http://www.youtube.com/watch?v=Uhy1fucSRQI

See these videos

http://www.nasa.gov/topics/solarsystem/features/asteroidflyby.html

http://www.nasa.gov/mission_pages/sdo/news/sdo-year3.html

http://www.nasa.gov/centers/ames/news/releases/2012/12-45AR.html

ASA's Mars rover Curiosity

The stars - the sun is a star- form inside large system of GAS and DUST called “molecular clouds”

Formation OF THE SOLAR SYSTEM

Gas: 72 % Hydrogen 27 % Helium and 1% other elements.H is in the form of molecules instead of atoms. Molecular clouds (MC).

Dust: tiny solid particles of silicates and metals, formed in the atmospheres of dying stars.1% of the mass of the MCs is dust.

dust grains:

- seeds where atoms agglomerate, to form planets

- absorb heat from stars preventing MCs from boiling off

The Orion Nebula in the visible

Molecular clouds: dust and gas

- On average low temp, 50 K

- Near stars it is hot and glows

- MCs contain CO that emits radio radiation allowing us to map them

The sun formed when a molecular cloud core collapsed under its gravitational pull.

Visible IR

Radio map of Orion constellation

The sun and the planets formed after a molecular cloud collapsed

Solar Nebula

proto-planets

planets

Molecular Cloud

A parenthesis to explain “ Conservation of angular momentum”

Conservation of Angular Momentum (L).

L= m(mass) ω(angular velocity) r2 (square of radius)

L= m ω r2 . Or Lω r2 Essentially this law tells that that the angular momentum of an isolated system remains constant.

(r1)2 ω1 = (r2)2 ω2

To spin faster a skater brings her arms in reducing her radius of rotation. To slow down she opens up her arms increasing her radius of rotation.

(r1)2 ω1 = (r2)2 ω2

Example of conservation of angular momentum

http://www.youtube.com/watch v=AQLtcEAG9v0

Formation of a Solar Nebula.

The original MC is cold (10 to 50 K) and has a small amount of rotation,

The collapsed cloud is smaller and conservation of angular momentum tells that it rotates faster.

Planets revolve in the same direction and almost in the same plane.

consequence

Lω r2

As the MC collapses potential energy is converted into heat, so collapsed nebula gets hotter, and protosun is hot.

“solar Nebula” = collapsed molecular cloud where sun forms

Tem

p. (

K) 2 000

1 000

The Solar Nebula Develops a Temperature Gradient.

ColdHot

Distance (AU)

Gradient = change of temperature with distance

D- Density Differentiation (Only Terrestrial Planets).

B- Accretion ( planetesimals)

C- Formation of Proto-plantes.

A- Condensation

E-Formation of atmospheres

Formation of terrestrial planet took ~ 100 million years.

Most probable Steps for Planet Formation once the solar nebula is formed.

Step 1.Condensation: As the solar nebula cooled, atoms and microscopic particles condensed aroundthe dust particles, just as snow flakes condenses out of the atmosphere.

( a hot system of gas and dust tends to dissipate)

The temperature gradient determines the elements that condense in the different regions of the nebula

Tem

p. (

K) 2 000

1 000

ColdHot

Distance (AU)

Frost line

frost line

Tem

p. (

K) 2 000

1 000

ColdHot

Distance (AU)

Frost line

Inside the frost line where the temperature is high Fe, Ni, Al and silicates condense,

and the terrestrial planets form.

Tem

p. (

K) 2 000

1 000

ColdHot

Distance (AU)

Frost line

and the Jovian planets form.

Beyond the frost line, where the temperature is lower ices, water, silicates and metals condense

Step Two: Accretion and Formation of Planetesimals.

The larger objects formed by accretion are the planetesimals.

When condensation ends accretion begins.

Accretion: gradual growth of small particles by clumping together (electrostatic forces) and by soft collisions ).

Planetesimals = solid objects formed in the proto-planetary disks of the solar nebula.

Conservation of angular tells us:-planetesimals have different orbits around the protosun - move in almost the same direction.

Some collisions hppened

-By soft collisions planetesimals coalesced into larger ones.

