Everything I have read seems to explain or state that the telescope can see an object that is a certain amount of years old. It does seem to state how far away the object is, but it seems as though the capabilities of what it can see is measured in age.
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It’s not age. It’s measured in time, the unit is light years, which is the amount of distance light travels in a year.
Lighyear is a measure of distance. It tells you how far light would have traveled in that time duration. It is a unit used a lot when talking about space objects and distances.
The distance in space is so vast that measuring in miles is unintuitive. Our closest star is 4.3 light years away, which is how far light travels in 4.3 years, or about 25 trillion miles.
Edit: for more precise and clarity
Over the distances the JWST makes observations, they’re the same thing. An observation of an object 1 million light years away is 1 million years old.
It’s communicated that way both because people’s understanding of deep time is slightly more intuitive than extremely large distances (9 quintillion km–or 9 million million million km–is meaningless to me, but 1 million years isn’t), and because looking back in time at the universe is one of the main purposes of the telescope – understanding the history and evolution of the universe.
As a not JWST specific example, we can determine a lot about a star based on the light it emits. It’s composition, size, temperature, etc. If we look at lots and lots of stars further and further back in time, we can find out if stars were different in the early universe. And they are! Early stars were bigger, brighter, lived shorter lives, and had low metallicity (few or no elements heavier than hydrogen and helium) – indicating that heavier elements in younger generations of stars must have been produced by the deaths of their progenitors
K2-18b is a planet observed by JWST and all i have found is that its 120 light years away.
Im not sure what specific news you read but its for sure not a general rule to only use age.
Either you are not aware that light years is a distance measurment or you only have seen a smal amount of reports in some newspaper that does what you describe anf belive its a general thing but its not.
But JWST is desigend to observer low wavelengths and that can be used to observe objects that are far away unlike other telescopes, so it will be used to research more about verry old galacies and the early formation of start in our universe, and in that context age is often the important measurement.
The things you’re reading probably said ” x lightyears away” not just years, right?
Lightyears is a distance.
1 light year is how far light goes in 1 year. Astronomers use them like miles because the distances are so big. Even in light years, things are often thousands or millions of light years away. But again, that’s a length.
But it’s also kind of an age. If something is 32 light years away, its light takes 32 years to get here. So when the telescope sees that light here on Earth, the light is 32 years old and we’re seeing what the object looked like 32 years ago when that light left and began flying towards us.
When JWST sees things a million light years away, it’s seeing how the thing looked a million years ago. But I doubt the stuff you’re reading says the object is “a million years away” – it should say light-years away since that’s the proper unit for distance. But that light is a million years old when it gets here!
There are lots of different measurements of distances in space from kilometres, through astronomical units, to light years. The light year is a distance light travels in a year which is a huge number in kilometres, so for big distances light years are used to avoid having numbers with lots of zeros. https://youtu.be/35kQspMO2Jg