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