The Origin of Our Solar System II

What are the key characteristics of the solar system that must be explained by any theory of its origins? What are the key characteristics of the solar system that must be explained by any theory of its origins? How do the abundances of chemical elements in the solar system and beyond explain the sizes of the planets? How do the abundances of chemical elements in the solar system and beyond explain the sizes of the planets? How we can determine the age of the solar system by measuring abundances of radioactive elements? How we can determine the age of the solar system by measuring abundances of radioactive elements? Why do scientists think the Sun and planets all formed from a cloud called the solar nebula? Why do scientists think the Sun and planets all formed from a cloud called the solar nebula? By reading this unit, you will answer the following questions…

How does the solar nebula model explains the formation of the terrestrial planets? How does the solar nebula model explains the formation of the terrestrial planets? What are the two competing models for the origin of the Jovian planets? What are the two competing models for the origin of the Jovian planets? What are extrasolar planets and how are they detected? What are extrasolar planets and how are they detected? How do astronomers test the solar nebula model by observing extrasolar planets around other stars? How do astronomers test the solar nebula model by observing extrasolar planets around other stars? By reading this unit, you will answer the following questions…

The Solar Nebular Theory Interstellar Cloud (Nebula) Protoplanetary DiskProtosun Gravitational Collapse Terrestrial Planets AccretionNebular Capture Jovian Planets Asteroids Leftover Materials Comets Leftover Materials Metal, Rocks Condensation (gas  liquid  solid) SunGases, Ice Heating  Fusion (depends on temperature)

Major Physical Processes in Solar Nebular Theory Heating  Protosun  Sun -In-falling materials converts gravitational energy into thermal energy (heat)  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.

Major Physical Processes in Solar Nebular Theory Spinning  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.

Major Physical Processes in Solar Nebular Theory Flattening  Protoplanetary disk. -The solar nebula flattened into a disk. -Collision between clumps of material turns the random, chaotic motion into a orderly rotating disk.

Major Physical Processes in Solar Nebular Theory Heating Spinning Flattening This process explains the orderly motion of most of the solar system objects!

Core Accretion Model for Jovian Planet Formation Initially core of Jovian planets formed by accretion of solid materials Then, gas accreted onto solid core to form gas giant

Disk Instability Model for Jovian Planet Formation Gases rapidly accrete and condense to form Jovian planets without a solid core

Extrasolar Planets An extrasolar planet, or exoplanet, is a planet beyond our solar system, orbiting a star other than our Sun

Types of Extrasolar Planets Hot Jupiter A type of extrasolar planet whose mass is close to or exceeds that of Jupiter (1.9 × 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 (about one eighth the distance that Mercury orbits the Sun) Example: 51 Pegasi b

Types of Extrasolar Planets Pulsar Planet A type of extrasolar planet that is found orbiting pulsars, or rapidly rotating neutron stars Example: PSR B in the constellation Virgo

Types of Extrasolar Planets Gas Giant A type of extrasolar planet with similar mass to Jupiter and composed on gases Example: 79 Ceti b

-A super-Earth is an extrasolar planet with a mass higher than Earth's, but substantially below the mass of the Solar System's gas giants.extrasolar planetEarthgas giants -term super-Earth refers only to the mass of the planet, and does not imply anything about the surface conditions or habitability. The alternative term "gas dwarf" may be more accurate Types of Extrasolar Planets

OGLE-2005-BLG-390Lb

A hot Neptune is 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 Neptuneextrasolar planet astronomical unitmassUranusNeptune Types of Extrasolar Planets

Gliese 581 b

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.

Methods of Detecting Extrasolar Planets 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.

Methods of Detecting Extrasolar Planets Doppler Shift (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. A red shift means the star is moving away from Earth A blue shift means the star is moving towards Earth

Methods of Detecting Extrasolar Planets 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

Methods of Detecting Extrasolar Planets 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.

Methods of Detecting Extrasolar Planets 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.

-The radial-velocity method and the transit method are most sensitive to large planets in small orbits. -smaller planets more common than larger & are in larger orbits

Key Ideas Models of Solar System Formation: The most successful model of the origin of the solar system is called the nebular hypothesis. According to this hypothesis, the solar system formed from a cloud of interstellar material called the solar nebula. Models of Solar System Formation: The most successful model of the origin of the solar system is called the nebular hypothesis. According to this hypothesis, the solar system formed from a cloud of interstellar material called the solar nebula. This occurred 4.6 billion years ago (as determined by radioactive dating). This occurred 4.6 billion years ago (as determined by radioactive dating).

Key Ideas The Solar Nebula and Its Evolution: The chemical composition of the solar nebula, by mass, was 98% hydrogen and helium (elements that formed shortly after the beginning of the universe) and 2% heavier elements (produced much later in the centers of stars, and cast into space when the stars died). The Solar Nebula and Its Evolution: The chemical composition of the solar nebula, by mass, was 98% hydrogen and helium (elements that formed shortly after the beginning of the universe) and 2% heavier elements (produced much later in the centers of stars, and cast into space when the stars died). The heavier elements were in the form of ice and dust particles. The heavier elements were in the form of ice and dust particles.

Key Ideas Formation of the Planets and Sun: The terrestrial planets, the Jovian planets, and the Sun followed different pathways to formation. Formation of the Planets and Sun: The terrestrial planets, the Jovian planets, and the Sun followed different pathways to formation. The four terrestrial planets formed through the accretion of dust particles into planetesimals, then into larger protoplanets. The four terrestrial planets formed through the accretion of dust particles into planetesimals, then into larger protoplanets. In the core accretion model, the four Jovian planets began as rocky protoplanetary cores, similar in character to the terrestrial planets. Gas then accreted onto these cores in a runaway fashion. In the core accretion model, the four Jovian planets began as rocky protoplanetary cores, similar in character to the terrestrial planets. Gas then accreted onto these cores in a runaway fashion.

Key Ideas In the alternative disk instability model, the Jovian planets formed directly from the gases of the solar nebula. In this model the cores formed from planetesimals falling into the planets. The Sun formed by gravitational contraction of the center of the nebula. After about 10 8 ( ) years, temperatures at the protosun’s center became high enough to ignite nuclear reactions that convert hydrogen into helium, thus forming a true star.

Key Ideas Extrasolar Planets: Astronomers have discovered planets orbiting other stars. Extrasolar Planets: Astronomers have discovered planets orbiting other stars. Most of these planets are detected by the “wobble” of the stars around which they orbit. Most of these planets are detected by the “wobble” of the stars around which they orbit. A small but growing number of extrasolar planets have been discovered by the transit method, astrometry, radial velocity (Doppler), pulsar timing, gravitational microlensing, and direct imaging. A small but growing number of extrasolar planets have been discovered by the transit method, astrometry, radial velocity (Doppler), pulsar timing, gravitational microlensing, and direct imaging. Most of the extrasolar planets discovered to date are quite massive and have orbits that are very different from planets in our solar system. Most of the extrasolar planets discovered to date are quite massive and have orbits that are very different from planets in our solar system.

Key Ideas Types of Extrasolar Planets: Types of Extrasolar Planets: Hot Jupiters Hot Jupiters Gas Giants Gas Giants Super Earths Super Earths Hot Neptunes Hot Neptunes