How can the universe be larger than 90 billion light years, if the universe is only 13.7 billion years old?

It is not possible to travel faster than the speed of light. The Big Bang was 13.7 billion years ago. Why does the universe have a diameter of over 90 billion light years and not 27.4 billion light years?

A hundred years ago, astronomers thought the universe was infinitely old. This changed in the 1920s when scientist Edwin Hubble calculated the distances to the Andromeda Galaxy and dozens of other spiral galaxies. Hubble estimated the age of the universe at two billion years. The furthest spiral galaxies he saw were 140 million light-years away, giving astronomers a diameter of 280 million light-years.

We now know that the universe is much bigger. The most distant objects are 47 billion light-years from Earth, making the universe about 94 billion light-years in diameter. Examples of distant objects include the star Earendal (28 billion light-years), galaxy HD1 and galaxy UNCOVER Z-13 (33 billion light-years). Staggering distances.

How come these objects are so far away from us?
This is due to the expansion of the universe. When we look at the UNCOVER Z-13 galaxy with a telescope, we see the light from the galaxy that took 13.4 billion years to reach Earth. However, the universe was much smaller 300 million years after the Big Bang than it is today. The light therefore departed from a distance much closer to the Earth (which did not yet exist at the time).

Just imagine… You are standing on a road. There is a person one meter in front of you, another one meter further away and this goes on endlessly. Now imagine that the road is growing every minute. After one minute the person in front of you is two meters away, the next one is four meters away, the next one is six meters away and so on. After two minutes the distance between them is three meters, a minute later four meters and very gradually the furthest people can no longer be reached. You can compare the universe to this growing road. Mutual distances increase, while objects themselves do not (or hardly) move.

What if we now leave Earth with a spaceship at the speed of light: can we ever reach a distant galaxy like UNCOVER Z-13 or HD1? No, not so. As the universe expands, distances continue to increase and distant galaxies – even if we travel at the speed of light – can never be reached.

Space photo of the week
The space photo of the week is the photo above from HD1. The light from this galaxy was emitted 13.5 billion ago, but its distance today would be 33.4 billion light-years. Astronomers discovered this distant celestial body after spending more than 1,200 hours gazing at the night sky with different telescopes. HD1 is extremely bright in ultraviolet light, which may be because the galaxy is home to a supermassive black hole with a mass of a hundred million suns. We may learn more about HD1 thanks to the James Webb telescope.