![]() Space Science News home |
near Transylvania |
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?
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. |
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. |
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. |
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. |
|
Audio
eclipse may fill the sky
- August 4, 1999 story on investigations of ionization and radio
propagation in Earth's atmosphere during the eclipse References Total Eclipses of the Sun, J.B. Zirker, 1995, Princeton University
Press |
![]() More ![]()
|