Stars, starlight AND Light Information

OUTCOME QUESTION(S): S1-4-06: S1-4-07: How do astronomers measure the great distances in the universe? S1-4-07: What can an astronomer learn about a star by looking at light? Vocabulary & Concepts  Astronomical Unit Light-year Apparent magnitude Absolute magnitude Electromagnetic Energy Spectroscope

Scientific Notation (x 10X) 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 107 0.0000000055 is 5.5 x 10-9 2.6 x 105 is 260 000.0 2.6 x 10-5 is 0.000026 A positive exponent (107) means multiply by 10 that many times A negative exponent (10-5) means divide by 10 that many times

Earth to the Sun: 1 AU = 1.5 x 108 km (150000000) Distance and the Universe Common to use Astronomical Unit (A.U.) 1 A.U. = distance between the Earth and the Sun 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 Earth to the Sun: 1 AU = 1.5 x 108 km (150000000)

Nearest star - 4.1 x 1013 km away from Earth! That’s 41,000,000,000,000 km! Nearest star - 4.1 x 1013 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. 9.46 x 1012 km /year = 1 light-year P. Centari is 4.3 light-years away

Bright stars look close, but may be very far away Distances can be deceiving: Bright stars look close, but may be very far away Star Approx. Distance (LY) P. Centari 4.3 Sirius 8.8 Betelguese 700 Rigel 900 Most distant known galaxy 15,000,000,000 Star light takes years to get to Earth – this delay means we are looking at old “images” – it’s like looking into the past…

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

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

Despite being cooler, the Sun is still bigger than about 95% of stars Temperature of Colour Colour – shows how much energy a star emits. Colder star glows red Hotter star glows bluish white or even blue Colour Temperature (oC) Example Blue 25,000 – 50, 000 Bluish-white 11,000 – 25,000 Rigel (Orion’s belt) White 7,500 – 11,000 Sirius (brightest) Yellowish-white 6,000 – 7,500 Polaris Yellow 5,000 – 6,000 Sun Orange 3,500 – 5,000 Red 2,000 – 3,500 P. Centauri (closest) Despite being cooler, the Sun is still bigger than about 95% of stars

Notice bigger stars are not necessarily hotter…but usually brighter

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

Showing as the “black” lines of missing energy 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 The black lines in the spectrum are used to identify the elements that make up the star.

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!

CAN YOU ANSWER THESE QUESTIONS? S1-4-06: How do astronomers measure the great distances in the universe? S1-4-07: What can an astronomer learn about a star by looking at light? Vocabulary & Concepts  Astronomical Unit Light-year Apparent magnitude Absolute magnitude Electromagnetic energy Spectroscope

Stars, starlight AND The Big Bang

OUTCOME QUESTION(S): S1-4-07: What is the evidence for the Big Bang Theory? Vocabulary & Concepts  Electromagnetic spectrum Doppler Effect Red Shift Big Bang Astronomy Cosmology

Light /heat are types of Electromagnetic Energy Star light can be used to determine temperature, composition and size (mass) Light /heat are types of Electromagnetic Energy Hot objects (like stars) radiate different types of energies too – as temperature changes so does the main energy released

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

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

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

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

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

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 “s t r e t c h e d green”

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

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

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

CAN YOU ANSWER THESE QUESTIONS? S1-4-07: What is the evidence for the Big Bang Theory? Vocabulary & Concepts  Electromagnetic spectrum Doppler Effect Red Shift Big Bang Astronomy Cosmology