1. Parshati Patel Cronyn Observatory Public Nights 26 th May 2012

2. Outline:  Our Sun  Planets  Moons  Smaller Bodies Asteroids Trans-Neptunian Objects Comets

3. Our Sun  G2 type Main Sequence Star.  Age- 4.5 billion years old.  Mass- 99.8% of the Solar System’s mass (1.989*10 30 kg).  Temperature- 15.6 million Kelvin (center) and 5800 Kelvin (surface).  Size- 1,390,000 km (can fit 109 Earths in it).  Mostly made of Hydrogen (~75%) and Helium(~24%). Sun seen by Extreme Ultraviolet Imaging Telescope (EIT) in 1999.

4. Planets

5. Inner Planets  Terrestrial, rocky planets.  Primarily composed of metal and rock.  All 4 planets have atmospheres (thin/thick).  All have impact craters and tectonic surface features (such as rifts valleys and volcanoes).

6. Outer Planets  Jupiter and Saturn mainly made of Hydrogen and Helium.  Uranus and Neptune mainly made of ices such as water, ammonia and methane.  All four planets have rings.

7. Pluto- A Planet?

8. Dwarf Planets  A celestial body that Orbits around the Sun. Is not a satellite. Has sufficient mass for a self-gravity to overcome rigid body forces so that it assumes a nearly round shape. And has not cleared its neighbourhood around its orbit.  We know lots of them and lot of them still wait to be detected.

9. Moons/ Natural Satellite  Moon is a celestial body that orbits a planet or a small body.  ~170 and counting  They vary in shapes: Round to irregular in shape.  Ganymede (moon of Jupiter) is the largest moon of our Solar System.

10. Planets# of MoonsName/Misc. Earth1Luna-The only one we have landed on! Mars2Phobos and Deimos Jupiter63Ganymede (largest), Io, Calisto, Europa (Galilean Moons)+ many more! Saturn61Titan, Enceladus+ many more! Uranus27Titania, Miranda + many more! Neptune13Triton, Larrisa+ many more! Pluto4Charon, Nix, Hydra and S/2011 P1

11. Moon: Mars Top: Phobos, Bottom: Deimos

12. Galilean Moons L to R: Io, Europa, Ganymede and Calisto

13. Moon: Saturn Titan Titan as seen by Huygens Probe

14. Moon: Saturn Enceladus Geysers on Enceladus

15. Moons: Uranus

16. Moons: Neptune Triton

17. Smaller Bodies  Untouched remnants of planet formation process.  Date back to 4.5 billion years old.  Composition helps us understand the planet formation process.  Include: Meteoroids Asteroids Trans-Neptunian Objects Comets

18. Meteoroids, Meteors & Meteorites  Little chunks of rocks and debris in space are called Meteoroids.  Meteoroids become Meteors (or shooting stars) when they fall through the planet’s atmosphere; leaving a bright trail as they are heated by the friction of atmosphere.  The pieces that survive this journey and hit the ground are called meteorites.  Sizes range from few mms to few meters.

19. Asteroids  Asteroids are rocky, airless worlds that orbit our sun, but are too small to be called planets.  Most of them are found in the Asteroid Belt (a doughnut shaped ring) between Mars and Jupiter.  Range from 500 kms to 1 km in size. Composite image of Largest to smallest Asteroids imaged to the scale in high resolution.

20. Asteroids  Divided in 3 groups based on their location: Asteroid belt Trojans Near Earth Asteroids  Divided in 3 groups based on their composition: Carbon-rich type Stony/Silicate type Metallic type

21. Trans-Neptunian Objects (TNO)  TNO is any object with an orbit outside Neptune’s orbit.  3 areas where they can be found: Kuiper Belt ○ Is a disc-shaped region of icy objects. ○ Origin of Short-period comets. ○ Objects have close to circular orbits. ○ Found between 30- 50 AU from the Sun.

22. TNO- Kupier Belt

23. TNO  Scattered Disk Consists of icy objects with irregular orbits (hence scattered disk). Disk lie until around ~1000 AU.  Oort Cloud Spherical cloud of comets. Roughly up to ~50,000 AU. Objects contains mainly water, ammonia and methane. Origin of Long Period and Halley type comets.

25. Comets  A comet is an asteroid like object, basically loose collection of ice, dust and small rocky particles.  It orbits the Sun and exhibits a coma and/or tail from Solar radiation heating when near the Sun. Top: Comet 103/Hartley Bottom: Comet Hale-Bopp

26. Comets  Comet orbits range from a few years to hundreds of thousands of years.  Comet nuclei range from a few hundred meters to tens of kilometers, composed of rock, dust, water ice and frozen gases. Nucleus of Comet Halley (1992).

27. Comets  Two distinct tails: Gas tail Dust Tail

28. Thank you!