Where Did The Planets Come From?

Get out your mixing bowl (make it a really BIG one!). Here are the ingredients and instructions for making your own planets. Estimated cooking time: a few billion years.

Ingredients for making planets (lots of each):
Dust
Gas
Gravity
Time

Instructions and Background:
The sun and everything else in our solar system started off as a giant cloud of gas and dust. The cloud was between 50 to 100 light years across -- so that's how much of the two you'll need. (One light year is the distance light travels in a year -- 10-trillion kilometers.)

Once you have those 2 ingredients together, gravity and time come into play. Very slowly, everything in the cloud moves toward the center (pulled in by gravity). This makes the gas and dust in the center become very dense.

Eventually (over billions of years), the temperature of the centre of the dense cloud starts to rise. Heat and nuclear energy is created in the centre leading to the formation of a star, such as our Sun.

The newly formed sun has so much heat energy, it pushes much of the remaining dust and gas away. Some of the heavier stuff stays close to the sun and may become planets. This is what happened in our solar system.

Astronomers believe the newly formed planets were made mostly of gas and dust. They call new planets "proto-planets".

The planets in our solar system took a long time to form. They got their start at about the same time as the sun -- over 5-billion years ago.

Over time, the ones nearest the sun (such s Venus, Earth and Mercury) became very rocky, while those far away (such as Neptune and Jupiter) are still mostly gas.

By using strong telescopes such as the Hubble Space Telescope, astronomers are able to study giant dust and gas clouds in other galaxies.

An example of one they are studying is in the Orion constellation. The cloud there is called the Orion Nebula. Astronomers believe the cloud will eventually turn into stars and planets.

They think of it as a "stellar nursery";. (Stellar is just a fancy name for star). It will take billions of years for stars and planets to form there.

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