Comet Holmes
(This 869th Buffalo Sunday
News column was first published on November 18, 2007.)
Comet
Holmes
The
e-mail came from Bill Watson, a retired Buffalo science teacher who divides his
time today between bird watching and astronomy. In astronomical circles Bill is
best known as a world class recorder of meteor showers, but his message this time
called my attention to a remarkable comet whose sudden outburst has made it
visible to the naked eye.
This
extraordinary solar phenomenon is called Comet Holmes or officially Comet 17P/1892 V1. Alan MacRobert of Sky and Telescope
called its appearance "an extraordinary event
not to miss."
Despite
our recent series of clear skies, I couldn't follow up Bill's suggestion until
a few days ago. But then when I searched the sky, there was the comet, a kind
of blurry smudge, quite distinct in appearance from the nearby twinkling stars.
My eyes are not good and there is a great deal of light pollution in my
neighborhood; even so I could see it with naked eyes. With binoculars I could
then make out much greater detail.
You
too can see Comet Holmes and it does not take previous knowledge of astronomy
to find it. I hope that many families will venture out on a clear night to
observe it as this comet should not be missed. One California observer said of
it: "I think this is about the most amazing thing I've ever seen in the
sky." I hope it will serve as an stimulator of astronomical interest among
school-age kids.
Locating Comet
Holmes
Here's
how to find Comet Holmes in the evening sky. Start by facing northeast and
locating one of the most recognizable constellations, Cassiopeia. This five
star constellation will be almost overhead.
The
stars of Cassiopeia form a pattern that looks like a "W" turned on
end. (Star maps connect the stars to make the pattern more apparent. Remember
that the real stars are not so joined.) You should have no trouble finding this
constellation as those five stars are much brighter than other nearby stars. I
learned this constellation as Cassiopeia's chair and, when it is seen sideways,
it does have the appearance of a kind of folding deck chair.
Now
look down and to the right of Cassiopeia to find the brightest star in that
part of the sky, the star Capella.
Half
way between the constellation Cassiopeia and the star Capella is another
constellation, this one called Perseus. Find the brightest star in this constellation.
Close to that star you'll see Comet Holmes.
You
will find it easy to distinguish the comet from the stars. It is blurry whereas
the stars twinkle. If you can do so, look at the comet through binoculars or a
telescope. That way you may even see the beginnings of a tail, which a few
astronomers have already noticed.
Comet
Holmes was discovered on November 6, 1892 by London astronomer Edwin Holmes.
Looking for a distant galaxy with which he was familiar, he was heard by his
wife to exclaim, "There is something strange here." And indeed there
was an undescribed comet. Because Holmes first identified it, the comet was
named for him. (Note that the comet was not named for Sherlock Holmes, the man
you might have expected since a Watson called my attention to it.)
The
elliptical path of the comet was worked out based on careful observations.
Astronomers showed that it would approach no nearer than 190 million miles from
the sun. Since the Earth is 93 million miles from the sun, we are not threatened
by any possible impact. Their calculations also showed that the comet would
reappear approximately (but not necessarily be seen) every seven years.
On
this approach it was first located in July when it was visible only with powerful telescopes. But suddenly in
mid-October it became much brighter. It is now visible without a telescope.
Although blurry, it is about half as bright as the nearest star. It will
probably dim over the weeks ahead.
One
thing that is impressing astronomers is the fact that, as one observer
described it, Comet Holmes' luminous area is now greater than the huge area
encompassed within the moon's orbit around the
Earth.-- Gerry Rising