Inside the sky at night

The Sky at Night TV show, past, present and future

On 1 September 2022, the James Webb Space Telescope’s Twitter account (@JWSTObservation) posted: “I am now observing Supernova 1987A using NIRCam imaging for 20 hours and 25 minutes.” That was my observation! As viewers of The Sky at Night and readers of BBC Sky at Night Magazine that month might remember, I had two observation proposals for JWST that were both accepted, and now the first was actually happening!

Supernova 1987A, located 168,000 lightyears away, is the remnant of a stellar explosion witnessed on Earth in 1987. People think that because it’s relatively nearby, it must be bright. But more than 35 years after the explosion, the remnant is fading and getting fainter. Now we need 20 hours of observing time to examine it fully, even with a sensitive infrared telescope like JWST.

As soon as my first observation was finished, the JWST Twitter account announced: “I am now observing NGC 6302 using MIRI for 14 hours and 32 minutes” – my second observation project. I was surprised that the two programmes I’m leading would get the data back-to-back. It would be great to have all my data so early, but I did worry that we’d have too much to analyse, especially as we only had one year of priority time before everything was released to the public.

In the end, my worries were unnecessary. One of JWST’s instruments, MIRI, was having some problems and my second observation was postponed. I was disappointed, because the next opportunity to observe NGC 6302 would be half a year later, but also relieved to not have too much data all at once.

I received the Supernova 1987A data a week later. We soon found an issue. JWST takes frames of one target with slightly different positions, which are later aligned using known stars within the frames. But our images did not have enough registered stars. Eventually, I got the idea to create our own catalogue of stars around Supernova 1987A using historical images taken by the Hub