Think about the following questions as you watch the video

1. 00:36 What was the Solar System like before the sun formed?
2. 01:03 How did the process of forming the Sun start?
3. 01:33 Why did the Sun light up?
4. 02:00 Where did the planets in our Solar System come from?

00:14: NARRATOR: This is our cosmic neighborhood
00:17: nearly five billion years ago: a time before the sun.
00:22: GREG LAUGHLIN: If we go back
00:24: before the sun came into existence,
00:28: what we would see is sort of a vast cloud of gas and dust
00:32: about a light year across
00:34: and containing the entire mass of the sun.
00:40: NARRATOR: An ancient star explodes nearby.
00:43: It unleashes a shockwave that rips through the gas cloud
00:49: and sends it into a tailspin.
00:56: ALEX FILIPPENKO: It started collapsing
00:57: due to its own weight,
00:59: and it spun faster and faster as it collapsed.
01:03: NARRATOR: Gravity pulls together a dense cluster of debris
01:08: in the center.
01:11: The remaining cloud flattens out around it.
01:17: CRAIG BENJAMIN: So now we have a great spinning disc,
01:20: and in this spinning disc,
01:22: the sun eventually coalesces under gravity,
01:26: reaches this incredible temperature
01:27: of ten million degrees Celsius, and lights up.
01:29: The sun lights up.
01:36: Let there be light.
01:41: NARRATOR: The sun is born,
01:44: and in its wake, something else appears.
01:48: FILIPPENKO: The sun gobbled up 99% of the matter
01:51: in the cloud of gas,
01:53: but a little bit was left over in this flat plane,