While hundreds of tiny ધૂમકેતુs pass through the inner સૂર્યમંડળ every year, only a very few ધૂમકેતુs make any impact on the general public. About every decade or so, a ધૂમકેતુ will become bright enough to be noticed by a casual observer — such ધૂમકેતુs are often designated Great ધૂમકેતુs. In times past, bright ધૂમકેતુs often inspired panic and hysteria in the general population, being thought of as bad omens. More recently, during the passage of Halley's ધૂમકેતુ in 1910, the Earth passed through the ધૂમકેતુ's પૂંછ, and erroneous newspaper reports inspired a fear that cyanogen in the પૂંછ might poison millions, while the appearance of ધૂમકેતુ Hale-Bopp in 1997 triggered the mass suicide of the Heaven's Gate cult. To most people, however, a great ધૂમકેતુ is simply a beautiful spectacle.
Predicting whether a ધૂમકેતુ will become a great ધૂમકેતુ is notoriously difficult, as many factors may cause a ધૂમકેતુ's brightness to depart drastically from predictions. Broadly speaking, if a ધૂમકેતુ has a large and active nucleus, will pass close to the સૂર્ય, and is not obscured by the સૂર્ય as seen from the Earth when at its brightest, it will have a chance of becoming a great ધૂમકેતુ. However, ધૂમકેતુ Kohoutek in 1973 fulfilled all the criteria and was expected to become spectacular, but failed to do so. ધૂમકેતુ West, which appeared three years later, had much lower expectations (perhaps because scientists were much warier of glowing predictions after the Kohoutek fiasco), but became an extremely impressive ધૂમકેતુ.
The late 20th century saw a lengthy gap without the appearance of any great ધૂમકેતુs, followed by the arrival of two in quick succession — ધૂમકેતુ Hyakutake in 1996, followed by Hale-Bopp, which reached maximum brightness in 1997 having been discovered two years earlier. As yet, the 21st century has not seen the arrival of any great ધૂમકેતુs.
પ્રખ્યાત ધૂમકેતુઓ
ધૂમકેતુની બાહ્ય લાક્ષણીકતાઓ
ભ્રમણકક્ષાની લાક્ષણીકતાઓ
અસામાન્ય ધૂમકેતુઓ