3. Formation OF THE SOLAR SYSTEM
Gas: 72 % Hydrogen
The stars - the
27 % Helium and
sun is a star- 1% other elements.
form inside H is in the form of
large system of molecules instead of atoms.
GAS and Molecular clouds (MC).
DUST
Dust: tiny solid particles of
called silicates and metals, formed
“molecular in the atmospheres of dying
clouds” stars.
1% of the mass of the MCs is
dust.
4. The Orion Nebula in
dust grains:
the visible
- seeds where
atoms
agglomerate, to
form planets
- absorb heat from
stars preventing
MCs from boiling
off
5. - On average low
Molecular clouds:
dust and gas temp, 50 K
- Near stars it is
hot and glows
- MCs contain
CO that emits
radio radiation
allowing us to
map them
6. Visible IR
The sun formed when a molecular cloud core collapsed under its
gravitational pull.
8. Molecular Solar Nebula
Cloud
The sun and
the planets
formed after
a molecular proto-planets
cloud
collapsed
A parenthesis
to explain “
Conservation
of angular planets
momentum”
9. Conservation of Angular Momentum (L).
L= m(mass) ω(angular velocity) r2 (square of radius)
L= m ω r2 . Or L∝ω r2
Essentially this law tells that that the angular momentum of
an isolated system remains constant.
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
10. Example of conservation of angular momentum
(r1)2 ω1 = (r2)2 ω2
http://www.youtube.com/watch
v=AQLtcEAG9v0
11. 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.
consequence
Planets revolve in the same
direction and almost in the same
plane.
L∝ω r2
12. 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
13. The Solar Nebula Develops a
Temperature Gradient.
Hot Cold
2 000
Temp. (K)
Gradient =
change of
1 000
temperature
with distance
Distance (AU)
14. Most probable Steps for Planet Formation once
the solar nebula is formed.
A- Condensation
B- Accretion ( planetesimals)
C- Formation of Proto-plantes.
D- Density Differentiation (Only
Terrestrial Planets).
E-Formation of atmospheres
Formation of terrestrial planet took
~ 100 million years.
15. Step 1.
Condensation:
As the solar nebula
cooled, atoms and
microscopic particles
condensed around
the dust particles, just as snow flakes
condenses out of the atmosphere.
( a hot system of gas and dust tends to
dissipate)
16. The temperature gradient determines the elements
that condense in the different regions of the
nebula
Cold
Hot frost
line
Frost line 2 000
Temp. (K)
1 000
Distance (AU)
17. Inside the frost line where the temperature
is high Fe, Ni, Al and silicates condense,
and the terrestrial
planets form.
Cold
Hot
Frost line 2 000
Temp. (K)
1 000
Distance (AU)
18. Beyond the frost line, where the temperature
is lower ices, water, silicates and metals
condense and the Jovian
planets form.
Cold
Hot
Frost line 2 000
Temp. (K)
1 000
Distance (AU)
19. Step Two: Accretion and Formation of
Planetesimals.
When condensation ends accretion begins.
Accretion: gradual
growth of small
particles by clumping
together (electrostatic
forces) and by soft
collisions ).
The larger objects formed by accretion are the
planetesimals.
Planetesimals = solid objects formed in the
proto-planetary disks of the solar nebula.
20. Conservation of angular tells us:
-planetesimals have different
orbits around the protosun
- move in almost the same
direction.
L∝ r ω 2
Some collisions hppened
-By soft collisions planetesimals coalesced into larger
ones.
-Head on collision shatters the planetesimals.
Only a few large planetesimals survived.
21. Step Terrestril Planetesimals Grow
Three. to Form Proto Planets.
Larger
planetesimals
attract smaller
ones, and grow
faster than
smaller ones
given rise to
http://www.nature.com/nature/journal/v473/n734
proto-planets. 8/full/473460a.html?WT.ec_id=NATURE-
20110526
Terrestrial proto-planets are as big as the planets.
22. Important
Where the Jovian protoplanets Where the terrestrial
formed gas and ices were abundant protoplanets formed there
and the protoplanets attracted was no much matter
gasses and ices directly from the available, so when they
nebula forming large atmosphers. formed , they stopped
This process is known as growing and they begun the
gravitational collapse. process known as “density
differentiation “
Source NASA/JPL
23. Density Differentiation of terrestrial planets.
Density differentiation = separation of materials due
to density, mainly in the liquid state.
Before density
differentiation the
terrestrial
protoplanes were
homogeneous in
composition.
