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See a Supernova From Your Backyard

samzenpus posted more than 2 years ago | from the no-sunglasses-required dept.

Space 182

hasanabbas1987 writes "Want to catch a glimpse of the closest supernova astronomers have discovered in the last 25 years? All you need to do is get yourself a small telescope or a pair of binoculars (some DSLRs would do just fine as well). Astronomers think that they may have found the supernova within hours of its initial explosion on August 24. Generally, supernovas are around 1 billion light years away but this one is only 21 million light years away. The supernova is in the Pinwheel Galaxy and you can see it within the Big Dipper."

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182 comments

Discovered within hours of its explosion? (4, Informative)

freaktheclown (826263) | more than 2 years ago | (#37309354)

I'm pretty sure it exploded about 21 million years ago.

If a supernova were close enough to be seen within hours of its explosion, we probably wouldn't be here.

Re:Discovered within hours of its explosion? (1, Insightful)

Anonymous Coward | more than 2 years ago | (#37309390)

From our reference frame, this happened hours ago. The summary is correct. You are not.

Re:Discovered within hours of its explosion? (4, Informative)

freaktheclown (826263) | more than 2 years ago | (#37309426)

No the summary is not correct. It did not happen "hours ago" from any reference frame. Other articles written about this got it right; this one did not.

Re:Discovered within hours of its explosion? (0)

Anonymous Coward | more than 2 years ago | (#37309476)

The question you really need to be asking yourself is: does it really freaking matter? The summary is quoted from the article and slightly modified. The meaning was understood if the exact wording was not technically correct.

Re:Discovered within hours of its explosion? (1)

freaktheclown (826263) | more than 2 years ago | (#37309512)

I never made a big deal out of it, but then you insisted I was wrong.

Re:Discovered within hours of its explosion? (5, Interesting)

Kagura (843695) | more than 2 years ago | (#37311560)

TO READERS OF THIS STORY'S COMMENTS: If you want to read the real comments for this story, scroll 3/4 of the way down the page to skip that ridiculous "when is now in relativity" arguing that shows up in EVERY cosmology story on Slashdot. Seriously guys, shut up already.

Re:Discovered within hours of its explosion? (1)

Cyberax (705495) | more than 2 years ago | (#37310416)

Speaking "it happened millions years ago" is not correct since there's no absolute reference frame.

In our reference frame it happened days ago.

Re:Discovered within hours of its explosion? (0)

Anonymous Coward | more than 2 years ago | (#37310728)

Is this what they teach you kids at community college? You fail at relativity. From our reference frame it happened millions of years ago. The light just reached us a few days ago.

Dumb ass.

Re:Discovered within hours of its explosion? (1)

Cyberax (705495) | more than 2 years ago | (#37310942)

Nope, you've failed your community college.

Read about light cone. Assume that the point of the light cone is 1 week ago (at the time when explosion has been registered). What is the time difference between explosion and the apex of that light cone? Answer: zero, since light travels at time-like paths.

That's the _natural_ way of defining time distances in relativity.

Re:Discovered within hours of its explosion? (0)

Anonymous Coward | more than 2 years ago | (#37311210)

Is there a name for the phenomenon where someone hears about some advanced concepts like "light cone", and it causes him to get the easy stuff wrong with unusual level of certitude? FFS, just look at the figure on wikipedia [wikipedia.org] , it shows that the "hypersurface of the present" is flat, it is not one of the cones.

Re:Discovered within hours of its explosion? (0)

Anonymous Coward | more than 2 years ago | (#37311698)

Wow, the worst part of your ignorance is you don't even know how dumb you are.

You answer ignores causality or the speed of light, or both. In your construction either the speed of light is infinite, or the supernova has no causal relationship with the light being emitted and beginning the journey which would eventually reach us 21 million years later. Thus your construction violates relativity, and is wrong.

The light left the star that supernova'ed 21 million years ago, from our inertial frame of reference. It took 21 million years to cross the space in between, again from our frame of reference, ergo the supernova happened roughly 21 million years ago, from our frame of reference. All that happened a few days ago due to light cones is the arriving light caused us to know this fact.

Dumb ass.

Re:Discovered within hours of its explosion? (3, Informative)

Raenex (947668) | more than 2 years ago | (#37311278)

It did not happen "hours ago" from any reference frame.

Is that really true? Somebody mentioned elsewhere [slashdot.org] in this thread that:

"Yet, no time has passed for the traveling light. Or more precisely: if an observer had followed the light emitted from the supernova at almost the speed of light, very little time would have passed in his frame of reference. So what we take as 21 million years would have been nearly instantaneous for our traveling observer."

It seems that you can define a reference frame arbitrarily close to the speed of light at an arbitrary starting position and get the desired duration.

Re:Discovered within hours of its explosion? (0)

Anonymous Coward | more than 2 years ago | (#37309456)

There is no reference frame for time. It exploded 21 million years ago, not hours ago. What you are experiencing is known as real-time lag.

Summary is incorrect.

Re:Discovered within hours of its explosion? (0)

Anonymous Coward | more than 2 years ago | (#37309554)

You are obviously very wrong. Accepting your reasoning means every star you see at night still exists. By extension, background radiation we can measure from the big bang means the big bang is still occurring. We could get into multiverses etc (which would be fun), but...

