Hélène R. Dickel - "The Invisible Universe"

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


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 & 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