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?

Our Sun is an average star.

1 millionth the mass of the Sun?1 thousandth the mass of the Sun?

What Makes a Star a Star?

A body that satisfies two conditions: (a) It is bound by self-gravity(b) It radiates energy supplied by and internal source

An introduction to the theory of stellar structure and evolution

by Dina Prialnik

After detailed calculations, 0.08 Solar Mass is the smallest mass to start core fusion of Hydrogen.

Mass

Gravity

Central Pressure

Hotter Core

Fusion More Likely

Could a Star Have a Maximum Mass?

Compared to our Sun, how much mass could a star possibly have?

Our Sun is an average star.

Maximum mass of a star is an estimated

150 Solar Masses

Radiation PressureWinds - Mass loss!

Mass = Destiny

Hotter Cooler

Dimmer

Brighter

These stars, once made, will basically last forever

These stars pop off in an astronomical blink of the eye

Dimmer

Brighter

Hotter Cooler

100 Msun

120 Msun

150 Msun

Fusing H(CNO)

Blue Super Giant

Luminous Blue VariableWolf-Rayet

Supe

rnov

a?

Fusing core He, then core C,

All that takes around 3-4 million years

CarinaeWhat do we know?

Most luminous known star in our galaxy

Puts out as much energy in 6 seconds that our Sun does in 1 yearStellar winds ~100 billion times the Sun’s

Distance is ~ 7500 light years

Brightened 10 fold in 5 years (1840’s)

What have we inferred?

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)

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

Thanks! Ask me questions!

How heavy is a Star

Compared to our Sun, how much mass could a star possibly have?

Size of Betelgeuse

Size of Earth’s Orbit

Size of Jupiter’s Orbit

Betelgeuse is ~14 times the Mass of the Sun