Reading of planets billions of light years away

In summary, we can determine the chemical composition of distant galaxies and planets by analyzing their light spectra, even though the light may have taken billions of years to reach us. This is because the light carries information about the object's composition at the time it was emitted, and we can use telescopes to zoom in and analyze this light. However, the objects we are seeing may no longer exist in their current form, as the light has taken millions or even billions of years to reach us, and the distance to the object may have expanded significantly in that time.
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Niaboc67
249
3
We can see galaxies/planets light years away determine their composition such such as if they have water et cetera. My question is if light takes billions of years to reach us from there how is that we can determine such things? Is the speed at which a telescope can zoom faster than the speed at which light can travel? or are we merely seeing the photos of the planet/galaxy millions of years ago?Thanks
 
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Images of long ago and far away, but in an isotropic and homogeneous universe.
 
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Niaboc67 said:
We can see galaxies/planets light years away determine their composition such such as if they have water et cetera. My question is if light takes billions of years to reach us from there how is that we can determine such things?

We do see galaxies some billions of lightyears away
we don't see planets billions of light years away
the most distant exoplanets so far discovered are around 25 lightyears maximum
we determine chemical composition of star etc by their spectrum

Niaboc67 said:
Is the speed at which a telescope can zoom faster than the speed at which light can travel? or are we merely seeing the photos of the planet/galaxy millions of years ago?

we are seeing the objects as they were xx years ago
our Sun we see it as it was 8.25 minutes ago
Alpha Centauri one of the closest stars - as it was a little over 4 years ago
Andromeda Galaxy ( M31) as it was ~ 2.5 million years ago

and so oncheers
Dave
 
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Thanks Doug and Dave! That was on the lines of what I thought, just wasn't positive.
 
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Niaboc67 said:
We can see galaxies/planets light years away determine their composition such such as if they have water et cetera. My question is if light takes billions of years to reach us from there ...
Are you sure you understand what you just said? What you said was "we can see galaxies/planets so far a away that it takes years for their light to reach us but it takes billions of years for the light to reach us ... " Light takes one year to travel one light year, not a billion years to travel one light year.
 
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phinds said:
Are you sure you understand what you just said? What you said was "we can see galaxies/planets so far a away that it takes years for their light to reach us but it takes billions of years for the light to reach us ... " Light takes one year to travel one light year, not a billion years to travel one light year.

That's not what I meant. I was saying that since these galaxies/planets I am referencing are billions of light years away it would take light that long to travel through space.
 
  • #7
Niaboc67 said:
That's not what I meant. I was saying that since these galaxies/planets I am referencing are billions of light years away it would take light that long to travel through space.
OK, but you can perhaps see how I interpreted your statement "light years" as meaning "light years" not "billions of light years". Never mind. I'm an inveterate nit-picker. :smile:
 
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Cobain, if you are interested in comparing light travel times with the actual distance to the object now versus when it emitted the light, then click on this:
http://www.einsteins-theory-of-relativity-4engineers.com/LightCone7/LightCone.html
You can make the table bigger by increasing the number of steps. As it shows up at first it has only about 10 steps or 10 rows.
For example one row says
0.097 ...10.291 ...0.5223... 0.7851 ...30.918 ...3.004 ...

That means in year 522 million, when the galaxy was 3.004 billion LY from here, it sent us some light, traveling at the usual speed.
And it is now year 13.787 billion (that is, around 13.2 billion years later) and the light arrives! And the galaxy is now over 10 times farther from us. Its present distance is 30.918 billion LY. That is because distances expand while light is making its journey, on its way to us.

One reason we like the calculator and use it a lot (or use other calculators like it) is because there is no simple relation between the light travel time and the distances to the thing (now or back then when it emitted the light we are now getting from it.)

In the example the present is year 13.787 billion and the light was emitted in year 0.522 billion so the travel time is 13.787 - .522 = 13.265 billion years.
This travel time has no simple relation to the distances (now 30.9 billion LY and then 3.004 billion LY) because the rate of distance expansion is changing over time
according to the basic equation of cosmology.
 

1. How is it possible to read planets billions of light years away?

Scientists use various methods, such as telescopes and spectroscopy, to detect and analyze light from these distant planets. This light carries information about the planet's composition, temperature, and other factors that can help us understand its properties.

2. Can we see these planets with the naked eye?

No, these planets are too far away to be seen with the naked eye. Even with the most powerful telescopes, they appear as mere specks of light.

3. How do scientists know the exact distance of these planets?

Scientists use a variety of techniques, such as parallax measurements and redshift, to determine the distance of these planets from Earth. These methods involve measuring the angle of the planet's position in the sky or analyzing the shift in the wavelength of light from the planet.

4. Can we determine if these planets have life on them?

At this time, we do not have the technology or capability to determine if these planets have life on them. However, scientists are continuously working on new methods and technologies to search for signs of life on these distant planets.

5. How does the reading of these planets help us understand our own planet?

Studying these distant planets can provide valuable insights into the formation and evolution of our own planet. By comparing the compositions and characteristics of these planets to our own, scientists can better understand the processes that shaped our solar system and Earth.

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