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.

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

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”.

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 = 0.0 o –# of Satellites = 0

The Inner Solar System: Some Facts. Venus –Orbital axis = 0.72 AU –Orbital speed = 35.0 km/s –Axial Tilt = o (2.6 o ) and is retrograde. –# of Satellites = 0

The Inner Solar System: Some Facts. Earth –Orbital axis = 1 AU –Orbital speed = km/s –Axial Tilt = o –# of Satellites = Moon –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 = o –# of Satellites = 2

The Inner Solar System: Some Facts. –Phobos –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, H 2 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 = 3.08 o –# of Satellites = 61

The Outer Solar System: Some Facts. Jupiter –Best known of the satellites are the Galilean Moons, of which four exist. –Io –Europa –Ganymede –Callisto

The Outer Solar System: Some Facts. Io Europa Ganymede Callisto

The Outer Solar System: Some Facts. Saturn –Orbital Axis = 9.54 AU –Orbital Speed = 9.65 km/s –Axial Tilt = o –# of Satellites = 30 +

The Outer Solar System: Some Facts.

Uranus –Orbital Axis = AU –Orbital Speed = 6.80 km/s –Axial Tilt = o –# of Satellites = 21 +

The Outer Solar System: Some Facts. Neptune –Orbital Axis = AU –Orbital Speed = 5.43 km/s –Axial Tilt = 29.6 o –# of Satellites = 8 +

The Outer Solar System: Some Facts.

The Outer Solar System: Other Features.

The Outer Solar System: The Kuiper Belt. Also known as Edgeworth-Kuiper belt, named after Kenneth Essex Edgeworth ( ) and Gerard Peter Kuiper ( ). 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.

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 = AU –Orbital Speed = 4.74 km/s –Axial Tilt = 118 o –# of Satellites = 3 +

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 H 2, 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 ( ). 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

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.