Comets are fickle objects, never quite meet our expectations. When we predict an awe-inspiring display visible to the naked eye, they fizzle out. When we expect nothing they appear out of nowhere, shining brightly and dazzling us even into the light of dawn. These enigmatic visitors from the darkest corners of the solar system become increasingly volatile as they approach the sun, producing tails that fan out across the night sky, sometimes changing direction from a particularly violent outgassing or a close pass by Jupiter. Their stories are as unique as them.
Two notable examples from my own life were Comet McNaught and Comet ISON.
Comet McNaught, 2007
In 2006, Scottish-Australian astronomer Robert H. McNaught discovered a comet using the Uppsala Southern Schmidt Telescope at Siding Spring Observatory in New South Wales, Australia. Six months later in January 2007, Comet McNaught would go on to become the brightest, most visually striking comet of the 21st century. It was so bright that it punched through cirrus clouds with easy and dazzled the light polluted skies of major urban centres like Melbourne, Johannesburg, and Santiago. I wish I could have seen it with my own eyes but the countless images we have of it are an absolute treasure.
Comet McNaught over Santiago, Chile
The comet's exceptional brightness was caused by a fortunate alignment between it, the Sun, and the Earth. With the sun well beneath the horizon and the comet shining above the southern skies, the comet's tail reflected sunlight in such a way as to show a dazzling display feathery ripples or striae. These striae were caused by solar wind electrically charging dust particles within the tail, which gradually started to segregate the dust particles by size but remained mixed enough to produce the appearance of feathery striae. This was part of what made the "Great Comet of 2007" so spectacular.
If you missed the comet in 2007, don’t worry! You’ll be able to see it again in the year 94,707! :3
Comet ISON, 2014
Perhaps the most infamous comet in recent memory was the hype centred around Comet ISON, a comet co-discovered by Bulgarian astronomer Vitaly Nevsky and Russian astronomer Artyom Novichonok in September 2012 using the International Scientific Optical Network (ISON). Its predicted close encounter with the Sun and Earth raised a lot of questions regarding its brightness.
American astronomer Dennis Bodewits was quoted as saying:
Comet ISON has the potential to be among the brightest comets of the last 50 years, which gives us a rare opportunity to observe its changes in great detail and over an extended period.
Astrophysicist Karl Battam of the U.S. Naval Research Lab released the following statement:
Comet ISON is a sungrazer. The orbit of the comet will bring it very close to the sun, which we know can be a spectacular thing.
Senior NASA research scientist Don Yeomans later commented:
Predicting the behavior of comets is like predicting the behavior of cats – can’t really be done.
Despite this warning, the media brewed over the potential brilliance of such a comet. Look up any Tweet or news article from 2013 or 2014 about the comet leading up to perihelion and you'll see the hype for yourself. It spread from astronomy publications like Space(.)com and Astronomy Magazine to mainstream news outlets like NBC and even made the local news. A lot of news agencies would later delete their articles mentioning the comet, too embarrassed to admit they were complicit in hyping up the comet before its infamously anticlimactic perihelion.
Instead of dazzling the night sky in a naked eye display, the comet remained faint until the sun disintegrated it during perihelion. The destruction of Comet ISON was captured in exceptional detail by NASA's SOHO and STEREO-B solar observatories.
Timelapse series of images of Comet ISON as viewed by ESA/NASA's Solar and Heliospheric Observatory, or SOHO. It shows Comet ISON growing dim as it made the journey around the sun. The comet is believed to have broken up and evaporated.
Comet ISON wasn't the first comet to by overhyped, and it wont be the last.