galaxies captured in a fraction of the time!

Where the Hubble Space Telescope required an exposure time of over eleven days to create its “Ultra Deep Field” masterpiece, the James Webb Telescope needs just under a day to paint the same galaxies on the black canvas.

On October 11, 2022, the James Webb Telescope was tasked with spending 20 hours observing a patch of sky in the constellation Oven that had already been photographed by Hubble 16 years earlier. The result is amazing. It took the space telescope less than 10% of Hubble’s exposure time to achieve the same result.

Webb’s Ultra Deep Field shows distant galaxies that existed when the universe was only 800 million years old. These galaxies are barely visible: they are faint red dots on an inky black background. The largest foreground galaxies are relatively close when the Universe was about a billion years younger than it is now.

“We even see hot, ionized gas in galaxies. These are places where stars are born,” says Professor Michael Maseda of the University of Wisconsin-Madison. “This information is very important because we still do not know exactly how the galaxies came to be as they are today. Less than 24 hours of exposure time is not long, but in this relatively short time we have better understood how galaxies develop in this particular phase [reïonisatie, red.] of the universe.”

When the universe was very young, only neutral hydrogen gas existed. But the reionization process changed that. A few hundred million years after the big bang, the first supermassive stars, galaxies and black holes were born. Astronomers still don’t fully understand where the incredible amount of energy needed for this comes from.