Universe 1

Astronomy 25 1

The High Mass Stars

Spectacular lives,spectacular deaths

Astronomy 25 2

O/B Stars

High-Mass vs Low-Mass

!High-mass stars 8-40 Msun O, B

!Low-mass stars 0.4-8 Msun F, G, K

!Red dwarfs 0.08-0.4 Msun M

!Brown dwarfs <0.08 Msun

L, T

O stars in the Rosette Nebula

Mass

Astronomy 25 3

O/B Stars

Lives of Low-Mass StarsSun-like Stars

1. Protostar

2. Main-sequence (F, G, K)

3. Red Giant

4. Horizontal Branch

5. Red Supergiant

6. Planetary Nebula

7. White dwarf (carbon-oxygen)

Universe 2

Astronomy 25 4

O/B Stars

Life of High-Mass StarsBlue Giants

1. Protostar

2. Main sequence (O, B)

3. Supergiant stages

4. Supernova

5. Neutron star or

(rarely ) Black hole

Astronomy 25 5

O/B Stars

Dead Stars

White Dwarf

Neutron Star

Black Hole

Astronomy 25 8

O/B Stars

Check Question

! White dwarf stars are the size of:

1) Los Angeles

2) The Earth

3) The Sun

Universe 3

Astronomy 25 9

O/B Stars

Novae

R Aquarii Nova 1073

Observed in Korea • Nova Persei 1901

"White dwarf binary.

"Hydrogen accumulates surface of white dwarf.

"Fusion starts explosively.

"Star becomes 1000x brighter!

Astronomy 25 10

O/B Stars

SupernovaeStars that go boom!

!End of life of high-mass stars

!Create heavy elements

!Trigger star formation

!Two kinds

#White dwarf supernovae (Type Ia)

#Core-collapse supernovae (Type II)

Fritz Zwicky

Astronomy 25 11

O/B Stars

Supernovae of the Last Millenium

!1006 Lupus

!1054 Taurus

!1181 Cassiopeia

!1572 Cassiopeia (Tycho's)

!1604 Ophiuchus (Kepler's)

!1670 Cassiopeia (Cas A)

SN 1006

Universe 4

Astronomy 25 12

O/B Stars

Check Question

! White dwarf stars…

1) Are all the same luminosity.

2) Are all the same mass.

3) Have a maximum mass.

Astronomy 25 13

O/B Stars

White Dwarf Supernova(Type Ia)

!White dwarf (carbon) in binary system

!Matter falls onto white dwarf

!Mass exceeds 1.4 Msun

!Star goes boom!

!All such supernovae are alike

Astronomy 25 15

O/B Stars

Core-Collapse Supernovae(Type II)

!High mass stars

!Fusion of elementsup to iron

Universe 5

Astronomy 25 16

O/B Stars

Core-Collapse Supernova!Sudden collapse of core

!Formation of neutron star

!Rebound of outer layers

!Explosion of star

!Luminosity ~ 100 billion suns

Astronomy 25 20

O/B Stars

Explosion of SN 1987a

!Core collapsed in <1 sec

!Energy of 100 x Sun's lifetime energy

!Most energy taken away by neutrinos

!0.4% went to explosion of gases

!1 part in 30,000 into light

!Peak luminosity 200 million Suns

#1000x Moon if at distance of Sirius

Astronomy 25 23

O/B Stars

Neutron Star

!Big nucleus

!Mass 1-2 Msun

!Size~Torrance

!Density~1015

Universe 6

Astronomy 25 24

O/B Stars

Pulsars

!Rotating neutronstar

!3-30 flashes/sec

!Millisecond pulsars

Astronomy 25 25

O/B Stars

Magnetars

!Neutron stars with powerful magnetic fields.

!Superflares:27 Dec 2004: other side of Milky Way3 Nov 2005: M81

Astronomy 25 26

O/B Stars

Check Question

! The Sun will end its life as a…

1) White dwarf

2) Neutron star

3) Black hole

Universe 7

Astronomy 25 27

O/B Stars

Binary Neutron Stars

!Giant star + neutron star

!X-ray bursters

!Millisecond pulsars

S433

Astronomy 25 28

O/B Stars

Gamma Ray Bursts

Last a few seconds

Found in all directions

Astronomy 25 29

O/B Stars

Gamma Ray Burst21 Nov. 2001

HST

Visible light

Universe 8

Astronomy 25 30

O/B Stars

What causes GRBs?

Neutron star merger

Hypernova

Astronomy 25 31

O/B Stars

Cycle of Star Stuff