outline 1. in the beginning. The Big Bang 2. galaxies -- different types 3. stars -- life cycle 4. the solar system -- sun and planets

Transcription

1 Earth s Place in the Universe outline 1. in the beginning. The Big Bang 2. galaxies -- different types 3. stars -- life cycle 4. the solar system -- sun and planets

2 the big bang the universe is expanding and cooling it all began about 13.8 billion years ago how do we know?

3 light travels as a wave m/s

4 --> galaxies are moving away from Earth Doppler effect Johann Christian Andreas Doppler

5 redshift --> retreat velocity advancing galaxy receding galaxy

6 Edwin Hubble observed a red shift --> retreat velocity (apparent velocity of recession) increases with increasing distance --> Hubble s constant

7 distance is calculated by measuring parallax

8 Hubble s Law

9 age of the universe The Hubble parameter has the dimensions of inverse time, so a Hubble time t H may be obtained by inverting the present value of the Hubble parameter

10 at the beginning There was an enormous outward expanding gaseous cloud of hydrogen and helium. The cloud condensed under gravity and contracted into swirling, tabular masses --> became galaxies Further fragmentation of these spinning clouds formed proto-stars.

11 at the beginning

12 at the beginning Proto-stars continued to collapse under gravitational pull becoming hotter and denser until nuclear fusion began and collapse stopped. --> energy producing stars were born. 100 billion billion (10 20 ) stars!

13 galaxies spiral elliptical lenticular irregular

14 spiral galaxies Spiral galaxies are characterized by the presence of gas in the disk which means star formation remains active at the present time, hence the younger population of stars. Spirals are usually found in the low density galactic field where their delicate shape can avoid disruption by tidal forces from neighbouring galaxies.

15 Milky Way spiral galaxy with 100 billion stars interstellar matter 10% (equivalent to 10 billion stars) 100,000 light years wide, 10,000 light years thick speed of light is m/s (~ 186, mi/s) --> light year ~ 9.5 trillion km or 5.8 trillion miles

16 NGC 3370

17 M100

18 elliptical galaxies Uniform luminosity and are similar to the bulge in a spiral galaxy, but with no disk. The stars are old and there is no gas present. Ellipticals are usually found in the high density field, at the centre of clusters. The giant elliptical galaxy M87

19 lenticular galaxies Possess both a bulge and a disk, but have no spiral arms. There is little or no gas and so all the stars are old. They appear to be an intermediate.

20 irregular galaxies Small galaxies with no bulge and an ill-defined shape. The Magellenic clouds are examples

21 large magellanic cloud

22 star A star is a massive, luminous ball of plasma. Stars group together to form galaxies, and they dominate the visible universe. The nearest star to Earth is the Sun, which is the source of most of the energy on Earth, including daylight. Other stars are visible in the night sky, when they are not outshone by the Sun. A star shines because nuclear fusion in its core releases energy which traverses the star's interior and then radiates into outer space. Almost all elements heavier than hydrogen and helium were created inside the cores of stars.

23 proto-star A star begins as a collapsing cloud of material that is composed primarily of hydrogen along with some helium and heavier trace elements. Once the stellar core is sufficiently dense, some of the hydrogen is steadily converted into helium through the process of nuclear fusion. The remainder of the star's interior carries energy away from the core through a combination of radiative and convective processes. These processes keep the star from collapsing upon itself and the energy generates a stellar wind at the surface and radiation into outer space.

24 life cycle

25 Hertzsprung-Russell diagram

26 the sun a typical second generation star approximately 4.5 billion years old 92.1% hydrogen 7.8% helium 0.1% heavy elements oxygen, carbon, nitrogen, silicon, magnesium, neon sulfur,

27 solar system

28 solar system formed at the same time as the Sun geocentric theory (Aristotle, Ptolemy) planets revolve around Earth heliocentric theory (Aristarchus, Copernicus) planets revolve around the sun

29 Aristotle ( BC) geocentric theory

30 heliocentric theory Aristarchus ( BC)

31 Ptolemy ( AD) Almagest published 150 A.D.

32 Nicholaus Copernicus ( )

33 Johannes Kepler ( ) Law of ellipses Law of equal areas Law of orbital harmony p 2 = k x d 3

34 law of ellipses The orbits of the planets are ellipses, with the Sun at one focus of the ellipse.

35 law of equal areas The line joining the planet to the Sun sweeps out equal areas in equal times as the planet travels around the ellipse.

36 law of orbital harmony The ratio of the squares of the revolutionary periods for two planets is equal to the ratio of the cubes of their semimajor axes: p 2 = k x d 3

37 Solar System Planets and dwarf planets of the Solar System while the sizes are to scale, the relative distances from the Sun are not

38 Solar System The Sun Giant Planets Kuiper Belt Object Scattered disc

39 Asteroid Belt The asteroid belt is the circumstellar disc in the Solar System located roughly between the orbits of the planets Mars and Jupiter. It is occupied by numerous irregularly shaped bodies called asteroids or minor planets.

40 Kuiper Belt estimated to stretch across 20 astronomical units (AU) of space. It contains small solar system bodies made mostly of ices

41 Planets defined The 2006 definition of "planet" by the International Astronomical Union (IAU) states that, in the solar system, a planet is a celestial body that: 1. is in orbit around the Sun, has sufficient mass so that it assumes a hydrostatic equilibrium (nearly round) shape, and has "cleared the neighborhood" around its orbit. A non-satellite body fulfilling only the first two of these criteria is classified as a "dwarf planet A non-satellite body fulfilling only the first criterion is termed a "small solar system body" (SSSB) The definition was a controversial one, and has drawn both support and criticism from different astronomers.

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45 Mercury Composite image of Mercury taken by MESSENGER

46 Venus Mariner 10 image 5 February 1974 Global radar view of Venus (without the clouds) from Magellan between 1990 and 1994

47 Earth

48 Mars

49 Mars

50 Asteroid belt

51 Jupiter From top to bottom: Io, Europa, Ganymede, Callisto Jupiter, captured by the Hubble Space Telescope

52 Saturn Saturn, captured by the Hubble Space Telescope

53 Uranus Uranus, captured by the Hubble Space Telescope

54 Neptune Neptune from Voyager 2 August 1989

55 Pluto (Charon)

56 Pluto (Charon) New Horizons Pluto & Charon by NASA July 2015

57 moons

58 Moon

59 Dark side of the moon

60 Apollo 11

61 40 year anniversary of Apollo 11 mission