Original comment about the summary being incorrect is valid and true.

it's in our reference frame (2)

rubycodez (864176) | more than 2 years ago | (#37309852)

The star that exploded is not moving at relativistic velocities in relation to us, and the non-inertial part of our and its reference frames are tiny too. It exploded 21 million years ago in our reference frame.

Re:it's in our reference frame (0)

Anonymous Coward | more than 2 years ago | (#37310812)

No. http://en.wikipedia.org/wiki/Relativity_of_simultaneity. From our reference frame, it happened now, because the light gets here now. For an observer equidistant from the supernova and Earth, today on Earth and the supernova are separated by 21 million years.

Re:Discovered within hours of its explosion? (1)

Ex-MislTech (557759) | more than 2 years ago | (#37310246)

This is one of the major issues of society today.

The stupid strongly believe they are right.

The intelligent get modded troll...

Re:Discovered within hours of its explosion? (0)

Anonymous Coward | more than 2 years ago | (#37310566)

from our reference frame the light reached us now, light travels at c, in our frame the distance is 21 million light years, so we can calculate that it happened 21 million years ago. i.e. it is not 'now' in our reference frame. (in the frame of the photons the nova, and our observation are simultaneous).

however, in astronomy it is common to describe events like super nova as happening at the time that the light reaches us. for example we say Tycho's supernova was in 1572, not 9000 BC.

It happened 21M years ago in our frame too (1)

drnb (2434720) | more than 2 years ago | (#37310746)

From our reference frame, this happened hours ago. The summary is correct. You are not.

It happened 21 million years ago in both the frame of reference of the solar system of the star gone nova and in the frame of reference of our solar system. We may have only just seen the evidence but we know it is 21 million light years away, so we know when it happened. I don't think distance changes one's frame of reference, I think only motion does. Two travelers in our system, one at 0.25c and the other at 0.5c have different frames due to their respective velocities, not distance from the nova.

I will now patiently wait for actual physicists to correct my erroneous and simplistic belief. :-)

Re:Discovered within hours of its explosion? (0)

paiute (550198) | more than 2 years ago | (#37309392)

I'm pretty sure it exploded about 21 million years ago.

In the star's POV, yes. In our POV, it just exploded.

Re:Discovered within hours of its explosion? (0)

Anonymous Coward | more than 2 years ago | (#37309460)

Why would the star's POV be 21 million years ahead of our POV? Why not the other way around?

Re:Discovered within hours of its explosion? (0)

realityimpaired (1668397) | more than 2 years ago | (#37309818)

Not sure if you're trolling or what, but... the star is 21 million light years away. That means that the light which just reached us recently (actually about a week ago, but it was detected about 4h after it was possible to detect the supernova) was actually generated 21 million years ago.

From the star's POV, 21 million LY away, the explosion happened 21 million years ago. From our point of view, however, the light is only just recently observable, and as such it only just happened, for us.

To put it in more perspective... if you had a telescope that was capable of such a feat, you could travel to Procyon (11.4LY away) and watch Shrub take the oath of office on the White House lawn. For us, it happened 11 years ago. For Procyon, it's about to happen.

Re:Discovered within hours of its explosion? (0)

Anonymous Coward | more than 2 years ago | (#37310208)

Quote 1:

the light [...] was actually generated 21 million years ago.

Quote 2:

From our point of view [...] it only just happened, for us.

Which one is correct?

Re:Discovered within hours of its explosion? (1)

MokuMokuRyoushi (1701196) | more than 2 years ago | (#37310568)

You're mixing time and point of view(or more accurately, time and light's travel time).

you could travel to Procyon (11.4LY away) and watch Shrub take the oath of office on the White House lawn. For us, it happened 11 years ago. For Procyon, it's about to happen.

11 years ago, it happened. Period. It happened here and it happened in Procyon. The fact that Procyon doesn't see it happen til 11 years later doesn't mean it didn't happen 11 years ago, it simply means that Procyon is 11 light years away and can't know it happened until the point that they see it. You see?

Re:Discovered within hours of its explosion? (0)

Anonymous Coward | more than 2 years ago | (#37310854)

To put it in more perspective... if you had a telescope that was capable of such a feat, you could travel to Procyon (11.4LY away) and watch Shrub take the oath of office on the White House lawn. For us, it happened 11 years ago. For Procyon, it's about to happen.

Umm... yeah, if I had a telescope capable of FTL travel, I'd call it a starship, not a telescope. Or was that not the feat you were mentioning>

Re:Discovered within hours of its explosion? (2)

superdave80 (1226592) | more than 2 years ago | (#37310880)

Let's do a simple example to show you why you are completely wrong.

Let's say your grandma dies right in front of me at 12:00 noon. I call you, and leave a message saying what happened. You don't check that message until 6:00 p.m. Are you really going to try and convince people that grandma died at 6:00 p.m.? Of course not.

Re:Discovered within hours of its explosion? (1)

pyrosine (1787666) | more than 2 years ago | (#37309558)

You seem to be troubled here: The light from some number of hours after the star going supernova has finally reached us after 21 million years

Re:Discovered within hours of its explosion? (5, Informative)

gmueckl (950314) | more than 2 years ago | (#37309690)

Yet, no time has passed for the traveling light. Or more precisely: if an observer had followed the light emitted from the supernova at almost the speed of light, very little time would have passed in his frame of reference. So what we take as 21 million years would have been nearly instantaneous for our traveling observer. Simultaneity is a weird thing when time is relative.

Re:Discovered within hours of its explosion? (0)

Anonymous Coward | more than 2 years ago | (#37310922)

And yet there is no such observer, so your statement is more or less irrelevant.

