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    Nebular Hypothesis

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    saem ho
    The nebular hypothesis proposes that the Solar System formed from a giant cloud of dust and gas called a solar nebula. About 4.57 billion years ago, something caused the nebula to collapse under its own gravity. As it contracted, it formed a rotating disc that was heated at the center where the Sun formed. The disc cooled and dust particles collided to form larger bodies. Terrestrial planets like Earth formed close to the Sun from rocky material while gas giants like Jupiter captured hydrogen and formed further out where ices were more common.

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    Nebular Hypothesis

    Uploaded by

    saem ho
    69 views22 pages
    The nebular hypothesis proposes that the Solar System formed from a giant cloud of dust and gas called a solar nebula. About 4.57 billion years ago, something caused the nebula to collapse under its own gravity. As it contracted, it formed a rotating disc that was heated at the center where the Sun formed. The disc cooled and dust particles collided to form larger bodies. Terrestrial planets like Earth formed close to the Sun from rocky material while gas giants like Jupiter captured hydrogen and formed further out where ices were more common.

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    The nebular hypothesis proposes that the Solar System formed from a giant cloud of dust and gas called a solar nebula. About 4.57 billion years ago, something caused the nebula to collapse under its own gravity. As it contracted, it formed a rotating disc that was heated at the center where the Sun formed. The disc cooled and dust particles collided to form larger bodies. Terrestrial planets like Earth formed close to the Sun from rocky material while gas giants like Jupiter captured hydrogen and formed further out where ices were more common.

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    © All Rights Reserved
    Download as PDF, TXT or read online from Scribd
    Download as pdf or txt
    69 views22 pages

    Nebular Hypothesis

    Uploaded by

    saem ho
    The nebular hypothesis proposes that the Solar System formed from a giant cloud of dust and gas called a solar nebula. About 4.57 billion years ago, something caused the nebula to collapse under its own gravity. As it contracted, it formed a rotating disc that was heated at the center where the Sun formed. The disc cooled and dust particles collided to form larger bodies. Terrestrial planets like Earth formed close to the Sun from rocky material while gas giants like Jupiter captured hydrogen and formed further out where ices were more common.

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    T-H-E

    NE-BU-LAR
    HYPO-THESIS
    What is your idea about the
    origin of the solar system?

    How was the Solar System


    formed?
    THE NEBULAR HYPOTHESIS
    “NEBULA” “HYPOTHESIS”
    •Latin for “cloud” or •A supposition or
    “fog” proposed explanation
    •An interstellar or made on the basis of
    giant cloud of dust, limited evidence as a
    hydrogen, helium starting point for
    and other ionized further investigation.
    gases.
    NEBULAR THEORY
    •This theory states that the sun, the planets,
    and all other objects in the Solar System
    formed from nebulous material billions of
    years ago.
    •The sun and all the planets of our Solar
    System began as a giant cloud of molecular
    dust and gas.
    •About 4.57 billion years ago, something
    happened that caused the cloud to collapse.
    something happened…

    a. The birth of our Solar System began as


    dust and gases (nebula) started to
    gravitationally collapse
    -a small overdensity in the cloud caused
    the contraction to begin and the overdensity
    to grow, thus, producing a faster contraction
    ---collapse process.
    b. The nebula contracted into a rotating disc that
    was heated by the conversion of gravitational
    energy to thermal energy
    -As the cloud contracted, its gravitational
    potential energy was converted into kinetic energy
    of the individual gas particles.
    -Collisions between particles converted this
    energy into heat (random motions)
    -The solar nebula became hottest near the
    center where much of the mass was collected to
    form the protosun (the cloud of gas that became
    SUN)
    •Cooling of the nebular cloud caused rocky
    and metallic material to condense into tiny
    solid particles. (Condensation)
    •Repeated collisions caused the dust-sized
    particles to gradually coalesce into
    asteroid-sized bodies
    •Within a few million years, these bodies
    accreted into the planets
    -Around the Sun, a thin disc gives birth to
    the planets, moons, asteroids, and comets.
    INGREDIENTS OF THE SOLAR SYSTEM
    1. METALS: iron, nickel, aluminum. They condensed
    at temperature of 1,600 K and comprised only 0.2 %
    of the disc.
    2. ROCKS: silicon-based minerals that condense at
    temperature of 500 to 1300 K (0.4 % of the nebula)
    3. ICES: hydrogen compounds like methane (CH4),
    ammonia (NH3), water (H2O) that condense at
    temperature of 150 K and make up 1.4% of the
    mass.
    4. LIGHT GASES: hydrogen and helium that never
    condense in the disk (98% of the disk)
    FORMATION OF THE
    PLANETS
    Accretion
    •A gradual process in which layers of
    a material formed as small amounts
    are added over time
    Formation of Terrestrial Planets
    •Mercury, Venus, Earth and Mars
    •In the warmer inner solar system, planetesimals
    formed from rock and metal, materials cooked
    billions of years ago in cores of massive stars.
    •These elements made up only 0.6% of the material
    in the solar nebula (and the faster collisions
    among particles close to the Sun were more
    destructive on average), so the planets could not
    grow very large and could not exert large pull on
    hydrogen and helium gas.
    •Even if terrestrial planets had hydrogen
    and helium, proximity to Sun would
    heat gases and cause them to escape.
    •Hence, terrestrial planets (Mercury,
    Venus, Earth, and Mars) are dense
    small worlds composed mostly from 2%
    of heavier elements contained in solar
    nebula.
    Formation of Jovian Planets:
    •In the outer solar nebula, planetesimals
    formed from ice flakes in addition to rocky
    and metal flakes.

    •Since ices were more abundant the


    planetesimals could grow to much larger
    sizes, becoming the cores of the four jovian
    (Jupiter, Saturn, Uranus, and Neptune)
    planets.
    •The cores were sufficiently large (at least 15
    times Earth's mass) that they were able to
    capture hydrogen and helium gas from the
    surroundings (nebular capture) and form a
    thick atmosphere.

    •They became the large, gaseous, low-density


    worlds rich in hydrogen and helium, with
    dense solid cores.
    •Far from Sun (beyond Neptune), in coldest
    regions of the nebula, icy planetesimals survive.
    However, the density of the disk was so low that
    the icy/dusty planetesimals could only grow to
    the size of a few kilometers. They could not
    accrete the surrounding gas so they remained
    like small dirty snowballs. They constitute the
    family of Kuiper belt comets, a prediction of the
    theory of the formation of the solar system which
    was confirmed in 1990.
    •
    Quiz
    1. What is nebula?

    2-5. What are the ingredients of the Solar System?

    True or False
    6. Mars is a Jovian planet.
    7. The solar nebula became hottest near the center.
    8-10. Give at least three Jovian planets.

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