Transcript Lecture 4

The Formed Solar System
•
Now we will begin our investigation of the
Solar System as it is now. After we finish this,
we will discuss the binding forces for the
Solar System.
The Scientific Method
• What is the scientific method?
– Simply stated, it is the method by which science seeks truths.
It is not the point of the method to uphold the truth, but
attempt to disprove a hypothesis or theory.
• How does the scientific method work?
1. Identify a problem and pose a hypothesis.
2. Make observations and produce data concerning the problem
and hypothesis.
3. Test the hypothesis with the data generated with the goal or
refuting the hypothesis.
4. Continue this process forever. If the hypothesis cannot be
proven wrong, it can become a theory.
The Scientific Method
• What methods are used to support the scientific
method?
– The Empirical method: To document what is observed,
carefully, with great detail and as little if no interpretation as
possible.
– The Experimental method: To perform experiments where one
or more variable is changed in an attempt to produce and
reproduce data.
• Reproducing data is totally critical.
QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture.
The closest star to our star
• Proxima, found
within the Alpha
Centauri star system
is the closest.
• This system is 4.3
light years away.
Our Solar System is Differentiated
•
The solar system is divided into two major
regions.
1. The Inner Solar System - Composed of the
Sun, Mercury, Venus, Earth, Mars, and the
Asteroid Belt.
2. The Outer Solar System - The Jovian or Gas
Giant planets (Jupiter, Saturn, Uranus, and
Neptune) with the Kuiper Belt and its objects.
Our Solar System is Differentiated
QuickTime™ and a
decompressor
are needed to see this picture.
Definitions: Planets
•
•
First, what is a planet?
The classical definition: Any large (larger
than an asteroid) spherical, natural object
that directly orbits a star and does not
generate heat by nuclear fusion.
A minor planet is a body such as an asteroid.
•
–
However, what is the new definition?
Definitions: Planets
•
What is the ‘new’ definition of a planet?
According to IAU:
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 neighborhood around its orbit.
Definitions: Planets
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 neighborhood around its orbit,
and (d) is not a satellite.
Definitions: Planets
3. All other objects except satellites, orbiting
the Sun shall be referred to collectively as
“Small Solar System Bodies”.
QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture.
QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture.
QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture.
QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture.
QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture.
QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture.
QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture.
The Inner Solar System: Some Facts.
• Planets within the inner solar system are
rocky planets. They are essentially
spherical rocks that orbit a star.
• This means that the inner solar system
was warmer than the outer solar system
during the formation of the planets.
The Inner Solar System: Some Facts.
• Mercury
– Orbital axis = 0.38 AU
– Orbital speed = 47.9 km/s
– Axial tilt = 0.0o
QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture.
– # of Satellites = 0
The Inner Solar System: Some Facts.
• Venus
– Orbital axis = 0.72 AU
– Orbital speed = 35.0 km/s
– Axial Tilt = 177.4o (2.6o)
and is retrograde.
QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture.
– # of Satellites = 0
The Inner Solar System: Some Facts.
• Earth
QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture.
– Orbital axis = 1 AU
– Orbital speed = 29.79 km/s
– Axial Tilt = 23.45o
– # of Satellites = Moon
QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture.
– Key point: Earth is alive!
Plate tectonic and life!
The Inner Solar System: Some Facts.
• Mars
– Orbital axis = 1.52 AU
– Orbital speed = 24.1 km/s
– Axial Tilt = 23.98o
QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture.
– # of Satellites = 2
The Inner Solar System: Some Facts.
– Phobos
QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture.
QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture.
– Demos
The Inner Solar System: Snow Line.
• What was the Snow Line?
– The place within our solar system where
abundance ices and gases could condense
because the ambient temperature was cold
enough.
• Where was the last place the Snow Line
existed?
– Approximately just past the Asteroid Belt.
The Inner Solar System: Snow Line.
• What occurred beyond the snow line?
– The formation of the outer solar system and the Gas
Giant or Jovian Planets.
– Again, past the Snow Line temperatures were cold
enough for significant condensation of ices and
gases.
– These planets are mostly composed of gases, H2 and
He, etc.
The Inner Solar System: Snow Line.
• The Snow Line is an
extremely important
concept.
The Outer Solar System: Some Facts.
• Jupiter
– Orbital Axis = 5.20 AU
– Orbital Speed = 13.1 km/s
– Axial Tilt = 3.08o
– # of Satellites = 61
QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture.
QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture.
The Outer Solar System: Some Facts.
• Jupiter
– Best known of the
satellites are the Galilean
Moons, of which four
exist.
– Io
– Europa
– Ganymede
– Callisto
QuickTi me™ and a TIFF (U ncompressed) decompressor are needed to see this picture.
The Outer Solar System: Some Facts.
Io
Ganymede
QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture.
