Transcript Life and Death of Stars

Life and Death of Stars
Recapitulation of How Elements are
Formed
“If you wish to make an apple pie
from scratch, you must first invent
the universe.”
- Carl Sagan
Cosmos. New York: Random House. 1980.
The Big Bang and Soon After
The “Cosmic Microwave Background Radiation” (CMB), Present Day
"Ilc 9yr moll4096" by NASA / WMAP Science Team - http://map.gsfc.nasa.gov/media/121238/ilc_9yr_moll4096.png. Licensed under Public Domain via Wikimedia Commons http://commons.wikimedia.org/wiki/File:Ilc_9yr_moll4096.png#mediaviewer/File:Ilc_9yr_moll4096.png
The Big Bang and Soon After (ctd.)
Temp Cools from 10 Billion K to 1 Billion K
"Scheme of nuclear reaction chains for Big Bang nucleosynthesis" by Pamputt - Own work ; vectorisation de The main nuclear reaction chains for Big Bang nucleosynthesis.jpg. Licensed under CC BY-SA 4.0 via
Wikimedia Commons http://commons.wikimedia.org/wiki/File:Scheme_of_nuclear_reaction_chains_for_Big_Bang_nucleosynthesis.svg#mediaviewer/File:Scheme_of_nuclear_reaction_chains_for_Big_Bang_nucleosynthesis.svg
Life of a Small Star
Around the mass of
1 Sun up to ~5 Solar Masses
“Before she became a star…”
Nebula – Cloud of Gas (mostly H)
"Eagle nebula pillars" by Credit: NASA, Jeff Hester, and Paul Scowen (Arizona State University) - http://hubblesite.org/newscenter/newsdesk/archive/releases/2003/34/image/a. Licensed under Public Domain via
Wikimedia Commons - http://commons.wikimedia.org/wiki/File:Eagle_nebula_pillars.jpg#mediaviewer/File:Eagle_nebula_pillars.jpg
“On her way to the audition…”
Protostar (NOT A STAR YET)
"Witness the Birth of a Star" by NASA/JPL-Caltech/R. Hurt (SSC) - Image of the day gallery. Licensed under Public Domain via Wikimedia Commons http://commons.wikimedia.org/wiki/File:Witness_the_Birth_of_a_Star.jpg#mediaviewer/File:Witness_the_Birth_of_a_Star.jpg
Once it’s hot enough…
NUCLEAR FUSION
"FusionintheSun" by Borb. Licensed under CC BY-SA 3.0 via Wikimedia Commons - http://commons.wikimedia.org/wiki/File:FusionintheSun.svg#mediaviewer/File:FusionintheSun.svg
How Fusion Works
(Yes, you can actually know this.)
• Need very high temperatures, ~10-15 million K
• Protons overcome repulsion
– Stick due to “Strong Nuclear Force”
• Mass of 4 p+ > Mass of 1 He
– Where did the missing mass go?
How Fusion Works
(ctd.)
• E = mc2
• Lost mass is converted
to energy!
• Basis for all fusion
processes that release
(or absorb) energy
“A star is born!”
Main Sequence – Doing H Fusion
"The Sun in extreme ultraviolet" by NASA - [1]. Licensed under Public Domain via Wikimedia
Commons http://commons.wikimedia.org/wiki/File:The_Sun_in_extreme_ultraviolet.jpg#mediaviewer/File:Th
e_Sun_in_extreme_ultraviolet.jpg
"Sirius A and B Hubble photo" by NASA, ESA, H. Bond (STScI), and M. Barstow (University of
Leicester) - http://www.spacetelescope.org/images/html/heic0516a.html. Licensed under CC BY
3.0 via Wikimedia Commons http://commons.wikimedia.org/wiki/File:Sirius_A_and_B_Hubble_photo.jpg#mediaviewer/File:Siri
us_A_and_B_Hubble_photo.jpg
After billions of years…
• H fuel runs out in the
middle, He accumulates
• Not hot enough to fuse
together He atoms
• Gravity starts to take
over!
“She suffered a partial collapse…”
A Small Star Evolves
• Outside comes in, REHEATING DUE TO
GRAVITATIONAL POTENTIAL
• It’s Red Giant time!
• Hot enough to fuse He into C, N
• (See next slide for size comparison)
Red Giant Stage –
An Old “Small” Star
"The life cycle of a Sun-like star (annotated)" by ESO/M. Kornmesser - http://www.eso.org/public/images/eso1337a/. Licensed under CC BY 4.0 via Wikimedia Commons http://commons.wikimedia.org/wiki/File:The_life_cycle_of_a_Sun-like_star_(annotated).jpg#mediaviewer/File:The_life_cycle_of_a_Sun-like_star_(annotated).jpg
“So explosive!”
Losing the Shell – Planetary Nebula
• Fusion of He to C, N
releases much more
energy
• Gravity can’t hold it
together
• Loses the outer gases –
Planetary Nebula
– NOTHING TO DO WITH
PLANETS
"Seeing into the Heart of Mira A and its Partner" by ESO/S. Ramstedt (Uppsala University,
Sweden) & W. Vlemmings (Chalmers University of Technology, Sweden) http://www.eso.org/public/images/potw1447a/. Licensed under CC BY 4.0 via Wikimedia
Commons http://commons.wikimedia.org/wiki/File:Seeing_into_the_Heart_of_Mira_A_and_its_Partner.jpg#
mediaviewer/File:Seeing_into_the_Heart_of_Mira_A_and_its_Partner.jpg
Another Planetary Nebula
"M57 The Ring Nebula" by The Hubble Heritage Team (AURA/STScI/NASA) - http://hubblesite.org/newscenter/archive/releases/1999/01/image/a/ (direct link). Licensed under Public Domain via
Wikimedia Commons - http://commons.wikimedia.org/wiki/File:M57_The_Ring_Nebula.JPG#mediaviewer/File:M57_The_Ring_Nebula.JPG
“How do you feel inside?”
