Asteroids:
Asteroids are failed planets. During the formation of our solar system, there was a lot of dust cooling down and coming together due to gravity, called protoplanets. In these objects, heavy metals sank to the center, and lighter elements (carbon & silicates) remained on the surface. Some of these objects became planets, others became asteroids.
There are two kinds: rubble piles (small rocks held together with gravity) and solid metal cores.
Most of the asteroids live in stable orbits between Jupiter (largest planet; more gravity) and Mars. However, a large number of these rocks are between Mars and Earth (called near-earth objects).
The Chelyabinsk meteor was about 20 m in size and it hit Russia in the year 2013 causing damage to buildings and injuries to people. Bigger asteroids will cause more damage -> A few hundred meters → will wipe out a small country or Province in Canada.
Preventing a hit: Nuke the asteroids, gravity tractor, or covering the asteroid with reflective plastic.
Chance of an impact: Depends on the size. The big one, really nothing for the next 100 years. The smaller one is a yes and no answer. We haven’t seen all of them and predicting their trajectories is a very complicated task.
The Sun:
Three ways to damage the earth with the Sun: Solar flares, the energy from the Sun, and the death of the Sun.
The Sun is powered through nuclear fusion where it combines hydrogen atoms to create helium. This is a very energetic process. If all the energy created by the Sun could be pointed towards the Earth, it would be cooked in about a year.
Towards the end of its lifetime, the Sun will swell up like a balloon destroying the Earth.
Special thanks to Colin Vendromin for the music, also thanks to Zac Kenny for the logo!