Re:Discovered within hours of its explosion? (0)

Anonymous Coward | more than 2 years ago | (#37311792)

We are not the light nor is an observer measuring it following the light. We are measuring it from our frame of reference which we know to be 21 million light years away. It happened 21 million light years ago as far as we are concerned.

Velocity, not distance, brings relativity (1)

drnb (2434720) | more than 2 years ago | (#37310828)

I'm pretty sure it exploded about 21 million years ago.

In the star's POV, yes. In our POV, it just exploded.

No. Well not unless the speed of light is infinity all of a sudden. Given the speed of light we all know and love, and an object 21 million lightyears away, an event we observe happened 21 million years ago. IIRC its the velocity of the observer, not distance, that brings relativity into play.

Re:Discovered within hours of its explosion? (0)

Anonymous Coward | more than 2 years ago | (#37309400)

The claim is that the science station located within the (now) supernova star system noticed it within hours.
This is actually first contact with LGM's!

(free advice: RTFA before you spout drivel)

Re:Discovered within hours of its explosion? (0)

Anonymous Coward | more than 2 years ago | (#37309438)

Maybe I'm alone here on this, but why do people have to always bring up the lightspeed delay? While it didnt actually get discovered "hours" after it happened, it's a useless statement to point it out. Functionally, it WAS discovered hours after since we can't be causally connected to anything until we intersect it's lightcone. It may be an oversimplification, but for our purposes it did just happen.

Or maybe I'm just arguing the other side of vague semantics.

Re:Discovered within hours of its explosion? (2)

Iskender (1040286) | more than 2 years ago | (#37309526)

I suspect that a lot of the time the people pointing it out do so because they have nothing else to contribute to the discussion.

I'm guessing it's a form of disinterest really - someone sees news about an exceptional supernova and would rather discuss a sentence in a Slashdot summary.

Some other poster already posted a very constructive post though, I suggest we read that instead: http://science.slashdot.org/comments.pl?sid=2413680&cid=37309370 [slashdot.org] .

Re:Discovered within hours of its explosion? (3, Insightful)

Missing.Matter (1845576) | more than 2 years ago | (#37309740)

Because that's what nerds do (and consequently why everyone hates them). They're infuriatingly pedantic, and love to correct people even on the smallest details because it makes them seem smarter (and therefore better).

Re:Discovered within hours of its explosion? (4, Insightful)

fyngyrz (762201) | more than 2 years ago | (#37309860)

Because that's what nerds do (and consequently why everyone hates them). They're infuriatingly pedantic, and love to correct people even on the smallest details because it makes them seem smarter (and therefore better).

More accurately presented / corrected is better, and the reason the people you call "nerds" infuriate others is because the lazy and low-functioning hate being reminded the things they believe are imprecise because they don't take the time (or have the ability) to think things out to a more precise conclusion.

It is not anyone's job to dumb things down (or leave them down, when presented that way) so you'll be comfortable. If the status quo is to be moved, up is clearly the ethical and moral way to move it. If it is not to be moved, you'll need a better reason than "I'm uncomfortable with statements that are more accurate than mine."

"Getting things right" is a much more laudable human goal than "keeping things approximate."

Further, in this particular venue, the audience is generally a good deal smarter than, say, on Gawker. If you present in a clumsy or inaccurate manner here, it's really kind of silly to expect it to go unremarked.

Re:Discovered within hours of its explosion? (2, Interesting)

Missing.Matter (1845576) | more than 2 years ago | (#37310006)

Right, exactly what I was talking about. Sanctimonious, enlarged ego, inflated sense of self importance. This post is a good example why the people I call "nerds" infuriate me and most others. You really believe you're better and smarter than most people don't you?

Further, in this particular venue, the audience is generally a good deal smarter than, say, on Gawker.

In this particular venue it's especially annoying because we all know about relativity and it's entirely tangent to the discussion.

Re:Discovered within hours of its explosion? (0)

Anonymous Coward | more than 2 years ago | (#37310282)

In this particular venue it's especially annoying because we all know about relativity and it's entirely tangent to the discussion.

If we all knew about it there wouldn't be all that discord up ^there^, but you're right about the second part.

Re:Discovered within hours of its explosion? (1)

dmartin (235398) | more than 2 years ago | (#37310646)

Except we don't.

Many of the discussions are saying that an object 21 million years ago had to have blown up that long ago. There are even discussions of "there is no reference frame for time", suggesting that they are just using Galiean relativity. There are many other discussions pointing out incorrectly that in Earth's frame it was discovered within hours. The reason this is incorrect is that (to a good approximation) the star and Earth are not in relative motion, they are just separated by a considerable distance.

There have just been a couple of people pointing out the correct statement in terms of reference frames, namely that someone traveling at nearly the speed of light and following the beam would have experienced relatively little time. There are others that point out the statement actually means we detected the supernova within hours of the first rays of light reaching us.

I think the real reason people get infuriated with "nerds" is that they spend so much time insisting that they are right, being pedantic about the details while still harboring many misconceptions -- then getting defensive when these misconceptions are bought to their attention.

Re:Discovered within hours of its explosion? (0)

Anonymous Coward | more than 2 years ago | (#37310978)

There have just been a couple of people pointing out the correct statement in terms of reference frames, namely that someone traveling at nearly the speed of light and following the beam would have experienced relatively little time.

