SN 2002cx exploded (or, to be more techically accurate, was seen to have exploded) on May 12, 2002 by three people working with a 1.2m telescope on Mount Palomar [1, 2]. The first 26 supernovae seen in any year are named using capital letters ranging from A to Z, while the next 26 get named with two lower case letters ranging from aa to az, then the next 26 get ba to bz, and the next 26 get ca to cz. Giver this, we can say that SN 2002cx was the 102nd supernova explosion seen during the year 2002.
The explosion took place in a disk-shaped galaxy generally described as "anonymous" [1] located at a distance of roughly 360 million light years (110 Mpc) in the constellation Virgo [3]. In all seriousness, I don't think anyone really cares about the galaxy. It actually does have a name, but it contains so many letters and numbers that I'm not going to read it because no one cares about the galaxy anyway.
Supernovae are divided into two broad categories based on whether astronomers can see hydrogen in the explosion. Most people probably think of Type II supernovae at first, which are caused when a star much larger than the Sun can no longer fuse elements in its core. This type of star will collapse, and then a rebound shock causes the supernova explosion (and because the outer layers of this star still contain lots of hydrogen, astronomers will see a lot of hydrogen in the explosion). SN 2002cx was not this type of supernova.
Instead, SN 2002cx was a Type Ia supernova, which occurs when a white dwarf has been stripping the outer layers off of a second star for far too long. A typical white dwarf is just an inert but densley packed ball of mostly carbon and oxygen atoms left over from when a Sun-like star died. However, if a white dwarf continues to gain mass from somewhere, like a second star orbiting way to close to it, the white dwarf will eventually become unstable, and nuclear processes will be triggered in the white dwarf, causing it to explode. Because white dwarfs has virtually no hydrogen, astronomers see no hydrogen associated with Type Ia supernovae.
(By the way, astronomers have also identified two other general classes of supernovae where they see no hydrogen, and these are labelled as Type Ib and Type Ic, but they form when a very large star dies in a very similar way as Type II supernovae. Why they don't have hydrogen is a story for a different episode.)
Anyway, SN 2002cx looked like a typical Type Ia supernova, or at least at first it did. A more careful analysis of the observational data for this specific object showed that it looked a bit different from the typical explosion of a detonating white dwarf. First of all, the material ejected from the explosion in SN 2002cx was moving at a much slower speed than the material ejected from a typical Type Ia explosion [2]. Second, SN 2002cx did not seem to get as bright as the typical Type Ia supernova [2]. Third, the mix of elements in the ejected gas just looked weird. Astronomers had problems seeing some things that they normally see in other Type Ia supernovae, such as calcium, sulfur, and silicon, but it was really easy to see lots and lots of iron [2].
It turned out that SN 2002cx was the first of a subclass of Type Ia supernovae ever identified by astronomers [4]. This subclass of objects would be called Type Iax supernovae [4]. They are thought to differ from the "normal" Type Ia supernovae in one very distinct way. "Normal" Type Ia supernovae are expected to be caused by unstable white dwarfs where the nuclear fusion processes are very rapid and blow the white dwarf apart, leaving nothing behind. Type Iax supernovae like SN 2002cx are though to be caused by a process called thermonuclear deflagration in which a runaway fusion process propagates relatively slowly through the layers of the unstable white dwarf, producing a lot of energy without completely blowing the star apart [4]. (I also recommend just looking up some videos on YouTube that discuss deflagration to understand the concept better.) In any case, it's quite possible that some sort of object will be left behind after one of these Type Iax supernovae.
A lot of work is still needed to understand these supernovae and in particular to understand the thermonuclear deflagration in these sources, so every time a new Type Iax supernova appears in the sky, astronomers are going to get really excited, even if it's located in a boring, anonymous galaxy.