Wednesday, November 27, 2013

Old vs. Ancient - The Blasdel Barn and Comet ISON

Comet ISON (upper left) rises before dawn falls upon the 1909 Blasdel Barn, near Kalispell (click to enlarge)
The old Blasdel Barn was raised in 1909 and is now listed in the National Register of Historic Places. Sunlight has faded its red paint to a memory, and lots of shingles and boards have fallen by the wayside over the years. This grand old barn has stood tall for 104 years, but it's very slowly falling apart.

On another scale - one that, I think, puts our human endeavors in their proper place - when this old barn was built, Comet ISON was already 4.6 billion year old, give or take. On its first and only trip through our solar system, ISON is on a slingshot course around our sun. If it survives today's encounter, it will be flung back out into deep space, never to return.

In the next 24 hours, ISON will skim a mere 700,000 miles above the solar surface - a distance that's less than the sun's diameter. An incredible amount of solar radiation is blasting and aging the comet quickly. From a rock/ice core that's just over one mile wide, ISON's ice is being vaporized into a fuzzy "coma" that's about 80,000 miles wide, with a tail of dust and vapor that's 5 million miles long, pushed away from the sun. One astronomer calculated that the sun is blowing away 3 tons of comet material per second.

As ISON passes the sun, it will reach a top speed of 225 miles per second, or more than 1500 times faster than a commercial jet, which would cross the U.S. in 15 seconds at that speed. I'm not quite sure if there's a way to calculate how this compares to the speed of the horse-drawn stage that used to pull into the oversized passage, through the heart of the Blasdel Barn.

Like the days of horse power, this comet encounter will soon pass and never come back 'round. Enjoy it while you can.


Comet ISON image by NASA
Comes in as a comet (right), departs as a dust cloud (top).
SOHO Image by NASA (click for video)
UPDATE: Well I hope you got to see it in the pre-Thanksgiving, pre-dawn big sky, because Comet ISON is no more. Just prior to its closest approach to the sun ("perihelion") on November 28th, the indescribable heat and solar radiation ripped off the fuzzy coma and long tail, and nuked its nucleus into so many pieces. What emerged from the solar fire was a cloud of dust and small fragments. The glow from this cloud-of-dust-formerly-known-as-ISON is fading rapidly as it heads away from the sun. Unfortunately, instead of turning into the "Comet of the Century" as hoped, ISON's remnants will not even be visible to ground-based telescopes.

Highlights of Comet ISON from NASA Science News.
Text version can be read here.
ISON at perihelion