That's a correct statement, but not the correct statement, and since it's such an unrealistic situation it's not even a useful correct statement.

Re:Discovered within hours of its explosion? (0)

Anonymous Coward | more than 2 years ago | (#37311046)

And by the way, if you think I'm being pedantic, I'm not. I'm objecting to your implication that anyone who didn't make that specific useless statement obviously doesn't understand relativity.

Re:Discovered within hours of its explosion? (1)

dmartin (235398) | more than 2 years ago | (#37311292)

And by the way, if you think I'm being pedantic, I'm not. I'm objecting to your implication that anyone who didn't make that specific useless statement obviously doesn't understand relativity.

That is not the statement that I am making. The statement that I am making is that of the people that make statements about reference frames, the majority are incorrect, particularly those that make the statement that it has only been a couple of hours in the Earth's frame.

I am ambivalent about people who took the statement at the intended reading "discovered within hours of the first light rays arriving at Earth" as they have not demonstrated a lack of knowledge about relativity.

Re:Discovered within hours of its explosion? (0)

Anonymous Coward | more than 2 years ago | (#37309440)

I wish to subscribe to your newsletter.

Re:Discovered within hours of its explosion? (2)

exploder (196936) | more than 2 years ago | (#37309584)

There's not some cosmic clock that marks a simultaneous "now" for every point in the universe, such that the light from that supernova actually traveled for 21 million years to reach us. Simultaneity doesn't exist, independent of reference frame. In our reference frame, the supernova exploding and the light reaching us are simultaneous events. If you don't believe it, pick up a physics book--even a very watered-down pop physics book from Barnes & Noble will set you straight on this issue.

Re:Discovered within hours of its explosion? (0)

Anonymous Coward | more than 2 years ago | (#37309768)

I'm having a hard time finding a physics book where light leaving the star and reaching us are simultaneous events. They all mention this "speed of light" thing, 299,792,458 m/s.

Thought experiment for you: if we pointed a mirror back at the star so they could see their own explosion, according to your logic the light leaving the mirror and reaching the star would be simultaneous events too. So putting A and B together, the light leaving the star, and its mirror reflection returning to the star would be simultaneous events. This would imply instant interstellar communication.

Re:Discovered within hours of its explosion? (1)

fyngyrz (762201) | more than 2 years ago | (#37309898)

Those same physics books have a few things to say about the amount of time that passes at lightspeed, too; as does the light that results from that supernova. Simultaneity is a little difficult to pin down in such cases.

Thought experiment for you: if we pointed a mirror back at the star so they could see their own explosion, according to your logic the light leaving the mirror and reaching the star would be simultaneous events too. So putting A and B together, the light leaving the star, and its mirror reflection returning to the star would be simultaneous events. This would imply instant interstellar communication.

If you were riding a particle of light in your experiment, that's pretty much what you'd see, yes.

Unless you're quite specific about your frame of reference here, it is easy to describe the event inaccurately, mismatching the frame with the description.

Re:Discovered within hours of its explosion? (1)

Anonymous Coward | more than 2 years ago | (#37310004)

Last time I checked, history books and news articles report time according to Earth's reference frame. Why do people have to bring in stuff like "If you were riding a particle of light"? If you make that assumption then of course dates are screwed up. Even the US independence is no longer 1776. Please stick to Earth's reference frame, people are already confused enough.

Re:Discovered within hours of its explosion? (1)

Cyberax (705495) | more than 2 years ago | (#37310498)

Yup. And in Earth's frame of reference the explosion happened some days ago.

Re:Discovered within hours of its explosion? (0)

Anonymous Coward | more than 2 years ago | (#37310680)

That statement is unfortunately not supported by any physics book. Light in vacuum travels at c in any inertial frame of reference. In particular, it travels at c in Earth's frame of reference. Doing the math, light takes light 21 million years to travel 21 million light-years. Therefore in Earth's frame of reference the explosion occurred 21 million years ago. To claim that in Earth's frame of reference the explosion happened some days ago, you need to find a physics book that claims that light travels at infinite speed when it's going towards you. And what would be the speed of light going away from you? Infinite too? 1/2 c maybe? LOL.

Re:Discovered within hours of its explosion? (2)

rubycodez (864176) | more than 2 years ago | (#37309872)

Except you pseudo-relativity experts don't understand we can establish our reference frame as a standard, and that the exploding star is essentially in our reference frame, as it is not in relativistic motion in relation to us, nor is it or we in huge potential well in relation to each other. It's just a real-time signal propagation lag we experience, no different than sound of firecracker two city blocks away taking a second to reach you.

Re:Discovered within hours of its explosion? (3, Informative)

Cyberax (705495) | more than 2 years ago | (#37310526)

It IS different. With a firecracker we have a flash which reaches us 'instantaneously' and then a sound which takes a few moments to reach us. Moreover, different observers with clocks synchronized to a same source would see the flash at the same time (we're ignoring relativity) so they can agree on a universal frame of reference (Earth + UTC time).

With light it's different. We have NO other faster channel. Imagine that you have no way of knowing that firecracker has exploded except by listening to a sonic boom. And you have no faster way to communicate except by shouting.

Re:Discovered within hours of its explosion? (0)

Anonymous Coward | more than 2 years ago | (#37310830)

It is different, but not how you think. There are no privileged frames of reference, and simultaneity is relative, sure. But you don't understand the consequences of these facts. It does not mean that light reaching a target is equivalent to the event the light bears witness to happening. You can prove that easily enough by taking a single inertial frame of reference, extending it out arbitrarily long, and watching the light speed delay. Since the frame of reference is the same, so is simultaneity, ergo the light speed delay doesn't delay simultaneity, just observation.

