We watched the spectacle unfold in almost real time on the internet. Oh, the wonders of today's technology. Ison was too close to the sun to watch with the eye, too much glare and far too dangerous to point a telescope in it's direction. But through space borne solar observatories like SOHO and SDO, we could see the show unfold through their eyes. Yet, with today's technology, we could not predict what was to come next.
Ison looked very healthy in the hours before perihelion, all seemed to be going well. It was very bright, in the negative magnitude range, and seemed to be behaving as a good comet should. Yet, as the comet started to close in on the sun, it started to dim a little bit. Then a little bit more, and a little more, and a little more. It continued to dim until it appeared as but as a ghost of it's former self. The bright coma, the head of the comet, seemed to warp and elongate until it was no longer recognizable. And it faded away even more. And we waited some more, waited to see what would emerge on the other side of the sun. Nothing came. All the excitement and anxiety that built up over the past few months turned into a 100 pound block of disappointment that slugged me in the stomach. I had watched the object that I researched and studied and imaged for the past several months die before my very eyes.
Or did I?
A bit later, when I checked the most recent imagery from the SOHO solar observatory, I noticed something. Right where I had expected Ison to emerge on the other side of the sun, something was emerging. It was faint, but it was there. A spark of hope flickered for a moment. After looking at the image, I concluded that I was seeing the remains of Ison's dusty tail moving along it's would be orbit. I checked again a bit later. The ghostly tail was more pronounced in the next image. And in the next, and in the next. And, it was getting brighter and looking more comet-like. Something made it through!
This is not typical comet behavior. But of course, Ison is not typical comet. From the very start, Ison has shown erratic behavior. After it's discovery, it seemed like a typical comet with a potential for greatness. It was found to be a comet who's orbit takes it very close to the sun...called a sun grazer. Comets that make this kind of trip tend to get very bright and form a very long tail...if they can survive the trip. Near the sun, Ison would have to endure temperatures of nearly 5000 degrees and powerful gravitational forces. All while making a hairpin turn at over 800,000 mph. Comets that can endure the punishment usually blossom into naked eye spectacles. Thus, Ison aquired it's "Comet of the Century" status. But later in it's orbit, Ison was observed to be exhibiting odd behavior. It was not brightening at the expected rate. In fact it was running 2 magnitudes dimmer than it should have been, As it got closer, it seemed to brighten up...but very slow. It started to vent gas and turned a nice green color, but it wasn't producing as much dust as it should. As it got even closer, it finally started to brighten substantially like it should. And then it dimmed again. Near perihelion, it exploded in brightness and gas/dust production. And then it dimmed again, and seemingly was vaporized in by the solar furnace. And then...it came back.
What is going on? Know one knows for sure, not even the comet experts. Scientists are dumbfounded by this behavior. It is still very much uncertain what came out the other side. All that is known is that it is there, it is getting brighter, and seems to be sporting a tail. It could be a large fragment of Ison's nucleus. It could be a stream of comet pebbles. And it could be days until we know for sure. But now, we will have to watch and wait...again...to see what happens next. Ison, are you still with us?
NASA photo from the Solar and Heliospheric Observatory (SOHO)
http://sohowww.nascom.nasa.gov/
