Observable objects existence

[jetstream]

Well after watching another show on the Discovery channel I have a question: are most, if any, distant objects we view still really out there?For example M81,M82 which are about 12,000,000 years away travelling @ about 671,000,000 mph-can we detrmine if these (& others) exist in the form that we see?

[JulianO]

No - we can't tell. Light is the fastest thing in the universe, so we can't know if they still exist right now. 

However, as far as we know things like M81 have been around for a good 12 billion years, so there is no expectation they could vanish in a mere 12 million years.

[nmoushon]

We have absolutely no idea if anything we see, visually or with images, is still there. As the light we see is anywhere from a couple years old (The closest known star) to billions of years old. We could find out tomorrow that the closet star, which is slightly over 4 light years away, exploded for some unknown reason. But it actually would not have exploded that night but slight over 4 years ago.

[jetstream]

The mail just arrived here & my Aunt sent me a clipping from the Washington Post-topic-Newfound galaxy is growing fast,dated Oct 24/2013.Says here z8_GND_5296 light left 13.1 billion years ago,giving a glimpse of the universe @ 700 million years old.I can see the use of Doppler shift to find the distances of the objects in order to form a map into the past-which has revealed the expanding bubble arangement of our universe-with dark matter being the "bubbles".....but the more I look through my scope and realize I must be looking at the past-whether near or distant-the more "time & reality" confuse me.I was wondering if any real evidence supported the actual existence of the objects in my scope,good point JulianO about no expectation they should dissapear in such a "short" period of time.

Back to raking the leaves

[JulianO]

Well, you just have to accept it in the end.

In just the same way you accept your Aunt is still the same, even though you haven't seen her for a minute, an hour, a day or whatever - unless you keep checking she may not be there, and as soon as you put the phone down, you are back to not knowing! That way probably lies madness!

Its just the time scale is different.

Betelgeuse may well have blown up - but we still see it's light currently (its relatively distant ~600 LY, and at the end of its life)

Alpha Centuri may likewise have blown up, but thats much less likely, as its only 4 years in the past, and its a relatively long lived star (billions of years) so its a good bet its still there.

[ScottS]

We have absolutely no idea if anything we see, visually or with images, is still there. As the light we see is anywhere from a couple years old (The closest known star) to billions of years old. We could find out tomorrow that the closet star, which is slightly over 4 light years away, exploded for some unknown reason. But it actually would not have exploded that night but slight over 4 years ago.

I know one that's a lot closer than 4 light years!

[nmoushon]

I know one that's a lot closer than 4 light years!

lol touche my friend. 

[nytecam]

When I showed my younger family members my galaxy pics etc their instant response was "But its gone now" as I suspect nobody enjoys being outlived. The OP question is really an extension of that perception:-)

[wxsatuser]

Some one out there in a distant galaxy is wondering if we still exist.

[Knight of Clear Skies]

It's like space invaders in reverse: you need to at shoot where the spaceship will be rather than where it is now. Same principle with light emitted from distant galaxies.

When we look at Andromeda we aren't even seeing a true representation of its structure in its past. It's inclined to us, so its near edge is several tens of thousands of light years closer than the far. The light from the near edge takes less time to travel to us, so we are looking at less distant history than when we look at the far edge.

[jetstream]

It's like space invaders in reverse: you need to at shoot where the spaceship will be rather than where it is now. Same principle with light emitted from distant galaxies.

When we look at Andromeda we aren't even seeing a true representation of its structure in its past. It's inclined to us, so its near edge is several tens of thousands of light years closer than the far. The light from the near edge takes less time to travel to us, so we are looking at less distant history than when we look at the far edge.Thanks Knight-excellent

Great point-this is the first time I've ever thought about the orientation of an object vs time.I can see where we can end up taking the objects as "2d",but in reality you are right-they still are "3d".Thanks Knight-Excellent.

[Knight of Clear Skies]

You're welcome, it only occurred to me the other day.

[Andy_E]

The weird thing that gets me is the fact that the Andromeda galaxy is so much closer than I see it. Wonder how big in the sky it actually 'is' so to speak. Fingers crossed the sun was still burning brightly eight minutes ago too .

[jetstream]

The other night out with the f7 refractor set up & with 3.37 deg TFOV M31 was still not contained....I think it must be huge,Be nice to hear from someone with a bigger faster refrator with more TFOV,from a dark site as to how much can really fit into the eyepiece.

[symesie04]

Andromeda is just shy of 6 times the diameter of a full moon to the naked eye, (from a dark site to see it all).

[wxsatuser]

The weird thing that gets me is the fact that the Andromeda galaxy is so much closer than I see it. Wonder how big in the sky it actually 'is' so to speak. Fingers crossed the sun was still burning brightly eight minutes ago too .

Every day it's approx 6million miles closer.