-Head on collision shatters the planetesimals.

Only a few large planetesimals survived.

L r2 ω

Larger planetesimals attract smaller ones, and grow faster than smaller ones given rise to proto-planets.

Terrestril Planetesimals Grow to Form Proto Planets.

Terrestrial proto-planets are as big as the planets.

Step Three.

http://www.nature.com/nature/journal/v473/n7348/full/473460a.html?WT.ec_id=NATURE-20110526

Where the Jovian protoplanets formed gas and ices were abundant and the protoplanets attracted gasses and ices directly from the nebula forming large atmosphers. This process is known as gravitational collapse.

Source NASA/JPL

Where the terrestrial protoplanets formed there was no much matter available, so when they formed , they stopped growing and they begun the process known as “density differentiation “

Important

Before density differentiation the terrestrial protoplanes were homogeneous in composition.

Density Differentiation of terrestrial planets.Density differentiation = separation of materials due to density, mainly in the liquid state.

a- heat of formation b- heat released by collision of captured planetesimals and

c- heat released by radioactive materials in the interior of these planets.

Initially the young terrestrial protoplanets melted due to the :

Terrestrial planets formed [~ 100 million years]

Core

Mantle

CrustAfter differentiation the Terrestrial planets essentially had three main regions: the core of mainly heavy elements, the mantle a mixture of heavy-light elements and a crust of light elements.

Condensation

Accretion and planetesimals Protoplanets

Graphic representation of the evolution of the Solar Nebula.

What type of particles condensed out of the solar nebula near the sun.a.ices b.ices and silicates.c.silicates and metals.d.Water and gases.c. silicates and metals

The Kuiper belt, and the Ort cloud were populated with ice planetesimals that formed out of the nebula but never made it into planets.

The rocky asteroids might be the remains of a planet that never formed.

Neptune and Uranus is believed to have formed nearer Jupiter’s orbit. Gravitational interaction with Jupiter pushed them outwardly.

Most planets formed in their present orbits.

http://cougar.jpl.nasa.gov/HR4796/anim.html

Atmospheres of Planets.

a- The atmospheres of the Jovian were drawn directly from the nebula.(Gravitational collapse.)

Jovian have primary atmospheres and they never evolved.

b- The gases in the atmospheres of terrestrial planets were the result of:

out- gassing: (volcanic eruption)

collision of comets with the surface of the planets.

As comets collided with the young terrestrial planets gases and water were released.

Initially the atmospheres of the terrestrial planets were hot. Earth’s and Mars’ cooled down and the water condensed: rain happened. ( Maybe it did not rain much on Mars!!!)

On Earth the rain removed the carbon dioxide from the atmosphere.

Mercury lost its atmosphere because it is too hot and because it has a low escape velocity.

Earth is the only planet with running water and with a Secondary Atmosphere.

Venus’ atmosphere never cooled down. So water did not condensed, (no rain). Its atmosphere remains hot and unchanged, primeval atmosphere.

There is evidence that long time ago, more than 4 billions year, Mars had running water. Mars What went wrong there? Where is the water?

When the terrestrial planets were young large impacts were common, every 100 years or so.

The Barringer Meteor Crater (Arizona), formed ~ 20 to 40 million years ago, by a meteorite of 90 meters in diameter.

Planetary impacts:

Small impacts of meteorites are still occurring .

The HST imaged the Shoemaker-Levy comet as it fell in Jupiter's atmosphere.

A giant impact 65 million years ago might have produced the extinction of the dinosaurs.

Most traces of larger impacts, on Earth, have been erased by the movement of the plates and by erosion.

Tunguska, 1908Tunguska, 1908

http://science.nasa.gov/science-news/science-at-nasa/2008/30jun_tunguska/

Most larger moons probably formed with their parent planets, directly from the nebula.

Moons

Terrestrial Planets: Mercury and Venus do not have moons.Mars’ two small moons are captured asteroids.

Jovian Planets:

The smaller moons were probably captured asteroids.

The moons are rocky and some are larger than Mercury and have atmospheres.

