Kevin's Watch

If not then read this:

www.dailygalaxy.com/my_weblog/2010/04/a ... recor.html

From the linked article:

The entire star explodes. No neutron star, no black hole, nothing left behind but an expanding cloud of newly radioactive material and empty space where once was the most massive item you can actually have without ripping space. The explosion alone triggers alchemy on a suprasolar scale, converting stars' worth of matter into new radioactive elements.
And we saw this. This really happened. Someday, somewhere, another massive explosion will occur and no one will be left to tweet it.

Most astronomers today believe that one of the plausible reasons we have yet to detect intelligent life in the universe is due to the deadly effects of local supernova explosions that wipe out all life in a given region of a galaxy.

While there is, on average, only one supernova per galaxy per century, there is something on the order of 100 billion galaxies in the observable Universe. Taking 10 billion years for the age of the Universe (it's actually 13.7 billion, but stars didn't form for the first few hundred million), Dr. Richard Mushotzky of the NASA Goddard Space Flight Center, derived a figure of 1 billion supernovae per year, or 30 supernovae per second in the observable Universe!

Certain rare stars -real killers -type 11 stars, are core-collapse hypernova that generate deadly gamma ray bursts (GRBs). These long burst objects release 1000 times the non-neutrino energy release of an ordinary "core-collapse" supernova. Concrete proof of the core-collapse GRB model came in 2003.

I, for one, hope we don't have anything like that in the stellar neighborhood in the next 20 or so billion years.

I love astronomy... I just wish that I had more time to study it...

Yeah, I have been aware of them for some time.

Lore,

For a Layman I'm pretty well versed in Astromonical phenomenons. Is this a relatively recent discovery due to investigations into Gamma Ray Bursts?

SerScot wrote:Lore,

For a Layman I'm pretty well versed in Astromonical phenomenons. Is this a relatively recent discovery due to investigations into Gamma Ray Bursts?

It's been in the math and theory for a while...but until this link, I was unaware that it was more than an uncertain implication.

Vraith,

Interesting. Given that the article says there's a supernova about every 30 seconds and that it goes on to say these Hypernova occur only about once a day I guess these things are incredibly rare. I also wonder if they occured only in the distant past? It seems that if they don't occur very very far away and long ago they could spell real trouble for large portions of individual galaxies.

I imagine it has to do with age. We find these novas happen far away because they'll happen in older parts of the universe. We're in a (relatively) younger part of the universe, so we don't have to worry about anything like this... yet... not that we'd know what hit us

Orlion,

The further from us a part of the Universe is the younger it is, right?

SerScot wrote:Orlion,

The further from us a part of the Universe is the younger it is, right?

Not necessarily, I'd think. In fact, if we found something further and further away, I'd think it'd be older than our part of the Universe... I mean, if something is 50 billion light years away, that part of the Universe existed at least 50 billion years plus (I presume) the time it took us to expand to where we are *shrug* I'm not as well-versed in these things as I'd like to be... I blame my upbringing

Orlion,

Here's what I think you are forgetting. The light or EM radiation we are perceiving started is journey to Earth, in your example, 50 Billion years ago. It took that long for the EM Radiation to get here. Therefore, the event we are observing is 50 Billion years in the past.

We cannot perceive the Universe as it is now at great distences. We can only see it as it was when the information was hurled out into the universe for us to percieve at some later date. That's how vast the distances are when discussing astronomy.

SerScot wrote:Orlion,

Here's what I think you are forgetting. The light or EM radiation we are perceiving started is journey to Earth, in your example, 50 Billion years ago. It took that long for the EM Radiation to get here. Therefore, the event we are observing is 50 Billion years in the past.

We cannot perceive the Universe as it is now at great distences. We can only see it as it was when the information was hurled out into the universe for us to percieve at some later date. That's how vast the distances are when discussing astronomy.

Not at all, I remember that. I think I just misread what you were saying

Orlion wrote:

SerScot wrote:Orlion,

The further from us a part of the Universe is the younger it is, right?

Not necessarily, I'd think. In fact, if we found something further and further away, I'd think it'd be older than our part of the Universe... I mean, if something is 50 billion light years away, that part of the Universe existed at least 50 billion years plus (I presume) the time it took us to expand to where we are *shrug* I'm not as well-versed in these things as I'd like to be... I blame my upbringing

Well...a far away thing looks younger [a picture of your mom in high school]...but is actually older [it happened a long time ago]. Younger than us things can, certainly do, exist further away...but we won't be able to observe them till a long time in the future, unless we can somehow circumvent/massively exceed speed of light]
There are no "older parts" of the universe itself...it was all born at the same time, though things within the universe are made and unmade all the time, so have varying "ages."
It's one of those things that makes me laugh in a dark/ironic way whenever someone in a novel or whatever says something like "You're already dead, you just don't know it yet." Cuz, for all we know, the sun blew up just now, we don't know it...but in @8 minutes...b-bye us.

SerScot wrote:The light or EM radiation we are perceiving started is journey to Earth, in your example, 50 Billion years ago. It took that long for the EM Radiation to get here. Therefore, the event we are observing is 50 Billion years in the past.

