Käufl, Hans-Ulrich Infrared Instrumentation Department, European Southern Observatory, Garching bei München, Germany.
- Properties of comets
- Nagging questions before Deep Impact
- Additional Readings
The word “comet” is rooted in the ancient Greek word κoμ˙ητης (komētēs), literally, hairy star. Indeed, this wording is a concise synthesis of naked-eye observations, in line with our modern understanding. A comet consists of a small nucleus of volatile material. Close to the Sun, evaporation forms large tails of gas and dust. In the twentieth century comets were finally recognized as the most pristine remnants of the formation of our solar system, about 5 billion (5 × 109) years ago. Comets are heralds of the physical conditions during the formation of our solar system. Starting from the first orbit determination by Edmund Halley, modern comet research suffered from the paradox that many very specific details were known with high precision, while rather fundamental quantities, such as mass or detailed consistency of the nuclei, had to remain the subject of educated guessing. Fly-by spacecraft imagery, starting with the European Space Agency's Giotto passing comet 1P/Halley in 1986 at a distance of 5000 km (3000 mi), is spectacular, but most basic questions can be addressed only by spacecraft directly encountering the nuclei of comets.
The content above is only an excerpt.
for your institution. Subscribe
To learn more about subscribing to AccessScience, or to request a no-risk trial of this award-winning scientific reference for your institution, fill in your information and a member of our Sales Team will contact you as soon as possible.
to your librarian. Recommend
Let your librarian know about the award-winning gateway to the most trustworthy and accurate scientific information.
AccessScience provides the most accurate and trustworthy scientific information available.
Recognized as an award-winning gateway to scientific knowledge, AccessScience is an amazing online resource that contains high-quality reference material written specifically for students. Its dedicated editorial team is led by Sagan Award winner John Rennie. Contributors include more than 9000 highly qualified scientists and 42 Nobel Prize winners.
MORE THAN 8500 articles and Research Reviews covering all major scientific disciplines and encompassing the McGraw-Hill Encyclopedia of Science & Technology and McGraw-Hill Yearbook of Science & Technology
115,000-PLUS definitions from the McGraw-Hill Dictionary of Scientific and Technical Terms
3000 biographies of notable scientific figures
MORE THAN 17,000 downloadable images and animations illustrating key topics
ENGAGING VIDEOS highlighting the life and work of award-winning scientists
SUGGESTIONS FOR FURTHER STUDY and additional readings to guide students to deeper understanding and research
LINKS TO CITABLE LITERATURE help students expand their knowledge using primary sources of information