Hélène R. Dickel - abstracts of talks

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 more recent 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"


Visible light that is detectable by our eyes is only a very small part of the "electromagnetic spectrum" which includes gamma-rays and x-rays at the short wavelength end of the spectrum through ultraviolet, optical and infrared radiation to radio waves at the long-wavelength end. The earth's atmosphere protects us from most of this radiation. Clouds bursting apart at thousands of kilometers per second from the sites of exploding stars give off radiation in x-rays, infrared, and radio as well as in the optical. Observations made by radio telescopes (developed after World War II) and more recently from telescopes which orbit above the earth's atmosphere have allowed us to "glimpse" this invisible radiation. Observations made with the Einstein x-ray observatory in the early 1980's have expanded our understanding of such energetic events. Far-infrared radiation delineates regions of dust which are warmed by recently-formed, embedded stars; examples are the Horsehead nebula and the molecular cloud associated with the Orion Nebula whose far-infrared radiation was been mapped by the InfraRed Astronomical Satellite (IRAS). The newer space telescopes with their greatly improved sensitivity and resolution are producing images in exquisite detail - in x-rays with Chandra (1999) and in the infrared with Spitzer (2003) to match the high resolution images obtained in the radio with arrays of telescopes such as the Very Large Array (VLA) at centimeter wavelengths and the Berkeley-Illinois-Maryland Association millimeter array (BIMA). Even in the visible part of the spectrum, observations by space vehicles can give new insights. For example, after the last servicing mission in 2002, the Hubble Space Telescope observed a "blank" patch of sky for 1 million seconds (11.3 days) between September 2003 and mid January 2004 and detected 10,000 galaxies, some of which formed as far back in time as only about 800 million years after the Big Bang. Examples of these observations and what we've learned from them will be described with the aid of slides.

Need: Power Point Projector and Computer (pc)
Alternative titles to lecture:
"The Visible and Invisible Universe"
"Astronomy: the ultimate in remote sensing"

Public Lecture (ACS Topic 1B): Subject Category AC, GSc, GP; Audience Level 2,3,4


The space between the stars is not a perfect vacuum but contains a small amount of hydrogen plus various contaminating atoms and molecules. This material is collected into giant cloud complexes. Although typical densities are only a few particles per cubic centimeter, the volumes are so vast that the clouds often contain several thousand times the mass of the sun. Such regions are continually in violent activity - material in some spots is contracting to create brand new stars, other clouds are bursting apart at thousands of kilometers per second from the sites of exploding stars, and many areas are being heated and disturbed by the excitation of starlight and interstellar shock waves. We shall describe the results of recent research which is beginning to see order in this chaos: old stars throw off heavy elements which block energy transfer, enhancing the process of star formation. The new stars in turn excite their surroundings and eventually spew their material back into the interstellar medium to complete the cycle.

Need: Power Point Projector and Computer (pc)
Alternative titles to above lecture:
"Cosmic Recycling Center"
"Birth and Death of Stars"

AAS: Evening Public Lecture

ACS: Public Lecture (ACS Topic 1A): Subject Category AC, GSc, GP; Audience Level 2,3,4

Abstracts of Additional Talk for Shapley Lectures


An informal round-table (lunch, tea, after-dinner ...) discussion
of issues facing women (and often men) in science-- as students, professionals, two-career families, career advancement, etc.

Both men and women welcome to join us.
[High school students (and their parents) who are interested in a career in science may also wish to attend.]