Starship Asterisk*

The NGC 7293 Helix Nebula image really stirs my theological imagination!

http://antwrp.gsfc.nasa.gov/apod/ap070803.html

Hello all, I'm new to this forum and also fairly un-enlightened when it comes to matters of time and space so I'm easily puzzled by the vastness of our universe and the tools we use to explore it. A couple of questions if I may:

I've referenced the Helix Nebula (APOD 8/3/2007) as an example.
If this nebula is seven hundred light years from Earth, doesn’t that mean that if we could see it with our naked eye, then we would be seeing it as it looked seven hundred light years ago? And probably today it’s completely blown up or disintegrated or whatever happens to a dying star?

Ok…then when we use a high powered telescope to view the object….aren’t we really gaining on the actual time it takes for the light to reach us? Kind of like looking back toward the present.

I realize even our most powerful scopes are only capable of looking out so far but if we had a telescope of unlimited power (I know...please don't laugh too hard) would it not be possible to see the Helix Nebula (or whatever's left of it) in real time as it is at this very moment?

rmulanax wrote:http://antwrp.gsfc.nasa.gov/apod/ap070803.html

Hello all, I'm new to this forum and also fairly un-enlightened when it comes to matters of time and space so I'm easily puzzled by the vastness of our universe and the tools we use to explore it. A couple of questions if I may:

I've referenced the Helix Nebula (APOD 8/3/2007) as an example.
If this nebula is seven hundred light years from Earth, doesn’t that mean that if we could see it with our naked eye, then we would be seeing it as it looked seven hundred light years ago? And probably today it’s completely blown up or disintegrated or whatever happens to a dying star?

Ok…then when we use a high powered telescope to view the object….aren’t we really gaining on the actual time it takes for the light to reach us? Kind of like looking back toward the present.

I realize even our most powerful scopes are only capable of looking out so far but if we had a telescope of unlimited power (I know...please don't laugh too hard) would it not be possible to see the Helix Nebula (or whatever's left of it) in real time as it is at this very moment?

In order to see it from today's perspective you'd need to see it at a distance of less than one light day. The telescope can only see things from the perspective of the distance it takes light to travel from the object to your telescope lens/mirror. It's a shame though.
We see out own sun as it was about 8 minutes ago (I think it's 8 light minutes away - please correct me if I'm wrong). If our sun went nova now then we would know in 8 minutes time.

I believe that the way it works is this.

The more powerful the telescope, the smaller the angular area of sky you will be looking at. Thus, you will be able to see farther but at the cost of less overal sky coverage in a single image.
(imagine holding a Dime up to the sky and seeing the ammount of sky covered by it. This represents a small Earth bound telescope looking at the moon. Now do the same thing with the head of a pin, This represents a much larger telescope). It would take approx 100 or so Images from this larger telescope to cover the same area as the smaller scope so each individual image would contain the same ammount of information as one image from the smaller telescope. This makes the images from the larger scope clearer which also allows it to view things that are farther away.

Now the other factor is the ammount of light gathered to produce the image.

From Earth, you are limited to the ammount of night "time" and clear sky view to produce your images. In Space, there is no "Day time" or atmosphere to cause this time limit so the time spent trained on an area will be significantly greater allowing for much deeper images to be produced. But the light that gets gathered still needs to reach the light gathering surface (mirror) of the telescope before it can be detected and interpreted to produce an image.

So, the only way to see the current state of the Nebulae is to physically go there.

Thank you both for your responses and observations and it has helped me to grasp a slightly better understanding of these things but I'm afraid I'm still hopelessly befuddled and I haven't even had a drink.

When I think about it, I’m not sure we can ever see or realize anything in absolute real time. Even up close, there must be a teeny tiny slight delay in the time it takes, not only for the light to reach our eyes, but also for the reaction time it takes our brains to analyze what we’re looking at and then to translate the information so that we recognize what we see….or at least for us to realize that we’re seeing something whether we actually recognize it or not.

