The Amateur Academic’s Guide to Comets, Asteroids and Meteors

Because of our cultural paranoia over civilization-ending comet and asteroid collisions, studying the otherwise dry topic of astronomy can be quite a thrill. With conventional wisdom holding that the dinosaurs were wiped-out by a large asteroid hitting the Yucatan peninsula, many fear the consequences of large rocks hurtling into Mother Earth from outer space, particularly if they were to damage large cities such as New York or San Francisco. Learn more about the threat from space with these resources.


Basics of Asteroids, Comets and Meteors

Both asteroids and comets are small, and both orbit the sun. Comets will display a coma, including the famous tail, as they approach the sun; asteroids do not. Meteoroids are like small asteroids, and when they burn as they pass through Earth’s atmosphere, they are called meteors.

Asteroids, comets and meteors are near Earth objects (NEOs), and they are classified according to the danger they pose to life on Earth; in 2012, there were nearly 9,000 NEOs identified. NEOs that orbit sufficiently close to Earth and are larger than 500 feet in diameter are classified as potentially hazardous objects (PHOs); as of May 2012, over 1,000 such objects had been identified.

Because of concerns of collisions, global efforts are being taken, including the development of mitigation and deflection techniques, as well as the National Aeronautic and Space Administration’s (NASA) Sentry website.

Historic Collisions

Yucatan: Still just a theory, many scientists believe an asteroid six to nine miles in diameter crashed into the Earth at the Yucatan peninsula about 65 million years ago. Known as the Alvarez hypothesis, this theory  holds that the energy released caused global destruction. Firestorms, dust kicked up from the impact and that from the fires combined to create a “long winter” with thick clouds that made the Earth’s climate uninhabitable for all but a few species. This theory concludes that the asteroid impact was responsible for the extinction of the dinosaurs.

Tunguska: On June 30, 1908, a meteoroid or comet approximately 300 feet in diameter is believed to have exploded over the forest in Siberia. The impact from the event is said to have released 1,000 times the energy released when the United States dropped an atomic bomb on Hiroshima, Japan in 1945. The ensuing explosion from the NEO impacted an area greater than 800 square miles and blew down 80 million trees.

To date, the largest recorded asteroid impact crater in the US occurred in Virginia and is 90 km in diameter.

Best Web Resources

NASA’s Jet Propulsion Laboratory (JPL) at CalTech has Asteroid Watch. With radar images, galleries, maps and photographs, the merely curious will be as entertained as the astronomical researcher. Space nerds will enjoy downloading the watch widget and taking the NEO quiz.

The European Space Agency (ESA) supports a number of NEO programs and provides details of their operations online, including Rosetta. Launched in March 2004, the space probe Rosetta will match its orbit with that of Comet 67P/ Churyumov-Gerasimenko in May 2014, and by the end of the year, will try to land on the comet!

At Iowa State University’s Asteroid Deflection Research Center (ADRC), aspiring astronomers (whether an Iowa student or not) will find the latest research on the first deflection research project to be formally funded by NASA.

The Minor Planet Center designates minor planets and comets, and the NEO Checker helps astronomers identify NEOs in a particular region.

Budding astronomers will find the basics, statistics and the latest research on NEOs from NASA’s Near Earth Object Program.

A joint effort between the ESA, the Universita di Pisa and SpaceDys, NEODyS-2s offers separate pages for every near Earth asteroid (NEA). As of fall 2012, information such as the Keplerian elements, magnitude, arc length, orbital period and perihelion was available for over 9,000 objects.

The Secure World Foundation’s Planetary Defense, hosts a wealth of resources on the latest efforts to defend against and plan for the impact of a near Earth object.

The Smithsonian Astrophysical Observatory has galleries, information on what to expect in the night sky, and links to research on comets and other fascinating astronomical topics.

Best Books and Movies about NEOs

In Armageddon (1998), Bruce Willis and Ben Affleck save the world by destroying the NEO before it hits Earth.

Starring Morgan Freeman and Téa Leoni, Deep Impact (1998) examines how humanity deals with its potential extinction by a direct hit from a mile-wide comet.

Defending Planet Earth: Near-Earth Object Surveys and Hazard Mitigation Strategies, written by a committee of specialists, provides comprehensive coverage of the problems, risks and the latest in mitigation plans.

Lucifer’s Hammer by Larry Niven and Jerry Pournelle is a bit dated, but a fun read. Focusing on the devastation to society after a comet hits the Earth, this novel illustrates why impact mitigation is so important.

With Moonfall, Jack McDevitt explores what would happen if a large comet hit the moon, causing lunar debris to crash into the Earth, potentially extinguishing all life.

David Yeomans’ Near-Earth Objects: Finding Them Before They Find Us covers the basics of the threat NEOs pose to life on earth.

Whether you are an expert astronomer or amateur stargazer, asteroids, meteors and comets provide fascinating study for every level of interest. Take advantage of the wealth of resources online and at the library to develop a fuller understanding of near Earth objects and the potential threat they pose to humanity.

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