Comet ISON is out in the early morning
sky. Back in 2012 when it was discovered, at the International
Scientific Optical Network (ISON) in Russia, the hopes were that it
would be a bright and impressive comet. As it has gotten closer
expectations have been scaled back. But just recently the brightness
increased and it has now become visible to the naked eye.
It is whipping toward the Sun with the
closest approach to the Sun expected for the 28th or Thanksgiving.
(Closest approach is called perihelion.) Just before that the comet
might become very bright, though with a close approach to the Sun
might also destroy the comet. We'll just have to wait and see. If
Comet ISON survives it will swing away from the Sun and may
potentially have a long tail making it even more visible. Though it
will be moving away from the Sun and begin growing dimmer. Though it
might still be visible until about January.
Like all comets predicting it's
appearance is difficult. Mainly this is due to the fact that it is
difficult to know what a comet is made of. The tail and the visible
parts are generally gas and small particles and the core can be rocks
or frozen gases or a mixture of both. When the comet is heated up by
the Sun, the gases come off and create a cloud known as the coma.
Then pressure from the Sun in the form of both solar radiation and
solar wind push against the coma to create a tail out behind the
comet.
Now ISON made news recently since the
comet was appearing green. This isn't rare for comets and is likely
due to the chemical makeup of the gases forming the comet. In
particular, cyanogen, a poisonous gas and diatomic carbon, which are
both common in comets glow green when exposed to the Sun's energy.
Both cyanogen and diatomic carbon have carbon which is necessary for
life as we know it. And comets are often considered a source for
some of the carbon that is found on Earth because of comet impacts
during the formation of the Earth about 4 billion years ago. (A
source of the building blocks of life, not life itself.)
But we don't have to worry about Comet
ISON. Even if it is difficult to predict what a comet will look like,
we don't have the same problem with predicting its path. So no comet
impact for Christmas. We're just going to have to hope that ISON will
continue to brighten. Hopefully in early December when the comet will
be visible both in the morning before sunrise and in the evening just
after sunset, we'll all get a chance to see it.
And if we get to see it, think back to
when comets were considered omens, which for some folks might be
right now, and consider how much comets still have to teach us about
the origin of the Solar System. There's still a lot to learn. And are
still people out there wanting to learn it. To me that's a good omen.
For more information about viewing the
comet check out http://isonatlas.wordpress.com/december-2013/.
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