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Five Comets of the Last 25 Years

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Five Recent Comets

Since the beginning of mankind comets have amazed and mystified us. Over the past twenty years, our solar system system has witnessed some notable examples. These comets have been quite the spectacle for both astronomers and amateur stargazers alike. This five-page lens touches on some of the more important comets that have visited us over the past two decades.

Creative Commons photo courtesy Wikimedia/Sternwarte

Public domain animation courtesy Wikimedia/Anarchemitis

hale bopp comet

hale bopp comet

Comet Hale-Bopp

I can vividly remember observing the Hale Bopp Comet back in 1997. What an amazing thing it was to see. The comet was perhaps the most observed comet ever, having been visible to the naked eye for a period of 18 months. Coincidentally, it was also one of the brightest to have passed near our planet in recent years.

Creative Commons photo courtesy Wikimedia/Schnobby

comets last 25 years

comets last 25 years

The 1997 Hale-Bopp Comet was one of the brightest comets to reach the inner solar system in history.

Public domain photo courtesy Wikimedia/mkfairdpm

comet

comet

Background

The Hale-Bopp Comet, also known as the Great Comet of 1997, was discovered separately by two amateur astronomers; Alan Hale, in New Mexico, and Thomas Bopp, located in Arizona, on July 23, 1995. The comet's extreme brightness was notable, as it was able to be seen by the naked eye for a record 18 months, more than twice as long as the previous record holder, the Great Comet of 1811.

During its visit, the Hale-Bopp Comet provided a massive amount of scientific information. NASA launched an unprecedented investigation of the comet, spearheaded by it's two most advanced observatories- the International Ultraviolet Explorer and the Hubble Space Telescope. Most astronomers thought that Hale-Bopp had a sizable nucleus up to 25 miles in diameter, while the average comet has a nucleus of about three or four miles in diameter or smaller. It is theorized that the asteroid, (or possibly comet), that struck Earth and led to the extinction of the dinosaurs around 65 million years ago, was roughly seven or eight miles in diameter.

Hale-Bopp was also notable because of it's properties. Scientists were shocked to discover that different types of ices that make up the comet's nucleus are somehow isolated from each other. The scientists also discovered that the comet had a third tail. While it is widely known that comets generally have 2 types of tails, dust and gas, this comet also had a sodium tail. This extremely long tail was found to contain neutral atoms. It was found to be located between the gas tail, which pointed away from the Sun, and the dust tail, which followed the comet's trajectory. Additionally, the Hale-Bopp Comet was also found to carry a huge amount of deuterium and argon. Argon had never before been discovered on any other comet.

Creative Commons photo courtesy Wikimedia/P. Salzgeber

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Hale-Bopp Video

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Hyakutake comet 1996

Hyakutake comet 1996

Creative Commons photo courtesy Wikipedia/Sternwarte

Hyakutake's Visit

In early March 1996, Comet Hyakutake first became visible to the naked eye. By the middle of March, the comet was still relatively faint, but as it neared its closest distance to Earth, it quickly became brighter, and its tail grew greatly in length. By the end of March, Hyakutake was one of the brightest night sky objects, taking on a greenish-blue color.

On the 25th of March the Hyakutake would be at its closest point to Earth. The comet was moving so quickly across the night sky that its motion could be seen against the stars in just a matter of minutes; it moved the diameter of a full moon about every half-hour. The head of the comet was a greenish hue, due to the diatomic carbon emissions.

Hyakutake was only at its peak brightness for a few days. Because of this, the comet it did not have time to capture the public's attention in the way that Comet Hale-Bopp would the next year. Many people Europe were unable to see in comet at its best due to poor weather across the area during that period.