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How would the sun appear if it exploded?

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#1 chrisg

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Posted 20 April 2014 - 07:38 PM

Perhaps this isn't how the sun will die, but this question has always puzzled me. Given that it takes light about 8 minutes to reach us at it's current distance, how would the sun's explosion appear as this distance decreases? Mucho apologies for the grim exercise!

#2 AustinAstronomer

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Posted 20 April 2014 - 08:33 PM

I don't understand your question. If the sun exploded, you would see that explosion eight minutes later, and you would be vaporized about a second after that. In short, the light from the explosion would travel outward from the sun at the speed of light, just like all the other light from the sun.

#3 gdd

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Posted 20 April 2014 - 08:45 PM

You mean how far out would you have to be to watch the explosion progress without vaporizing from the intense light? Pluto? Out in the Oort cloud? Nearest star?

Gale

#4 GlennLeDrew

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Posted 20 April 2014 - 10:34 PM

The only difference in appearance would be angular scale (apparent size, which scales inversely with distance) and brightness (which scales inversely as the square of the distance.) In other words, like any object or event as view distance varies.

Tbe light travel time has no bearing; from the observer's point of view all events occur only as they are observed. The arrival of the photons and the gravitational effects (gravity waves) attending the event arrive/occur in step.

#5 TCW

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Posted 20 April 2014 - 10:39 PM

It would depend if it were a super nova or "just" a nova. Either way you die before your brain could process what was happening unless you were on the night side of the earth and that might only buy you seconds at best.

#6 chrisg

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Posted 21 April 2014 - 12:06 AM

Apologies about the grammatical error of my original question, I just edited it!

Maybe I'm too dense to see that my question was answered but here is my issue:

Say we're looking at the sun one day, but we don't realize that 8 minutes ago, the sun has started to explode. I'm assuming the sun's expansion is moving much more slowly than the speed of light. 8 minutes later, we can see that the sun has started to explode, all the while the sun's surface has been traveling towards us for those 8 minutes and is now closer to us than it was at the beginning.

At this point, the surface is say, 4 light minutes away. At some, eh, moment, the surface and light will be close enough to the earth that they'll arrive at the same time, and be in sync with each other. My question is, would the sun appear to explode faster or slower than it actually did? Would it start fast, then slow down? I just can't seem to wrap my head around how this would actually appear on this awful but perhaps beautiful moment in time.
Also, what filter should I use? Which eyepiece, Ethos or Delos? :cool:

#7 Dodge2013

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Posted 21 April 2014 - 12:19 AM

Sounds to me like someone is at work or it has been cloudy for days.

#8 Midnight Dan

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Posted 21 April 2014 - 06:57 AM

Apologies about the grammatical error of my original question, I just edited it!
Maybe I'm too dense to see that my question was answered already but here is my issue:
Say we're looking at the sun one day, but we don't realize that 8 minutes ago, the sun has started to explode. I'm assuming the sun's expansion is moving much slower than the speed of light. 8 minutes later, we can see that the sun has started to explode, all the while the sun's surface has been travelling towards us for those 8 minutes and is now closer to us than it was at the beginning. Now, the surface is say, 4 light minutes away. At some, eh, moment, the surface and light will be close enough to us that they'll be in sync with each other. My question is, would the sun appear to explode faster or slower than it actually did? Would it start fast, then slow down? I just can't seem to wrap my head around how this would actually appear on this awful but perhaps beautiful moment in time.
Also, what filter should I use? Which eyepiece, Ethos or Delos?


There would be no speeding up or slowing down. It would be linear. And clearly, it would appear to occur faster than actual.

Take an example. Let's say the surface of the sun explodes outward at 1/2 the speed of light for ease of calculation. The initial light would take 8 minutes to get here, while the surface would take 16 minutes ... eight minutes behind the initial light. So the event would appear to take 8 minutes, even though the surface required 16 minutes to arrive.

-Dan

#9 ianfromoz

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Posted 21 April 2014 - 07:06 AM

In answer to your question.
If you live long enough you will see for yourself :-)

#10 GlennLeDrew

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Posted 21 April 2014 - 09:13 AM

Even supernova ejecta do not much exceed 4,000 km/s. Compared to the 300,000 km/s for light, this is a speed ratio of about 8,000. The material is essentially at a standstill.

#11 mrchunks

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Posted 21 April 2014 - 10:48 AM

I respectfully disagree. Light is constant leaving the object at the speed of light not speeding up to it. Although its true the actual physical part of the surface would reach earth 16 min later the visual part would be in real time as we see the surface as it was 8 mm in ago not as it is. But we would be dead before the physical part reached us..

#12 csrlice12

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Posted 21 April 2014 - 12:56 PM

A very bright, hot flash....you'd be dead before you knew it.....

#13 sickfish

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Posted 21 April 2014 - 12:58 PM

I dont think you would see anything. You are dead. :(

#14 csrlice12

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Posted 21 April 2014 - 01:07 PM

Hey all, I'm a Zombie!

