Hélène R. Dickel - "Molecules in Interstellar Space"

American Astronomical Society - Harlow Shapley Visiting Lecturer (1981-2007)
American Chemical Society Tour Speaker (1986-2008)

Adjunct Professor of Physics and Astronomy
University of New Mexico
Emerita Research Professor of Astronomy
University of Illinois


Only a few molecules were known to exist in outer space when the first interstellar molecule discovered by radio techniques, the hydroxyl radical (OH), was observed in 1963. Since then, over 140 molecules have been detected. Space is a good vacuum so the times between collisions can be hours to several years as opposed to fractions of seconds on earth; therefore, in addition to the radicals, ions also remain stable for many years and long carbon chain molecules can form. The most complex carbon chain molecule discovered so far is HCCCCCCCCCCCN with 13 atoms. The simple molecules are formed in gas-phase reactions while the more complex ones involve surface chemistry on grains.

Molecules are found in clouds of cold gas and dust which are distributed throughout the Milky Way Galaxy. These clouds are huge; they can have masses 100,000 times the mass of the sun and diameters of 300 light years. Molecular clouds fragment into small clumps which collapse to form stars which ionize their surroundings and begin to disrupt the remaining molecular clouds. The disruption can create new clumps which, in turn, collapse to form the next generation of stars. Because molecular clouds are opaque to "visible" light, infrared and radio telescopes are used to study the dramatic activity within them.

Among the images to be presented are the 35-ton-each radio antennas of the Berkeley-Illinois-Maryland-Association (BIMA) mm-wave array; one of the first maps of the carbon monoxide emission from a molecular cloud (in this case from the Cygnus dark rift); and additional high resolution observations of the same region made with the BIMA array, which show a massive, bipolar outflow of gas moving at tens of miles per second.

In 2005, The BIMA array of telescopes was moved to a new, higher and dryer, site in the White Mountains of California where the BIMA telescopes were joined by the telescopes of California Institute of Technology to form the CARMA array (Combined Array for Research in Millimeter-wave Astronomy). CARMA is now fully operational. Some photos of the move will be shown.

The talk is suitable for all ages from professional scientists to Middle School students interested in science and space. A current list of the known interstellar molecules will be available.

Need: Power Point Projector and Computer (pc)
Alternative title to above lecture: "Cosmic Chemistry"

Appropriate for a science, physics, chemistry, and/or astronomy seminar; available also as a Public Lecture

Science Lecture (ACS topic 2): Subject Category AC; Audience Level 2,3
available also as a Public Lecture C: AC, GP; 2,3,4