But back to the nebula! I'm still stuck so please bear with me for a moment. If we could somehow see edge-on the space between the actual nebula and where we are at any given moment….couldn’t the traveling light be likened to a series of frames? Not too much unlike movie frames on film. Each frame would present a slightly earlier or later image of the original object, depending on which end of the spectrum we’re on.

I have no idea what the actual numbers might be (or probably even what I'm talking about) but to drastically simplify, let’s say that there are 700 frames between Helix Nebula and ourselves. If we’re looking at the object with our naked eye, we’re probably only able to see the last frame to reach us (the one that took seven hundred light years to get here). But let’s say our most powerful telescope can see through the first 100 frames. Then wouldn't we be seeing the nebula as it appeared only six hundred light years ago? Maybe not? I don’t know. I guess at those great distances, there’s still a time delay based on the speed of light and relative movement of the objects, including our own planet, as we move through space, that would have to be factored into the formula.

no matter how powerful telescope is, it sees only light that is here and now, that's on Earth at the moment of observation. NOT light that is lightyears away.

the same way, you don't see light that objects reflect, you see light that your retina adsorbs.

Well, that's a good explanation makc. Thanks! Now I can mark a big red "X" through my faulty hypothesis.

However, your answer has prompted another question in my mind:
If the light from the Helix Nebula took 7 hundred light years to reach us, what did that point in space look like, say 8 light minutes before it got here? In otherwords, was it just a black or blank space and then suddenly the nebula appeared? And, could a telescope that just happened to be pointed at that exact point have actually seen the nebula first (or at least a few light minutes or seconds before someone here could have seen it with the naked eye? I apologize if I'm sounding too lame for anyone to answer.

I do not understand you. "Light minute" refers to distance, not time.

Thousands of years ago it was just another star that was nearing the end of its life. To those viewing it then, it would be just another unremarkable point of light in the night sky (as unremarkable as they believed them to be anyway.)
Then something remarkable happened, The star blew up though no one here knew about it not alteast until 700 years after the fact. So 700 years after this star blew up, the light finally reached Earth.
Man, at that point in time, noticed that a star in the evening sky suddenly brightened and over the course of a couple of weeks it started to dim until it became, once again, unnoticeable. Man, at that point in time, had no means by which to continue observing this stellar phenom. as they posessed nothing capable of magnifying and focusing the light from the dimming nova. (or did they?)

Sorry Makc, I was only trying to make reference to time. Thanks for your explanations. I now believe my entire premise is probably wrong. I will go back to the books.

you need a diagram
o and about the telescope. it doesn't look "farther" into space as much as it is looking deeper into the light


a bit of a non sequitor but it makes me think of fractals

A diagram would be good. I do better with visuals and I also understand the fractal analogy, thanks.

I guess I was mistakenly thinking that a light image (the reflection of an object) traveling through great distance in space, would somehow stretch out almost from its origin to it's final destination (or at least to wherever it runs into something...Earth for instance. And then the tail end of that image would eventually catch up.

My logic (faulty or not) would therefore be...if we could remain observers for 7 hundred light years right here on Earth...wouldn't the entire destruction of the Helix Nebula finally "play out" right before our eyes? If so, then it seems to me that there must be a long continum of the original image traveling through space.

At some point the light from the disentegrating nebula would finally diminish and there would be nothing left to see.

Are the blue and red true color representations?

Here are some other images of the nebula (past APODS)

http://www.seds.org/messier/xtra/ngc/n7293.html

http://antwrp.gsfc.nasa.gov/apod/ap070223.html

http://antwrp.gsfc.nasa.gov/apod/ap060112.html

http://antwrp.gsfc.nasa.gov/apod/ap970901.html IR

http://antwrp.gsfc.nasa.gov/apod/ap000828.html

http://antwrp.gsfc.nasa.gov/apod/ap960422.html CLOSE UP

I see the colors are quite relative and not necessarily in the normal (average) human eye visible spectrum... right??? The Feb 2007 image is also fascinating...

Maybe the message "you will see Me coming on the clouds" will stem from work done in astronomy??? Fun food for playful thought anyway...

