Young Supernova in Milky Way
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The most recent supernova in our Milky Way happened around 1680 or so we thought; it was called Cassiopeia A. Astronomers have estimated about three supernovae every century occur in Milky Way galaxy. Doing the math, since 1680 there should have been about 10, or one every thirty-two years or so.
Why haven’t we seen one? Well aside from the fact that the Milky Way is a very big place, it’s also pretty dusty in spots. Keep in mind that while the estimate was a supernova about every thirty-two years, but they may have happened long ago and the light it just getting here.
In 1985 astronomers using the Very Large Array spotted the radio image of what they identified a supernova remnant near the center of the galaxy ~ 26,000 light-years away (left image). The supernova was not visible to us because it was hidden by a thick cloud of gas and dust; they named the supernova G1.9+0.3 and gave it an age of somewhere between 400 and 1,000 years,
In 2007 a team of astronomers being led by North Carolina State University’s Stephen Reynolds too a look at G1.9+0.3 with the Chandra X-Ray Observatory and whoa, this thing grew! The supernova expanded by roughly 16 percent. To be sure the team was seeing what they thought they were seeing they got a very fast approval to use the VLA to look at the supernova again just like the first time (right image).
They have found surprises not the least of which is based on the expansion rate the supernova was much younger than they thought, just 140 years.
Check out the press release at the National Radio Astronomy Observatory for more detail and they also have a short but really good back ground on supernovae.
Image Credit: Green, et al., NRAO/AUI/NSF via NRAO
The press release states, “The newly-discovered object is the remnant of an explosion only about 140 years ago.”
But the explosion certainly didn’t occur in 1868, since the former star is 25,000 light years from the Earth. I wonder how many people reading the news reports will be confused about exactly when the explosion occurred. (Unless I’m the one who is confused.)
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There are a couple ways to figure out how far it is. It’d be nice if there’s a light echo visible in some wavelength. We know how fast light moves.
I’m with you Rodney, I wrestled a little with that when I wrote the post. Cassiopeia A is less than half the distance of the one in the post it HAS to be younger by 10,000 years. In other words let’s say both Cassiopeia A and G1.9+0.3 happened at the exact same moment; we would have to wait over 10,000 years AFTER we detected Cassiopeia before we’d be able to detect G1.9+0.3. I can agree with “Youngest” if it defined as age when detected, but if we use the typical definition of the word, no.
I’ve written quite a bit (to and for myself) about the speed of light not being constant and therefore time would be variable by the same amount.
That said, I watched (and missed quite a bit) of a scientist on one of the Discovery channels who is a proponent of a variable speed of light (VSL) theory and got a bit of vindication for some of my own thoughts. I suppose you could say I’m a philosophical astronomer and it gets sticky in spots.
I’m sure dark matter is in there somewhere but so far I’ve only skirted the edges of the subject. Anyway, thanks again, Tom, for the venue.
I’m particularly impressed by the lack of “flaming” in here and it’s a welcome change. Apparently your site appeals to a higher class of speculators and observers.
One of the things I’ve become convinced of is there is some form of energy or wave that’s ubiquitous and has a velocity that is faster than C. I only hope I live long enough to see it discovered.