~15 GA. (Giga Annum: Billion Years) today

Transcription

1 ~15 GA (Giga Annum: Billion Years) today

2 ~ 300,000 years after the Big Bang The first map of the Universe. Not homogeneous. Cosmic microwave background (CMB) anisotropy. First detected by the COBE DMR instrument.

3 ~ 100 Billion Stars ~100,000 light years across We would be about here Typical spiral galaxy. Similar to our Milk Way Galaxy

4 Stars Massive, dense balls of incandescent gas Powered by fusion reactions in their core Sun (E = mc 2 ) An average star Reference for understanding other stars Origin of stars Gaseous nebula Mostly hydrogen Shock waves induce gravitational collapse Gravitational energy released into higher temperatures and pressures Protostar Accumulation of gases that will become a star

5 Star Birth and Formation

6

7 Core Very hot, most dense region Nuclear fusion releases gamma and x-ray radiation Radiation zone Radiation diffuses outward over millions of years Convection zone Structured by hot material rising from the interior, cooling, and sinking Upper reaches: visible surface of star Sun surface temp. ~5,800 K Stellar modeling

8 Lifetime of the Sun Converts about 1.4x10 17 kg of matter to energy each year About 2, lb SUVs! Lifetime depends on stellar mass Less massive stars have longer lifetimes More massive stars have shorter lifetimes Born 5 billion years ago Enough hydrogen for another 5 billion years But not every star is like the Sun

9 .the most violent event ever seen in the universe flashed into view on the morning of March 19th.

10 "This burst was a whopper," said Swift principal investigator Neil Gehrels of NASA's Goddard Space Flight Center in Greenbelt, Md. "It blows away every gamma ray burst we've seen so far.".the March 19th burst had a redshift of 0.94, corresponding to a look-back time of 7.5 billion years several thousand times more than the nearby galaxies. The farthest object ever seen by the naked eye. Most gamma ray bursts occur when massive stars run out of nuclear fuel. Their cores collapse to form black holes or neutron stars, releasing an intense burst of high-energy gamma rays and ejecting particle jets that rip through space at nearly the speed of light like turbocharged cosmic blowtorches. When the jets plow into surrounding interstellar clouds, they heat the gas, often generating bright afterglows. Gamma ray bursts are the most luminous explosions in the universe since the big bang.

11 Brightness of stars Differences in stellar brightness 1. Amount of light produced by star 2. Size of star 3. Distance to star Apparent magnitude Scheme to quantify observed brightness First magnitude star 100 times brighter than sixth magnitude star Five uniform divisions in between

12 Absolute magnitude Brightness adjusted to a defined, standard distance Example: Sun Apparent magnitude = Absolute magnitude = +4.8 Luminosity Total energy radiated into space per second Directly related to absolute magnitude Units correlated to Sun: 1 solar luminosity

13 Star temperature Color variations apparent: red, yellow, bluish white Color related to surface temperature Blackbody radiation curves Red: cooler stars Blue: hotter stars Yellow: in between (Sun) Classification scheme Based on temperature: hottest to coolest O, B, A, F, G, K, M

14 Protostar stage Gravitational collapse Density, temperature and pressure increase 10 million K: fusion ignition temperature Dynamical equilibrium Inward force of gravity Outward pressure of fusion energy Star enters main sequence Life of a star

15 Hertzsprung- Russel Diagram

16 A stars fate depends on its mass

17 Fate of the Sun. First a Red Giant, then a White dwarf within a planetary nebula

18

19 Magnetic fields around a sunspot

20 Winds' and Waves on the surface of Sol

21 SUN Hydrogen (74%), some helium (24%) Rocky inner planets Silicates with Iron/Nickel cores The giant Gas planets of the outer solar system Hydrogen, Helium, methane, water, ammonia

22 Planet summary

23 Mercury

24 Venus

25

26

27 Earth

28 Mars

29 The Martian ice cap Frozen water?

30 Craters on Mars

31 Olympus Mons ~ 625 km (324 miles) diameter Scarp Height ~ 6 km (4 miles) The largest mountain in the Solar System Why is it so big?

32

33 Olympus Mons on an overcast day

34 Evidence for water on mars

35 Wind-formed dunes on Mars Atmosphere: 0.7% of the Earth s atmospheric pressure; 95% Carbon Dioxide (CO 2 ), 3% Nitrogen (N 2 ); 1.7% Argon, 0.1% Oxygen (O 2 )

36 View of the surface of Mars from the Martian lander

37 Figure 15.09a Jupiter

38 Figure 15.09b

39 Movie of Jupiter

40

41

42 Saturn

43

44

45 Titan: moon of Saturn landing400.mov

46 Uranus

47

48 Neptune

49 Pluto

50 Smaller bodies of the Solar System Comets, asteroids, meteorites Leftover from solar and planetary formation Mass of smaller bodies may be 2/3 of total Solar System mass Bombard larger objects Comet Shoemaker-Levy 9 fragments (bottom) and strikes Jupiter (July 1994)

51 Comet structure Small, solid objects Dirty snowball model Frozen water, CO 2, ammonia, and methane Dusty and rocky bits Comet head Solid nucleus and coma of gas Two types of tails 1. Ionized gases 2. Dust Tail points away from Sun

52 Meteors and meteorites Meteoroids Remnants of comets and asteroids Meteor Meteoroid encountering Earth s atmosphere Meteor showers: Earth passing through comet s tail Meteorite Meteoroid surviving to strike Earth s surface Iron, stony (chondrites and achondrites) or stony-iron

53 Figure 15.19b

54 Figure 15.19a

55 Our moon: Luna

56 Current hypothesis: Luna was formed as a result of an impact by a Mars-sized object in the early stages of Solar System formation.

57 Lunar impact craters

58 Crater Tycho

59 Close up of Tycho

60 The lunar interior: crust, mantle core Mostly rock, very small iron core; cooled and tectonically inactive

61