The object for this episode is a supernova remnant named SN 1995N. As can be inferred from the name, this supernova was first spotted in 1995 (or, to be more specific, May 5, 1995 [1]), and the capital N indicates that it was the fourteenth supernova spotted that year. However, this supernova was spotted about 3 months after it would have first appeared in the sky (although people originally thought that it was spotted 10 months afterwards) [2]. The supernova was located within the galaxy MCG -02-38-017 [1], which is also one of a pair of distorted looking galaxies named Arp 261 that are in the process of merging. The two galaxies are located at a distance of roughly 99 million light years (30.5 Mpc) in the constellation Libra [3].
Two different types of objects can produce supernova explosions. The first type of supernova is produced in a binary star system with a white dwarf and a second star where the stars are close enough to each other that the white dwarf can strip the outer layers off of the other star. If the white dwarf absorbs so much material that it becomes gravitationally unstable, it will collapse, which then triggers an explosion. This is not the type of explosion that produced SN 1995N. The second type of supernova is produced when a star multiple times the mass of the Sun gets to the end of its lifespan. The star will try fusing heavier elements within its core to produce energy, but its core will eventually fill up with iron, which cannot produce energy when fused with other elements. This star will eventually collapse, and then a rebound shockwave will produce a supernova explosion. SN 1995N was produced when one of these really massive stars exploded.
When SN 1995N was first spotted in 1995, it did not generate that much interest right away. By the 1990s, supernovae were being spotted so frequently in other galaxies that SN 1995N just did not look that interesting. Well, except that its spectrum was a bit weird. Follow-up ultraviolet and visible light spectroscopy observations that were published in 2002 indicated that the gas blowing outwards from SN 1995N might be colliding with gas in the surrounding interstellar medium [4]. Additionally, observations with the Chandra X-Ray Observatory that were published in 2005 indicated that the shockwave expanding from the supernova included a shell of relatively cool and dense gas [5].
This made SN 1995N a little interesting to study, but only a little. Astronomers had also spotted a few other supernovae with similarly weird spectra as well as a few supernova remnants where the expanding gas shell was colliding with the surrounding interstellar medium, so SN 1995N really didn't stand out too much.
Things with SN 1995N got really interesting when Schuyler Van Dyk, working with archival mid-infrared data from the Spitzer Space Telescope acquired in the early 2000s, spotted an abnormally large amount of mid-infrared emission from the supernova remnant [6]. In astronomy, mid-infrared light is often produced by very small dust grains floating around in space. Dust is typically found in a few places in space, including intermixed with interstellar gas, especially in the interstellar gas in nebulae where stars are forming, and in shells of gas produced when Sun-like stars have reached the ends of their lives (passing through through the red giant phase and a few other phases) and have started expelling their outer gas layers to form planetary nebulae.
However, people have been debating for decades about where exactly dust in space comes from. One possibility is those dying Sun-sized stars that I just mentioned; the dust would form within the shells of gas expelled by these small dying stars. The other possibility is that dust could form within the material ejected from when very large stars die and explode as supernovae. However, it has been really tricky to produce observations of supernova remnants that clearly demonstrate that dust is forming this way. It seems like Van Dyk got really lucky with SN 1995N. The extra-strong infrared emission from this supernova remnant that just happened to be observed around a decade after the explosion seemed to indicate that it is indeed producing rather large amounts of dust [6]. The most recent estimate that I saw indicated that the amount of dust is equivalent in mass to roughly half the mass of the Sun [2]. Imagine what you could do with that much interstellar dust. (Well, I can imagine what I could do with that much interstellar dust. I would make a giant sphere of dust out of it and then compress it down to make a giant planet. Too bad that's not what's going to happen with the dust in real life. It'll probably just end up dispersed in the interstellar medium of the galaxy that it's in.)
Anyway, it has been a bit tricky to intepret all of this data. The primary issue is that it's a bit difficult to tell the difference between dust that was produced within the expanding shell of material ejected from the supernova itself and dust that was in the interstellar medium before the explosion that is being accumulated by and heated up by the expanding shockwave. Even though follow-up visible light spectroscopic observations seem to corroborate the finding that the extra infrared emission seen from SN 1995N originates from dust forming within the supernova remnant [2], the general discussion about whether dust forms in supernova remnants in general is a debate that I expect to continue for quite a long time.