Thanks to Neutrino Detector, We Might Get a Good Look At the Next Supernova 85
sciencehabit writes "The last star to go supernova in the Milky Way—that astronomers know of—exploded in 1604, before Galileo first turned a telescope to the heavens. But with a neutrino detector now being built within a Japanese mountain that could come online as early as 2016, researchers might be able to do something as yet undone: Make detailed observations of a supernova in our galaxy before it visibly explodes. First, astronomers would be alerted to the unfolding event by the flood of neutrinos generated when a supernova collapses. Within minutes, they could determine the general area of the sky where the explosion would occur, point their infrared telescopes in that direction, and wait for the fireworks. With the new sensor in place, instruments—especially infrared telescopes—would have an almost 100% chance of observing the next supernova in our galaxy, the researchers report."
Re:When I read news like this (Score:5, Informative)
If the supernova that this detector is designed to spot comes from within our galaxy, as they are looking for, then the star that exploded did so less than 100,000 years ago (approximately). That is well within the lifespan of our solar system.
Our sun is not likely to generate a supernova, as it has too little mass. Because there is no companion star in orbit of our sun, it is not even likely to go nova. The expectation is that several hundred million, or a billion or so years from now the sun will run out of hydrogen and switch to burning helium. At that time the energies involved will cause the sun to grow to become a red giant, which is likely to have consumed both Mercury and Venus, and possibly Terra as well. Once the energy of that process is released, (i.e. the sun runs out of Helium) the sun will collapse to a white dwarf, that will be about the size of the earth. It will continue to consume whatever remaining Hydrogen and Helium atoms are in it, but unless it collides with another star or star remnant, that's going to be the end of it's energy releasing days.
As to it destroying all traces of our existence, not so much. Even if everything in orbit and on the moon, and even the planet earth itself are destroyed, we have a lander on Titan that is likely to survive, several landers on Mars that may still be recognizable, and several interstellar missions that will still be moving. Voyager 1 is currently traveling at 17km/s, or 61,200km/h. (Which does exceed escape velocity for the sun.) While that speed will drop over time before the gravity of the sun is overcome by the gravity of other stars that will affect the flight path of Voyager 1, it is not expected to drop below 10km/s or 36,000km/h. At that speed it will travel 315,360,000 kilometers per year, a little over 1051 light seconds. (over 17 light minutes.) It will take over 1,800,000 years to travel a light year. In 100 million years it will be over 40 light years from the sun. While that may not be any great shakes as far as intergalactic distances go, it's definately far enough to avoid the effects of even a supernova if our sun were massive enough to go that route. It is possible that it will be destroyed by other stars going supernova in that time, or more likely later, but that is not a given. So even if we don't get off this rock, which I sincerely hope we can accomplish before we destroy ourselves, I expect that there will still be a trace of our existence in the universe.
Re:When I read news like this (Score:3, Informative)
I think you are off by two orders of magnitude on the voyager data. Assuming you are correct that it will be coasting at around 10km/s, the speed of light is about 3x10^8 m/s or 3x10^5 km/s so voyager will travel a light year in approximately 3x10^4 = 30,000 years, not 1.8 million years. In 100 million years it will have traveled ~3,333 light years.
Re:When I read news like this (Score:4, Informative)
The expectation is that several hundred million, or a billion or so years from now the sun will run out of hydrogen...
Make that slightly more than five billion years. Although, a few hundred million years from now, Earth will be a nasty place anyway, because of the fairly regular 1% increase in solar luminosity per every 100 My.
....and switch to burning helium. At that time the energies involved will cause the sun to grow to become a red giant, which is likely to have consumed both Mercury and Venus, and possibly Terra as well.
You mean that a helium flash will occur. But isn't that actually supposed to happen AFTER the Sun becomes a red giant? I think it is.
Once the energy of that process is released, (i.e. the sun runs out of Helium) the sun will collapse to a white dwarf, that will be about the size of the earth. It will continue to consume whatever remaining Hydrogen and Helium atoms are in it, but unless it collides with another star or star remnant, that's going to be the end of it's energy releasing days.
Again, vastly simplified and potentially misleading.
it is not expected to drop below 10km/s or 36,000km/h. At that speed it will travel 315,360,000 kilometers per year, a little over 1051 light seconds. (over 17 light minutes.) It will take over 1,800,000 years to travel a light year.
Your numbers are somewhat off, because 1,800,000 years at 10 km/s actually gives sixty light years. Obviously, the figure can become substantially different depending of the actual trajectory.
Re:Neutrino Detection? (Score:4, Informative)
Why yes, neutrinos have been detected. The relevant paper is this: C. L Cowan Jr., F. Reines, F. B. Harrison, H. W. Kruse, A. D McGuire (July 20, 1956). "Detection of the Free Neutrino: a Confirmation [sciencemag.org]". Science 124 (3212): 103â"4. Note the date. Frederick Reines won the 1995 Nobel Prize for these experiments [wikipedia.org] that established the existence of the neutrino.
It's hard to say that they're indirect detections. How do we even detect something like an electron? By the fundamental forces like electromagnetism, which is no different in principle from the methods used to detect neutrinos, which work by weak nuclear force interactions. The trouble is that neutrinos are affected only by gravity and the weak nuclear force (making them an example of a dark matter WIMP), so detecting them is rather hard, given that the forces involved are so weak.
Multi-variable Detector Performance (Score:5, Informative)