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SPEED OF LIGHT
• 186,000 miles a second
• 300,000,000 meters per
second
• 700 million miles an hour.
• For scale, the distance from
the Earth to the Moon is
about 239,000 miles.
• The distance light can travel
in a year is called a "light
year." The light year is one of
the basic measures of
distance for astronomy.
• NOTHING TRAVELS FASTER THAN THE SPEED OF LIGHT.
Distance
Because space is so vast, astronomers
have a created different unit for
measuring the distances in space
known as an astronomical unit.
This is the distance from the Sun to
the Earth.
• Earth is 93million miles from Sun (150million
km)
– 1 AU (astronomical unit)
http://www.northern-stars.com/solar_system_distance_scal.htm
AU’s
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Mercury .38
Venus- .72
Earth- 1.0
Mars- 1.5
Jupiter- 5.2
Saturn- 9.5
Uranus- 19.2
Neptune- 30.0
Pluto- 39.4
• Scale solar system
• 1AU= 1m
(earth 1m away from sun)
General Characteristics of the Solar
System
Planetary orbits and rotation
• planet and satellite orbits are in a common plane
• nearly all planet and satellite orbital and rotation
motions are in the same direction
What is a planet?
• The definition of planet set in 2006 by the
International Astronomical Union (IAU) states
that in the Solar System a planet is a celestial
body that:
– is in orbit around the Sun,
– has sufficient mass to assume hydrostatic
equilibrium (a nearly round shape), and
– has "cleared the neighborhood" around its orbit.
Nearly all planet and satellite orbital and rotation motions are in the same direction
General Characteristics of the
Solar System
– Terrestrial planets- small, composed of
rock and metallic elements (metals)
– Jovian planetslarge,
composed of
gases and
frozen
compounds
4 Terrestrial Planets
The Inner Planets
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Mercury, Venus, Earth, Mars
Rocky and metallic
Small
No rings
Very few moons
MERCURY
• closest to our Sun
• small, rocky planet
- much like our
Moon
• It is covered with
craters and has
changed very little
from when it was
first formed
One side HOT: 800o F
Other side COLD: -275o C
Mercury Facts
•Average Distance From Sun
– Kilometers: 57,000,000
– Miles: 36,000,000
• Astronomical Units: 0.387
• Length of Day: 58 days 15
hours 30 minutes
• Length of Year: 87.97 days
– Average Orbital Speed
– Kilometers/Second: 47.89
– Miles/Second: 29.76
• Number of Known
Satellites: 0
VENUS
• Intense heat and
volcanic activity.
• Similar in structure and
size to Earth
• Venus' thick, toxic
atmosphere traps heat
in a runaway
"greenhouse effect."
VENUS
• Average Distance From Sun
Kilometers: 108,200,000
Miles: 67,000,000
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Astronomical Units: 0.723
Length of Year: 224.7 days
Length of Day: 243 days
Number of Known
Satellites: 0
EARTH
• Only planet
known to have
life
• Only planet not
named after a
Greek/Roman god
Earth
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Average Distance From Sun
Kilometers: 149,600,000
Miles: 93,000,000
Astronomical Units: 1.000
Length of Year: 365.26 days
Length of Day: 23 hours 56
minutes 4 seconds
Volume (Earth=1): 1.000
Number of Known Satellites: 1
The Asteroid Belt
• Separates Inner and Outer planets
• Asteroids left-overs from the formation of the Solar
System. While some have suggested that they are the
remains of a proto-planet that was destroyed in a
massive collision long ago, the prevailing view is that
asteroids are leftover rocky matter that never
successfully coalesced into a planet.