(Ignoring for the moment that this light started its journey 35 billion or so years before the Big Bang ... ) There seems to be something else that's not being taken into account here, something I believe Orlion may have been right to take into account: the expansion of the universe itself. If we're seeing something that is (let's say) 5 billion light years away, I'll grant that it took 5 billion years to get here. But does that necessarily mean that it happened 5 billion years ago? What about the extra time it took for that light to cross the increased amount of space? When this light began its journey, the distance between us and it was considerably less. If there was no expansion at all, this light would have come to us sooner, which means that the event didn't happen as long ago as it seems to us now. Right?

If so, is there some formula that takes this expansion into account, so that we can definitively say that object at X light years distant happened Y years in the past, so that Y=X-E (where E is the light years of expansion)? Or is the expansion's effect on light more complicated than that? Or is light unaffected in the amount of time it travels, and simply shifts to a lower frequency (red shift) as space "stretches?"

Zarathustra wrote:

SerScot wrote:The light or EM radiation we are perceiving started is journey to Earth, in your example, 50 Billion years ago. It took that long for the EM Radiation to get here. Therefore, the event we are observing is 50 Billion years in the past.

(Ignoring for the moment that this light started its journey 35 billion or so years before the Big Bang ... ) There seems to be something else that's not being taken into account here, something I believe Orlion may have been right to take into account: the expansion of the universe itself. If we're seeing something that is (let's say) 5 billion light years away, I'll grant that it took 5 billion years to get here. But does that necessarily mean that it happened 5 billion years ago? What about the extra time it took for that light to cross the increased amount of space? When this light began its journey, the distance between us and it was considerably less. If there was no expansion at all, this light would have come to us sooner, which means that the event didn't happen as long ago as it seems to us now. Right?

If so, is there some formula that takes this expansion into account, so that we can definitively say that object at X light years distant happened Y years in the past, so that Y=X-E (where E is the light years of expansion)? Or is the expansion's effect on light more complicated than that? Or is light unaffected in the amount of time it travels, and simply shifts to a lower frequency (red shift) as space "stretches?"

That's interesting, it also seems to imply that the universe, at this moment anyway, isn't expanding at the speed of light, it'd have to be slower or light from sources we were moving from would never reach us.
I trust there has been studies into the rate of expansion of the universe, and analysis to see if this rate would significantly alter distances involved (I imagine it'd be relative: The further the object, the less the distance will be affected by the expansion).

Specifically, I think redshift could be used to determine this.

Zarathustra wrote: If so, is there some formula that takes this expansion into account, so that we can definitively say that object at X light years distant happened Y years in the past, so that Y=X-E (where E is the light years of expansion)? Or is the expansion's effect on light more complicated than that? Or is light unaffected in the amount of time it travels, and simply shifts to a lower frequency (red shift) as space "stretches?"

Yes, the calculations take all that into account so age/distance are pretty accurate...there a lots of different ones, though...I once saw a site that listed 26 different methods/calculations.
In your question, well...there isn't any "extra" time/distance it traveled, light years is a compound measurement. If someone fires a bullet at me, it doesn't make a difference if I'm running towards, away, or motionless, at the moment our paths intersect [I'm hit] it has by definition "covered" the time/distance to my current position/time from the guns position/firing time...
Another way, maybe...The light isn't coming to us on a path that keeps stretching longer...we are intercepting the lights path at the point where it has traveled 5 billion light years [which by definition takes 5 billion years].

Edited to add to Orlion: Actually, they're pretty sure there ARE stars/galaxies so far away, and moving so fast [relative to us] that we will never see them. Unless something starts a collapse.

The whole mess got really weird, though, in the late 90's. Until then it was mostly believed the rate of expansion was almost certainly slowing, possibly steady. Almost everyone was shocked to discover it is actually accelerating. AFAIK, no one knows why that is the case. Most speculations I've seen are about "dark energy" that in some way opposes gravity. [so where mass is farther apart, this "push" becomes, relatively, stronger than gravitational "pull"] But no one really has a clue what "dark energy" is, exactly, AFAICT.

Hashi Lebwohl wrote:Things like "dark matter" and "dark energy" are scientific fudge factors that allow an explanation for things that aren't really understood. In short, since cosmologists don't know why the universe is accelerating in its expansion they came up with an explanation, albeit a less-than-satisfying one. This makes it so that they don't have to say "we don't know", the most difficult words for scientists to utter.

In fact, "the universe" leave out one very important word: observable. The parts of the universe we cannot see yet may have so much more mass that gravity from out there explains why galaxies we can see are accelerating away from us.

The peeps working on this kind of stuff are the most likely people in the world [generally speaking] to say "we don't know."
But your solution doesn't work. Those enormous amounts of mass, if they were there, would slow expansion, not accelerate it.

Hashi,

Didn't Godel present Einstein (for his 75 birthday) with a proof showing that if the universe rotated it would be possible to travel back in time based upon Einstein's theory of General Relativity?