Home Lesson for Students
 A cloud of gas can cool off when it's molecules bump into cool, slow moving molecules.  This kind of cooling is called conduction.

But, the Local Bubble ISM is very, VERY spread out - only one molecule per 1000 cubic centimeters, and molecules are unimaginably tiny.   The odds that one of these molecules is going to bump into a cooler molecule is pretty slim. (If you're having trouble imagining this, picture two tiny fleas hopping around in a football stadium - they could hop around for a VERY long time before accidentally bumping into each other.   If they were in the space of three or four stadiums, it would take even longer.  This is about the same odds that molecules in the Local Bubble ISM have of bumping into each other.)

So how does the ISM cool off to form new stars?

Conduction is only one way of cooling off - can you think of others? (HINT: On a molecular level, "cooling off" means that the molecules lose kinetic energy, or slow down. Besides bumping into other molecules, what might make a gas molecule slow down?")


The question above is part of what the CHIPS mission is all about! In the Spring of 2002, the CHIPS instrument will be launched into space to gather evidence that will help to answer this question!

The instrument will be carried on a mini-satellite called CHIPsat provided by SpaceDev Inc.  aboard a Delta II Rocket.


CHIPsat shown separating from the second stage of a Delta II Rocket

A Delta II Rocket