Planetary Nebulae

Dr. Bill Pezzaglia

Stellar Evolution Part III 1

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. Introduction

II. Discovery

III. Spectra

IV. Evolution

V. Summary

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II. Discovery

A. Messier’s Catalog

B. Herschel names them

C. Nebular Hypothesis Interpretation

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A. Messier Catalog 6

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!

The Summer TriangleDeneb

CygnusThe Swan Lyra

The Harp

Vega

Altair AquilaThe Eagle

M27: July 12, 1764Dumbbell NebulaIn Vulpecula6’ in diameter

M57 (1779)Ring NebulaIn Lyra1’ in diameterMade of stars?

(accidentally!) by William Herschel using a 6 inch telescope

B. 1781: Uranus Discovered8

Herschel Classifies Nebulae 9

• 1785 Catalog of 1000 objects• 1788 another 1000 objects• 1802 another 500 objects

Classifies objects into star clusters and nebulae. The “types” were:

1. Bright Nebulae 2. Faint Nebulae 3. Very faint Nebulae 4. Planetary Nebulae (Uranus-like in color & shape)5. Very large Nebulae 6. Very compressed and rich star clusters 7. Compressed clusters of small and large

(i.e., faint and bright) stars 8. Coarsely scattered clusters of stars

C. Nebular Hypothesis 10

• 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)

III. The Message in the Light

A. Atomic Spectra Lines

B. Huggins & Nebulium

C. Central Stars are White Dwarfs

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A.1. Dark Line Spectra• 1802 Wollastan sees lines in solar spectra

• 1814 Fraunhofer Labelsthem A, B, C, D

• Later measures over 500 lines!

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A.2. Solar spectrum 13

A.3. Bright Line Spectra• 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 Laws15

B. 1786 Herschel discovers:16

Ursa Major

Ursa Minor

Polaris

Draco the Dragon

H IV 37 (NGC6543)Cats Eye Nebula

B.2 William & Margaret Huggins 17

• (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

Tom Lehrer: Elements

B.2 William & Margaret Huggins 19

• (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

C. Central Star: White Dwarf! 20

• 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!

IV. Evolution & Age

A. Age of Planetary Nebula

B. Distance to Planetary Nebula

C. Did it explode?

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A. Exploded Stars 22

• (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

B.1. Doppler Effect with Sound1842 Christian Doppler shows “detected” frequency fd

depends upon:

• fs frequency of source• 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%

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c

vff sd 1

B.2. Doppler Effect with Light 22

Amount of shift of color is proportional to speed: v/c = /

A 10% shift in wavelength means 10% speed of light

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:

• In 15,000 years has expanded to size:

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yearday

dayhr

hrkm 36524360030 secsec Billion km

kmbillionyr000,15 15 trillion km(1.5 light year)

C.2. Distance to Dumbbell

• Recall the “parallax triangle”

• Hence if the size is 100,000 AU and makes an angle of 300”, how far away is it?

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"300

000,100 AU

angle

sizeD 333 parsecs

Review

• First Planetary Nebula Discovered was• (a) Ring Nebula• (b) Cats Eye Nebula• (c) Double Helix Nebula• (d) Dumbbell Nebula• (e) Orion Nebula

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LyraThe Harp

Vega

Cats Eye Nebula 6

Where: DRACO

Type: Planetary Nebula

Dumbell Nebula 6

Catalog: M27

Where: VULPECULA

Type: Planetary Nebula

Double Helix Nebula 6

Where: AQUARIUS

Type: Planetary Nebula

Hourglass Nebula 6

Where: MUSCA

Type: Planetary Nebula

Review

• First Planetary Nebula was discovered by• (a) Huggins• (b) Herschel• (c) Fraunhofer• (d) Messier• (e) Kant

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Review

• 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

• 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

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