So construct this supernova from our frame of reference, we can do that, it's cool, there are no privileged frames so ours is as good as any, just be aware that your mileage will vary with reference frame. The supernova explodes. The speed of light is constant. It takes millions of years to reach us. We witness it happening.

From this, and information we have inferred on the distance of the star from us, we also infer when it happened in our frame of reference. While this is completely different than when another observer in another frame of reference would infer the supernova to happen, it is consistent with our frame of reference.

From our frame of reference, the supernova exploded millions of years ago.

Re:Discovered within hours of its explosion? (1)

Cyberax (705495) | more than 2 years ago | (#37310912)

"You can prove that easily enough by taking a single inertial frame of reference, extending it out arbitrarily long, and watching the light speed delay"

Except you can't do this. There's such a thing called 'light cone' and events outside of our light cone are NOT well-defined from physical point of view. And if you try to define it naively by extrapolating observer's future path - you're going to be in a world of hurt because galaxies move relative to each other and the space itself expands.

For example, imagine an observer on Earth ten weeks ago watching the star that is going to become supernova. It is going to become a supernova a few weeks later, but there's no way to know this.

Another example, when I speak "I was born in 30 years ago" that means I can get my diary from ten years old which say that I was 20 years old at that time. Not so with the supernova - it has not HAPPENED few weeks ago here.

Re:Discovered within hours of its explosion? (0)

Anonymous Coward | more than 2 years ago | (#37311178)

Yes, and you don't understand what a light cone means, obviously. Events outside of our light cone are not yet causally linked, but that doesn't imply anything about simultaneity of events within a single inertial frame of reference. Your problem is you are mixing frames of reference. We aren't defining things from multiple frames of reference, but from that of a single observer, or at least from frames of reference so similar as to mean no difference when referencing supernova millions of light years away (i.e., all of planet Earth).

All you are doing is exposing your ignorance by conflating causal relationships with temporal relationships. While we can't predict causal relationships outside of our light cone, i.e. we can't predict that we will see light from a supernova before our light cone intersects with the supernova, it does not mean the supernova happened when our light cones intersected. Your assumption destroys either causality, or the constancy of the speed of light, because for your construction to work either the speed of light would have to vastly increase so that the light reaches us the instant the supernova happen, or that the light from the supernova had no causal relationship with the supernova itself.

In short, you are wrong. What's worse, you don't know you are wrong.

Re:Discovered within hours of its explosion? (0)

Anonymous Coward | more than 2 years ago | (#37311106)

Are you really so thick you don't think we can establish the speed of sound and thus simultaneity with sound only?

Establish three equidistant stations. measure round-trip time, subtract 3x the retransmission latency, and you have the speed of sound, and can synchronize clocks at the three stations. Now you can make measurements of sounds from distant events, whether in the same reference frame, or in other reference frames moving relative to yours, and compare timestamps afterward through low-speed communication.

What's missing here? Nothing.

Re:Discovered within hours of its explosion? (0)

Anonymous Coward | more than 2 years ago | (#37310884)

Not to be a jerk here, but before you continue to post, I think you have some serious misunderstandings of relativity. "The exploding star is essentially in our reference frame" is meaningless. Things are not "in" reference frames. (Unless you are really talking about light cones, which you don't seem to be)

Re:Discovered within hours of its explosion? (2)

gstrickler (920733) | more than 2 years ago | (#37311396)

This is correct. From the Earth's reference frame, this supernova just occurred, and it occurred 21M LY away. As I demonstrate with an example below, it is misleading and meaningless to talk about how long ago it occurred, or in which order things occurred using any other frame of reference.

Suppose a supernova 1000LY away had two stars near enough that the supernova had an effect on them, and one of those stars (star B) was 5 LY from the supernova and one (star C) was 15 yr from the supernova. However, star C is 990 LY from earth, while star B is 1005 LY from earth. The high energy rays from the supernova will have an effect on star C 15 years after the supernova, and we'll observe that effect 990 years afterward for a total 1005 years after the supernova. Star B will be effected 5 yrs after the supernova, and we'll observe it 1005 years after that, or 1010 years after the supernova. So, 1010 years after the supernova, we will have seen all three events reach earth, but not in the order in which they occurred relative to the supernova. We observe the effect on star C 5 years before we observe the effect on star B, even though star B was 10 LY closer to the supernova and "happened first" or "longer ago".

Now suppose (purely hypothetically, since we don't know that it's even possible) that stars B & C both emit deadly gamma ray bursts directed at earth as a result of the supernova. The burst from star C would reach us 5 years after we observe the supernova, and 5 years before we even observe the effect on star B. We would be dead and never see the effect on star B. It doesn't matter that B also emitted a deadly burst, or that "it happened first". What matters is the order in which they effect the destination, and as this example shows, that doesn't depend upon what order they occurred in from another reference frame (e.g. the frame of the supernova), or "how long ago" they happened. The effect on star B clearly happened "10 years before" star C, but what had an effect on earth first was star C, therefore making the effect on star B irrelevant to earth's frame of reference. While it's accurate that from earth's reference 10 yrs after we observe the supernova that the effects on star B happened 1005 years ago while star C was 995 yrs ago, it's also misleading and meaningless because the "more recent" event is the one that first caused a problem on earth. Causality is only relevant at the destination frame of reference, and everything occurs when it is observed, not "xx years ago".

