I have heard a lot about Betelgeuse exploding in 2022. But, I had a doubt about this. Astronomers are still receiving signals from Betelgeuse. And if Betelgeuse is going to explode in 2022, then wouldn't we see the exploding of Betelgeuse in the night sky, 642 years later? Has Betelgeuse already exploded? If it has, how are astronomers able to still receive signals from Betelgeuse?
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asked Nov 17, 2021 at 10:19
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13$\begingroup$ "I have heard a lot about Betelgeuse exploding in 2022" -- Have you?? I haven't. Please tell us exactly where you heard this. You can include a link, if possible. $\endgroup$– James KCommented Nov 17, 2021 at 19:42
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10$\begingroup$ For what its worth, the chance of Betelgeuse going supernova in 2022 is about 1 in 500000. Any website that claims it is likely to explode in 2022 is lying to get you to click on adverts. $\endgroup$– James KCommented Nov 17, 2021 at 22:27
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3 Answers
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Light travels at a finite speed, 299 792 458 meters per second. Hence the term light year is the distance it takes light to travel in one year.
Most of what is observed in the cosmos occurred some time ago. The more distant an object is the longer it has taken for the light from that object to reach our location.
If Betelgeuse has exploded we don't know about it yet. Betelgeuse is 724 light years away. If it is going to explode in 2022, we won't see it until 2746 CE. If we do see it explode in 2022, the explosion occurred in 1298 CE
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9$\begingroup$ We don't really know exactly how far away Betelgeuse is, and that's for the same reason that some think it might explode. What will it finally take to accurately measure the distance to Betelgeuse? and also Can New Horizons be used to measure the distance to Betelgeuse (despite its fickle photocenter)? $\endgroup$– uhohCommented Nov 17, 2021 at 14:00
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Has Beteleguse exploded? No, as we have not seen the explosion.
From the reference frame of the Earth we have not seen it explode (yet). It does not matter that in Betelgeuse's frame it may have exploded already. When people discuss what happens to any object in the Universe we are always talking about what we have seen on Earth. Just because it takes a long time for us to receive the signal is irrelevant, all that matters is what we have seen.
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2$\begingroup$ Has Beteleguse exploded? No, as we have not seen the explosion. You sure this sentence is accurate? It could have already exploded, but we haven't seen it yet. As far as I know "the reference frame of the Earth" isn't usually taken to mean "an observer on Earth" either - reference frames cover the entire universe, once defined. $\endgroup$– AllureCommented Nov 19, 2021 at 0:24
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8$\begingroup$ Yes it is accurate, we can not see nor determine what has happened to any object outside of our light cone. As the information from Betelgeuse exploding has not reached us yet, then as far as we on Earth are concerned is has not happened. Worrying about events outside our light cone is what leads to the OP's confusion in the first place (as well as probably some badly written popular science webpage). $\endgroup$– RobCommented Nov 19, 2021 at 9:23
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$\begingroup$ @Rob; Light cones are a fundamental point which doesn't seem to have percolated through to the public as well as has others. Reality (for others who might be reading), in a very real sense, travels at the speed of light, the light cone you reference. People know that the speed of light is the "universal speed limit" (not including space-time, of course), but even interested and well-educated people at large seem to miss the implications of that. $\endgroup$– JohnHuntCommented Feb 19, 2022 at 15:13
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All this recent Betelgeuse hype is artificially inflated, we have absolutely no way of predicting the timeline with such accuracy and resolution. It is just the tabloids' way of exploiting the topic that allows for perpetual hype. The tabloids you are talking about, saying it's exploding in 2022, probably intend to mean that the event of its explosion will supposedly be visible from Earth in 2022, not that the actual explosion itself will occur in 2022 (with the exercise left to reader to find out that the explosion will already have occurred hundreds of years ago if it is to be visible from Earth in 2022).
If nothing changes from our perspective in 100 years, the lowest quality tabloids from 2121 will still be exploiting this subject with overinflated hype and tell you that Betelgeuse's explosion will supposedly be visible from Earth in 2122.
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$\begingroup$ Do you have anything to cite where you got your information? $\endgroup$ Commented Nov 22, 2021 at 16:48
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1$\begingroup$ @fasterthanlight There is no source for such precise information about the timeline of events for such distant celestial bodies as Betelguese, so there is no source I could cite, that's the point of my post. $\endgroup$ Commented Nov 22, 2021 at 20:45