System
• Our solar system formed about 4.5
- 5 billion years ago from a giant
cloud of gas and debris.
• Planets were formed by the
accumulation of material in the
solar nebula.
– The type of planet that forms depends
upon conditions existing at that
distance from the star; such as
temperature and material present.
What is a planet?
• Planet = a
massive
collection of
matter that
revolves around
a celestial body,
or star.
The Eight Planets
•
•
•
•
•
•
•
•
Mercury
Venus
Earth
Mars
Jupiter
Saturn
Uranus
Neptune
– Pluto has recently been classified as a
“dwarf planet”
Planets are divided into two categories
• Terrestrial Planets
are “land-based”
planets that are
solid, dense, “hot”
and have few
moons:
– Mercury
– Venus
– Earth
– Mars
• Dwarf Pluto
• Jovian or
Gaseous Giants
are “gaseous”
planets that are
big, low density,
“cold” and have
many moons:
– Jupiter
– Saturn
– Uranus
– Neptune
Mercury
•
•
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•
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57.9 million km from Sun
88 day period of revolution
59 day period of rotation
0.206 eccentricity of orbit
4,880km diameter
0.553 mass of Earth
Density of 5.4 g/cm3
No moons
Venus
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•
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108.2 million km from Sun
224.7 day period of revolution
243 day period of rotation
0.007 eccentricity of orbit
12,104 km diameter
0.815 mass of Earth
Density of 5.2 g/cm3
No moons
Earth
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•
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149.6 million km from Sun
365.26 day period of revolution
23hr 56min 4sec period of rotation
0.017 eccentricity of orbit
12,756 km diameter
1.00 mass of Earth
Density of 5.5 g/cm3
1 moon
Mars
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•
•
•
•
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227.9 million km from Sun
687 day period of revolution
24hr 37min 23sec period of rotation
0.093 eccentricity of orbit
6,787 km diameter
0.1074 mass of Earth
Density of 3.9 g/cm3
2 moons
Jupiter
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•
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•
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778.3 million km from Sun
11.86 year period of revolution
9hr 50min 30sec period of rotation
0.048 eccentricity of orbit
142,800 km diameter
317.896 mass of Earth
Density of 1.3 g/cm3
16 moons
Saturn
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1,427 million km from Sun
29.46 year period of revolution
10hr 14min period of rotation
0.056 eccentricity of orbit
120,000 km diameter
95.185 mass of Earth
Density of 0.7 g/cm3
18 moons
Uranus
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2,869 million km from Sun
84.0 year period of revolution
17hr 14min period of rotation
0.047 eccentricity of orbit
51,800 km diameter
14.537 mass of Earth
Density of 1.2 g/cm3
21 moons
Neptune
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4,496 million km from Sun
164.8 year period of revolution
16hr period of rotation
0.009 eccentricity of orbit
49,500 km diameter
17.151 mass of Earth
Density of 1.7 g/cm3
8 moons
Earth’s Moon
• 149.6 million km from Sun (0.386
from Earth)
• 27.3 day period of revolution
• 27 day 8hr period of rotation
• 0.055 eccentricity of orbit
• 3,476km diameter
• 0.0123 mass of Earth
• Density of 3.3 g/cm3
Dwarf Planet
• A dwarf planet is an object
within the Solar System that
meets four criteria:
– is in orbit around the Sun
– has sufficient mass to become
spherical (hydrostatic
equilibrium)
– has not cleared it’s orbital
neighborhood
– is not a satellite
Pluto
• Examples of dwarf planets
are Ceres which is the
largest asteroid in the
Asteroid Belt, Pluto which is
in the Kuiper Belt, and Eris
which is beyond the Kuiper
Belt.
The Kuiper Belt
• The Kuiper Belt is a region of
the solar system which begins
beyond the orbit of Neptune and
is 3 – 5 trillion miles wide.
• The Kuiper Belt consists of
small objects composed largely
of ices, such as methane,
ammonia and water.
• The Kuiper Belt is consisdered
the source of many comets.
Other Objects in the Solar System
• Other objects in the solar
system include:
– Comets
– Asteroids
– Meteoroids
Asteroids
• Asteroid = a large chunk of rock
traveling through space.
– Most, not all, are found in the Asteroid
Belt located between Mars and Jupiter.
What is a Comet?
• A Comet is a
large chunk of
ice, dust,
frozen gas and
rock fragments
that moves
through space.
Comets form in an icy cloud, called the Oort Cloud, as the
gravity of a passing star pulls material out of the cloud.
Most comets have very elongated
orbits around the Sun
Comets Have Two Tails
The Ion Tail
always
points away
from the sun
The Dust
Tail is left
behind in
the comets
path
Halley’s Comet
Comet - Liner
Meteoroid, Meteor, Meteorite
• Meteoroid = a small pieces of rock
moving through space.
• Meteor = a small pieces of rock
moving through space (a meteoroid)
that enters Earth’s atmosphere.
• Meteorite = a small pieces of rock
moving through space that hits the
Earth.
Perseid Meteor Shower
Meteor Showers
• Meteor showers are very
likely from the debris left
behind by a comet that
passed at an earlier time.
• Perseids – August 10-14
• Orionids – October 18-23
• Taurids – November 1-15
• Geminids – December 10-16
Impact Events
• Most material reaching the Earth’s
surface is very small, however there is
evidence of comets hitting Earth in
the past.
• If large meteoroid fragments collide
with the surface then the result is an
impact crater.
• Example is Barringer Crater in
Arizona which is 1.2km across and
200m deep.
– Est. object size = 50m at 25,000 mph
Asteroid approaching Earth
Asteroid Impact