The physical universe is called space-time for a reason, you can not refer to space and time independently except from a single reference frame. Causality in relativistic frames (and all frames in space-time are relativistic, even if you're not moving at relativistic speeds), requires that all events be sequenced by the frame of the observer, otherwise you will encounter paradoxes of causality where some observers in different reference frames (different places in space-time) will observe two effects a and b in the opposite order. Each is correct from the frame of reference, yet it's inconsistent to say that a occurred before b, or that b occurred before a, and it's misleading to say that a occurred x years ago and b occurred y years ago because the effects on the observer are based upon their arrival at the observer's frame of reference, not the order in which they occurred in any other reference frame.

Re:Discovered within hours of its explosion? (1)

hawkinspeter (831501) | more than 2 years ago | (#37309626)

No - it just exploded, but it took 21 million years for it's 'now' to arrive here.

Re:Discovered within hours of its explosion? (0)

Anonymous Coward | more than 2 years ago | (#37311836)

It exploded about 21 million years ago in all non-relativistig timeframes. It's the light which took 21 million years to reach us, not the 'now'.

Think about seeing, then hearing a lightning strike. The sound and the light happened at the same time, it just took more time for the sound to reach you. You wouldn't say the strike happened "now" when you heard the thunder, it happened (just before) you saw the flash. The "now" of the strike didn't take time to reach you, the sound did.

Re:Discovered within hours of its explosion? (4, Funny)

interkin3tic (1469267) | more than 2 years ago | (#37309702)

Important lesson here: there is no "+1 pedantic" mod. On slashdot or in real life, which is why no one was too interested in making out with you new year's eve 1999 when you were telling everyone that the millennium wouldn't start until the next year.

Re:Discovered within hours of its explosion? (0)

Anonymous Coward | more than 2 years ago | (#37311432)

Technically, it wouldn't start until the year AFTER the next, since it was still 1999.

(Can I get a +1 Pedantic too?)

Convenient (0)

Anonymous Coward | more than 2 years ago | (#37309360)

I know it's just algorithms to blame, but conveniently there is an ad for a cheap telescope up there. Could be conspiracy, I suppose.

Supernova fun! (5, Informative)

Mr. Underbridge (666784) | more than 2 years ago | (#37309370)

Just as a warning to those trying star-hunting for the first time: finding this guy can be tricky. Best thing is to get some charts from AAVSO.org. Use 2011fe as the search. Print a 15 degree chart for finding the general area from the big dipper, then 1 degree and 2 degree charts for finding the supernova.

For now, the supernova is getting easier to find by the day - I tried last week and couldn't find it, but now it's pretty bright. However, finding the correct area can be tough because there's no obvious landmarks in the area unless your sky is dark enough to make out the face of the galaxy. And, unless you live in an exurban or rural area, it won't be. Otherwise, you'll need to rely on patterns of stars at the 1 degree scale. Otherwise, you can easily be looking at the supernova but not know which star it is.

There are good threads over at cloudynights.com that provide helpful images and advice. Good luck all! It's really fun to know that you're looking at something that didn't exist last month (correcting for travel time of the light, of course).

Re:Supernova fun! (0)

Anonymous Coward | more than 2 years ago | (#37309412)

I live in Las Vegas, and was wondering if you could help me locate the full moon in the night sky. TIA!

Re:Supernova fun! (0)

Anonymous Coward | more than 2 years ago | (#37309530)

I live in my mother's basement, and was wondering if you could help me locate the hamster in my rectum. TIA!

TFTFY, TANSTAAFL, YMMV, and so on.

Huge Optics Needed (5, Informative)

Iskender (1040286) | more than 2 years ago | (#37309486)

Another warning from another astronomy enthusiast: note that the guy in the video talks about "decent-sized" binoculars and then specifies 20x80 or 20x100.

That 100 at the end means the lenses at the front have a diameter of ten centimetres (four inches) each! So under any normal circumstances those are considered HUGE rather than decent binoculars.

My advice on how to see this supernova: ask someone into astronomy who has a telescope or huge binoculars. Doing the observing "from scratch" is probably a too tall order.

Re:Huge Optics Needed (1)

hedwards (940851) | more than 2 years ago | (#37309606)

I was wondering about that, because even with my 200mm lens with a 1.6x crop factor trying to take a photo of the moon is really tough to do, as it's far enough away that metering doesn't really work very well.

This event is happening significantly further away, which makes me wonder what sort of a lens one would need in order to observe it. I'm guessing that you'd need something on the order of a 1000mm lens to get a halfway decent view. At 500mm you're getting a 5 degree view, and I'm guessing that you'd need to get closer than that. And even that's probably underestimating things.

Re:Huge Optics Needed (4, Informative)

Iskender (1040286) | more than 2 years ago | (#37309694)

1.6x crop probably means you have a Canon DSLR. All I can say is that you should really explore the manual modes - with digital you can just try different shutter speeds until you get it right. The moon is illuminated by the sun so the settings that work in sunny daylight should work for photographing the moon too.

Photographing stars often isn't a matter of magnification, but rather of light gathering. Only few stars are close/large enough to be imaged as disks, and that's with professional equipment - you'll never resolve a star into a disk yourself.

