First Evidence of Supernovae Found In Ice Cores 145
KentuckyFC writes "Supernovae in our part of the Milky Way ought to have a significant impact on the atmosphere. In particular, the intense gamma-ray burst would ionize oxygen and nitrogen in the mid to upper atmosphere, increasing the levels of nitrogen oxide there by an order of magnitude or so. Now a team of Japanese researchers has found the first evidence of a supernova's impact on the atmosphere in an ice core taken from Dome Fuji in Antarctica. The team examined ice that was laid down in the 11th century and found three nitrogen oxide spikes, two of which correspond to well known supernovae: one event in 1006 AD and another in 1054 AD, which was the birth of the Crab Nebula (abstract). Both were widely reported by Chinese and Arabic astronomers at the time. The third spike is unexplained, but the team suggests it may have been caused by a supernova visible only from the southern hemisphere or one that was obscured by interstellar dust."
The Crab Nebula wasn't born in 1054 AD (Score:3, Insightful)
The Crab Nebula is 6,500 light years away from earth (http://en.wikipedia.org/wiki/Crab_Nebula).
This means the birth of the Crab Nebula was in the year 5446 BC. Mankind witnessed it 6,500 years later.
News stories on such phenomena invariably leave out this little fact, i.e., that which is witnessed by man in the sky usually happened thousands of years earlier than when he actually saw it. This makes it confusing for the average reader.
Re:The Crab Nebula wasn't born in 1054 AD (Score:3, Insightful)
But isn't it more sensible when speaking in a historical tone to refer to a celestial objects birth relative to our time line and not the objects actual birth?
I suppose it would be astute to word it in the tune of, "1054 AD, which was when man observed the Crab Nebula". This isn't accurate either as it may suggest that the Nebula could have existed prior to the observed date. ::shrug::
Re:The Crab Nebula wasn't born in 1054 AD (Score:5, Insightful)
Re:The Crab Nebula wasn't born in 1054 AD (Score:5, Insightful)
Try: 1054 A.D. which is when man observed the birth of the Crab Nebula
One thing I'm curious about. Does this mean that we admit freely that extra-solar events affect the climate of this planet? Anyone have a slide rule handy and some star charts or galactic weather maps? Can we calculate probable effect on current climate conditions from extra-solar events?
Re:The Crab Nebula wasn't born in 1054 AD (Score:3, Insightful)
the birth of the Crab Nebula was in the year 5446 BC. Mankind witnessed it 6,500 years later.
Traveling at the speed of light no time passed between the explosion and the observation at Earth. So the explosion really did happen in 1054.
Re:The Crab Nebula wasn't born in 1054 AD (Score:3, Insightful)
Re:The Crab Nebula wasn't born in 1054 AD (Score:5, Insightful)
AIUI, it's customary in Astronomy to ignore the time it took for the light to reach us and consider that things in the sky happen when we see them happen. Not that they're not aware of it, it's just that it makes things easier to talk about, especially to laymen. In general, people either understand about the time lag and take it for granted, or neither understand nor care.
Re:The Crab Nebula wasn't born in 1054 AD (Score:2, Insightful)
No. I know perfectly well that all inertial frames are equals.
I object to parent's statement that the true birth of the Crab Nebula was in 5446 BC. It just makes no sense because it assumes that time is absolute.
Also, why 5446 BC? The Earth (and the whole Solar System) moves relative to the Crab Nebula, so we need to compensate for the time dilation. It'll be small, but it's there.
And it gets even more fun if you are talking about quasars and remote galaxies when you need to consider effects of space expansion.
Re:The Crab Nebula wasn't born in 1054 AD (Score:2, Insightful)
Point of view is contentious, after all, our point of view should take into account the knowledge of the time taken for the photons to reach us.
Correct! In fact, one could accurately say that 1054 AD was the birth year of the Crab Nebula from the point of view of the photons!
Since they are traveling at the speed of light, all points along their path occupy the same time. Hence, 1054 AD on Earth coincides with the birth of the Nebula. The summary is photocentric.
Re:The Crab Nebula wasn't born in 1054 AD (Score:4, Insightful)
Glaring error? Frankly, I thinking giving 1054 AD as the birth of the Crab Nebula is the most precise way of pinpointing that event. We could have obtained absolutely no information about the event before that date anyhow.
Given general/special relativity, appealing to some objective background time and saying that the supernova occurred "simultaneous" to events in 5446 BC on Earth is the truly ridiculous claim on a cosmic scale. To another equally valid observer, those two events are not simultaneous, and could be in a different order.
If our understanding of cosmology or general relativity ever fundamentally changed, it's the date of the observation that's going to actually be relevant. If your audience *is* a bunch of scientists, they're going to recognize this...
Re:parent is troll (Score:3, Insightful)
Debate is good, and everyone is permitted to have there opinion and ideas, more so when there is perhaps new data.
Why should we not discuss them? Being denied to speak anything against the consensus is what church and queen have done for centuries to keep everyone inline. It not science when you must agree with consensus or get silenced.
Snow crystal structure? (Score:3, Insightful)
Why peculiar? That's exactly what I would expect. As snow gets piled higher, there will come a point when the weight from the accumulated snow is more than the strength of snow crystals can support. At the crystals get crushed, the structure will change from a porous mass of snow crystals to solid ice with some bubbles of gas.
This shift from snow to ice will happen quickly, because as a snow crystal breaks the weight it supported will shift to nearby crystals, increasing the stress on them. It could well be that the shift from porous to solid ice happens in a short period of time and, depending on average amount of snowfall, this could take tens of years of accumulated snow to happen.
Re:The Crab Nebula wasn't born in 1054 AD (Score:3, Insightful)
There is a lot of material for the layman to easily understand. Enjoy the reading
Re:The Crab Nebula wasn't born in 1054 AD (Score:4, Insightful)
You know that this is what a relativistic physicist will tell you, right?
Depends on how fast he's moving.
Re:The Crab Nebula wasn't born in 1054 AD (Score:3, Insightful)
However, this is being posted on an astro physics website.
And as such, wouldn't it make sense that they assume certain knowledge (such as the fact that the impact of events here on Earth will occur on a timeline relative to the distance from the event) without needing to spell it out?
Would you expect a math journal to explain how addition works before using it in a proof?