Origin of the Solar System Worksheet

Astronomer: Astronomy 12 Origin of the Solar System TEST REVIEW

Learning Outcomes (Students will…):  explain the theories for the origin of the solar system  distinguish between questions that can be answered by science and those that cannot, and between problems that can be solved by technology and those that cannot with regards to extrasolar system formation.  describe and apply classification systems and nomenclature used in the sciences (i.e. classifying different objects in the solar system)

1. List the planets in order from nearest to farthest from the Sun.  Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune

2. Describe Bode’s Law.  A pattern of roughly determining the distances to each planet in the Solar System from the Sun (in AU)  Start with 0, 3, 6, 12, 24, 48, 96, 192, 384  Then add ‘4’…4, 7, 10, 16, 28, 52, 100, 196, 388  Divide by ‘10’…0.4, 0.7, 1.0, 1.6, 2.8, 5.2, 10.0, 19.6, 38.8 (note: 2.8 AU is the distance to the Asteroid Belt)

3. Construct a Venn Diagram in order to compare and contrast the properties of terrestrial and jovian planets. Properties to consider in your analysis: mass, density, chemical composition, moon and rings, distance from the Sun, outer (or surface) temperatures.

4. De Terrestrial Jovian fin e  Lower mass  Both planets in Solar  Higher mass  Higher density Systems  Lower density  Heavier  Travel around Sun in nearly  Lighter elements/compounds (i.e. circular orbits elements/compounds (i.e. iron, silicates)  Have cleared out debris in hydrogen, helium)  Few or no moons/no rings their orbital path over time  Numerous moons/rings  Closer to Sun  Have nearly a spheroidal  Farther from Sun  Higher surface/atmospheric shape due to gravity  Lower surface/atmospheric temperatures temperatures

planet. Why is Pluto not a planet?  A planet is any object that orbits a star, is rounded due to its own gravity and has cleared out debris in its orbit  Pluto is not a planet because it has not cleared out material in its orbit (i.e. is Charon its moon or part of a double-moon binary system? Is Pluto a Kuiper Belt object) and not sufficiently spherical

5. Where are asteroids mostly found in the Solar System?  Asteroid Belt

6. Contrast the Asteroid Belt and the Kuiper Belt, in terms of their location in the Solar System and the objects they contain.  The Asteroid Belt between Mars and Jupiter contains numerous small, rocky planetoids. The Kuiper belt, which extends from Neptune's orbit out to 50 AU, is thought to be the source of short-period comets, which are icy, “dirty snowballs” composed mostly of silicates and water.

7. Contrast the Kuiper Belt and the Oort Cloud, in terms of their distance from the Sun and the objects they contain.  The Kuiper belt, which extends from Neptune's orbit out to 50 AU, is thought to be the source of short-period (orbital period of less than 200 years) comets, which are icy, “dirty snowballs” composed mostly of silicates and water. The Oort cloud, is also a comet reservoir of long-period comets (orbital period greater than 200 years), and is perhaps as far as 50,000 AU from the Sun.

8. What is the relationship between the extent to which a planet or satellite (i.e. moon) is cratered and the amount of geologic activity on that planet or satellite?  Geologic activity on a planet or satellite will erase evidence of cratering.

9. Why do smaller planets retain less of their internal heat?  The smaller the planet or satellite, the greater its surface area relative to its volume, and it radiates energy more readily into space.

10.Why is a large planet more likely to have a magnetic field than a small planet?  A larger planet has more temperature and pressure in its core that causes material to become ionized (or lose electrons) and thus charged. Movement of this material as magma develops an electric current which produces a magnetic field.

11.How are magnetic fields in terrestrial planets produced? In Jovian planets?  In terrestrial planets, magnetic fields are produced by magma currents in liquid iron-nickel core; in jovian planets, magnetic fields are produced by liquid metallic hydrogen

12.What are 3 key properties of the Solar System that must be accounted for when developing any model of its formation?  Sizes and compositions of terrestrial vs. jovian planets  Directions and orientations of planetary orbits  Sizes of terrestrial planet orbits vs. jovian planet orbits

13.Describe the nebular theory of Solar System formation. Be sure to elaborate how  Terrestrial planets and asteroids were formed (i.e. planetesimal accretion).  Jovian planets and comets were formed (i.e. core accretion and disk instability models). Note: a diagram would assist any response to the question.

A. Solar Nebula Forms  A huge cloud of cold gas and dust.  Many times larger than our present solar system.  Probably spinning very slowly.

B. Formation of the Protosun  Under the influence of its own gravity, the solar nebula condensed into a dense central region (the protosun) and a diffuse outer region (the protoplanetary disk).  Began to spin faster, flattened out, and central region heated up.

C. Planetesimals  Instabilities in the rotating disk caused regions within it to condense into rings under the influence of gravity.  Gradually, planetesimals formed in these rings through accretion and collisions.

