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 some parts of the Galaxy, stars are much closer together, and the odds of collisions are much higher.

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.

Galactic CollisionsGalaxy 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 AGNUnless the galaxies have supermassive black holes which ``feed'' on interstellar gas and become active.

Merger to AGNUnless the galaxies have supermassive black holes which ``feed'' on interstellar gas and become active.

Conclusion:

Conclusion:

Don’t Panic