Great Comets: What Are They and When Is the Next One?
What is a great comet, and when was the last time it showed up? Read this article to find out! To locate any comet ("great" or "regular") in the sky, use the Sky Tonight app. It has one of the largest comet databases that is constantly updated.
Contents
What is a great comet?
There is no official definition for this phenomenon. Often, comets that are bright enough to be noticed by the naked eye and are well-known outside the astronomical community can be called great.
Since it's quite difficult to measure comets’ "well-knownness", we'll only consider their brightness. In this article, we'll define great comets as those that are as bright as the first-magnitude stars — in other words, magnitude 1 or brighter.
Although usually, comets are named after their discoverers, names of great comets contain the year they became great, for example, the Great Comet of 1811.
The list of 6 last great comets
The Great Comet of 1996: Comet Hyakutake
Comet Hyakutake (C/1996 B2) was discovered on January 30, 1996, by the Japanese amateur astronomer Yuji Hyakutake. At the time of its discovery, the comet was shining at a magnitude of 11.0. In March 1996, the comet’s approach to the Earth was one of the closest in the last 200 years. The Hyakutake had the longest known tail for a comet, was exceptionally bright, and easy to gaze at with an unarmed eye. The comet reached a peak magnitude of 0.4. According to the comet’s orbital period forecast, it won’t be back to the inner Solar System for 70000 years.
The Great Comet of 1997: Comet Hale–Bopp
Comet Hale-Bopp (C/1995 O1) was discovered independently on July 23, 1995, by two American observers, Alan Hale and Thomas Bopp. The comet had an apparent magnitude of 10.5, and its orbital position was calculated as 7.2 AU from the Sun. It was seen by the naked eye for an amazingly long period — 18 months, which is twice more than the previous record that was set by the Great Comet of 1811. At its peak brightness, it reached a magnitude of -1.8.
The Great Comet of 2003: Comet NEAT
Comet NEAT (C/2002 V1) was discovered on November 6, 2002, on an image taken by the 1.2-meter Schmidt telescope located at the Near-Earth Asteroid Tracking (NEAT) observatory in Hawaii. At the moment of discovery, it had a magnitude of 17.1. Despite its small size, the comet survived perihelion. Near its maximum brightness in February 2003, comet NEAT shone at a magnitude of -2.0.
The Great Comet of 2007: Comet McNaught
Comet McNaught (C/2006 P1) was caught in the sky on August 7, 2006, by British-Australian astronomer Robert H. McNaught. It was easy to gaze at with the naked eye in the Southern Hemisphere in January and February 2007. The comet shined vividly as the second brightest since 1935. Comet McNaught had a magnitude of -5.5.
The Great Comet of 2011: Comet Lovejoy
Australian amateur astronomer Terry Lovejoy discovered comet Lovejoy (C/2011 W3) on November 27, 2011. He reported that it was a fuzzy 13th-magnitude object. Upon closer inspection, the comet was found to belong to the Kreutz sungrazers group — several comets from this group have already been called “great”. At its brightest, comet Lovejoy had an apparent magnitude between -3 and -4 but was difficult to observe due to its proximity to the Sun.
The Great Comet of 2020: Comet NEOWISE
Discovered by astronomers during the NEOWISE mission on March 27, 2020, comet NEOWISE (C/2020 F3) was all the news in June and July of that year. It became the brightest comet in the Northern Hemisphere since Hale-Bopp. Even people living near city centers and in light-polluted areas saw it. At the time of its discovery, NEOWISE was a magnitude 18 object; at its maximum brightness, it reached magnitude 0.9.
Upcoming great comets
C/2023 A3 (Tsuchinshan-ATLAS) is currently the most promising comet. It was discovered at the beginning of 2023 and is expected to reach a visual magnitude of -4.0 by October 2024. We are keeping an eye on this comet and will provide updates on it in our dedicated article. You can locate C/2023 A3 in the sky using the Sky Tonight app. The comet isn’t available for amateur observations yet, but you can use the Time Machine feature to check the comet’s trajectory in your sky near its peak brightness in October 2024.
Bottom line
Great comets are exceptionally bright and well-known. Their arrival is unpredictable, but always an event to remember for a lifetime. The next great comet could be C/2023 A3 (Tsuchinshan-ATLAS) in 2024 — astronomers believe it will be as bright as the planet Venus.