These posts are great because everyone's right! But rmulanax your logic is not faulty -

if we could remain observers for 7 hundred light years right here on Earth...wouldn't the entire destruction of the Helix Nebula finally "play out" right before our eyes? If so, then it seems to me that there must be a long continum of the original image traveling through space.

- this is absolutely true - it's just that a telescope can only view the very end that reaches us here...

Theoretically, if we could travel (with our telescope!) at or above light speed we could visit different points in that continuum and view events at different periods of history (didn't Einstein say that if you travelled away from a clock at light speed the hands would never move?) So you're correct, if you could travel faster than light away from the Helix Nebula you could see it un-disintegrate?! Although there would be a lot of optical problems associated with operating a telescope travelling at light speed I'm sure!

emc wrote:Maybe the message "you will see Me coming on the clouds" will stem from work done in astronomy??? Fun food for playful thought anyway...

Let's not forget that the Heavenly New Jerusalem is 1,500 miles big also.

Kinda hard to miss that one coming, , ,

Norval

I'm not certain exactly when the nebula came into being but if it's parent star exploded 10000 years ago, we have been able to view it for the last 9300 years. It will continue to expand, at most likely it's current rate, and in another 9300 years it will likely be twice its current size and half as dense. Then it will have been visible for 18600 years. In another 18600 years it will grow to twice again its then current size and be again 1/2 as dense.

http://amazing-space.stsci.edu/resource ... php&a=,eds

The caption states the inner region of the nebula is about 3 light years across. There are a large number of stars that appear to be in the foreground... (maybe they are not??? or likely I just don't understand what I am seeing???) if those stars are in the foreground, then how close are they to each other on average?

http://antwrp.gsfc.nasa.gov/apod/ap070803.html

Seeing as there is more than 700 light years between us and this spectacular nebula, Longitudenally speaking, there could be quite a few light years between the forefront stars.

emc wrote:The caption states the inner region of the nebula is about 3 light years across. There are a large number of stars that appear to be in the foreground... (maybe they are not??? or likely I just don't understand what I am seeing???) if those stars are in the foreground, then how close are they to each other on average?

IIRC all the 'individual' stars we can see are in our own Milky Way galaxy, so they are all actually in the foreground in relation to other galaxies that we can see.
Stars which appear to be right next to each other may be many light years apart, it's just by chance that they happen to line up from our point of view. One could be much further away from us than the one which 'seems' to be right next to it.

Sorry about my dumb question I did not realize the Helix Nebula is outside our galaxy. I should do more research before posting... Thanks!

emc wrote:Sorry about my dumb question I did not realize the Helix Nebula is outside our galaxy. I should do more research before posting... Thanks!

As one of the closest planetary nebulae, I don't think it is outside our galaxy. 700 light-years is not much, astronomically speaking. Some of the stars you see could be foreground and some backgroud. Although some of the stars appear to be quite close together, (the helix itself is less than 3 ly across), they could be separated by hundreds or even thousands of light years.

I truly appreciate everyone's kind comments. Most were both informative and interesting and I think I can say I've actually learned something about space and optics and should be able to look at these incredible APODs with a new perspective.

BMAONE23 wrote:I'm not certain exactly when the nebula came into being but if it's parent star exploded 10000 years ago, we have been able to view it for the last 9300 years. It will continue to expand, at most likely it's current rate, and in another 9300 years it will likely be twice its current size and half as dense. Then it will have been visible for 18600 years. In another 18600 years it will grow to twice again its then current size and be again 1/2 as dense.

http://amazing-space.stsci.edu/resource ... php&a=,eds

BMAONE23,

You mentioned twice in this thread that the star "exploded". Do I assume that you were not talking about the star that created this nebula? It is a planetary nebula, not a supernova or even a nova. It was created when a dying star, previously a red giant, blew off its outer layer, not exploded, leaving the exposed core as a white dwarf and the outer layer as an expanding cloud of gas illuminated by the white dwarf's light.