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chrisg
sage
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Reged: 02/15/09

How would the sun appear if it exploded?
      #6478029 - 04/20/14 08:38 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!

Edited by chrisg (04/21/14 12:44 AM)


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AustinAstronomer
sage


Reged: 03/04/10

Re: What would the sun appear if it exploded? new [Re: chrisg]
      #6478115 - 04/20/14 09:33 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.

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gdd
Pooh-Bah


Reged: 11/23/05

Loc: N Seattle suburb, WA
Re: What would the sun appear if it exploded? new [Re: AustinAstronomer]
      #6478125 - 04/20/14 09:45 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


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GlennLeDrew
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Re: What would the sun appear if it exploded? new [Re: gdd]
      #6478266 - 04/20/14 11:34 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.


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TCW
Pooh-Bah


Reged: 11/05/13

Loc: The North 40
Re: What would the sun appear if it exploded? new [Re: chrisg]
      #6478271 - 04/20/14 11:39 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.

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chrisg
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Reged: 02/15/09

Re: What would the sun appear if it exploded? new [Re: TCW]
      #6478354 - 04/21/14 01:06 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?

Edited by chrisg (04/22/14 12:13 AM)


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Dodge2013
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Reged: 01/05/14

Loc: Jackson, Tennessee
Re: What would the sun appear if it exploded? new [Re: chrisg]
      #6478374 - 04/21/14 01:19 AM

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

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Midnight Dan
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Reged: 01/23/08

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Re: What would the sun appear if it exploded? new [Re: chrisg]
      #6478557 - 04/21/14 07:57 AM

Quote:

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


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ianfromoz
professor emeritus


Reged: 12/21/13

Re: What would the sun appear if it exploded? new [Re: Midnight Dan]
      #6478562 - 04/21/14 08:06 AM

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


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GlennLeDrew
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Re: What would the sun appear if it exploded? new [Re: ianfromoz]
      #6478758 - 04/21/14 10:13 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.

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mrchunks
member


Reged: 03/23/14

Re: What would the sun appear if it exploded? new [Re: Midnight Dan]
      #6478940 - 04/21/14 11:48 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..

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csrlice12
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Re: What would the sun appear if it exploded? new [Re: mrchunks]
      #6479196 - 04/21/14 01:56 PM

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

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sickfish
super member


Reged: 01/13/09

Loc: Watertown Ma.
Re: What would the sun appear if it exploded? new [Re: csrlice12]
      #6479205 - 04/21/14 01:58 PM

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

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csrlice12
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Reged: 05/22/12

Loc: Denver, CO
Re: What would the sun appear if it exploded? new [Re: sickfish]
      #6479226 - 04/21/14 02:07 PM

Hey all, I'm a Zombie!

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howard929
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Reged: 01/02/11

Loc: Low End of High Ground
Re: What would the sun appear if it exploded? new [Re: chrisg]
      #6479228 - 04/21/14 02:09 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.

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TCW
Pooh-Bah


Reged: 11/05/13

Loc: The North 40
Re: What would the sun appear if it exploded? new [Re: chrisg]
      #6479296 - 04/21/14 02:45 PM

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

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.


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howard929
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Reged: 01/02/11

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Re: How would the sun appear if it exploded? new [Re: chrisg]
      #6479315 - 04/21/14 02:59 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.

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csrlice12
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Reged: 05/22/12

Loc: Denver, CO
Re: How would the sun appear if it exploded? new [Re: howard929]
      #6479428 - 04/21/14 03:56 PM

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

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Midnight Dan
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Loc: Hilton, NY, Yellow Zone (Bortl...
Re: What would the sun appear if it exploded? new [Re: mrchunks]
      #6479443 - 04/21/14 04:04 PM

Quote:

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


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chrisg
sage
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Reged: 02/15/09

Re: What would the sun appear if it exploded? new [Re: Midnight Dan]
      #6479530 - 04/21/14 04:55 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?


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