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Stellar Evolution Part III
1
Planetary
Nebulae
Dr. Bill Pezzaglia
Updated March 23, 2009
I. Introduction
According to CNN the world will end
Dec 21, 2012
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As usual, they got it wrong
The world will end:
Dec 21,
5,000,002,012
The sun will….
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Planetary Nebulae
I.
II.
III.
IV.
V.
Introduction
Discovery
Spectra
Evolution
Summary
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II. Discovery
A. Messier’s Catalog
B. Herschel names them
C. Nebular Hypothesis Interpretation
A. Messier Catalog
Charles Messier (1730-1817) was
hunting for comets. People kept
reporting the same fuzzy blobs that
were NOT comets, so from 1758-1782
he made a catalog of about 100 of
these fuzzy things to “ignore”.
In fact, these 110 objects are nebulae,
star clusters and galaxies, which are
the best things to look for in an
amateur telescope!
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The Summer Triangle
Deneb
Cygnus
The Swan
Vega
Lyra
The Harp
Altair
Aquila
The Eagle
M57 (1779)
Ring Nebula
In Lyra
1’ in diameter
Made of stars?
M27: July 12, 1764
Dumbbell Nebula
In Vulpecula
6’ in diameter
B. 1781: Uranus Discovered
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(accidentally!) by William Herschel using a 6 inch telescope
Herschel Classifies Nebulae
• 1785 Catalog of 1000 objects
• 1788 another 1000 objects
• 1802 another 500 objects
Classifies objects into star clusters and
nebulae. The “types” were:
1.
2.
3.
4.
5.
6.
7.
Bright Nebulae
Faint Nebulae
Very faint Nebulae
Planetary Nebulae (Uranus-like in color & shape)
Very large Nebulae
Very compressed and rich star clusters
Compressed clusters of small and large
(i.e., faint and bright) stars
8. Coarsely scattered clusters of stars
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C. Nebular Hypothesis
• Herschel (1786) thought that “Planetary
Nebulae” might be a cloud of gas
coalescing into a star to be surrounded by
planets (hence the name)
• “Nebular Hypothesis” had been theoretically
proposed earlier
(1734 Swedberg, 1755 Kant)
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III. The Message in the Light
A. Atomic Spectra Lines
B. Huggins & Nebulium
C. Central Stars are White Dwarfs
A.1. Dark Line Spectra
•
1802 Wollastan sees lines in solar spectra
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1814 Fraunhofer Labels
them A, B, C, D
•
Later measures over 500 lines!
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A.2. Solar spectrum
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A.3. Bright Line Spectra
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•
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1857 Bunsen’s burner, a clean
flame with no color
1859 Kirchhoff suggest using
it to study spectra of elements
in flame
Each element has a unique
set of “bright line” (emission)
spectra
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A.4. Kirchhoff’s Laws
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B. 1786 Herschel discovers:
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Draco the Dragon
Ursa Major
H IV 37 (NGC6543)
Cats Eye Nebula
Ursa Minor
Polaris
B.2 William & Margaret Huggins
• (1864) Spectra of Cat’s Eye Nebula
shows single emission line in green
• Implies it’s a gas, NOT made of stars
(which would have absorption lines)
• Unknown element “Nebulium” makes
greenish color
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Tom Lehrer: Elements
B.2 William & Margaret Huggins
• (1864) Spectra of Cat’s Eye Nebula
shows single emission line in green
• Implies it’s a gas, NOT made of stars
(which would have absorption lines)
• Unknown element “Nebulium” makes
greenish color
• (1926) Bowen shows Nebulium is
really Oxygen & Nitrogen under
extraordinary conditions
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C. Central Star: White Dwarf!
• 1800 Friedrich von Hahn
discovers central star of Ring
Nebula (very faint)
• Central Stars have Hydrogen,
Helium and sometimes Carbon
& Oxygen lines.
• 1918 Wright identifies as type
“O” [VERY HOT 125,000 C],
hence must be very very small
to be so faint!
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IV. Evolution & Age
A. Age of Planetary Nebula
B. Distance to Planetary Nebula
C. Did it explode?
A. Exploded Stars
• (1956) Iosif Shklovsky proposes that
red giant stars explode and form a
planetary nebular
• In 100 years, M27 has expanded 2”
• Today it is 5’=300” in size
• How old is it?
• (300”)(100 yr/2”)= 15,000 years
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B.1. Doppler Effect with Sound
1842 Christian Doppler shows “detected” frequency fd
depends upon:
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 v
f d  f s 1  
fs frequency of source
c


v relative speed between detector and source
•
•
• c velocity of sound in medium
• So if moving 10% speed of sound towards you, the
frequency will be increased 10%
B.2. Doppler Effect with Light
Amount of shift of color
is proportional to
speed: v/c = /
A 10% shift in
wavelength means
10% speed of light
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C.1. Size of Dumbbell
•
•
(1970) Dumbbell has Doppler shift of 0.01%
(0.0001)c=(0.0001)(300000km/s)=30 km/sec
•
In 1 year expands:
30 3600 24 365   Billion km
km
sec
•
sec
hr
hr
day
day
year
In 15,000 years has expanded to size:
15,000 yr billion km 
15 trillion km
(1.5 light year)
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C.2. Distance to Dumbbell
•
Recall the “parallax triangle”
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Hence if the size is 100,000 AU and makes
an angle of 300”, how far away is it?
 size   100,000 AU  333 parsecs
  
D  

300"

 angle  
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Review
•
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First Planetary Nebula Discovered was
(a) Ring Nebula
(b) Cats Eye Nebula
(c) Double Helix Nebula
(d) Dumbbell Nebula
(e) Orion Nebula
Vega
Lyra
The Harp
Cats Eye Nebula
Type: Planetary Nebula
Where: DRACO
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Dumbell Nebula
Catalog: M27
Type: Planetary Nebula
Where: VULPECULA
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Double Helix Nebula
Type: Planetary Nebula
Where: AQUARIUS
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Hourglass Nebula
Type: Planetary Nebula
Where: MUSCA
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Review
•
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First Planetary Nebula was discovered by
(a) Huggins
(b) Herschel
(c) Fraunhofer
(d) Messier
(e) Kant
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Review
•
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Age of a planetary nebula is about
(a) 100 years
(b) 10,000 years
(c) 100,000 years
(d) 10 Million years
(e) 10 Billion years
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Review
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Size of a planetary nebula is about
(a) 1 AU
(b) 1 km
(c) 1 light year
(d) 1000x size of sun
(e) 1 MPC
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Review
4. Planetary Nebula
(a) are the disk of material left over from a star formation that will form its planets
(b) are made of a close group of stars that are hard to resolve
(c) Are exploded stars
(d) are a nebula that has yet contracted to form a star
(e) Are Uranus-like planets
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V. Summary
•
•
Discovered by Messier (first one M27)
Herschel interprets as planetary systems forming
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VI References
• Historial M27 http://www.maa.clell.de/Messier/Mdes/dm027.html
• Huggins http://www.maa.clell.de/Messier/E/Xtra/Bios/huggins.html
• History: http://en.wikipedia.org/wiki/Planetary_nebula#Observations