When NASA releases images of objects that are light years away, are we viewing the image in 'real time'?

Question

I'm talking about images that say the Hubble has captured. Let's say this object is 172 million miles from Earth when the Hubble Telescope took the photograph. Are we viewing the object as it looks right now, or are we looking at light reflections that have traveled 172 million miles making the object we are viewing in the photograph hundreds of years old, which means that the object we are viewing no longer looks like that? What I mean is, perhaps these galaxies have already formed into a new galaxy or solar system or perhaps exploded for some reason. Here is a link of the image that sparked my question.

http://hubblesite.org/newscenter/archive/releases/2006/2006/46/image/a/format/large_web/

Answer 1

You're looking at an image of the past.  Most are millions if not billions of years old. That's why scientists are interested in studying them.  That's also what makes them so interesting to a space fanatic such as myself.

Answer 2

When you see the light from anything - from your mother across the room to a distant galaxy you see the object at a later time.  If your mother is 6 feet away you see her as she was about 6 nanoseconds ago.  The moon you see as it was about one and a half seconds ago - the sun 8 minutes ago.

In your example the object is 172 million miles from earth.  In that case the object would look as it was 15.4 minutes ago.  Light travels 186,324 miles per second.

If an object such as a star is billions or trillions of miles away the time delay gets longer and longer.  For really large distances we use a unit that is the distance it takes light to travel in a year.  That is a light year.  Many of the pictures from Hubble are of objects, such as galaxies, that are millions to hundreds of millions of light years away.  

Yes, in those cases we are looking at the objects as they were millions of years ago just as when you look at your mother 6 feet away you see her as she was 6 nanoseconds ago.

Answer 3

>When NASA releases images of objects that are light years away, are we viewing the image in 'real time'?

No. Although we can see the effects of time passing on another object (assuming it is moving slower than the speed of light), the time actually experienced on the other object will always be ahead of the time we see it at. So for example if we have two clocks that are synchronized, and we remove one to one light-hour (about 1.08 billion kilometers) away, then when both the clocks actually read 4:00 PM, we will see the other clock reading 3:00 PM, and anyone standing with the other clock will see our clock reading 3:00 PM. An hour later, both clocks will have advanced one hour, but both places will still see the other clock as being an hour behind. The same effect applies to everything else as well, so if you see something happening on an object that is ten light years away, that event actually happened ten years ago.

The Hubble telescope is mostly used for taking pictures of very large, distant objects such as nebulae, galaxies and so on. However it can also be trained on closer objects inside our own Solar System. 172 million miles away from the Earth is well within our Solar System, and it takes light approximately 15 minutes and 23 seconds to travel that distance through a vacuum. So an object such as Mars or Jupiter seen 172 million miles away appears to us as it was 15 minutes and 23 seconds in the past. And if any change is occurring on its surface right now, we won't see the change for another 15 minutes and 23 seconds. This is a relatively short period of time, and although it is long enough to make communications difficult (imagine having to wait half an hour to get an answer when you phone someone!), most of the time there will be essentially no change in the object's appearance during that time. Over longer distances, the effect is more important, so for example a star across the galaxy might have just exploded in a powerful supernova, but we wouldn't see the explosion until about 50000 years in the future. Distant galaxies may not even be the same now as they appear, because over a period of hundreds of millions of years even galaxies can collide, break up or form into a different shape.

Answer 4

You are looking at it in "proper time"  i.e. you see the object as it was when the light left it.

If the object is 172 million miles (917 light-seconds) then you see it as it was 917 seconds before the picture was snapped.

If the object is at a million light-years, you see it as it was a million years ago.

This distance (the distance traveled by the light to get here) is called "proper distance".

The "real" distance at which the object is now (where we would see it if light travel were instantaneous) is called "comoving distance".

Astronomers talk in proper distance.  Cosmologists often talk in comoving distance.

The radius of the visible portion of the universe is 14 billion light-years in proper distance.

The diameter of the visible universe in comoving distance is around 156 billion light-years.

(they both represent the same object: the portion of the universe we can see).

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The Antennae galaxies are 45 million light-years away, so we are seeing them as they were 45 million years ago.  At the speed that these things go, if you were miraculously given a picture of what they look right now (in comoving coordinates), the picture would look strangely familiar (the overall image would be very similar -- there would be minor changes).  The entire collision would take almost a billion years.

But you are correct:  the galaxies are "now" 45 million years older than what we see in the picture.

Answer 5

You are looking at the light image when it arrived at the Hubble telescope, which in your case is what the image appeared as when it left the object.  Since it takes time for that image to travel the distance to the telescope, you do not see it in real time, but as it appeared when the light left the object, however much time has elapsed.

Even our Sun appears like it was about 8 minutes ago, not right now, since it takes about 8 minutes of travel time for the light from the Sun to reach the Earth.

Answer 6

when you look into the sky at night you are whitnessing

HISTORY

the light that you precieve as stars is millions or billions of years old because light can only travel  300,000 km per sec

add in a few trillion km and you have hundreds of years for the light to go from the star to the Earth.

So when you see a photo of a star or a galaxy that was taken last night, you can see how that galaxy looked hundreds of years ago. The possible truth is that a star you see died years ago.

Answer 7

No, on two levels. One, light speed is a definite limit, so when you see Mars in a telescope, you are now seeing Mars "that instant", you are seeing the light from Mars that left it some minutes earlier.

Ditto the Sun, you never see the Sun as it is right now, you see the Sun as it WAS, eight minutes ago.

So, when you see a picture of a star 172 million light years away, that light left that star 172 million years ago. Then, when the Hubble takes the image, there is more time to record, store, download, and process that image on Earth. Then, its more time for the picture to be publically released.

There is no way for light to get around the light speed limit.