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 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? By reading this unit, you will answer the following questions…
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 extrasolar planets and how are they detected? 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 Gravitational Collapse Protosun Protoplanetary Disk Heating Fusion Condensation(gasliquidsolid) Sun Metal, Rocks Gases, Ice Accretion Nebular Capture Leftover Materials Terrestrial Planets Jovian Planets Leftover Materials Asteroids Comets Interstellar Cloud (Nebula) (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 × 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 (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 B1257+12 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
Types of Extrasolar Planets -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. -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 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 Neptune
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.