1. Stars, starlight AND The Big Bang

2. OUTCOME QUESTION(S): S1-4-06: How do astronomers measure the great distances in the universe? S1-4-07: What is the evidence for the Big Bang Theory? Vocabulary & People Astronomical UnitLight-yearApparent magnitude Absolute magnitudeSpectroscope Electromagnetic spectrumDoppler Effect Red ShiftBig BangAstronomy Cosmology

3. Scientific Notation (x 10 X ) Express very large or very small numbers “Power of 10” equals the number of places the decimal was moved (+) large, (-) small 32 000 000.0 is 3.2 x 10 7 0.0000000055 is 5.5 x 10 -9 2.6 x 10 5 is 260 000.0 2.6 x 10 -5 is 0.000026 Putting values into Sci. Notation is a very useful skill

4. Distance and the Universe Common to use Astronomical Unit (A.U.) 1 A.U. = distance between the Earth and the Sun Sun to the Earth: 1 AU = 1.5x10 8 km Common Distances: Sun - Pluto: ~ 40 AU Sun - Saturn: ~ 10 AU Sun - Jupiter: ~ 5 AU Sun - Mars: ~ 1.5 AU So Pluto is 40x farther away from the Sun than Earth

5. Nearest star - 4.1x10 13 km away from Earth! This star is Proxima Centari Light-year (LY): The distance a beam of light travels in one year Light moves outward fast – about 300,000 km/sec. 9.46x10 12 km /year = 1 light-year P. Centari is 4.3 light-years away That’s 41,000,000,000,000 km!

6. Distances can be deceiving: Bright stars look close, but may be very far away Star Approx. Distance (LY) P. Centari4.3 Sirius 8.8 Betelguese 700 Rigel 900 Most distant known galaxy15,000,000,000 Star light takes years to get to Earth – this delay means we are looking at old “images” – it’s like looking into the past…

7. Luminosity (brightness) There are two amounts (magnitudes) of brightness: Apparent magnitude – brightness as we see it. Absolute magnitude – actually brightness. The Sun has a higher apparent magnitude, since it is so much closer than other stars Star light can be used to determine temperature, composition and size (mass)

8. Star B looks brighter – more apparent magnitude Star B is closer to us than Star A Star B and A have the same absolute magnitude

9. Temperature of Colour Colour – shows how much energy a star emits. Colder star glows red Hotter star glows bluish white or even blue ColourTemperature ( o C)Example Blue25,000 – 50, 000 Bluish-white11,000 – 25,000Rigel (Orion’s belt) White7,500 – 11,000Sirius (brightest) Yellowish-white6,000 – 7,500Polaris Yellow5,000 – 6,000Sun Orange3,500 – 5,000 Red2,000 – 3,500P. Centauri (closest) Despite being cooler, the Sun is still bigger than about 95% of stars

10. Notice bigger stars are not necessarily hotter…but usually brighter

11. Star Composition Scientists use a spectroscope to analyse the light energy coming from stars Light is a type of energy called: Electromagnetic Energy Spectroscope – tool that splits light into a pattern of colours, like a rainbow.

12. The black lines in the spectrum are used to identify the elements that make up the star. The elements that make the star will absorb unique parts of the spectrum as energy is released. Showing as the “black” lines of missing energy

13. Remember your chemistry: heated compounds give off a unique colour spectrum. Scientists have heated elements and recorded the unique light energy patterns The “missing” black lines in the spectra of the Sun match with the known spectra of Hydrogen but not with Mercury – so the Sun contains Hydrogen!

14. Electromagnetic Spectrum of Energies Low energy High energy Red light is low energy – cool Blue is high energy - hot Because of the shape of the waves, the colours always separate into this same organized pattern HEAT This is why other telescopes and tools are needed – we can only access a small amount of informational energy from stars

15. There is evidence that the universe is expanding: - Red-shift of light from stars and galaxies - Cosmic Microwave Background Radiation - Gravitational waves (new) We’re going to focus on the oldest, and simplest – “red-shift” 1. Light waves work exactly like any other wave: Waves can be far apart - long wavelength Waves can be close together - short wavelength Red-Shift and the Big Bang Long wavelegth Short wavelength

16. 2. Waves are also affected by motion. Noticeable effect is called the Doppler Effect Stationary: all waves move outward evenly Moving – compressed in front, spread out in back You have experienced this effect with sound waves

17. Higher pitch Lower pitch You brain hears the distorted wave pattern as a different sound then is really being made by the ambulance Doppler effect: Sound waves

18. You brain sees the distorted wave pattern as a different colour then is really being made by the object Doppler effect: Light waves Bluer colour Redder colour

19. a compressed green light appears more blue “blue shift” a s t r e t c h e d green light appears more red “red shift” Your eyes don’t know what colour it “should” be, it can only interpret the waves it sees – it can’t tell the difference between “red” and “stretched green”

20. 3. Spectra of ALL stars / galaxies show red shift. Far away galaxies show more red shift - faster “red shift” spectra “blue shift” spectra Normal spectra Evidence that the universe is expanding and speeding up too – think of it as the first half of an explosion

21. The universe is expanding: Must have started out from one point – singularity Reverse the explosion – the Universe must have started from a packed, dense mass of material under pressure Big Bang Rapid expansion of Universe from the singularity Evidence suggests Universe is 14 billion years old Scientists cannot yet explain all “how” or “why” Not the only explanation of the universe origin BUT beliefs are not theories – only scientific theories can be tested and proven

22. Astronomy – study of all objects in the universe. Cosmology – study of the origin of the universe.

23. CAN YOU ANSWER THESE QUESTIONS? S1-4-06: How do astronomers measure the great distances in the universe? S1-4-07: What is the evidence for the Big Bang Theory? Vocabulary & People Astronomical UnitLight-yearApparent magnitude Absolute magnitudeSpectroscope Electromagnetic spectrumDoppler Effect Red ShiftBig BangAstronomy Cosmology