[10][11][12] Alan Hale and Thomas Bopp discovered Comet Hale–Bopp separately on July 23, 1995, before it became visible to the naked eye.

The comet was discovered independently on July 23, 1995, by two observers, Alan Hale and Thomas Bopp, both in the United States.

[1][17] Hale–Bopp's orbital position was calculated as 7.2 astronomical units (au) from the Sun, placing it between Jupiter and Saturn and by far the greatest distance from Earth at which a comet had been discovered by amateurs.

[15] Hale–Bopp became visible to the naked eye in May 1996, and although its rate of brightening slowed considerably during the latter half of that year,[22] scientists were still cautiously optimistic that it would become very bright.

It was too closely aligned with the Sun to be observable during December 1996, but when it reappeared in January 1997 it was already bright enough to be seen by anyone who looked for it, even from large cities with light-polluted skies.

[23] The Internet was a growing phenomenon at the time, and numerous websites that tracked the comet's progress and provided daily images from around the world became extremely popular.

On March 9, a solar eclipse in China, Mongolia and eastern Siberia allowed observers there to see the comet in the daytime.

The last naked-eye observations were reported in December 1997, which meant that the comet had remained visible without aid for 569 days, or about 18+1⁄2 months.

In October 2007, 10 years after the perihelion and at a distance of 25.7 au from the Sun, the comet was still active as indicated by the detection of the CO-driven coma.

Pepi's pyramid at Saqqara contains a text referring to an "nhh-star" as a companion of the pharaoh in the heavens, where "nhh" is the hieroglyph for long hair.

However, in April 1996 the comet passed within 0.77 AU (115 million km) of Jupiter, close enough for its orbit to be measurably affected by the planet's gravity.

It would also be extremely bright, due to a combination of closeness to the Sun and nuclei size, potentially exceeding Halley's Comet in 837 AD.

Such polarization is the result of solar radiation getting scattered by the dust particles in the coma of the comet and depends on the nature of the grains.

Theoretical modelling of ice formation in interstellar clouds suggests that comet Hale–Bopp formed at temperatures of around 25–45 kelvin.

Observations of the material streaming away from these jets allowed astronomers to measure the rotation period of the comet,[52] which was found to be about 11 hours 46 minutes.

[54] This analysis was confirmed by observations in 1996 using Wide-Field Planetary Camera 2 of the Hubble Space Telescope which had taken images of the comet that revealed the satellite.

In November 1996, amateur astronomer Chuck Shramek of Houston, Texas took a CCD image of the comet which showed a fuzzy, slightly elongated object nearby.

UFO enthusiasts, such as remote viewing proponent and Emory University political science professor Courtney Brown, soon concluded that there was an alien spacecraft following the comet.

However, astronomers Olivier Hainaut and David Tholen of the University of Hawaii stated that the alleged photo was an altered copy of one of their own comet images.

[62] Thirty-nine members of the Heaven's Gate cult died in a mass suicide, in March 1997 with the intention of teleporting to a spaceship which they believed was flying behind the comet.

[64] Her original date for the apocalypse was May 2003, which passed without incident, but various conspiracy websites continued to predict the coming of Nibiru, most of whom tied it to the 2012 phenomenon.

[66] Its lengthy period of visibility and extensive coverage in the media meant that Hale–Bopp was probably the most-observed comet in history, making a far greater impact on the general public than the return of Halley's Comet in 1986, and certainly seen by a greater number of people than witnessed any of Halley's previous appearances.

Gene died in the crash and his ashes were sent to the Moon aboard NASA's Lunar Prospector mission along with an image of Hale–Bopp, "the last comet that the Shoemakers observed together".