The supernova is in the top right corner (yellow) and is so powerful that it shot a nearby asteroid through an entire planet like a needle through thread. This is an illustration, but shows some of the blast power involved in supernovae
Even a galaxy cannot hide a
supernova! The many specks
are entire stars and planetary
Unfortunately, although these supernovae probably take place once every 50 years in the Milky Way, the last actual supernova sighting was in 1604. However, when this old age or loss of balance occurs, the matter and energy fusion processes pretty much go out in a bang of cosmic proportions, making them easy to spot if they are close enough to Earth, but we usually only see them after they explode, not during since the explosions last only a few hours. Thankfully, for our viewing pleasure, these large stars die horribly in an explosion of around 10 octillion megatons (10,000,000,000,000,000,000,000,000,000 or 1028) where the star matter is completely cast off and the resulting blast of fire and matter can fly out into space at around 70,000,000 mph out as far as 200 light years! That's an explosion stretching out 200 light years in all directions at 10% the speed of light with an equivalent force of nonillions of atomic bombs. Only gigantic amounts of antimatter could explode larger and faster than this.(see my article called "Force of Space Propulsion" for antimatter specific blast yields and comparisons.
1×1044 joules or 100 tredecillion or 100,000,000,000,000,000,000,000,000,000,000,000,000,000,000
1×1030 Atomic bombs (21 Kt) or 1 nonillion or 1,000,000,000,000,000,000,000,000,000,000
2×1026 50 MT Tsar Bomba (biggest bomb ever) or 200 septillion or 200,000,000,000,000,000,000,000,000
A 200 light year blast area is equal to 1,175,725,074,636,720 miles. This means simply that about 148,330,085,705 Earth's side-by-side would all die or better 5,592,340,728 Solar Systems! Or better, the blast radius of our mightiest bomb (Tsar Bomba) had stretched out a microscopic destructive blast of 34 miles, where up to 64 miles away people got 3rd degree burns only. A supernova's lethal blast distance equals about 34,580,149,254,021.2 Tsar Bombs' lethal blast distance at 50 mt. (Blast radius and megatons of force for bombs and supernovae are simply two different categories of types of bombs, just as how an atomic bomb even matching the 50 MT yield of the Tsar Bomba would still not match the Tsar's power.)
A supernova from one of these large stars has about the same blast/energy output of our glorious Sun after 4,500,000,000 years! That's our Sun's entire life so far, all blasted out in a single explosion of a few hours! Now, our Sun can warm our planet to a comfy temperature and it's about 93 million miles away on average from Earth. If the Sun suddenly went supernova, the blast itself would very, very, very, very easily annihilate all life on Earth and turn the entire Solar System to dust, and then rape that dust into atoms and then spread those atoms for 200 light years. Thankfully our Sun is not large enough to turn into a supernova. It'll just cool down and then go cold, more or less, where the Earth would be an ice cube long, long before the Sun would dissipate in its own coldness.