QuickTi me™ and a TIFF (U ncompressed) decompressor are needed to see this picture.
Callisto
Quic kT i me™ and a T IFF (Unc ompres s ed) dec ompres s or are needed t o s ee thi s pi c ture.
Europa
QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture.
The Outer Solar System: Some Facts.
• Saturn
– Orbital Axis = 9.54 AU
– Orbital Speed = 9.65 km/s
– Axial Tilt = 26.73o
– # of Satellites = 30+
QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture.
The Outer Solar System: Some Facts.
The Outer Solar System: Some Facts.
• Uranus
– Orbital Axis = 19.19 AU
– Orbital Speed = 6.80 km/s
– Axial Tilt = 97.92o
– # of Satellites = 21+
QuickTime™ and a TIF F (Uncompressed) decompressor are needed to see this picture.
QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture.
The Outer Solar System: Some Facts.
• Neptune
– Orbital Axis = 30.07 AU
– Orbital Speed = 5.43 km/s
– Axial Tilt = 29.6o
– # of Satellites = 8+
QuickTime™ and a TI FF (Uncompressed) decompressor are needed to see this pict ure.
QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture.
The Outer Solar System: Some Facts.
The Outer Solar System: Other Features.
QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture.
The Outer Solar System: The Kuiper Belt.
• Also known as Edgeworth-Kuiper belt, named
after Kenneth Essex Edgeworth (1880 - 1972)
and Gerard Peter Kuiper (1905-1973).
• An accumulation of small icy bodies that are in
orbit around our Sun outside the orbit of
Neptune.
• There could be ~ 200 million such objects.
• This area is the source of the short-period
comets.
The Outer Solar System: The Kuiper Belt.
• Pluto’s orbit is very
similar if not the same to
Kuiper Belt objects.
• It wasn’t until 1992 that
Kuiper Belt objects were
discovered. To date over
660 objects have been
discovered.
QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture.
The Outer Solar System: The Kuiper Belt.
• The Kuiper Belt may
extend out to
approximately 50 AU.
• In October 2002, Chad
Trujilo and Mike Brown
discovered Quaoar
(Tongva name). Largest
body in the solar system
discovered since Pluto in
1930.
The Outer Solar System: The Kuiper Belt.
The Outer Solar System: Poor Old Pluto
• Poor Old Pluto
– Orbital Axis = 39.48 AU
– Orbital Speed = 4.74 km/s
– Axial Tilt = 118o
– # of Satellites = 3+
QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture.
The Outer Solar System: Poor Old Pluto
• Is poor old Pluto a planet?
– Some argue that it is not. Let’s investigate.
• What drives this discussion?
– Science or something else?
The Outer Solar System: Poor Old Pluto
• What are planets composed of?
– Gases such as H2, He, and others.
– Rocks (two or more minerals combined
together).
– Ices including water, ammonia, methane,
carbon dioxide, etc.
The Outer Solar System: Poor Old Pluto
• So, is poor old Pluto a planet?
–
–
–
–
–
It orbits the Sun, but highly elliptical.
It is larger than an asteroid.
It does not generate heat by fusion.
It is likely composed of ices and rock.
It even has 3 satellite, Charon, Nix, and Hydra.
• Could it be the largest Kuiper Belt object?
– Some think so…
Poor Old Pluto
The Outer Solar System: The Oort Cloud
• Named for Jan Hendrik Oort (1900 1992).
• A cloud of icy bodies that lies ~ 50,000 AU
from the Sun.
• The source of long-period comets.
• It is essentially the outer most limit of the
Solar System where planetary materials
end.
The Outer Solar System: The Oort Cloud- Hyakutake
Extra - Solar Planets
• These are planets that orbit other stars in
other solar systems.
• Most of these objects are twice as large as
Jupiter and orbit less than 2 AU from
their star (stars).
• The oldest is ~ 13.2 billion years old.
• Most detected by indirect methods.
• Over 310 have been detected.
Extra - Solar Planets
QuickTime™ and a
decompressor
are needed to see this picture.
Extra - Solar Planets
• Astrometry: Astrometry consists of
precisely measuring a star's position in
the sky and observing the ways in which
that position changes over time.
– If the star has a planet, then the
gravitational influence of the planet will
cause the star itself to move in a tiny circular
or elliptical orbit about their common center
of mass.
Extra - Solar Planets
• Radial velocity or Doppler method: Variations
in the speed that a star moves towards or away
from Earth.
• Basically variations in the radial velocity of the
star with respect to Earth can be deduced from
the displacement in the parent star's spectral
lines due to the Doppler effect.
– This technique has been the most productive.
Extra - Solar Planets
• Transit method: If a planet crosses in front of
its parent star, then the observed brightness of
the star drops by a small amount.
– The amount by which the star dims depends on its
size and on the size of the planet.
• At least 6 other methods can be used to
discover these planets.