24. Initially the young terrestrial protoplanets melted due to
the :
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.
25. After differentiation Crust
the Terrestrial planets
essentially had three Mantle
main regions:
the core of mainly
Core
heavy elements, the
mantle a mixture of
heavy-light elements
and a crust of light
elements.
Terrestrial planets formed [~ 100 million years]
26. Graphic representation of the evolution of the Solar Nebula.
Condensation
Accretion and
planetesimals Protoplanets
27. What type of particles condensed out of the
solar nebula near the sun.
a.ices
b.ices and silicates.
c.silicates and metals.
c. silicates and metals
d.Water and gases.
28. 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.
29. Most planets formed in
their present orbits.
Neptune and Uranus is
believed to have formed
nearer Jupiter’s orbit.
Gravitational interaction
with Jupiter pushed them
outwardly.
31. 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.
32. 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.
33. 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.
34. Mercury lost its atmosphere because it is too hot and
because it has a low escape velocity.
Venus’ atmosphere never cooled down. So water did
not condensed, (no rain). Its atmosphere remains hot
and unchanged, primeval atmosphere.
Earth is the only planet with running water and with
a Secondary 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?
35. Planetary impacts:
When the terrestrial
planets were young
large impacts were
common, every 100
years or so.
The Barringer Meteor Small impacts
Crater (Arizona), of meteorites
formed ~ 20 to 40 are still
million years ago, by a occurring .
meteorite of 90 meters
in diameter.
36. The HST imaged
the Shoemaker-
Levy comet as it
fell in Jupiter's
atmosphere.
37. Most traces of larger impacts, on Earth,
have been erased by the movement of the
plates and by erosion.
A giant impact 65 million years ago
might have produced the extinction of
the dinosaurs.
39. Moons
Jovian Planets:
Most larger moons probably formed with their parent
planets, directly from the nebula.
The smaller moons were probably captured asteroids.
The moons are rocky and some are larger than
Mercury and have atmospheres.
Terrestrial Planets:
Mercury and Venus do not have moons.
Mars’ two small moons are captured asteroids.
41. Origin of EARTH and MOON
Earth–Moon system may have formed after a collision with a planetesimal
(the size of Mars).
42. Solar nebula theory explains:
a- the existence of:
TERRESTRIAL, JOVIAN and DWARFS.
b- common age of solar system
c- Origin of space debris.
d- Craters Produced by debris falling on planets.
43. Solar nebula theory explains:
e- the existence of many moons around the
Jovians and a few or none around the Terrestrials.
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)
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).
44. Clearing the Nebula
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
ejected by close encounters with planets.
This populated the Kuiper and Oort cloud.
45. 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.
46. Stars are a billion
…than the planet times brighter…
V
VVVisual detection
is difficult.
…hidden
in the glare.
From
http://planetquest.jpl.nas
a.gov/gallery/frequentIma
ges.cfm
47. NASA Kepler Mission is a
telescope whose aim is to to
look for Earth-like planets.
NASA's Kepler space
telescope, was designed
to find Earth-size
planets in the habitable
zone of sun-like stars.
Kepler detects planets indirectly, using the "transit"
method.
48. 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/
49. The Transit Method
http://eo.ucar.edu/staff/dward/sao/exoplanets/methods.htm
50. Kepler MissionFebruary 02, 2012
P = 28 days 25 Earth masses
New super-Earth detected within the habitable zone
of a nearby star.
http://planetquest.jpl.nasa.gov
51. Anbother method of detection of planets.
Invisible
planet.
The gravitational attraction of the invisible planet
causes the star to wobble.
52. 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
.
53. A planet around 51 Pegasi, 48 ly away,
was the first planet discovered using
this technique.
Beyond our own solar system, the planets
found so far tend to be large Jovians with
orbits more like terrestrial planets.
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.
54. Summary of the Nebula
Theory.
I- A slowly rotating cloud of gas and
dust, 2 ly across, collapses under its own
gravity.
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
V -As luminosity of sun increases, gas
and dust is eventually blown away
55. 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 above
e. all of the above
57. Select the correct sequence of the figures in order of
occurrence. (Planet formation)
a- a b c d e b- d a b a c
c- e d c a b d- c e b a d
a
d
b
e
c
58. The image represents
a- FAU’s football stadium b- the Daytona car race
track
c- the Oort cloud d- the Kuiper belt
59. What are the name of the objects inside the
closed dotted lines?
Mars
Sun
Jupiter