Download light energy

Stars, starlight
AND
Light
Information
OUTCOME QUESTION(S):
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
Apparent magnitude
Light-year
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
A positive exponent (107) means multiply by 10 that many times
2.6 x 105
2.6 x 10-5
is 260 000.0
is 0.000026
A negative exponent (10-5) means divide by 10 that many times
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 - Jupiter: ~ 5 AU
Sun - Saturn: ~ 10 AU
Sun - Mars: ~ 1.5 AU
40x farther
away
Sun
8 than
EarthSo
toPluto
the isSun:
1 AU
= from
1.5 the
x 10
km Earth
(150000000)
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
• 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
Star light takes years to get to Earth – this delay means
Rigel
we are looking at old “images” – it’s like looking into the
past…
900
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
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.
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
Apparent magnitude
Light-year
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
Effect
Red Shift
Cosmology
Doppler
Big Bang
Astronomy
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
Low energy
High energy
Because
of the
shape
of the waves,
the colours
always –
separate
This
is why
other
telescopes
and tools
are needed
we can
into this
sameof
organized
pattern
only access a small
amount
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
wavesexactly
(new) like any other wave:
1.
Light waves work
•
•
We’re going
focus
the oldest,
and simplest
– “red-shift”
Waves
cantobe
faronapart
- long
wavelength
Waves can be close together - short wavelength
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
Doppler effect:
Sound waves
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:
Light waves
Bluer colour
Redder colour
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
Normal spectra
“red shift” spectra
“blue shift” 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
Effect
Red Shift
Cosmology
Doppler
Big Bang
Astronomy