The fate of super-massive stars Supermassive stars (> 25 M ☉ ), will collapse under a force of...
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Transcript of The fate of super-massive stars Supermassive stars (> 25 M ☉ ), will collapse under a force of...
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
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.
Accretion Disc swirling from binary twin toward the event horizon
Binary Star SystemBinary Twin(Blue Giant)
Black Hole
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.
• (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
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:
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.
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 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…
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…