Once in how many years comets are seen?

Question

Once in how many years comets are seen?

Answer 1

Dozens (perhaps hundreds) are seen a year.  For the bigguns it could be every 76 years (Halley's) or longer.  It would depend on if you mean with the naked eye or not.

Answer 2

There are two possible meanings to your question.

1) How many comets are seen each year? Answer, lots. Dozens.

2) How often is a typical comet visible? Answer: many comets orbit the sun in ellipses, coming back anything from every 3 years to every 50 years. Comet Halley is quite unusual in that it comes back every 76 years - this is quite long. A second class of comet orbits in what appears to be a parabolic orbit which means that it is essentially stationary out there in the Oort cloud, something disturbs it and itcomes in towards the sun once only, heading back out towards the Oort cloud again. Some scientists think these comets come back after 10,000 or 50,000 years, but others think they are a once-off.

Answer 3

I'm a fairly active amateur astronomer. I'd say that I've seen an average of two comets a year over the last dozen years.

Answer 4

You can often see at least one of them when you watch SOHO live images - sungrazers are very common.

Great comets, which are visible to the naked eye are very rare and happen usually only once every 10 years.  

Answer 5

A lot. Here's a list for the Northern Hemisphere:

http://www.aerith.net/comet/future-n.htm...