Transcript Star

Big Questions
•If astronomers measure an object’s apparent
brightness (flux), what do they need to know to figure
out how far away that object is?
•Why are astronomers interested in different parts of the
electromagnetic spectrum?
•How do an object’s size and temperature affect the
light it emits, both the quantity and the color?
•How can astronomers take a star’s temperature from
so far away?
Below are four Honda Civics driving toward you at sunset
with their headlights turned on. Each car is equipped with
identical headlights.
QuickTime™ and a
TIFF (LZW) decompressor
are needed to see this picture.
Rank the distance that each car is from you from
greatest to least.
Below are four Honda Civics driving toward you at sunset
with their headlights turned on. Each car is equipped with
identical headlights.
QuickTime™ and a
TIFF (LZW) decompressor
are needed to see this picture.
Rank the apparent brightness (flux) of each car’s
headlights from greatest to least.
Below are four Honda Civics driving toward you at sunset
with their headlights turned on. Each car is equipped with
identical headlights.
QuickTime™ and a
TIFF (LZW) decompressor
are needed to see this picture.
Rank the absolute brightness (luminosity) of each
car’s headlights from greatest to least.
The figure below shows five stars (A-E) as they appear
in the night sky from Earth. A darker shade is used to
indicate the appearance of a dimmer star. The
distances to each star are unknown.
Rank the flux of each star from greatest to least.
1
3
2
4
5
The figure below shows five stars (A-E) as they appear
in the night sky from Earth. A darker shade is used to
indicate the appearance of a dimmer star. The
distances to each star are unknown.
Rank the luminosity of each star from greatest to
least.
1
3
2
4
5
Visible Rusty
Infrared Rusty
USA - Visible
USA - IR
USA - gamma
QuickTime™ and a
TIFF (Uncompressed) decompressor
are needed to see this picture.
USA - radio
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TIFF (Uncompressed) decompressor
are needed to see this picture.
The Whirlpool Galaxy, M51
Infrared: warm dust
Radio: cold gas &
magnetic fields
Visible: stars
Ultraviolet: young stars
X-ray: black holes
and neutron stars
 Atomic H gas
 GMCs
 dust
 Forming stars
 Stars
 Hot gas & binaries
 Cosmic rays
colliding with the
interstellar meduim
Infrared light has
1-greater
2-less
energy than ultraviolet light
X-ray photons have
1-longer
2-shorter
wavelengths than gamma ray photons
Visible electromagnetic radiation has a
1-higher
2-lower
frequency than radio wave electromagnetic
radiation
Infrared light has a
1-faster
2-slower
speed than microwave light
Of all the types of light the sun gives off, it emits the
greatest amount of light at visible light wavelengths. If
the sun were to cool off dramatically and as a result
start giving off mainly light at wavelengths longer than
visible light, how would the frequency, energy and
speed of this light given off by the sun also be different?
Frequency :
Energy:
Speed:
A
B
C
D
E
The hot plates are shaded according to
temperature (darker shading means colder).
Rank the hotplates in order by how much light
they emit.
Emits most light ___ ___ ___ ___ ___ Emits least light
Below is the information about several stars.
Rank the stars in order by the total amount of light
they emit.
Star
Radius [Rsun] Temperature [K] Distance [lyr]
alpha
1
4,000
25
beta
1
2,000
78
gamma
2
8,000
13
delta
4
16,000
104
epsilon
2
2,000
57
Emits most light ___ ___ ___ ___ ___ Emits least light
Which stars are hottest? Coolest?
Which stars are hottest?
Color  Temperature!
The figure below is a graph of luminosity and temperature.
Which group of stars is the red giants?
2
1
3
4
The figure below is a graph of luminosity and temperature.
Which group of stars is the white dwarfs?
2
1
3
4
The figure below is a graph of luminosity and temperature.
Which group of stars is the red dwarfs?
2
1
3
4
Flux
Blue
Red
Wavelength (nm)
Which star is the hottest?
Star 1
Star 3
Star 2
What color is Star 2?
(The visible part of the
spectrum goes from 4000 to
7000 on this scale).
Star 3
Star 1
Star 2
Big Questions
•How does light interact with matter?
•How does quantum mechanics affect these
interactions?
•How do the spectra of opaque and non-opaque objects
differ?
•When do astronomers observe absorption lines vs
emission lines?
•What information can astronomers learn directly from
the spectrum of an object?
Questions about Emission and Absorption:
The picture to the right is of the Ring Nebula -a bubble of gas surrounding a small star.
A
B
If you aimed the Hubble Space Telescope at
box A and took a spectrum, what would you
expect to see?
1- Emission lines
2- Absorption lines
3- Blackbody continuum
4- None of the above
Questions about Emission and Absorption:
The picture to the right is of the Ring Nebula -a bubble of gas surrounding a small star.
A
B
If you aimed the Hubble at box B and took a
spectrum what would you expect to see?
(Note - box B contains a star)
1- Emission lines
2- Absorption lines
3- Blackbody continuum
4- None of the above
Below is the spectrum for the planet Mars
from UV to IR.
Which portion of the spectrum is created by
reflected sunlight?
1
2
3
4
5
Below is the spectrum for the planet Mars
from UV to IR.
Which portion of the spectrum is created by
hot carbon dioxide gas in the upper
atmosphere of Mars?
1
2
3
4
5
Below is the spectrum for the planet Mars
from UV to IR.
Which portion of the spectrum is created by
Mars’ own blackbody radiation?
1
2
3
4
5
Below is the spectrum for the planet Mars
from UV to IR.
What color does Mars appear?
1
2
3
4
5
Below is the spectrum for the planet Mars
from UV to IR.
Which portion of the spectrum is created by
absorption by the red soil of Mars?
1
2
3
4
5
The visible light emitted by hydrogen is caused by
transitions from higher energy levels down to the 1st
excited state. Below is the emission spectrum of
hydrogen gas.
• Draw an atom, including a nucleus and five energy
levels.
• Using a dot to represent the electron and an arrow to
represent its motion, sketch and label what happens to
the electron to create the red emission line.
• On the same drawing, sketch what happens to the
electron to create the blue emission line.