The fate of super-massive stars

The fate of super-massive stars

Supermassive stars (> 25 M☉), will

collapse under a force of gravity

which is so strong that nothing

can escape its pull - not even light.

They become .Black Holes

Death of a giant star

25 to 100

Hertzsprung - Russell Diagram

Main Sequence Stars

Supermassive stars 25 – 100 X the mass of the sun…

Hertzsprung - Russell Diagram

Main Sequence Stars

Supermassive stars 25 – 100 X the mass of the sun turn into Red Supergiants.

The fate of super-massive stars

come in a variety of sizes,

ranging from mini-black holes with event

horizons no larger than an atomic nucleus

to stellar black holes with event horizons

10 - 50 km across, to supermassive black

holes with event horizons billions of miles

across (found at the core of many galaxies).

Black Holes

Around a black hole

If no light can escape from a black hole, how can we “see” them to know that they really exist?? • Black holes pull in swirling clouds of

gas from neighboring stars. • These gases are moving so fast that

they become very hot…

Around a black hole

• Very hot objects give off streams of X-Rays. • When astronomers first found a strong X-

ray source with no star is visible at that

location (using a regular light telescope),

they figured that it must be a black hole -

a massively huge star that has collapsed

under its own weight and “winked out” of

visibility.

X-Ray images of Cygnus X-1

(First Discovered Black Hole)

X-Ray images of black holes

Where do the X-Rays come from??

Black Hole with Plasma Jet

Event horizon

Accretion disk

Plasma jet

Accretion Disc swirling from binary twin toward the event horizon

Binary Star SystemBinary Twin(Blue Giant)

Black Hole

Hot Swirling Gases of Accretionary Disk Give Off X-rays

X-rays also come from plasma jets

Tidal Forces

Approaching a black hole

• Tidal forces are caused by

gravity pulling with different

degrees of force on objects

which are different distances

from the gravity source.

Tidal forces and ocean

tides

High Tide

Low Tide

• (Ex: the center of the earth is 4,000 miles farther

from the moon than the oceans, moon’s gravity

pulls harder on the ocean,

• creating tides)

Tidal forces and ocean

tides

High Tide

Low Tide

Tidal forces and ocean

tides

Tidal forces and ocean

tides

Spring Tides:

Sun and moon

pull together -

Higher tides;

Neap Tides:

Sun works

against Moon –

Tides not as high

High TideHigh Tide

High Tide

High Tide

Low TideLow Tide

Low Tide

Low Tide

• Black holes have an incredibly huge

masses packed into an incredibly

tiny point called a singularity.

• This causes the force of gravity to

skyrocket.

Tidal forces and black holes

Tidal forces Approaching a black hole

As a result, the distance needed to create a noticeable tidal force is very small: • A 6 foot tall human approaching a black

hole would have much greater gravity pulling on his feet than on his head.

Approaching a black hole

• The tidal forces would s t r e t c h him like “Gumby”.

• This would actually pull the person apart (as well as his spacecraft) as he approached the event horizon:

“Spaghettification”

The event horizon

• The event horizon is the “edge” or

boundary of the black hole - the “point

of no return” (and no escape).

• All matter which passes the event

horizon is trapped inside the black hole

forever .

The event horizon

• If a spaceship reached this point intact,

it would not be able to send signals

back - the radio waves and

microwaves would be pulled back by

the black hole’s immense gravity.

The event horizon

• From a distance, the space- ship would appear to be permanently hovering on the event horizon.

• Once inside the event horizon, all matter is shredded and compressed down to a single point called the singularity.

The event horizon

The “Point of no Return”

Accretion disk

Accretion Disk

verse or even to an entirely different universe!

The scientists know that a black hole can be formed by the death of a very massive star. During the stable life of the star, radiation and heat and gravity remain in balance. When the star exhausts its nuclear fuel. However, it begins to collapse. As its volume diminishes to zero, its gravity and density becomes infinitely great. It is now what physicists call a “singularity”. The star has literally crushed itself out of this universe.

…as the robot passes through the “accretion disc” of swirling gases, gravitational tides begin to stretch it…

Of course, there is a slim chance that the robot might survive after all, according to some theories, the black hole might act as a “wormhole” or passageway to another part of the universe or even to an entirely different universe!

Spaceship observers see the robot hovering at the “event horizon” - the “point of no return” - from which even the robot’s radio messages cannot escape. as the robot is sucked in, all its molecules and atoms are shredded, and it is compressed into the singularity.

Gravitational Lens –-

Black Hole bends light from distant star.

Gravitational Lens –-

Black Hole bends light from distant star.

Gravitational microlensing

Black Hole

bends light

from distant

star.

Microlensing

creates a single,

overlapped

brighter image

What if somebody could actually survive entering a black hole? • The black hole could become a

wormhole, a passageway meandering across space/time and connecting with a black hole in another universe (and possibly with another time as in “Bill & Ted’s Excellent Adventure” and “Contact”).

Beyond black holes…

Wormhole –

Gateway to another universe??

Worm hole vs black hole

• A worm hole is a funnel that tapers down to a “throat” (but doesn’t pinch off) which connects to another funnel that opens up somewhere else. 

• A black hole is a funnel that pinches off at a singularity. 

• A traversable worm hole needs to be large and “mellow” enough that it doesn’t have an event horizon (a black hole’s “point of no return”), or any fatal tidal forces. 

• Another possibility is a white hole, spewing out cosmic debris in another corner of the universe.

• Odd features such as wormholes and white holes are mathematically possible, but may not actually exist.

• Black holes, on the” other hand, do exist and are quite common throughout the universe.

Beyond black holes…

Review –- 3 lifecycles of stars

8 to 25

25 to 100

8

Star cycles

Old “starstuff” becomes the fuel for new stars.

Small-Medium Stars Large Stars