Nobody really knows. However we do know that is a spherical object - not an oblate spheroid - about the size of Manhattan (about 12km in diameter) with a very smooth surface. Smoother than anything on Earth.
A young one will be very hot, and it will have a massive gravitation density.
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Well its the death of a star so yes it would look like a massive explosion and its left over radiatiion light can last for weeks or even months!
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The entire sky lights up for days.
Comment: It depends how close the supernova was.
The supernova would look like an explosion and also like the biggest star but like 2km smaller.
That depends entirely on how far the supernova is from Earth. If it is our Sun going supernova, a little over 8 minutes. And a few Milli-seconds later all life on Earth would be gone. Any other star, it would just appear slightly brighter for a while and then disappear. It could take centuries for the light to reach us.
A near Earth supernova [See Link] is a supernova that occurs close enough to the Earth (less than 100 light-years away) to have noticeable effects on its biosphere. Gamma rays from a supernova induce a chemical reaction in the upper atmosphere, converting molecular nitrogen into nitrogen oxides, depleting the ozone layer enough to expose the surface to harmful solar and cosmic radiation. This has been proposed as the cause of the Ordovician extinction - [See link], which resulted in the death of nearly 60% of the oceanic life on Earth. Type Ia supernova [See Link] are thought to be potentially the most dangerous if they occur close enough to the Earth. Because these supernova occur from dim, common white dwarf stars, it is likely that a supernova that could affect the Earth will occur unpredictably and take place in a star system that is not well studied. The closest known candidate is IK Pegasi [See Link] Recent estimates predict that a Type II supernova would have to be closer than 26 light-years to destroy half of the Earth's ozone layer.
A supernova can't occur on any planet. A supernova occurs when a very large star, at least 8 times more massive than the sun dies.
It would look a little different because there will be no living particle on earth
If a supernova - or any star, for that matter - would have hit Earth, the Earth would have been utterly destroyed. Earth still exists, ergo this didn't happen._____________________However, it is likely that a supernova - more precisely, SEVERAL supernovas - CREATED the Earth.The Earth is made of heavy elements; iron, lead, uranium, gold, and heavy metals in addition to the lighter stuff like carbon, oxygen, silicon, and magnesium. The point is that the original Big Bang was composed of mostly hydrogen, a little helium, and traces of lithium; the LIGHTEST elements. So where did the metals come from? Supernova explosions are the only way that heavy elements can be created and thrown back into space.So the dust and gas left over from a few supernovas gathered together as a nebula. But what would cause a nebula to collapse and form a star and a solar system? Our theories indicate that the shockwave of a "nearby" supernova might easily have been the final impetus to cause a nebula to coalesce and form a solar system.Other supernova explosions may have been responsible for some of the mass extinctions that we see in our historical record. Several times in the past, we know that most living things on Earth all died quite suddenly. Some of these - for example, the dinosaurs - were probably caused by asteroid impacts into the Earth. But some may have been caused by the radiation from a supernova explosion.
A supernova is an exploding star. The Earth would be instantly incinerated, of course. There is approximately zero chance this will ever happen, though. If there was a supernova near Earth ... it would depend on how near. Betelgeuse is a good candidate for a supernova "soon" (within the next million years or so). Scientists who have modeled supernova explosions don't expect it will have much of an impact. If a star nearer than Betelgeuse were to go supernova, then it might be more serious.
That depends entirely on how far the supernova is from Earth. If it is our Sun going supernova, a little over 8 minutes. And a few Milli-seconds later all life on Earth would be gone. Any other star, it would just appear slightly brighter for a while and then disappear. It could take centuries for the light to reach us.
There are huge spaces between stars. The biggest threat to Earth would be the gamma radiation emitted, which could sterilize the Earth from as far as 10 light-years away.
A supernova while the Earth was being created.
The nearest likely supernova candidate I know of is Betelgeuse, which is about 640 light years away, and is already well off the main sequence in a Red Giant phase. In order to seriously disrupt Earth, a supernova would probably have to be significantly closer than that.
Yes
A near Earth supernova [See Link] is a supernova that occurs close enough to the Earth (less than 100 light-years away) to have noticeable effects on its biosphere. Gamma rays from a supernova induce a chemical reaction in the upper atmosphere, converting molecular nitrogen into nitrogen oxides, depleting the ozone layer enough to expose the surface to harmful solar and cosmic radiation. This has been proposed as the cause of the Ordovician extinction - [See link], which resulted in the death of nearly 60% of the oceanic life on Earth. Type Ia supernova [See Link] are thought to be potentially the most dangerous if they occur close enough to the Earth. Because these supernova occur from dim, common white dwarf stars, it is likely that a supernova that could affect the Earth will occur unpredictably and take place in a star system that is not well studied. The closest known candidate is IK Pegasi [See Link] Recent estimates predict that a Type II supernova would have to be closer than 26 light-years to destroy half of the Earth's ozone layer.
It's not really possible to tell, as it would have had to be before the Earths formation, so at least 4.6 billion years ago, probably much longer. Any remnants of the supernova would have vanished.
About 50 to 100 light-years as the closest safe distance between Earth and a supernova. But, if a supernova to go off within about 30 light-years of us, that would lead to major effects on the Earth, possibly mass extinctions.
Much bigger. Earth is a relatively small planet, much smaller than even a dwarf star. A supernova is a very large star exploding.
A supernova can't occur on any planet. A supernova occurs when a very large star, at least 8 times more massive than the sun dies.
Brightness is related to luminousity and distance. On Earth, the brightest thing would be a nuclear explosion. In space, the brightest thing would be a supernova, but it all depends on the distance from it.