With the launch of the James Webb Space Telescope astronomers are now able to peer so far back in time that we are approaching the epoch where we think that the first galaxies were created.
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Throughout most of the history of the universe, galaxies seemingly tend to follow a tight relation between how many stars they have formed, and how many heavy elements they have formed.
But for the first time we now see signs that this relation between the amount of stars and elements does not hold for the earliest galaxies.
The reason is likely that these galaxies simply are in the process of being created, and have not yet had the time to create the heavy elements.
The universe is teeming with galaxies—immense collections of stars and gas—and as we peer deep into the cosmos, we see them near and far.
Because the light has spent more time reaching us, the farther away a galaxy is, we are essentially looking back through time, allowing us to construct a visual narrative of their evolution throughout the history of the universe.
Observations have shown us that galaxies through the last 12 billion years that is, 5/6 of the age of the universe have been living their life in a form of equilibrium: There appears to be a fundamental, tight relation between on one hand how many stars they have formed, and on the other hand how many heavy elements they have formed. In this context, "heavy elements," means everything heavier than hydrogen and helium.
This relation makes sense, because the universe consisted originally only of these two lightest elements. All heavier elements, such as carbon, oxygen, and iron, was created later by the stars.
The very first galaxies should therefore be "unpolluted" by heavy elements. But until recently we haven't been able to look so far back in time.
In addition to being far away, the reason is that the longer light travels through space, the redder it becomes. For the most distant galaxies you have to look all the way into the infrared part of the spectrum, and only with the launch of James Webb did we have a telescope big and sensitive enough to see so far. ■