The Leftover Core – White Dwarf
• Core is white hot, but
NOT hot enough to fuse
C with C
• Most white dwarfs
simply fade out over a
LONG time
– Theoretical “black
dwarf” is typical fate
• But there may be
another way to go out!
"Sirius A and B Hubble photo.editted" by Bokus http://upload.wikimedia.org/wikipedia/commons/f/f3/Sirius_A_and_B_Hubble_photo.jpg.
Licensed under Public Domain via Wikimedia Commons http://commons.wikimedia.org/wiki/File:Sirius_A_and_B_Hubble_photo.editted.PNG#mediaviewe
r/File:Sirius_A_and_B_Hubble_photo.editted.PNG
Type Ia Supernova
“She got help from a friend…”
Enough energy is released to fuse C into
elements heavier than C.
"Progenitor IA supernova" by NASA, ESA and A. Feild (STScI); vectorisation by chris 論 - http://hubblesite.org/newscenter/archive/releases/star/supernova/2004/34/image/d/. Licensed under CC BY
3.0 via Wikimedia Commons - http://commons.wikimedia.org/wiki/File:Progenitor_IA_supernova.svg#mediaviewer/File:Progenitor_IA_supernova.svg
Type Ia Supernova –
Example
High-Z Supernova Search Team/HST/NASA
Life of a Large Star
Around the mass of
8 Suns and up
Large Stars on the Main Sequence
More mass → More gravitational energy →
Higher core temperature → Faster fusion rate
→ Shorter time on the main sequence
"Hot and brilliant O stars in star-forming regions" by ESO - http://www.eso.org/public/images/eso1230b/. Licensed under CC BY 3.0 via Wikimedia Commons http://commons.wikimedia.org/wiki/File:Hot_and_brilliant_O_stars_in_star-forming_regions.jpg#mediaviewer/File:Hot_and_brilliant_O_stars_in_star-forming_regions.jpg
A Large Star Evolves –
Red Supergiant Stage(s)
• Akin to small mass star,
fuel runs out, core
reheats, fusing He to C
• Enough mass to repeat
the process, fusing
heavier and heavier
elements
– Ne, Mg, Al, for example
– All the way up to Fe
• Resembles an onion
Betelgeuse at upper left is a red supergiant
"Orion Head to Toe" by Rogelio Bernal Andreo - http://deepskycolors.com/astro/JPEG/RBA_Orion_HeadToToes.jpg. Licensed under CC BY-SA 3.0 via Wikimedia Commons http://commons.wikimedia.org/wiki/File:Orion_Head_to_Toe.jpg#mediaviewer/File:Orion_Head_to_Toe.jpg
“A total collapse!”
End of a Large Star
• Fe builds up in the core
• Not enough outward
pressure
– Gravity takes over
• Outer layers rush in,
and BOUNCE off the
core
– Enough energy released
to fuse ANY naturally
occurring element
– Surplus of energy can
form Au, Pb, I, etc.
"HST SN 1987A 20th anniversary" by NASA, ESA, P. Challis, and R. Kirshner (HarvardSmithsonian Center for Astrophysics) http://hubblesite.org/newscenter/archive/releases/2007/10/image/a/ (direct link). Licensed under
Public Domain via Wikimedia Commons http://commons.wikimedia.org/wiki/File:HST_SN_1987A_20th_anniversary.jpg#mediaviewer/File:
HST_SN_1987A_20th_anniversary.jpg
The Aftermath –
Neutron Stars and Black Holes
"IsolatedNeutronStar" by Original uploader was Northgrove at en.wikipedia - Transferred from
en.wikipedia. Licensed under Public Domain via Wikimedia Commons http://commons.wikimedia.org/wiki/File:IsolatedNeutronStar.jpg#mediaviewer/File:IsolatedNeutro
nStar.jpg
"BH LMC" by User:Alain r - Own work. Licensed under CC BY-SA 2.5 via Wikimedia Commons http://commons.wikimedia.org/wiki/File:BH_LMC.png#mediaviewer/File:BH_LMC.png
Other Element Formation –
Cosmic Rays
• High-energy particles
either left over from the
Big Bang or ejected
from stars/supernovae
• Slam into heavier
elements occasionally
and split them into
smaller nuclei
– E.g., Li, Be, B
Earth’s Moon blocks muon cosmic rays
"Moon's shadow in muons" by http://hepweb.rl.ac.uk/ppUKpics/POW/pr_990602.html. Licensed
under Fair use via Wikipedia http://en.wikipedia.org/wiki/File:Moon%27s_shadow_in_muons.gif#mediaviewer/File:Moon%27s_
shadow_in_muons.gif
Summary –
Different Processes Make Elements
• Big Bang – H, He, Li (a little)
• Small Mass Stars
– He (main sequence)
– C, N (red giant)
– Heavier than C (only type Ia supernova)
• Large Mass Stars
– He (main sequence)
– C, N, etc., all the way up to Fe (red supergiant)
– All natural elements (only type II supernova)
• Cosmic Rays – Li, Be, B (split off from larger atoms)