#15 howard929

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Posted 21 April 2014 - 01:09 PM

Realizing that light travels at speed C regardless of the benchmark of the observer, no filter would be required but a Delos for sure. ;)

#16 TCW

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Posted 21 April 2014 - 01:45 PM

As Sarah Conner said - anyone not wearing two million sunblock is going to have a really bad day. :roflmao:

The shockwave would arrive after the radiation blast but when the temperature goes up several million degrees in a nanosecond you won't be wondering what eyepeice is best.

#17 howard929

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Posted 21 April 2014 - 01:59 PM

Possibly this helps some-what. Anyone outside in view of daylight sees that light from the Sun as it left the Sun X light minutes ago. The Sun explodes in what would likely be a blinding all encompassing to Earth flash of light. Since we are seeing what was, not what is, heat/light from such a blast would arrive that same X number of light minutes later but I seriously doubt that it's possible for eye to brain realization of such an event prior to vaporizing.

#18 csrlice12

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Posted 21 April 2014 - 02:56 PM

Think of how cheap solar scopes would become....

#19 Midnight Dan

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Posted 21 April 2014 - 03:04 PM

I respectfully disagree. Light is constant leaving the object at the speed of light not speeding up to it. Although its true the actual physical part of the surface would reach earth 16 min later the visual part would be in real time as we see the surface as it was 8 mm in ago not as it is. But we would be dead before the physical part reached us..


Hi MrChunks:

Not sure what you're referring to here. I didn't make any comments regarding the speed of light speeding up.

But just to clarify though, here is the timeline

1:00 pm on Earth
- Sun begins to explode. No visible sign of it on earth.

1:08 pm on Earth
- Light from sun's initial explosion reaches Earth. We see sun's surface beginning to move outward
- Actual surface of sun is now 1/2 way to Earth (based on fictitious example of surface moving at 1/2 light speed)

1:12 pm on Earth
- Light from sun's 1/2-way explosion point reaches Earth, after 4 minutes of travel
- Actual surface of sun is now 3/4 of the way to Earth

1:16 pm on Earth
- Sun's surface reaches Earth
- When sun's surface reaches Earth, light from the surface now arrives at the same time because it's right here.

So, if you look at the time line, the sun's surface took from 1:00pm to 1:16pm to get here - 16 minutes. But the first time we could observe it started at 1:08pm. Therefore the visible explosion took from 1:08pm to 1:16pm, or just 8 minutes.

I believe the OP is interested in this thought experiment, not whether we'd live or die or at what point our retinas burn out, so of course I'm ignoring all that.

-Dan

#20 chrisg

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Posted 21 April 2014 - 03:55 PM

Exactly! Since the sun's light and surface are moving towards us at different speeds, but will eventually be in sync, then I'm assuming that the sun will appear to expand more quickly than it actually did. But, as the surface of the sun gets closer to earth, the expansion will appear to slow to it's actual rate.
I'm definitely no expert on the lives of stars but LeDrew has it right, the surface would probably be moving much more slowly, a quick look at Wikipedia/internet, seems like the sun should take around two hours to engulf the earth.
Either way, I'm intrigued with the idea that the appearance an event like this could be distorted by distance effects. Though please chime in if the logic is wrong!
My vote would be a pair of 20mm ethos in a binoscope. Isn't that what you have Glenn?

#21 kfiscus

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Posted 21 April 2014 - 04:52 PM

You're dead and vaporized before you could squint. No thought, no pain, no fear, no problem. I read somewhere that we drastically over-estimate the speed that thought and pain travel. Pain sensations travel something like 130 mph, if I remember correctly.

#22 GlennLeDrew

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Posted 21 April 2014 - 05:02 PM

Whenever velocity becomes an appreciable fraction of light speed there must entail relativistic effects such as time dilation. Even at the paltry speed of 8km/s in Earth orbit, clocks (atomic, anyway) run at measurably different rates to those on the ground.

My eyepiece pair is the 13mm Ethos, which with my 60mm f/4.5 objectives delivers 20.8X at a spectacular 4.7 degrees.

#23 gdd

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Posted 21 April 2014 - 05:25 PM

How about those observing the explosion blow by from the midnight sky, or from the far side of the moon should the explosion occur during a lunar eclipse?

Gale

#24 Achernar

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Posted 21 April 2014 - 05:26 PM

An average nova outbursts would flash vaporize and melt the Earth's crust, blow away the atmosphere and boil off the oceans. It goes without saying everything alive on the planet would die of vaporization, the planet would be heat sterilized. All of the other planets, asteroids would be similiary affected because a typical nova outburst shines at least 100,000 times brighter than the Sun. A supernova would not only boil off the surfaces and atmospheres of the planets, they would most likely hurtle off into space from the destruction of the Sun, or be ripped apart when the blast wave hits them at ten percent of the speed of light. You would see the photosphere flare up and then you're vapor. From that close, there would be little to see if the Sun exploded as a nova or supernova. The surge in x-rays and gamma rays would kill you eight minutes after the blast, long before the ejecta hits at least an hour and twenty minutes later.

Taras

#25 Noisykids

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Posted 21 April 2014 - 05:32 PM

find and read The Year of the Jackpot. this is exactly what happens at the end.






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