Rather, stars are point sources. Everything comes from a single point, only the intensity and colour of that point varies. If you want to see fainter stars with a camera, you just need to expose longer. An 18-55 kit lens might very well be able to image this given the right other circumstances. The resolution of 500 mm would be more than enough in any case.

In fact, the hardest problem would probably be to get low enough magnification - the sky moves all the time and therefore everything is blurred when you make the shutter speeds longer. This means you need large apertures more than you need long focal lengths, and pretty fast you need a tripod/mount that's capable of tracking the sky.

Re:Huge Optics Needed (2)

ceoyoyo (59147) | more than 2 years ago | (#37310366)

The focal length of the lens and the distance of the object has very little to do with it.

You can't get a good picture of the moon in an automatic mode because it's very bright. Go to a manual mode, dial in 1/250 s (to start) at f8 and move around until you get a picture you like.

Focal length isn't going to make a bit of difference when you're looking at something 21 million light years away. It's a point, no matter what. The focal length of your lens will determine whether you JUST get a point of light in the frame, or whether you get some surrounding stars for context.

No matter what, your light meter is completely useless when taking pictures of stars.

Re:Huge Optics Needed (1)

hedwards (940851) | more than 2 years ago | (#37310988)

If focal length isn't going to make a difference, then why did the astronomers recommend using binoculars that are giving that much magnification?

And yes, it's going to be worthless for taking photos of stars, but by the same token, if you need that much magnification to see the super nova, then I'm not sure why a camera would be any different.

Re:Huge Optics Needed (1)

ceoyoyo (59147) | more than 2 years ago | (#37311302)

They recommend 20x100 binoculars. The 20 is the magnification. The 100 means 100 mm, which is the "aperture," or light gathering capability of the binoculars. I put that in quotes because I mean actual aperture, not the aperture/focal length ratio photographers usually mean when they say "aperture." Think of it (roughly) as the diameter of the main lens. The supernova is dim, so you need a fair amount of light gathering power to brighten it to where you can see it with your eyes. If you're using a camera you can make up for a smaller aperture with a longer exposure.

Magnification is completely irrelevant when you're looking at a point source like a star or a supernova, except that it determines your field of view, which makes a more or less pretty picture. But a point is still a point no matter how much you magnify it.

Re:Huge Optics Needed (2)

GumphMaster (772693) | more than 2 years ago | (#37311314)

They recommended 20x80 or 25x100 binoculars. The second number is the diameter in mm of the objective (front) lens. It needs to be this big in order to collect sufficient light to make the object clearly visible to a naked eye. The first number is the magnification (crudely speaking the ratio of objective to eyepiece focal lengths). 20 is simply the common magnification in binoculars, which have fixed eyepieces, with objective lens sizes large enough to be useful.

You'll also notice that when recommending a telescope there's no mention of focal length or magnification at all, just object lens/mirror size > 75mm. Eyepieces in telescopes can be changed to change magnification and field of view but it is the collecting area that is truly important to making the dim visible.

Now, if only someone could move M101 about 10 or 15 degrees further south I might have a hope of seeing it.

Re:Supernova fun! (0)

Anonymous Coward | more than 2 years ago | (#37309656)

Search for 2011fe take you to a page in spanish...gee..thanks a lot.

Re:Supernova fun! (1)

ArsenneLupin (766289) | more than 2 years ago | (#37310126)

Search for 2011fe take you to a page in spanish...gee..thanks a lot.

Indeed, thanks alot. Someone really should explain to those damn spaniards the difference between a supernova and the moon! So, how do I now get that horrible image wiped off my retina?

Re:Supernova fun! (0)

Anonymous Coward | more than 2 years ago | (#37309682)

Just as a warning to those trying star-hunting for the first time: finding this guy can be tricky.

Oh c'mon. Just look upward for something made of champagne.

Re:Supernova fun! (0)

Anonymous Coward | more than 2 years ago | (#37311776)

The problem won't be observing the supernova; it will be observing Messier 101 (the galaxy the supernova is in) to confirm that what you're seeing is the supernova and not just another dim star. Supernovas often outshine the galaxies they occur in.

The supernova itself will just look like a point of light, and will be hard to distinguish from a star, but if you see the galaxy as well, and the point of light is in the right place, you're seeing the supernova. With a good enough optical system and a dark enough site you can do that. Probably you could see just the supernova with less, but not the galaxy.

ha, triangles (0)

rim_namor (2454342) | more than 2 years ago | (#37309384)

Triangles. I knew that the geometry classes will become useful for something one of these days, and there you go. That, and playing pool. Also chicks dig geometry. I get lots and lots of chicks... I think.

Re:ha, triangles (2)

Dunbal (464142) | more than 2 years ago | (#37309404)

Also chicks dig geometry. I get lots and lots of chicks... I think.

I think that has a lot more to do with you pouring bread-crumbs all over yourself than geometry.

Gamma rays? (0)

Yvan256 (722131) | more than 2 years ago | (#37309472)

Any danger of gamma rays? Though I suppose if my skin were to turn green, that'd be a sign that something's happening.

Re:Gamma rays? (0)

Anonymous Coward | more than 2 years ago | (#37309538)

It is 21 million light years away, there is no risk at all. Exponentially lowered risk the farther away you are.

Re:Gamma rays? (1)

Anonymous Coward | more than 2 years ago | (#37311202)

Would you and every other fool kindly stop abusing "exponentially"? It means O(e^bx), not O(x^2).

It's quadratically lowered risk the further away you are!

