Such stars are found in Clusters, but these were 300 light-years away from the nearest Galaxy.The Amazing aspect about this is that, if they would no of exploded, we would not know of their existence.
Stars in such low numbers emit too little light to be observable.
If they are not part of a larger group, usually containing millions of neighbors, telescopes do not see or focus on them, since the focal point is always chosen to contain as much activity as possible.
This area was originally observed in 2008 and 2010 and this new discovery confirm the existence of the previously reported 3 supernovae. While the area was studied at first by the Multi-Epoch Nearby Cluster Survey using the telescope on Mauna kea Hawaii, the resolution was not good enough to exclude faint galaxies hosting these stars.
The Hubble Telescope has a much better resolution and showed that these stars indeed exploded far away from any other cluster.
A supernovae is a massive explosion of a star, during this explosion the light emitted is greater than the energy radiated during its entire lifetime. It can outshine entire galaxies and makes objects that were not even visible in certain sectors into the brightest bodies observable.
The explosions were classified as type Ia supernovae which means they were part of at least a binary system. Binary systems are composed of 2 stars orbiting each other.
Supernovae send shockwaves of incredible power and destroy any planets in the system with brutal force.
There is not much known about what lies between the vast space between galaxies. The distance between our own galaxy the Milky Way and the nearest other galaxy which is Andromeda, is about 2.5 Million light years.
Our galaxy and Andromeda are expected to collide in about 4 Billion years. Considering the vast space that normally separates star systems, it is possible that none of the 1.3 billion stars that would be drawn together will ever collide.
So much space can hide a lot and sometimes events of interest are discovered only by change during scanning of other objects in the same focal point.
Image Source: mpg.de