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Given that the stars' distances to Earth are measured in light-years (for example, Sirius is 8.6 light-years away from Earth), what we are seeing as Sirius now is actually its state 8.6 years ago, right?

So it is possible that a star (maybe not Sirius, I don't know, it's just an example) somehow explodes and creates a supernova, and if this is the case, we will see this event 8.6 years later (I assume everything is right up to this point).

So my question is, is it possible for me while looking at the sky on a lucky day, suddenly see the explosion of a star that happened x years ago and be the first eye witness of this event? In other words, is there a technology on Earth (emphasis on "on Earth" here, the satellites or space shuttles do not count since they might be slightly closer to the star than the Earth is) that can see this before me?

My logic is that even the greatest telescope "sees" whatever light it receives. So since a telescope cannot increase the speed of light it receives, it shouldn't be more fast than me. And since light is the fastest way of transferring information, I assume that I am as possible as NASA to see such an event. Is there any way this assumption is wrong?

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Naked eye nova are fairly common, several per year. Here's one. Naked eye supernova are far rarer. SN1987a in the large Magellanic cloud was naked eye visible (vid). From this list, it appears the supernova in 1987 was the most recent naked eye supernova. There was a naked eye gamma ray burst in 2008, but I don't think anyone actually got outside in time to see it.

If you have 50 years to look at the stars, you might see a supernova. If you have a small telescope, you can pick them up pretty regularly in nearby galaxies.

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  • $\begingroup$ Thanks! I do have a telescope but it hardly lets me to see the satellites of Jupiter. Do you think I can be able to see one? And how frequent do you mean by "regularly"? $\endgroup$
    – jeff
    Commented Aug 27, 2015 at 12:09
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    $\begingroup$ They're usually one or two a year in one or another of the Messier object galaxies. You have to keep up with Sky and Telescope skyandtelescope.com or similar, to find out when and where. $\endgroup$
    – Wayfaring Stranger
    Commented Aug 27, 2015 at 12:13
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Supernova create huge spikes in neutrino emissions. Since neutrinos pass through a stellar mass mostly unimpeded, they're visible up to 3 hours before the shockwave even starts to affect the star's surface.

Since neutrinos travel at the speed of light, they will always keep their 3 hour head start. Thus, unless you have a neutrino detector buried a few miles below your house, you're unlikely to be the first to observe a naked eye supernova, even with a telescope pointed directly at the star.

The first supernova definitively detected by a neutrino spike before it was visible was SN 1987A.

As more neutrino detectors come online, and as their ability to pinpoint the exact direction that neutrinos come from is improved, it's almost certain that the next naked eye supernova will have dozens of observatories and thousands of amature telescopes pointed at it before it's even possible for these telescopes to detect the event.

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    $\begingroup$ Slight clarification: We don't know if neutrinos can travel at the speed of light. $\endgroup$
    – HDE 226868 ♦
    Commented Aug 27, 2015 at 18:54
  • $\begingroup$ Just curious, where are you getting the three hour figure from? Does it take that long for a Supernova to propagate from the center of the star to the star's surface? $\endgroup$
    – Sidney
    Commented Aug 27, 2015 at 18:58
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    $\begingroup$ @HDE226868 -- It is close enough to the speed of light that, over 180,000 lightyears, the neutrinos arrived between 2 and 3 hours before the photons for SN 1987A. $\endgroup$
    – Ghedipunk
    Commented Aug 27, 2015 at 19:10
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    $\begingroup$ @Sidney -- The 3 hours comes from the Wikipedia article on SN 1987A, which says: "Approximately two to three hours before the visible light from SN 1987A reached Earth, a burst of neutrinos was observed at three separate neutrino observatories." ---- Other sources say it could be up to tens of hours, such as Dr. Ian O'neill of Discovery News: astroengine.com/2008/03/10/… -- though that's not based on a scientific paper, so put your skeptic hat on. $\endgroup$
    – Ghedipunk
    Commented Aug 27, 2015 at 19:13
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    $\begingroup$ If you're watching a supernova from up close, make sure you don't get radiation poisoning from the neutrinos. $\endgroup$
    – Mark
    Commented Aug 28, 2015 at 0:17

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