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Scientists drawn to midday darkness near Transylvania

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Scientists drawn to midday darkness
near Transylvania

Serious eclipse science is planned
near home of legendary monster

Aug. 10, 1999: Watching a solar eclipse in the foothills of Transylvania might sound like a scriptwriter's concept for a bad science fiction movie, but it's part of the plan for some serious science and science education.

Right: The Bucharest Observatory's twin astrograph refractor telescopes, with a 40 cm aperture and 6-meter focal length, will produce large images of the eclipse, with the lunar disk spanning 5.3 cm (2 in). Credit: Jay Pasachoff, Williams College

For the past few days, teams of astronomers have been converging on parts of Europe in preparation for the last total solar eclipse of the year (or of the millennium, depending on how you count). The path of totality, where the moon will completely block the sun, starts over the North Atlantic, hits land in Cornwall, western England, and arcs across Europe and into Western Asia before it disappears.

With lots of viewing spots, why pick a part of Romania that is next door to the legendary home of Dracula?

Educators!visit Thursday's Classroom Please visit
Thursday's Classroom
for lesson plans and activities related to the August 11, 1999 total solar eclipse.
"Totality is longest where we'll be observing it," said Mitzi Adams, a solar physicist at NASA's Marshall Space Flight Center. Adams will be working with an observing team assembled by Dr. Jay Pasachoff of Williams College in Williamstown, Mass. "The centerline almost goes directly through Rimnicu-Vilcea where we'll be based. It's not quite in Transylvania, but I believe you can see the Transylvania Mountains from there."

In an age of advanced orbital telescopes, eclipses are still valued by scientists because they give the clearest views of the sun's tenuous corona. Although the moon's orbit carries it in between the Earth and Sun every month, conditions are right for a total eclipse only about every 19 months. Then the bright central disk of the sun is blocked out and the corona becomes visible for several seconds to a few minutes, depending on the observer's position along the eclipse path and other factors.

Manmade coronagraphs provide much the same effect, but have a problem. Light sort of spills over the edges of objects (the effect is called diffraction), which is why the sun appears to take a bite out of the edges of a lightpost if you line yourself up behind the post.

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The same effect takes place in a coronagraph, so solar scientists have to design the occulting disk so it blocks the inner corona as well as the disk of the sun. This means they can't see some of the more interesting coronal activities just above the surface of the sun.

Unless the Moon gets in the way. The Moon is just the right size and distance so that it leaves the corona unobscured when it blocks the Sun. Further, the distance to the Moon means that diffraction effects around the edges virtually disappear by the time light arrives here.

This also means that scientists can observe fine details that even the best instruments can't normally see. It's also fun.

Web Links
EclipseCast.com will keep you up to date.
Information about the Williams College expedition to Romania.
Thursday's Classroom debuts with the eclipse.
More eclipse science and information are available from Dr. Jim Miller of the University of Alabama in Huntsville.
"Pasachoff is a well-known eclipse chaser," Adams explained. But he does it for a reason. "One of the unique things about his expedition is he's bringing a number of undergraduate students who will assist him in his work. He will be making measurements to look for oscillations in the corona."

Further, Pasachoff's team will join with Dr. Magdalena Stavinschi, director of the Astronomical Institute of the Romanian Academy of Science to take high resolution images of the solar corona. The work will also be supported by the coronagraphs aboard the Solar and Heliospheric Observatory (SOHO) which orbits with the Earth. SOHO has a continual view of the sun, but its coronagraphs still cannot see the innermost corona.

Adams is supporting Pasachoff's work.

"I'm going to take videos of the eclipse so we'll have a record through all phases," she said, "and I'll photograph the active regions before the eclipse" to see how they relate to features seen in the corona. "If they're on a limb we'll see prominences and other activity."

Left: A stamp issued by Romania commemorates the eclipse and its passage directly over their capital city.

Adams also will record temperatures as part of an educational activity she is developing with Elizabeth Simmons, a teacher at Huntsville High School, and Beth Bero, a lecturer at the Von Braun Astronomical Society in Huntsville.

The Von Braun Astronomical Society will sponsor a vicarious trip to Romania for Huntsville Boy Scouts who will get a lecture from Dr. Stefan Dieters, an astrophysicist at NASA/Marshall, the evening before the eclipse, camp on the observatory grounds, and then rise at 5 a.m. to watch the eclipse by webcast. Dr. Dave Hathaway, a solar physicist at NASA/Marshall will be also be available to help answer the scouts' questions. Adams plans to make a long-distance phone call to the observatory to describe events during the eclipse. Adams, Bero, and Simmons are part of a team of 12 people developing eclipse installments for Thursday's Classroom activity of Science@NASA.

Web Links

Audio eclipse may fill the sky - August 4, 1999 story on investigations of ionization and radio propagation in Earth's atmosphere during the eclipse
Peering through a Hole in the Sky - June 17, 1999 story on exotic gravity measurements to be carried out during the eclipse
The Millennium's Last Solar Eclipse -- from Sky &Telescope
Solar Eclipse Home Page -- at the NASA/Goddard Space Flight Center

References

Total Eclipses of the Sun, J.B. Zirker, 1995, Princeton University Press
The Sun in Eclipse, Michael Maunder and Patrick Moore, 1998, Springer-Verlag
Totality: Eclipses of the Sun, Mark Littmann, Ken Willcox and Fred Espanek, 1999, Oxford University Press
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Author: Dave Dooling
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NASA Official: M. Frank Rose