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4 Jovian Planets
The Outer Planets
Jupiter, Saturn, Uranus, Neptune
Gases & frozen gases
Very large
All have rings
Many moons
JUPITER
Jupiter
• 5th planet (1st outer planet)
• 9.84 hours to rotate
• 4,333 days to revolve
– (12 earth years)
• 66 moons
• 4 Rings
• Largest Planet
Atmosphere - Hydrogen, Helium, Oxygen,
Nitrogen and Methane
Saturn
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6th planet
10.2 hours to rotate
10, 759 days to revolve (29 earth years)
62 moons
23 Rings
Atmosphere Hydrogen and Helium
Uranus
• 7th planet
• 17.9 hours to rotate
• 30,688 days to revolve
– (84 earth years)
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27 moons
13 Rings
Atmosphere: Methane, Hydrogen and Helium
Tilted on its side
Neptune
• 8th planet
• 19 hours to rotate
• 60,181 days to revolve
(164.8 earth years)
• 13 moons
• 9 Rings
• Methane atmosphere
gives it bluish color
• Dwarf planet
Is Pluto a Planet?
• From its time of discovery in 1930 to 2006 it was considered to be the ninth
planet in the solar system, but because additional objects have been
discovered including Eris which is 27% more massive, the IAU reclassified
Pluto and the other objects as dwarf planets. The New Horizons spacecraft
was launched on January 16, 2006 and will make its closest approach to Pluto
on July 14, 2015. This mission will provide an increased amount of information
about this peculiar dwarf planet.
• Unlike planets, dwarf planets lack the gravitational muscle to sweep up or
scatter objects near their orbits. They end up orbiting the sun in zones of
similar objects such as the asteroid and Kuiper belts.
How far is the Moon from Earth?
The moon is 30 Earth’s away
COMETS
A comet is an icy ball that
releases gas or dust. They are
often compared to dirty
snowballs.
COMETS
• Halley's Comet
ASTEROIDS
• Asteroids are rocky, airless worlds that orbit
our sun
• too small to be called planets
• Tens of thousands of these "minor planets"
are gathered in the main asteroid belt, a vast
doughnut-shaped ring between the orbits of
Mars and Jupiter.
• Asteroids that pass close to Earth are called
Near-Earth Objects (NEOs).
METEORIODS
• Little chunks of rock and debris in space are
called meteoroids.
• They become meteors -- or shooting stars -when they fall through a planet's atmosphere
• Pieces that survive the journey and hit the
ground are called meteorites.
KUIPIER BELT and OORT CLOUD
• The Kuiper Belt is a discshaped region of icy objects
beyond the orbit of
Neptune -- billions of
kilometers from our sun.
• Oort cloud is a sphere
of ice dwarfs and ice
particles that surround
our solar system.
Pluto and Eris are the best known of these icy worlds. There may be hundreds
more of these ice dwarfs out there. The Kuiper Belt and even more distant
Oort Cloud are believed to be the home of comets that orbit our sun.
General Characteristics of the Solar
System
Planetary orbits and rotation
• planet and satellite orbits are in a common plane
• nearly all planet and satellite orbital and rotation
motions are in the same direction
How do we classify stars?
A.Size
B.Temperature
and Color
C.Brightness
Temperature and color
• The color of the star is dependent on the
temp of the star.
• Red – coolest stars
• Blue – hottest stars
Stars have Different colors
which indicate different temperatures
• Order from coolest to hottest
• Red, red-orange, yellow, white, blue
3000K
6000K
30,000K
Temperature and Color
Size
Giants/supergiants- large and very large stars.
Many of these are very far away
White dwarfsvery small stars –
about the size of
the Earth
Neutron starseven smaller stars
– only 20 km in
diameter.
Medium sized
stars- many stars
this size. The size
of our Sun.
Binary star systems contain two stars
that orbit around their common center
of mass. Many of the stars in our
galaxy are part of a binary system.
Binary Stars are
used to
determine the
mass of the star.
How do we measure stars?
Parallax- the apparent change in position of
an object when you look at it from different
places.
Parallax
The closer the star is to Earth, the larger the shift will be
Parallax
Only good for measuring stars
close to us. Not farther than
1000 light years away. Why?
The movement would be
too small to measure
accurately.