Re:Gamma rays? (1)

TheRaven64 (641858) | more than 2 years ago | (#37309546)

No. 25 million light years is a long way. To put it in perspective, that's 250 times the diameter of our galaxy. The fact that you need a telescope to spot it should give you a clue - it's spewing out vast amounts of radiation (or, it was, 25 million years ago), of which visible light is just part, but it's still barely visible with the naked eye. Even if it was emitting 1,000 times as much gamma radiation as visible light, it would be a negligible amount.

It's actually naked eye visible? (2)

NotSoHeavyD3 (1400425) | more than 2 years ago | (#37309676)

Really? I mean I know the Andromeda galaxy is normally the furthest naked eye visible object and that's 2 million LY away. (This thing is 10X further and is still naked eye visible? That's amazing.)

Re:It's actually naked eye visible? (0)

Anonymous Coward | more than 2 years ago | (#37310162)

This thing is 10X further and is still naked eye visible? That's amazing.

It would be, but it's not visible to the naked eye - hence the advice on telescopes and binoculars.

Re:Gamma rays? (1)

Iskender (1040286) | more than 2 years ago | (#37309586)

You're probably joking, but let's put it like this:

The star Betelgeuse could go supernova tomorrow or a million years from now. It's about 600 light years distant. The consensus is that it won't pose any danger to us.

The supernova we're discussing here, SN 2011fe, is about 20 million light years away from us. So if this supernova was 30 000 times closer to us it would most likely still be safe. =)

Re:Gamma rays? (1)

Anynomous Coward (841063) | more than 2 years ago | (#37310338)

Hmm. It would be quite dangerous to us - some sorry fellow on the road and me - as I'd surely notice it driving home late in the evening and would be terribly distracted.

Money (2)

udachny (2454394) | more than 2 years ago | (#37309556)

Here is a great idea for improving the economy - stimulate more R&D, research and development, more supernovas need to be found, more telescopes must be built, put the money into this, get some engineering going. Fuck wars, lets build telescopes. Build more telescopes, build more space ships. Need more engineers for this, need more scientists, need more architects, need more of everything. Build more, spend on building, stop wars and get going.

Re:Money (3, Informative)

mikech2000 (1230790) | more than 2 years ago | (#37309652)

Sorry but discovering interesting things about the universe offers no ROI during the next fiscal quarter.

Re:Money (2)

dotancohen (1015143) | more than 2 years ago | (#37309714)

Here is a great idea for improving the economy - stimulate more R&D, research and development, more supernovas need to be found, more telescopes must be built, put the money into this, get some engineering going. Fuck wars, lets build telescopes. Build more telescopes, build more space ships. Need more engineers for this, need more scientists, need more architects, need more of everything. Build more, spend on building, stop wars and get going.

Go check how many space exploration lobbyists exist in Washington then check how many petroleum and military-tech lobbyists exist in Washington. Now try to rephrase your suggestion in terms of oil usage and military technology.

How Long Do They Last? (1)

Doc Ruby (173196) | more than 2 years ago | (#37310462)

I'm always curious about these observed supernova events. How long do they last in a well-defined event? Even if not visible to the unassisted human eye at cloudless night, how long by optical telescope? How long can the more subtle beginnings and endings be seen with radar telescope and our more advanced instruments?

Milliseconds? Minutes? Hours? Days? Months? Lifetimes? Planetary lifetimes? Depends on the supernova?

Re:How Long Do They Last? (4, Informative)

mojo-raisin (223411) | more than 2 years ago | (#37310916)

I don't know how long it lasts, but its daily intensity is being plotted here [aavso.org] . From what little I've read, it can be expected to increase like this for ~14 days from the initial explosion

Re:How Long Do They Last? (5, Informative)

jmichaelg (148257) | more than 2 years ago | (#37311272)

This web page [gsu.edu] has a graph that shows the different light curves for type 1 and type 2 supernovae.

A Type 1 supernova reaches it's peak light output around 10-15 days of the initial explosion and then exponentially decays over a period of years. As the curve is exponential, a good chunk of the luminosity is lost within a couple of months and then the loss rate tapers off somewhat.

A type 2 supernova reaches its peak output in a few days decays, plateaus for a few months and then begins decaying again over a span of years.

The mechanism behind a type 1 is fairly well understood but the variation in modeled and observed luminosity is greater than 2%. A paper a few years back suggested that the variation might be evidence of dark matter but subsequent modeling has shown that the 2% variation can be accounted for by where the observer happens to be relative to the explosion as the explosions aren't symmetric.

Re:How Long Do They Last? (1)

thrich81 (1357561) | more than 2 years ago | (#37310960)

The "event" of spectacular brightness lasts a couple of months or so and depends on the type of supernova. As far as the "endings" are concerned, the remnant debris can be seen for thousands of years at least -- the Crab nebula and its central pulsar is a supernova remnant from a supernova seen on Earth in 1054 AD.

Supernova are generally 1B LY away?? (0)

Anonymous Coward | more than 2 years ago | (#37311746)

Generally, supernovas are around 1 billion light years away but this one is only 21 million light years away..

Huh? Supernova regularly occur much closer, in our own galaxy, and some have occurred in our galactic neighborhood. The Crab Nebula is a supernova remnant from 1054AD and is only 6500 LY away. SN1987 was in the LMC and is something like 200,000 LR away. Betelgeuse is a prime candidate to go supernova soon and it's just a short 600 LR away.

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