File: 7 October 2026 · Source date: 7 October 2026 · NASA Webb
looking back
Light from a distant galaxy travels billions of years. Webb therefore observes not only the distant, but also the younger periods of the universe. The expansion of the universe lengthens the wavelength of light, shifting the light of early galaxies into the infrared.
How to verify distance?
Any source that appears red in the image is not automatically too far away. Astronomers test the color choice with spectroscopy, spectral lines, and data from different telescopes. Photometric candidate and spectroscopic confirmation are separate levels of evidence.
Why is a model needed?
The telescope measures photons; Galaxy age, mass, and star formation rate are inferred by models. These results are the joint product of the data and the model. New observations may narrow parameters or change assumptions.
discussion question
Is it more valuable for cosmic history to find a single bright galaxy in the early universe or to measure the distribution of hundreds of fainter galaxies? From where?
Resources and further reading
NASA Science — Webb: Early Universe ↗Share your answer
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