🚀 go-pugleaf

Frank Ney writes:

> On the radio news this morning, I heard a report that an Australian
> astronomer by the name of Duncan Steele predicted that the
> Smith-Tuttle comet will strike the earth sometime in the 22nd century.
> 
> The news report gave an exact date, but I couldn't write fast enough
> to catch up.
> 
> Is anyone else hearing these stories, and how true are they?

First of all, the comet's name is P/Swift-Tuttle, and it's the parent comet
of the Perseid meteor shower, recently recovered heading in toward its late
1992 perihelion passage, the first since the discovery apparition in 1862
(though the comet has now been linked with the comet observed by Kegler in
1737).

Second, replace the "will strike" by "might strike".  Just like any Perseid
meteor, the parent comet also has the potential for running into the Earth.
The uncertainty in the time of perihelion passage at its next perihelion
passage in 2126 includes the date of the Perseids, namely August 14, so it
could theoretically hit the Earth, though the probability is something like
less than 1 in 10,000.  Actually, considering the 10-year error in the
current perihelion passage, one could have claimed in 1862 that the comet
might hit the Earth in 1992, but it isn't going to happen this time around.
Then again, once the identification with Kegler's comet was made, that 10
year uncertainty shrank substantially, and August 14 was no longer within
the uncertainty.

Continued observation of the comet as it rounds perihelion and heads back
out should allow a better determination of its orbit and nongravitational
parameters, permitting a more definitive calculation of it 2126 perihelion
date.  In the meantime, don't get too excited about "The Mother of all
Perseids".