The Search for the Unknown (yet Visible) Clouds of the Universe

Below is a short sound slide featuring UW Madison graduate student Mark Stockett and his research project to understand what distant clouds in outer space are made of.



The composition of the universe is a fairly well-understood mixture of different substances. Standing out, however from the usual hydrogen, helium and rock structures found in the universe, are large solar system sized clouds called diffuse interstellar bands (DIBs) or interstellar clouds.

Mark Stockett is a UW Madison physicist is trying to understand exactly what these clouds are made of. And to do this he must recreate the same conditions found in outer space on Earth. The laboratory is located at the Synchrotron Radiation Center in Madison, WI. There, Stockett has access to a synchrotron which acts as a mock Sun. The outer space experiment consists of a vacuum chamber in the shape of a tube which is used to house various sample molecules.

“The important thing in doing an experiment like this is that you need the molecules to be in a similar state as they are in the interstellar clouds. So these molecules need to be very cold, because space is very cold,” said Stockett. “In the tube there is a large liquid nitrogen reservoir that cools the gas [molecules] inside to 200° Celsius below zero.”

Once the sample molecules are in a similar state to those that would be found in outer space, Stockett shines the synchrotron radiation onto the sample and takes a spectroscopic measurement to be later compared to the observed interstellar clouds spectrum seen in outer space.

Getting the conditions exactly right is difficult due to the extreme nature of outer space. Stockett and the project’s P.I. Jim Lawler, physics professor at UW Madison, have had problems with getting the conditions exact. The team has been dealing with problems with the sample molecules clumping together and not dispersing into the more uniform gas, as observed in outer space.
Stockett and Lawler plan to continue crafting the vacuum chamber with the goal to eventually have the ability to quickly canvas a wide-variety of sample molecules. This wide-sample range will ultimately create an index to compare against the complex spectrum observed in space, revealing the interstellar cloud’s true makeup.