Saturday, November 9, 2013

FANTASTIC HYPE or just FANTASTIC? Comet ISON in the waning days of 2013

Are we in for a spectacular stellar show?   We're going to be seeing and reading a lot of hype on social media pages, newspapers and on television really soon. 

Over a year ago a tiny speck of moving light was discovered in the far reaches of our solar system.  This was a brand new comet hurtling through space towards our sun.  This was given the name C/2012 S1 or, more commonly, COMET ISON. 

Comet Ison November 4, 2013 by Damien Peach

Ison was on track and IS on track to reach our sun the end of November on the 28th.    Early reports and speculation have labeled ISON  "the Comet of the Century."  In the photo below, ISON is visible in the dead center, looking like a star with a tiny tail aimed to the right.  It's also (if this photo works right) the only thing in the image that is moving. This photo was taken early this year.
Some astronomers (especially amateur ones) have great hopes for ISON.  ISON is a "virgin" comet, meaning that this is its first pass around the sun.  Tracking estimates that it will make a swing around the sun that will bring it less than 800,000 miles from the very hot surface (in excess of 10,000 degrees Fahrenheit).  Because it is a "virgin" comet, there has been a lot of excitement AND hype in the astronomy community.  If it survives that encounter, as it swings around the Sun, it MAY develop a very bright tail and possibly be visible to the naked eye.  Unfortunately, comets are HIGHLY unpredictable.

Since I'm writing this for folks who are not generally "astronomy geeks" I suppose I should give a little background.

ISON and all other comets are often referred to as "dirty snowballs."  That's because they are made up of ice, dust, gasses, and rocks left over from the formation of the stars and planets millions of years ago.  They reside in a part of our Solar System, called the Oort Cloud which is located at the fringes of our Solar System (some measurements say it is nearly a light year away from us--about 6 trillion miles).  Nothing in space sits still and occasionally the balls of rock and ice are "grabbed" by our (and its) Sun's gravity and pulled out of the Oort Cloud towards the sun.  There are a number of regular comets that make their journey from deep space to our sun and back again, the most famous is likely Halley's Comet, last seen in our neighborhood in 1986.
NASA photo of ISON from a land-based telescope in September, 2013

As the "dirty snowball" begins to melt from the heat of the sun (and this begins to occur very far from the sun), it creates a "tail" of vaporized gas which  is ionized by the sunlight and solar wind (yes, the sun creates a type of "wind") and those condensed ions are illuminated.  Some comets' tails can be hundreds of thousands or millions of miles long depending on the size of the comet and how close it gets to the sun (this is a short explanation of a long, complicated process).
Photo by Hubble Space Telescope
Now Comet ISON is a big comet, at least that's what I've been reading.  As I mentioned above, early hope was that ISON would be one of the "wonder" comets that all on our Earth will be able to see in the twilight skies of dusk and dawn.  Several of the Astronomy publications were shouting that fact.  Unfortunately, ISON is not living up to its reputation and this might be "much ado about nothing" for the general public.

In early August, 2013, ISON emerged from behind the Sun from our orbital perspective.  It wasn't nearly as bright as astronomers calculated it should be (about 2 magnitudes dimmer in fact).  We really only know when ISON is going to graze the sun.  We also know when we should begin to see it as it leaves the sun behind.  That's all we really know now.  As it gets close to the sun, it may break up into small pieces, many falling into the sun and disintegrating and leaving some astro folks pretty red-faced as they stand with their friends waiting in the wee hours for a show that won't occur.  It may emerge from its sun-grazing orbit still in one  huge piece and fill the eastern sky at dusk with a tail that covers half the sky, brightly outshining most, if not all, night sky objects. That would be magical to say the least!  OR it may be something in between, a "yawner" for many but still exciting for those of us who have binoculars or a telescope and know where to look to see it.

Only time will tell.  In recent years, many of the predicted "great comets" have been nothing more than a fizzle for most. BUT there is a chance, and according to comet expert John Bortle, likely the best show ISON will give us will be the end of December (because of the brightness of the moon prior to this time) and ISON may be its most spectacular on the nights of December 24 and December 25.   A comet for Christmas, how magical is that?

I will update this, hopefully weekly, from this point on and give some tips on how to observe ISON as well as where to look to find it.