Slide 1

Lesson 9b extra-planets Origin of the Solar System And extra-solar planets

Slide 2

In the inner solar system it was cool enough for iron and silicate compounds to form and make rocky material. But not cool enough for ice to accumulate. The inner planets were devoid of these volatile compounds.

Slide 3

Slide 4

Today it is thought that virtually all the water on Earth came from collisions with icy bodies. Many of these bodies probably came to Earth from the migration of Neptune and Uranus caused by the 1:2 resonance of Jupiter and Saturn. Even more interesting, comets have been found to contain amino acids. The building blocks of proteins and DNA. Comets might have seeded the Earth with the compounds of life.

Slide 5

Importance of comets Life needs water. Comet collisions provide this. Comets have amino acids, life needs this. It seems to be the case that without the giant planets in the solar system, we (humans) would not be here today. The planets shot almost all of the small icy bodies out into the Oort cloud.

Slide 6

Orion Nebula

Slide 7

Proto-stars with tails and disks

Slide 8

http://www.youtube.com/watch?v=YbdwTwB 8jtc http://www.youtube.com/watch?v=YbdwTwB 8jtc http://www.youtube.com/watch?v=jhYEQgLW 5NM http://www.youtube.com/watch?v=jhYEQgLW 5NM

Slide 9

Formation of the Solar System Gas and dust in a nebula collapse under the force of gravity This cloud of gas and dust fragments into smaller clumps anywhere that the density is a little higher. The smaller clumps form stars with dust and gas still orbiting around the newly formed star.

Slide 10

Proto-stars with tails and disks

Slide 11

Although the new proto-Sun is not yet a star, it emits enough radiation, from gravitational potential energy as it shrinks, to make the inner solar system hot. There is a frost line out to the asteroid belt, where no ice can form. It must be a gas. Planets inside the frost line are built up, first by weak electrical forces between molecules, rich in silicates and iron. These become meteroids and small asteroids.

Slide 12

The largest of these have the strongest gravity, though very weak. At first the gravity just helps smaller objects to latch on to the little asteroid. As the object grows in mass, the gravity is stronger and soon these collisions are impacts. Outside the frost-line, a similar thing is occurring, only here ice (which is more abundant) helps in the growth of mass for a planet.

Slide 13

After a while the outer planets have enough mass to start pulling hydrogen and helium right out of the disk of material. They then grow to enormous size compared to the inner planets. Finally, after about 500 million years, the Sun becomes a STAR!

Slide 14

Slide 15

Star formation A proto-star is hot and emits light from this heat before it actually becomes a star. It is considered a star the internal temperature is high enough to fuse hydrogen into helium.

Slide 16

Nuclear Fusion via the proton-proton chain

Slide 17

The new star gives off enough radiation and charged particles to drive the entire disk out of the solar system. (Remember the comet tail) The only thing that remains around the Sun at this point, are object that cant be pushed away by the solar wind. (small meteoroids, asteroids, moons, and planets) The planets continue to grow, at this point only from collisions.

Slide 18

Although the gas is now gone, there are billions upon billions of small objects that remain in orbit around the Sun. These continue to impact the planets and moons. This is the Early Heavy Bombardment. (Remember the Highlands on the Moon?) Collisions between planets and smaller objects is aided by migration of the planets. As planets migrate, the smaller objects end up on elliptical orbits. Why do elliptical orbits help cause impact?

Slide 19

. 1.Objects on elliptical orbits break apart easily and make more objects increasing the chances of impacts. 2.Objects on elliptical orbits cross the orbits of planets which are circular.

Slide 20

One very great event like this occurred when Jupiter and Saturn hit a 1:2 resonance and moved Neptune and Uranus out into the Kuiper Belt. This was the Late Heavy Bombardment. (Remember the Maria on the Moon?) As time went by the Solar System was cleared of debris and the number of impacts dropped. (Remember the Moon crater analysis) The planets were still very hot inside and geologic activity continued to resurface parts of the surface.

Slide 21

The smaller planets cooled the fastest and eventually geologic activity stopped. From then on, virtually all impacts were preserved. Planets, like Mars, that were a little bigger continued geologic activity for longer than the smaller objects, but also eventually stopped. (Remember crater density to determine surface age?) Atmospheres arose from volcanic activity but only planets with enough mass and/or low enough temperature could hold on to it.

Slide 22

Result Rocky smaller planets in the inner Solar System. (Mercury, Venus, Earth, Mars). Gas giants beyond the asteroid belt (Jupiter, Saturn, Uranus, Mars. Outer moons, planetoids and comets have lots of ice. (H 2 O, CO 2 ) The asteroid belt are rocky pieces left over.

