Download The Solar System

The Solar System
The Solar System
The Sun and all of the objects that travel around it
•the Sun is a star
•planets
•natural satellites of the planets; rings
•the asteroid belt (rocks between Mars and Jupiter: meteoroids)
•comets (frozen masses of gas and dust)
Solar System
Terrestrial Planets: Mercury
Venus
Earth
Mars
Solid rocky surfaces
Gas Giants: Jupiter
Saturn
Uranus
Neptune
Pluto
solid, very icy surface
What is Pluto?
• Pluto, 1930
• Charon,1978.
• Eclipses allowed
measurements of diameters,
separation, masses.
• Pluto 2300 km across,
Charon 1200 km, separation
20,000 km.
• Combined mass only 1/6 of
Earth's Moon.
• Density ~ 2g / cm3, implies
rock/ice composition
•Dwarf planet
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Planetary Orbits
Center of Mass
http://pluto.jhuapl.edu/science/everything_pluto/10_binary_planet.html
Asteroid belt
http://www.mistupid.com/astronomy/orbits.htm
The AU and
the size of
Solar System
• Defined as the average distance between the
Earth and the Sun
• It is approximately 150 million km (93
million miles) (how many meters?)
• Mercury - 1/3 of an AU from the Sun
Ceres
1000 km across
• Pluto - about 40 AU from the Sun – the
size of the Solar system
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Measuring distances
• Measuring distances on Earth
Measuring distances in
Astronomy
• Light Year
– Inch, foot, yard, mile
– Centimeter, meter, kilometer
• Measuring distances within the Solar System
– Astronomical unit (AU)= 150, 000, 000 km
• Measuring distances outside the Solar System
– Light Year (LY) = 9,500,000,000,000 km
– Parsec (pc) = 3.262 LY
– Kpc = 1000 pc, Mpc = 1,000,000 pc
–
–
–
–
a unit of distance
the distance that light can travel in one year
speed of light ~ 300,000 kkm/second
So in one year, it can travel 9,500,000,000,000
kilometers (10 trillion km)
The nearest star to the Sun is Proxima Centauri
40 000 000 000 000 km
The Kuiper
Belt
Trans-Neptunian Objects (TNO)
Any object in the solar system that orbits the Sun at a greater
distance on average than Neptune
The Kuiper belt,
Scattered disk, and
Oort cloud are
names for three
divisions of this
volume of space.
Courtesy of Windows to the
Universe,
http://www.windows.ucar.edu
Courtesy of
Windows to the
Universe,
http://www.windo
ws.ucar.edu
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Kuiper belt objects: Planet
candidates in the Solar System
The
scattered
disk objects
and the
Oort Cloud
50,000 to 100,000 AU from the Sun
The largest: Pluto, Charon, 2003 UB313
Courtesy of Windows
to the Universe,
http://www.windows.uc
ar.edu
The new Solar System?
12 planets? How to define the lower end of the planet scale?
http://www.iau2006.org/mirror/www.iau.org/iau0601/iau0601a.html
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How should the word “planet” be defined?
Three new planets?
26th GENERAL ASSEMBLY of
the International Astronomical
Union
14-25 August 2006
IAU Resolution (August 24, 2006)
Definition of a “Planet” in the Solar System
• (1) A “planet” is a celestial body that (a) is in orbit around the Sun, (b) has
sufficient mass for its self-gravity to overcome rigid body forces so that it
assumes a hydrostatic equilibrium (nearly round) shape, and (c) has cleared
the neighbourhood around its orbit.
• Mass larger than 5x1020 kg
• Diameter larger than 800 km
The eight planets are: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and
Neptune.
• Pluto (Kuiper belt), 2003 UB313 (Kuiper belt), Ceres (Asteroid belt) are not
planets
http://www.iau2006.org/mirror/www.iau.org/iau0601/iau0601_release.html
IAU Resolution (August 24, 2006)
Definition of a “Planet” in the Solar System
• (2) A “dwarf planet” is a celestial body that (a) is in orbit
around the Sun, (b) has sufficient mass for its self-gravity to
overcome rigid body forces so that it assumes a hydrostatic
equilibrium (nearly round) shape, (c) has not cleared the
neighbourhood around its orbit, and (d) is not a satellite.
• A process will be established to assign borderline objects into either “dwarf
planet” and other categories.
Pluto is a “dwarf planet” by the above definition and is recognized as the
prototype of a new category of Trans-Neptunian objects.1This category is
to be called “plutonian objects”.
http://www.iau2006.org/mirror/www.iau.org/iau0601/iau0601_release.html
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List of dwarf planets
• The IAU has officially identified three celestial bodies that have
immediately received "dwarf planet" classification:
• Dwarf planets Name
Ceres
Pluto
2003 UB313 ("Xena")
• Region of Solar system Asteroid belt
Kuiper belt Scattered disc
• Category
Asteroid
Plutino
• Diameter
975×909 km
2306±20 km 2400±100 km
IAU Resolution (August 24, 2006)
Definition of a “Planet” in the Solar System
• (3) All other objects , except satellites, orbiting the Sun shall
be referred to collectively as “Small Solar System Bodies”.
These currently include most of the Solar System asteroids, most TransNeptunian Objects (TNOs), comets, and other small bodies
Scattered disc object
http://www.iau2006.org/mirror/www.iau.org/iau0601/iau0601_release.html
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