D. Terrestrial or Rocky Planets  The planetismals attracted each other by gravity (accretion) and collided to build planets.  Closest to the protosun, only rocky material and metals with higher condensation temperatures, and so the planets in this region are made mainly of these materials. Lighter elements, like hydrogen and helium, were driven out towards the outer regions due to solar wind from protosun.  Leftover planetesimals that did not accrete into planets became the asteroids.

E. Jovian or Gas Giants  In the outer part of the disk where temperatures are lower, lighter elements with lower condensation temperatures accreted to form planets  Jovian planet formation occurred either through core accretion or disk instability models o Core accretion model: Initially core of Jovian planets formed by accretion of solid materials; then, gas accreted onto solid core to form gas giant. o Disk instability model: Gases rapidly accrete in denser regions of the outer protoplanetary disk and condense to form Jovian planets without a solid core.  The remaining gases/ices that did not accrete to into gas giants were ejected to the furthest regions of the disk to form the comets (in either the Kuiper Belt or Oort Cloud).

14.What role did condensation temperatures play in the formation of the planets?  The condensation temperature of a substance is the temperature at which the substance solidifies from gas. In the inner part of the solar system where the temperature was high, only substances with high-condensation temperatures could become planets (i.e. heavier materials like iron, nickel and silicates formed the terrestrial planets). In the outer part of the solar system, substances with low- condensation temperatures could also become part of planets (i.e. lighter materials like hydrogen and helium formed the jovian planets).

15.The Solar System is approximately 4.6 billion years old. How is the age of the Solar System determined?  Radioactive elements are present in meteorites which is material leftover from the origin solar nebula that formed the Solar System. Radioactive elements decay at a set rate (i.e. half-life). Knowing this rate, and the amount of a radioactive sample in a meteorite, makes it possible to find the age of meteoritic material. Meteorites have been found to be 4.6 billion years old.

16.Describe 3 physical processes that are essential in the nebular theory of solar system formation.  Heating, as the protosun becomes the current Sun  In-falling materials converts gravitational energy into thermal energy (heat) (i.e. Kelvin- Helmholtz contraction).  The dense materials collides with each other, causing the gas to heat up.  Once the temperature and density gets high enough for nuclear fusion to start, a star is born.  This process accounts for the chemical differentiation and location of the terrestrial and jovian planets.  Spinning, which causes smoothing of the random motions  Conservation of angular momentum causes the in-falling material to spin faster and faster as they get closer to the center of the collapsing cloud.  This process accounts for the direction and orientation of planetary orbits.  Flattening Þ Protoplanetary disk  The solar nebula flattened into a disk.  Collision between clumps of material turns the random, chaotic motion into a orderly rotating disk.

17.Describe 5 types of extrasolar planets.  Hot Jupiter - A type of extrasolar planet whose mass is close to or exceeds that of Jupiter (1.9 × 1027 kg), but unlike in the Solar System, where Jupiter orbits at 5 AU, hot Jupiters orbit within approximately 0.05 AU of their parent stars  H ot Neptune - An extrasolar planet in an orbit close to its star (normally less than one astronomical unit away), with a mass similar to that of Uranus or Neptune  Pulsar Planet - A type of extrasolar planet that is found orbiting pulsars, or rapidly rotating neutron stars  Gas Giant - A type of extrasolar planet with similar mass to Jupiter and composed on gases  Super-Earth – A gaseous extrasolar planet with a mass higher than Earth's, but substantially below the mass of the Solar System's gas giants

18.Describe 6 methods of detecting extrasolar planets.  Transit Method - If a planet crosses ( or transits) in front of its parent star's disk, then the observed visual brightness of the star drops a small amount.The amount the star dims depends on the relative sizes of the star and the planet.  Astrometry -This method consists of precisely measuring a star's position in the sky and observing how 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. If the star is large enough, a ‘wobble’ will be detected.  Doppler Shift or Radial Velocity - A star with a planet will move in its own small orbit in response to the planet's gravity. The goal now is to measure variations in the speed with which the star moves toward or away from Earth. In other words, the variations are in the radial velocity of the star with respect to Earth. The radial velocity can be deduced from the displacement in the parent star's spectral lines (think ROYGBIV) due to the Doppler effect.  Pulsar Timing - A pulsar is a neutron star: the small, ultra-dense remnant of a star that has exploded as a supernova.•Pulsars emit radio waves extremely regularly as they rotate. Because the rotation of a pulsar is so regular, slight changes in the timing of its observed radio pulses can be used to track the pulsar's motion. Like an ordinary star, a pulsar will move in its own small orbit if it has a planet. Calculations based on pulse- timing observations can then reveal the geometry of that orbit.  Gravitational Microlensing - The gravitational field of a star acts like a lens, magnifying the light of a distant background star. This effect occurs only when the two stars are almost exactly aligned. If the foreground lensing star has a planet, then that planet's own gravitational field can make a detectable contribution to the lensing effect.  Direct Imaging - Planets are extremely faint light sources compared to stars and what little light comes from them tends to be lost in the glare from their parent star. It is very difficult to detect them directly. In certain cases, however, current telescopes may be capable of directly imaging planets.