Slide 23

Extra-solar Planets. Today, we know of over 2000 planets orbiting other stars. Detecting these planets are very difficult because they are small compared to the stars they are orbiting. Directly imaging them is virtually impossible today because they only reflect the brilliant stars light. It will be possible when the James Webb Telescope is launched in the next 5 years.

Slide 24

Slide 25

NOT DRAWN TO SCALE!!!!

Slide 26

Where are we in the Milky Way?

Slide 27

Slide 28

The Fifth-Thirds Bank Building is 410 feet tall.

Slide 29

Slide 30

So try to picture this.. The solar system is the width of a hair. The Milky Way is about 3 times the size of New Circle Drive. It has a thickness almost 2 times the height of the largest building in Lexington. And the distance from us to the next closest star is about 1 meter. Our current planetary search extends to about 75 meters on this scale.

Slide 31

How do we find planets? One way is by searching for planets that eclipse their stars.

Slide 32

Slide 33

How do we find planets? One way is by searching for planets that eclipse their stars. For this technique to work, what must be true?

Slide 34

How do we find planets? One way is by searching for planets that eclipse their stars. Another way is to measure the wobble of the star as the planet orbits. (Remember Newtons Third Law)

Slide 35

Slide 36

This is done by measuring slight changes in the velocity of the star, as it wobbles.

Slide 37

Velocity changes in a star

Slide 38

Real data

Slide 39

This is done by measuring slight changes in the velocity of the star, as it wobbles. It has only been in the past 15 years that our technology has advanced to the point that we can make this measurement. What exoplanets are going to be the easiest to discover?

Slide 40

. 1.Large planets near the star. 2.Large planets far from the star. 3.Small planets near the star. 4.Small planets far from the star. 5.Small planets because there are more of them.

Slide 41

Jupiter Mass Earth Mass Earth Orbital Distance

Slide 42

It is easiest to detect large mass planets that are close to their stars. The high mass gives a bigger wobble to the star, and the closer distance also makes gravity stronger, causing a larger wobble. The vast majority of these planets are gas giants (like Jupiter) and less than 1 A.U. from their star. Some are even 100 times closer than the Earths distance to the Sun.

Slide 43

It is easiest to detect large mass planets that are close to their stars. The high mass gives a bigger wobble to the star, and the closer distance also makes gravity stronger, causing a larger wobble. The vast majority of these planets are gas giants (like Jupiter) and less than 1 A.U. from their star. Some are even 100 times closer than the Earths distance to the Sun. How can a gas giant planet be that close to its star?

Slide 44

. 1.The frost line must have been closer to the star than it was for the Sun. 2.There must have been enough silicates and iron to grow a planet large enough to capture the gas from the disk. 3.They must have formed farther out and migrated to their current orbit.

Slide 45

There is no known way for gas giants to form close to a star. They likely migrated there through interactions between either planets or other stars.

Slide 46

Super-Earths There have, in the past few years, been discoveries of a few planets that have been called super-Earths. They are have masses that are 5 10 times the Earths mass. These some of these planets are likely a transition between a gas planet like Neptune and a terrestrial world like Earth. Density estimates show several are lower density than Earth and scientists suspect

Slide 47

.. They are ocean worlds

Slide 48

Super-Earth size

Slide 49

Gliese 581 C

Slide 50

Given the number of super-Earths found so far, and the expectation that there should be more smaller planets than big planets, it is possible to at least estimate the number of Earth-like planets, orbiting Sun-like stars in the Milky Way Galaxy. Sun-like stars represent 7.6% of the stars in the Galaxy.

Slide 51

Slide 52

There are 400 billion stars in the Milky Way. That means there are 30 billion Sun-like stars. Current exoplanet research only concentrates on Sun-like stars. So if 15% have Earth-like planets, then there are about 4.5 billion Earth-like planets in the Galaxy.

Slide 53

There are 400 billion stars in the Milky Way. That means there are 30 billion Sun-like stars. Current exoplanet research only concentrates on Sun-like stars. So it 15% have Earth-like planets, then there are about 4.5 billion Earth-like planets in the Galaxy. One caveat: For life to exist, like on the Earth, these planets need to be at the correct distance, where water can exist as a liquid.

Slide 54

Continuing this on, there are 100 billion known galaxies in the observable universe. That would mean 450

Slide 55

Continuing this on, there are 100 billion known in the observable universe. That would mean 450 million

Slide 56

Continuing this on, there are 100 billion known in the observable universe. That would mean 450 million, trillion Earths in the Universe. (4.5 x 10 20 ) Do you think it is probable that there is life somewhere else in the Universe?

Slide 57

. 1.Yes 2.No

Slide 58

Do you think it is probable that they are visiting us in UFOs?

Slide 59

. 1.Yes 2.No