The Discovery Story of Supernova 2002jy

Mid 2002, I started an automated supernova search program at my CBA Belgium Observatory. Although my prime interest clearly is the study of cataclysmic variable stars, I have been intrigued by supernovae for many years already. Combine this with my strong focus on robotic observing ("automate your telescope to do the tedious observing work in an unattended manner"), and the step towards an automated supernova search program is more or less logical. If you're interested to learn more about the way I realised the search program, and the tools I'm using for the hunting and analysis, click here.

Wednesday December 18th, 2002 - an evening starts ...

I came home from work late in the evening of December 18th, after a really stressful day. The sky was very clear, but the almost-full winter moon was very dominant. I was feeling hungry and tired, but decided to start up the telescope even before dinner, as I was sure this would relax me. 

Normally, I would point the telescope to one of the cataclysmic targets of the CBA network, I belong to. Unfortunately, the prime target at that moment was an object far too faint for my telescope, with this kind of moonlight. The two alternatives were FO Aqr and AO Psc, but both were already too low in the sky to start working on.

Next in the priority queue were 2 variable stars in Cepheus, for which my Belgian friend Patrick Wils had asked me to do some observations. However, using an ephemeris that Patrick had provided to me, it turned out that both  variables were not expected to produce any interesting activity tonight, so I had to skip those targets as well.

I therefore decided to launch my supernova search program SNHunt. This is a Visual Basic program, written by myself, that is at the core of my automated supernova search system. Five minutes after I had entered the observatory, the telescope was already slewing to the first target galaxy. I waited for another minute, to see the first CCD image appear on the screen of my observatory laptop, and then left the building, knowing that the equipment was working fine.  

After dinner, my wife Kathleen and I watched some television. Outside, in the observatory, the telescope was still doing its job sweeping from one galaxy to another, taking CCD images and correcting itself whenever necessary. The Supernova Control Dashboard of my home computer, which is directly connected to the observatory's laptop, was showing 3 green lights, indicating that everything was working as expected.

SNHunt - the core of my Supernova Search Program. After loading the list of target galaxies - a simple Excel file - the program will slew the telescope from one galaxy to another, instruct the CCD camera to take the proper exposures, and consult TheSky to ensure that each CCD image contains the target galaxy sufficiently close to the image's center.

Around 10:30pm, I started screening the CCD images, acquired that night by the telescope, while more images were still being captured. The screening itself is something I do manually, using a software program SNViewer, that I wrote myself. It allows to compare every CCD image with images acquired on previous occasions. The comparison itself is rather straightforward, due to the experience I have built up over the previous months. On average, it takes no more than half a minute or so, to securely determine if an image has a suspect star on it, or not.

That 36th image ...

I had been screening images for about half an hour, when my SNViewer tool brought up image number 36, showing galaxy NGC 477. Almost immediately, I noticed a rather bright, star like object to the northwest of the galaxy, that was not present on my comparison image. It was also lacking from the Digital Sky Survey image in my Supernova Viewer SNViewer

I had seen CCD image flaws, producing ghost stars, in many of my CCD images before. But I was convinced that this one could not be a flaw. So, I pressed the "Priority" button in my SNViewer tool. Doing so, the home computer immediately notifies the laptop computer in the observatory that a priority target has been identified, and that the telescope has to move to the target, upon completion of the current imaging sequence.

Meanwhile, I launched my Internet browser to visit the Minor Planet Center's web page for checking the presence of minor planets in the neighborhood of NGC 477. I was most surprised to see that no known objects were listed. 

Discovery image of supernova 2002jy. 80-sec CCD image, obtained on 2002, Dec 18.96 UT, using a 0.35-m f/6.3 telescope and SBIG ST-7 CCD.

I then launched the International Supernova Network web page, which gives an up-to-date overview of all recently discovered supernovae. Nothing about NGC 477.

By the time I had finished this check, the telescope already had completed the sweep to NGC 477, and two more CCD images of the galaxy were waiting for me. It turned out that the new object was present on both images.

I couldn't believe my eyes and restarted the whole procedure : was I looking at the right Digital Sky Survey image, was the object really not present on a previous image of mine ? I checked the Minor Planet Center's web page two more times, did the same with the International Supernova Network page, and then decided I had done everything I could do myself to exclude errors or misinterpretations.


Time for a confirmation

It was close to midnight now, and I had to find someone who could confirm my discovery. I have good contacts with a few supernova-minded amateur astronomers in the US and South Africa, whom I had asked before to confirm suspect supernovae. I knew it would take several hours, maybe even a day, before I would know the result of their confirmation efforts.

Since it was still clear outside, I considered a better alternative. My very good friends Paul Van Cauteren and Patricia Lampens (the latter is a professional astronomer), owners of Beersel Hills Observatory, had already indicated before they would be happy to confirm any suspect supernova. So, I decided to give Paul a ring. A few minutes later, he interrupted an ongoing observing campaign to try and confirm my finding. He would ring me back as soon as possible.

The SNViewer tool will load newly acquired CCD images one after the other. Every image is presented in MaxIm DL, together with a so called 'reference image', acquired on previous occasions. In addition, SNViewer will also load a Digital Sky Survey image of the galaxy under investigation. I have included a "blink images" button in SNViewer, that allows to blink-compare CCD images (by overlaying them). 