Origin of EARTH and MOON

Earth–Moon system may have formed after a collision with a planetesimal (the size of Mars).

Solar nebula theory explains:

a- the existence of:

TERRESTRIAL, JOVIAN and DWARFS.

b- common age of solar system

d- Craters Produced by debris falling on planets.

c- Origin of space debris.

Solar nebula theory explains:

g- disk shape of the solar system and common direction of revolution of planets around sun . (The planets orbit the sun in the same direction that the sun rotates).

f.- large tilt of rotation of Uranus and Pluto and backward rotation of Venus due.

Lack of crust on Mercury. . ( It seem that Mercury lost its crust when a large planetesimal collided ith the planet)

e- the existence of many moons around the Jovians and a few or none around the Terrestrials.

The gas and dust left over after the solar system was formed was cleared by the solar wind and by the sun’s radiation pressure.

The planetesimals left over were :gravitationally attracted by the planets

or

Clearing the NebulaClearing the Nebula

This populated the Kuiper and Oort cloud.

ejected by close encounters with planets.

Planets Around Other Stars or Exoplanets.

The solar nebula theory tells us that planets around other stars are to be expected.

A total of 777 exoplanets (in 624 planetary systems and 101 multiple planetary systems) have been identified as of July 5, 2012

The vast majority were detected through various indirect methods rather than actual imaging.

Stars are a billion times brighter……than the planet

…hidden in the glare.

From http://planetquest.jpl.nasa.gov/gallery/frequentImages.cfm

VVVVisual detection

is difficult.

NASA Kepler Mission is a telescope whose aim is to to look for Earth-like planets.

Kepler detects planets indirectly, using the "transit" method.

NASA's Kepler space telescope, was designed to find Earth-size planets in the habitable zone of sun-like stars.

Analyzing the depth of the dip in brightness of the light curve when a plant transits its “stars” astronomers can find the radius of the orbit of a planet. Image Credit: NASA Ames

http://kepler.nasa.gov/Mission/discoveries/kepler14b/

The Transit Method

http://eo.ucar.edu/staff/dward/sao/exoplanets/methods.htm

New super-Earth detected within the habitable zone of a nearby star.http://planetquest.jpl.nasa.gov

P = 28 days 25 Earth masses

Kepler MissionFebruary 02, 2012

Anbother method of detection of planets.

The gravitational attraction of the invisible planet causes the star to wobble.

Invisible planet.

As the invisible planet orbits the star its speed of rotation constantly changes. The changes are detected as a Doppler shift. Most of the exoplanets have been detected in this way

.

Until we can observe terrestrial planets, we will not be able to draw conclusions about the uniqueness of our own system. Kepler telescope is looking out for Earth like planets.

Beyond our own solar system, the planets found so far tend to be large Jovians with large Jovians with orbits more like terrestrial planets.orbits more like terrestrial planets.

A planet around 51 Pegasi, 48 ly away, was the first planet discovered using this technique.

I- A slowly rotating cloud of gas and dust, 2 ly across, collapses under its own gravity.

Summary of the Nebula Theory.

V -As luminosity of sun increases, gas and dust is eventually blown away

II- Proto- sun forms at center of the collapsed cloud or SOLAR NEBULA.

III- rotation flattens cloud, forming disk around proto-sun

IV - planets gradually formed in rotating disk

Which of the following is (are) are explained by the solar nebula theory?a- the orbits of the planets are nearly circular, and almost in the same plane.b- the planets orbit the Sun is the same direction that the sun rotates. c- the terrestrial planets have higher density and lower mass.d- comets do not necessarily orbit in the plane of the solar system.e. all of the abovee. all of the above

Image ____ shows the planet Uranus.

a b c d

Select the correct sequence of the figures in order of occurrence. (Planet formation)a- a b c d e b- d a b a cc- e d c a b d- c e b a d

a

b

c

d

e

The image represents

a- FAU’s football stadium b- the Daytona car race track

c- the Oort cloud d- the Kuiper belt

Jupiter

Mars

Sun

What are the name of the objects inside the closed dotted lines?