1. The Solar System

2. Nebula is very hot, and generally is made of gas that is rotating. The Solar System

3. Rotation Small amount of rotation about the axis Large amount of rotation near the equator Hot, rotating nebula

4. The Solar System Rotation Small amount of rotation about the axis Large amount of rotation near the equator

5. The Solar System Rotation Gravity dominated More ability to establish orbit because of large amount of rotational speed

6. The Solar System Rotation Gravity dominated flattening More ability to establish orbit because of large amount of rotational speed

7. The Solar System Rotation Gravity dominated flattening More ability to establish orbit because of large amount of rotational speed

8. The Solar System Rotation Hotter Solar Nebula – The swirling, pancake shaped mass destined to become the solar system The sun is located at the center of the solar nebula.

10. The Solar System Rotation Hotter Within the solar nebula, hot gases contain too much energy (recall relation between kinetic energy and temperature.

11. New Hubble Image Reveals Details in the Heart of the Trifid Nebula Three huge intersecting dark lanes of interstellar dust make the Trifid Nebula one of the most recognizable and striking star birth regions in the night sky. The dust, silhouetted against glowing gas and illuminated by starlight, cradles the bright stars at the heart of the Trifid Nebula. This nebula, also known as Messier 20 and NGC 6514, lies within our own Milky Way Galaxy about 9,000 light-years (2,700 parsecs) from Earth, in the constellation Sagittarius. This new image from the Hubble Space Telescope offers a close-up view of the center of the Trifid Nebula, near the intersection of the dust bands, where a group of recently formed, massive, bright stars is easily visible The Solar System The Role of Dust

12. Current theories hold that interstellar dust clouds entered the solar nebular. The dust particles were relatively cool, and are composed of rocky and icey matter with a size of approximately.001 cm. The Solar System The Role of Dust

13. The Solar System Rotation Condensation Theory – Interstellar dust cools the nebula, and the dust particles act as sites of nucleation or condensation of the particles around them.

14. The Solar System Rotation As the nebula cools, gravity from the condensation sites attract more and more material, and the condensed grains sweep away more and more of the material around them.

15. The Solar System Rotation Accretion – gradual growth of small objects by collisions and sticking.

16. The Solar System Rotation Protoplantets – accumulated matter that eventually grows into planets.

17. The Solar System Temperature Profile Rotation Near the sun, the temperature of the condensing solar nebula is high (a few thousand degrees K. Further out, temperature drops to hundreds down to tens degree Kelvin.

18. Loose discussion: More massive elements will be migrate toward the sun as a result of a stronger gravitational pull. Lighter elements will populate reagions farther from the sun. Temperature: T  KE = ½ m v 2 At a given temperature, more massive objects will move slower, and are more likely to stick. More massive particles can condense at the high temperature reagions near the sun, low lighter particles will condense further from the sun. The Solar System Temperature Profile

19. The Solar System Temperature Profile Rotation High temperatures closer to sun can condense only heavier molecules, father away, only simpler elements condense.

20. As a result the higher density planets will be closer to the sun, the lower density planets will be further from the sun. The inner, more dense planets are called the terrestrial planets. These planets are earthlike: Mercury, Venus, Earth, Mars The outer, less dense planets are called the Jovian Planets. The Jovian Planets are Jupiter, Saturn, Uranus, Neptune Pluto is in a category by itself The Solar System

21. Comparative Planetology – the study of the similarities and differences of the objects in the solar system. Stars: 1 Planets: 9 (?) Moons: 135 Large asteroids: 6 Smaller asteroids: Tens of thousands Comets: A whole bunch Meteors: A whole bunch The Solar System

22. The image (see next slide) is an up to date map of the solar system displaying the orbits of the terrestrial planets and the estimated position of thousands of known asteroids. This diagram is missing comets, space probes and, of course, the undiscovered asteroids. Even conservative estimates would suggest that for every asteroid on a dangerous Earth- Approaching orbit there are hundreds more which have yet to be discovered. There are over 300 known objects on Earth-crossing orbits, the majority of which are potentially capable of causing death and destruction on a scale unheard of in human history. The terrestrial planets (Mercury, Venus, Earth and Mars) are shown on the diagram by Cyan or White squares, and their orbits are represented by the blue ellipses around the Sun (the yellow dot at the centre). The Earth is highlighted because of its special importance to us. Small green points mark the location of asteroids which do not approach close to the Earth right now. This does not exclude the possibility that they will do so in the future but generally we can consider the Earth to be safe from these for the near future. Yellow objects (with the exception of the one in the middle which we astronomers call the Sun ;-) are Earth approaching asteroids which are called Amors after the first one discovered. Amors have orbits which come close to the Earth but they don't cross the Earth's orbit. However, their orbits are close enough to the Earth that they could potentially be perturbed by the influence of the planets and begin to cross the Earth's orbit in a short time. There are over 300 known objects on such orbits. Finally the red boxes mark the location of the Apollo and Aten asteroids. These cross the Earth's orbit and are the most directly identifiable astronomical threat for the near future. Included in this selection is the infamous asteroid, 1997XF11, which made a major impact on the world's headlines in March 1997 when observations indicated that it had a good chance of colliding with the Earth in 2028. Thankfully, new observations were made and the newly calculated orbit predicts a close approach of about 600,000 kilometres. Other asteroids which have orbits which may hit the Earth are 1999 AN 10 and 1998 OX 4. Further observation is required to determine their orbits in sufficient detail to predict an impact or a near miss. It is estimated that there are perhaps 100,000 to 1,000,000 undiscovered asteroids on similar Earth crossing orbits. The Solar System