Chapter 10: The Death of Stars (part b)
The evolution of low-mass vs. that of high-mass stars.
Planetary nebulae and the formation of white dwarf stars.
Supernova explosions: two types
Type I: due to “carbon detonation” of an accreting white dwarf in a binary.
Type II: due to “core collapse” in a high-mass star.
Both types of supernovae leave behind remnants.
Evidence from clusters confirms our theories of stellar evolution.
Compact objects: neutron stars, pulsars, quark stars, and black holes.
High-Mass stellar evolutionary tracks are quite different from the low-mass
stellar evolution tracks. Notice that
the core can heat up so fast that the
envelope of the star tends to lag behind. Carbon fusion can
start before the red giant phase.
Heavy Element Fusion- shells like an onion
Supernova 1987A seen near nebula 30 Doradus
1994
SN2005cs in M51(Whirlpool galaxy) discovered June 27, 2005
SN2005cs in M51(Whirlpool galaxy) discovered June 27, 2005
Supernovae in our galaxy have been infrequent.
• Historical supernovae in the Milky Way (none observed by telescope !!!!): http://www.seds.org/messier/more/mw_sn.html
• Recent supernovae by date: http://cfa-www.harvard.edu/iau/lists/RecentSupernovae.html
• All supernovae since 1885: http://cfa-www.harvard.edu/iau/lists/Supernovae.html
• Links for supernovae on the web: http://rsd-www.nrl.navy.mil/7212/montes/sne.html
• Latest supernovae (by current brightness !): http://www.rochesterastronomy.org/supernova.html
• Supernova SN2005cs in M51 (Whirlpool galaxy): http://www.rochesterastronomy.org/sn2005/sn2005cs.html also see: http://antwrp.gsfc.nasa.gov/apod/ap050719.html
Supernova Light Curves fall into two types
Two Types of Supernova (see following slides)
Type I Supernova is a “carbon detonation” and involves a white dwarf which completely explodes.
As material accretes on the white dwarf from a binary companion, it’s mass finally reaches a critical limit, and the entire carbon core fuses
to heavier elements, all at once.
A moreelaboratetheory of a Type Iasupernovamight show how someplanetarynebula get spiral shapes.
Type II Supernova is a “core collapse” and occurs when the core is finally pure iron, which cannot be fused to other elements. The core collapses
to a big ball of neutrons, which causes a shock wave to bounce back outward, which blows off the entire envelope
of the red giant, to form a supernova remnant.
Prior to detonation, the massive star can lose a large fraction of its mass. This material forms an expanding shell.
Computer simulations show lots of turbulence in the explosion.
Supernova Remnants
Vela supernova remnant
Other examples:
Cassiopeia A (link) (link) N63A (link)
Crab nebula
M1 – the Crab Nebula
is from a supernova seen in year A.D. 1054
The remnant is 1800 pc away and the diameter is currently 2 pc.
This supports the elaborate model of Type Ia supernovae
Supernova 1987A was not typical (link)
Supernova 1987A
link link link link
See mpeg animations of this.
Eta Carinae will probably go supernova
in the next 100,000
years or so.
SEDS link
Cluster Evolution on the H–R Diagram
Newborn Cluster after 10 million years
Newborn Cluster after 10 million
years
Notice that there are
already some red giants from massive
stars that have already run out of
hydrogen fuel.
Young Cluster after 600 million years
Young Cluster after 600 million years
Notice that the cutoff is at Type A stars and that there are already
some white dwarfs.
Old Cluster after 12 billion years
Old Cluster after 12 billion years
Many more stars give a better statistical
sample, and we see the main features
of stellar evolution.
The Cycle of Stellar Evolution
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