Instead of just waiting for his phone call, which probably would make me too nervous, I decided to already continue the analysis of the suspected supernova, assuming that it really was a new object. 

First of all, I had to determine the position of the supernova (astrometry). A month ago, I had downloaded an evaluation copy of Astrometrica, presumably the best astrometry tool in the world. Fortunately, I had been playing around with it some weeks ago, to get used to it. In doing so, I had also downloaded the complete USNO-A2.0 star catalog. It was quite easy now to get accurate coordinates of the new supernova, and its position relative to the core of galaxy NGC 477. I also had to perform photometry, to determine the magnitude of the new object. This is more or less a routine job to me.

Paul and Patricia rang me back, after they had acquired 9 CCD images of NGC 477, each 30 seconds exposed, using a V filter. I hadn't told him the location of the suspect, so we discussed a while over telephone if the new object was also present on his images or not. It turned out to be the case, and Paul emailed me a stacked image, for a last check.


A message to the IAU - CBAT 

The final step now was to inform the International Astronomical Union IAU, and more in particular the Central Bureau for Astronomical Telegrams CBAT, the clearing house for all astronomical discoveries. There's a rather strict procedure for reporting a discovery to the IAU, which I followed carefully. I checked every line of my report twice, before pressing the send button in my email program.

What would come next ? Would the IAU accept the discovery, and how long would it take before sufficient confirmative evidence had been collected by the IAU ? I knew from colleagues, that the whole procedure could even take a few days. So, I was not expecting any quick reply from the IAU.

I sent out a couple of emails to good friends of mine, to announce the likely discovery. Since clouds had entered the sky, I decided to shut down the observatory.  

Before going to bed, I did a last check of my email inbox. I was surprised to already find a reply from Daniel Green, head of the CBAT, saying that my report was an independent discovery, and that Ron Arbour in England had also reported the supernova.

Great news, that I decided to share with many friends of the Belgian Astronomical Association VVS, through their Bulletin Board. It had taken me nearly 3000 images, since the start of my automated supernova search program, to get to this result ! Time to go to bed now ...

The days after ...

Discovering the supernova was a real thrill, but what followed afterwards stroke me even more. I had never considered that this discovery would attract such a lot of attention in Belgium.

Circular No. 8035

Central Bureau for Astronomical Telegrams
Mailstop 18, Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A.
IAUSUBS@CFA.HARVARD.EDU or FAX 617-495-7231 (subscriptions)
URL ISSN 0081-0304
Phone 617-495-7440/7244/7444 (for emergency use only)


R. Arbour, South Wonston, Hampshire, England, reports his discovery of an apparent supernova (mag 16.3) on an unfiltered CCD image taken on Dec. 17.952 UT using a 0.3-m f/6.3 reflector. SN 2002jy is located at R.A. = 1h21m16s.27, Decl. = +40o29'55".3 (equinox 2000.0), which is 46".4 west and 37".6 north of the center of the galaxy NGC 477. Nothing is present at this location on a 1995 blue Palomar Sky Survey plate (Digital Sky Survey). Further images taken by Arbour on Dec. 18.713 and 18.719 show the new object at about the same brightness, and an unfiltered CCD image taken by T. Boles, Coddenham, Suffolk, England, on Dec. 18.731 yields mag 16.5 and position end figures 16s.23, 55".6. 
T.Vanmunster, Landen, Belgium, reports his independent discovery of SN 2002jy (providing position end figures 16s.26, 55".5) on unfiltered CCD images taken on Dec. 18.96 with a 0.35-m f/6.3 telescope during an automated supernova-search program; a confirming CCD image was obtained on Dec. 18.991 by P. Van Cauteren and P. Lampens at Beersel, Belgium, yielding V = 16.0 for the new object. SN 2002jy was not visible on Vanmunster's CCD image taken on Oct. 11.075 (limiting unfiltered mag 17.2) or on 1977 red Digitized Sky Survey images (limiting mag 19.5).

The day after the discovery, I was contacted by astronomers from the Belgian Royal Observatory. They were very pleased with this discovery, especially because it was the first supernova finding in Belgium. One of them prepared a press release, that was sent to the Belgian national press agency. When I came home that first evening, I found my email box loaded with dozens of mails, with congratulation messages from all over the world ! What a warm feeling ...

In the afternoon of Friday December 20th, I got a phone call at work from a reporter of one of the largest Belgian newspapers. He wanted an interview, for an article that would appear in the newspaper the next day. Ten minutes later, another reporter was asking for an interview later that evening, at my observatory. I accepted, not knowing exactly what to expect.


IAU Circular 8035 announcing the discovery of supernova 2002jy

It is now Saturday December 21st, and the discovery news has been announced in 4 national newspapers. I'm getting lots of emails from people I know and don't know, and over the past days, my website has received more visitors per day than ever before. 

I have invited some friends and relatives for a drink this evening. Tomorrow, things will become normal again .... 

Postscript by end of December 2002

The supernova discovery continued to attract attention and on Monday December 23rd, the national television VRT visited my observatory for an interview session, that was broadcasted later that evening as part of a "light", non-scientific program. Evidently, the amount of reactions peaked in the days after ... 

I never imagined a supernova discovery would attract so much public attention in Belgium - the Christmas period definitely had some influence on it. 





Copyright © 2003 - Tonny Vanmunster.