Transcript Massive Stars - University of Washington

Massive Stars:
Party Hard, Live Fast, Die Explosively
Phil Rosenfield
How did they come up with this?
Death Star Explosion
Goals of this talk
Understand how mass determines a star’s path to
ultimate demise
Appreciate the craziness of very massive stars
Be able to talk about our current understanding of
 Carinae
How Massive are Stars?
Compared to our Sun,
how little mass could a
star possibly have to still
be considered a star?
millionth the
1 1thousandth
themass
massofofthe
theSun?
Sun?
Our Sun is an
average star.
What Makes a Star a Star?
Fusion More Likely
A body that satisfies two conditions:
(a) It is bound by self-gravity
Hotter Core
(b) It radiates energy supplied by and internal source
An introduction to the theory of
stellar structure and evolution
by Dina Prialnik
Central Pressure
Gravity
After detailed calculations, 0.08 Solar Mass is the smallest mass
to start core fusion of Hydrogen.
Mass
Could a Star Have a Maximum Mass?
Compared to our Sun,
how much mass could a
star possibly have?
Maximum mass of a star is an estimated
150 Solar Masses
Our Sun is an
average star.
Radiation Pressure
Winds - Mass loss!
Brighter
Mass = Destiny
These stars pop off in an
astronomical blink of the eye
These stars, once made, will
basically last forever
Dimmer
Hotter
Cooler
Wolf-Rayet
Brighter
150 Msun Luminous Blue Variable
Blue Super Giant
120 Msun
Fusing core He,
Fusing H
100 Msun
then core C,
(CNO)
All that takes around 3-4 million years
Dimmer
Hotter
Cooler
 Carinae
What do we know?
Brightened 10 fold in 5
years (1840’s)
Most luminous known star
in our galaxy
What have we inferred?
Distance is ~ 7500 light years
Puts out as much energy
in 6 seconds that our Sun
does in 1 year
Stellar winds ~100 billion
times the Sun’s
Lost 5 solar masses in
1840’s event
Mass ~100-150 Msun
30-60 Msun star orbiting
every 5.5 years
 Carinae
“We really don’t understand the behavior and evolution
of 100 Msun stars”
Nathan Smith (University of Colorado)
Thanks! Ask me
questions!
Further Reading
Naeye, Robert. “Eta Carinae” Sky and
Telescope. Oct 2004, p43
Liu, Charles. “Shadowy partner:
astronomers may have detected
what lurks in the shadow of the
giant star Eta Carinae.” Natural
History, Oct 2004, p72
How heavy is a Star
Compared to our Sun,
how much mass could a
star possibly have?
Betelgeuse is ~14 times the Mass of the Sun
Size of Betelgeuse
Size of Earth’s Orbit
Size of Jupiter’s Orbit