Dawn breaks over Chews Ridge as Drs. Steve Naftilan (left) and Bruce Weaver conclude the first night of a three-night run.
Dr. Steve Naftilan, professor in the Claremont Colleges Joint Science Department, came to MIRA in June for an observing run of three nights at the Oliver Observing Station.
Dr. Naftilan, who has observed at MIRA in the past, proposed a research program which was not only astrophysically exciting but also depended on specialized MIRA equipment. Cooler stars, like the sun, have an outer convection layer which pulls material from near the surface deep into the hotter interior. The temperatures at the bottom of these zones are thought to be so hot that light metals, like lithium and beryllium, are destroyed in nuclear processes. The lithium absorption line, in the red part of the spectrum, is easy to observe and is commonly used by astronomers to estimate the age of a star.
The absorption line of beryllium, on the other hand, appears in the extreme ultraviolet, beyond the nominal cutoff due to the earth's protective ozone layer. In addition, most optics are opaque in this extreme UV spectral region. However, MIRA astronomers had designed a high-resolution camera for the spectrogram built with lenses made of special UV-transparent glasses. In addition, our recently acquired CCD camera was especially prepared to be UV sensitive.
Pushing the optics, CCD camera, and earth's atmosphere to their limits, success was not at all assured. Special modifications to the camera system, guided by experiments at the Oliver Observing Station and in the Knox shops, went through several revisions. When all the changes and adjustments were complete, we waited nervously for the first exposure of the spectrum of a bright test star to appear on the computer screen. A cheer went up on Chews Ridge when a weak but very real signal from the desired UV region first appeared. A few quick calculations confirmed that we had just made our first observation in the extreme region of the beryllium line!
In addition to providing a second measure of the age of a star, beryllium has another importance. The fact that it is destroyed at a different temperature than lithium means that the relative strengths of the lithium and beryllium lines will provide an observational measure of the depth of the convection zone inside the star.
Given these promising preliminary results, we expect Dr. Naftilan to return for a longer run later in the year.
| Summer 2002 Contents | Newsletter Index | Mira Home Page |
Last updated 12/15/02 DMC