Make a Comet    

General information

The general outline is:

  • review background material
  • observe teacher make a comet
  • each team makes their own comet
  • followup discussion


ASP's Project Astro Universe at Your Fingertips, section activity E-3 "Making a Comet in the Classroom "

This one is found in a number of places on the 'net, Dennis Schatz originated the one referenced above:


See Activity E-3.

  • couple of minor variations that seem to work well:
  • use 1 gal freezer zip loc bag *partially* zipped (zip a small one all the way, make for a good demonstration ...) and wrapped in newspaper for crushing the dry ice. The bags get brittle quick, but the newspaper will catch anything that leaks out.
  • we use triple bags in the mixing bowl, using 'free' bags from the supermarket - but make sure you check that they don't have holes (make sure they hold air.) If a bag leaks just dump the contents into the bag beneath it.
  • The directions call for 2 cups of dry ice but dry ice pellets are sold by the pound...about 1.5 lbs of pellets per comet seems to be about right for planning how much to buy and leaves some extra to play with.



General plan




time: 90 minutes

Despite what the writeups say, 4th graders can handle this one fine. We work in teams of 4. Yeah, it's a bit messy but they will remember this activity for a long time.

here's pictures from one of the times this was done:

The presentation uses some movies, Powerpoint is flaky at best when it comes to playing them. I used the "package for CD option" and then zipped the results (about 14 MB). You'll want to modify the impact site for your location.

For the formation movie, the one found here might be better (note that .mov's won't play in powerpoint):





The recipe calls for 2 cups of dry ice. If they're pellets I get about 1.5 lbs for each 2 cups a few hours before the event, plus extra to make the teacher's comet.

Remember that each comet started with 2 cups of water, so when it melts it's gotta go somewhere - if they're going to leave them out to watch them melt have some buckets or be around to drain them off every 15 minutes or so.

If a group ends up with a "rubble pile" instead of a comet that's fine, as that is also a reasonable description of a comet.

We have the teacher demonstrate the whole procedure first, and then the students make theirs. Except for the dry ice all of the ingredients are premeasured into plastic cups.

The dry ice is placed in a 1 gal freezer bag, folded over but not sealed. Place the bag in 8 sheets or so of newspaper, folded over so that if the freezer bar breaks the dry ice can be poured out of the paper.

Remind the students not to pulverize the dry ice, small pebble sized pieces seem to be what to aim for.