Scientists discover galaxy's youngest supernova Where have all the Milky Way's supernovas gone? Contrary to what would seem a basic survival instinct, many astronomers are positively keen to get more catastrophic, solar-system-busting explosions in our home galaxy. But until recently, a good Jerry Bruckheimer space opera hasn't appeared to reach Earth since the seventeenth …
... we're not seeing more Supernovas in our own Galaxy because they've already occurred and dissipated to the point of relative invisibility (ie: they're just dust now).
Consider: when we look at other galaxy, we are looking far back in time. (Andromeda is 2.5 million LY, so when you look at it you see it as it was 2.5 million years ago.)
Maybe supernovas were once very common (which is why we can observe them in other galaxies) but today are very are rare. Our own galaxy is only about 100,000 LY wide (and about 1000 LY thick, according to our best estimates).
The remnants of a supernova are light, radiation, and matter. It's this same matter that later forms planets (and us - don't forget, you're made of stardust!). In other, very distant galaxies, we see the light and radiation, but don't forget they occurred millions of years ago.
If we were in one of those other galaxies, we would be able to observe the supernovas of the Milky May. Maybe we don't see many here because the light and radiation has already passed, and all that's left is the dust.
Yes, Tim - your conjecture would be correct IF the number of super nova dropped in the last few million years and did so equally across the universe. There is no reason to believe that both of those items happened. This leave two simpler reasons
1) There are fewer nova in the Milky Way - again no real good reason for this - but one strange result is reasonable.
2) We are having a hard time seeing them thru the dust - a very likely issue. There is less dust between us and Andromeda there there is between us and the center of the milky way.... which seems to be correct. For example, there is reason to believe that there are very large black holes at the center of galaxies - we can't see the center of our own galaxy - so we do not know.
Now where DID I leave the flying saucer?
Tim, I'm pretty sure that the NASA scientists would have thought of that. They would be looking at Galaxy's that at the moment in time that we are seeing them are the same age as us. ie, if Galaxy A is 10 millions years old, and the Milky Way is 5 million years old then they would only look at Galaxy A for the comparison of numbers of supernova if Galaxy A was 5 million light years away, so we would be seeing Galaxy A when it was 5 million years old.
Lets face it NASA may hire people who are crazy (diaper astronaut lady) or have no common sense (the lady who gave out personal deatils to a 419er from her work computer) but they dont tend to hire overtly stupid people...
2.5e6 years is far too short for any measurable change in the rate of supernovas.
There are stars made out of hydrogen left over from the big bang, and eventually such stars will be few and far between. When such stars supernova, the release huge clouds of gasses including a variety of elements - not just hydrogen.
The sun formed about 4.5e9 years ago, from gasses ejected from supernovas. The sun will supernova in about 3.5e9 years, and the gasses ejected will eventually form new stars. Stars are still forming in our galaxy, and this is not going stop any time soon. There will be plenty of supernovas to watch in the next billions of years.
(Maybe aliens put up some dust clouds to protect us from supernova ratiation ;-)
Not likely. First of all, 2.5 million years is a tiny fraction of the lifetime of a galaxy. Observation of the two satelite galaxies of ours (the Large and Small Magellanic Clouds) also suggest a higher rate, and they are far closer than the Andromeda Galaxy (157,000 ly and 197,000 ly respectively). Unless all galaxies evolve in exact synchrony, your scheme is not very likely. Furthermore, we can estimate the number of supernova candidates from the spectral types of stars. In so-called starburst galaxies the fraction of supernova candidates is higher than average, but our galaxy seems to be quite regular in this sense. I think interstellar dust and gas are the main culprits in not seeing them
They suffer years of geek-hating abuse at school, do years of sex-less college and then University, then finally get a job in the super-competitve field of high level astronomy at NASA.
Finally, after suffering a life of ridicule to be taken seriously, a couple of jocks embarass them among their peers by shouting about their vaginas.
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