Comet Ison Taught Me A Lot

743538main_image001_0As a meteorologist on TV I was often called on to be a science generalist. From earthquakes to volcanoes to comets, I had to know enough get on the air and provide context. It was a part of the job I relished.

Comets appeared from time-to-time, allowing me to get some shaved ice and dirt and give a quick lesson. There are not many people who get the opportunity to teach science on TV. It was an honor.

What I knew would not have been enough for Comet Ison. This comet was unusual. I learned a lot.

Astronomers first caught sight of Ison in September 2012 when was 585 million miles away. Even at that distance it was bright enough to hint at big things ahead.

Automated spotting programs make comet discoveries easier. Computers look for objects that are moving while the rest of the star field stays relatively in place.

By October a paper delivered to the American Astronomical Society’s 45th Annual Division for Planetary Sciences meeting noted Comet Ison was rotating in such a way that only one side was getting heated by the Sun and it was already spurting water ice into space.

Comet Ison is/was a sungrazer. Sungrazer’s are comets which get close enough to the Sun to be intensely affected by its gravity and heat. We’d never spotted a sungrazer so far out. Probably from the Oort Cloud, this was Ison’s first trip to the rodeo.

Until Ison, all the comets I’d talked about stayed far enough away from the Sun and had ‘visited’ this part of the solar system often enough that they weren’t in peril. This one was headed inside the Roche limit.

The Roche limit, sometimes referred to as the Roche radius, is the distance within which a celestial body, held together only by its own gravity, will disintegrate due to a second celestial body’s tidal forces exceeding the first body’s gravitational self-attraction. – Wikipedia

So, if Ison was a mass of rocks, pebbles and dirt held together by ice and its own internal gravity, the Sun would probably break it apart. That’s what happened. If Ison was an asteroid or some other giant space boulder we’d probably be looking at it still. Whatever does exist today is a small fraction of its former self.

I know this now. I didn’t know this a week ago or when I was talking about much colder comets on TV.

We see comets and their signature tail because heat (usually not very much heat) allows ice to melt which in turn allows gases to vent and dust to be set free. A comet’s tail is blown by the solar wind, a field of energy blasted into space from the Sun. The tail points away from the Sun and has no relation to the direction the comet is actually moving.

If all the ice has melted and the nucleus disintegrated there’s nothing left to view. That seems to be the case. There will be no “Comet of the Century” in the December sky.

We’re very lucky it’s 2013. There are a few satellites, some far from Earth, specifically designed to monitor activity like this. They provided amazing images as Ison whipped its way around the Sun and back toward deep space.

Over the next few months, as astronomers and other specialists look at the tsunami of data produced, we’ll learn more. It’s likely we’ll find Ison’s exact makeup and what caused its demise. I wouldn’t be surprised to see some animations simulating Ison’s final interactions with the Sun.

This comet was a tease. We were told it could be the big one. Obviously, it was not.

It wasn’t a disappointment to me. My knowledge has expanded. I might have been a terrible student as a kid, but grown-up Geoff loves to learn.

Over the last few weeks I’ve heard a lot of those in the know compare comets to cats. The both have tails and they both do what they want to do.

Ciao, Ison.

Am I The Cometary Kiss Of Death?

comet-ison

Earlier today I posted a really cool animation from the Stereo-A satellite which monitors the Sun. It showed Comet Ison and Comet Encke heading toward the Sun while being blasted by the solar wind.

Many people feel (or felt) Ison might be the brightest and easily visible comet of our lifetimes! Almost as soon as I posted to my blog new information began to arrive suggesting hopes would be dashed.

We are seeing reports online that molecular emission from the comet has fallen dramatically, meanwhile dust production seems to be enormous. What this could indicate is that the nucleus has completely disrupted, releasing an enormous volume of dust while significantly reducing emission rates. Fragmentation or disruption of the nucleus has always been the highest risk factor for this comet so if this has indeed happened then while unfortunate, it would not be a surprise.

However, these reports are new, and while they are undoubtedly valid, we do still need to keep observing the comet to be sure what is happening. Karl Battams, Naval Research Laboratory

Simply put, it’s possible the comet has broken apart or disintegrated leaving a trail of dust and debris.

All along scientists hinted this was a possibility. Comet Ison has spent hundreds of thousands of years&#185 in the darkest reaches of space. It was safely removed from any source of heat, light or gravity. Now that was changing and changing in a hurry.

Today’s revelation is preliminary info. It points to a likely outcome, but that’s no guarantee. The more comets we see, the more we realize how little we know.

&#185 – It is being reported Comet Ison’s orbit arounnd the Sun takes 582,666 years!

Here Comes Ison

Comet Ison is getting a lot of attention as it heads toward the Sun. If all goes well (and there’s no guarantee) Ison will be visible to the naked eye in the evening sky within the next few weeks. All you’ll need is a dark location and no clouds.

Just below is animation produced by the Stereo A satellite which monitors the Sun. The waves moving in from the right are caused by the solar wind.

Seen along with Comet Ison is Comet Encke, a less exciting comet which returns every three years or so.

ison_encke_nov19_23_crop_hi1a