Download Cosmic Collisions

Cosmic Collisions
Josh Barnes
Stellar Collision
• A collision between the Sun and another star would take a few hours
• After, the Solar System would be a “disaster area”
Stellar Collision
• A collision between the Sun and another star would take a few hours
• After, the Solar System would be a “disaster area”
How Improbable are Stellar Collisions?
In our wildly unfashionable arm of the Galaxy, stars are spread so far
apart that they almost never collide. The chance that the Sun will
collide with another star during its ten billion year lifetime is roughly two
to the power of thirty-two against - or about one chance out of four
billion. That's not impossible, but it is very improbable.
The chances of our colliding with a Black Hole are even lower.
In some parts of the Galaxy, stars are
much closer together, and the odds of
collisions are much higher.
Galactic Collisions
Galaxy collisions happen all the time. The Milky Way has not had a major
collision for over 10 billion years, but it is now swallowing a small galaxy, the
Sagittarius dwarf. In a few billion years the Milky Way will begin colliding
with our larger neighbor, the Andromeda galaxy
This pair of galaxies, known as
``The Mice'' because of their long
tails, are in the middle of a
collision.
The Mice at Play
The two galaxies in The Mice first collided 170 million years ago,
and will merge about 300 million years from now.
The Mice at Play
The two galaxies in The Mice first collided 170 million years ago,
and will merge about 300 million years from now.
How Dangerous are Galactic Collisions?
Galactic collisions pose little threat to life. Planetary systems ride out
collisions; their central stars may be launched into tidal tails or
scattered in random directions, but gravity acts so gradually that
planetary orbits are not disturbed.
A collision takes about a billion years; during the last billion years, life
on Earth evolved from single-celled organisms to amazingly primative
apes who still think digital watches are pretty neat. Life forms evolving
during the Milky Way's collison with Andromeda may enjoy the
fireworks, but their worlds will not be demolished.
So galactic collisions are mostly harmless, unless...
Merger to AGN
Unless the galaxies have supermassive black holes which ``feed'' on
interstellar gas and become active.
Merger to AGN
Unless the galaxies have supermassive black holes which ``feed'' on
interstellar gas and become active.
Conclusion:
Conclusion: