Wide Field Camera 3's infrared view of the Hubble Ultra Deep Field

I am Massimo Stiavelli, an astrophysicist at the Space Telescope Science Institute (STScI). I am the STScI Project Scientist for Hubble¡¯s successor, the James Webb Space Telescope. I came to the institute in 1995, and before working on Webb, I worked on all of Hubble¡¯s cameras.

My main scientific interest is understanding the formation and evolution of galaxies and the processes occurring in the early universe. I led the team responsible for the Hubble Ultra Deep Field observations, the deepest view of the distant universe ever done in visible light. The telescope had to stare at the same spot for 27 days to make these observations, and I have continued to study this field, trying to understand as much as possible from this large investment of Hubble¡¯s time.

Last summer, I was part of a team that used one of Hubble¡¯s new cameras, Wide Field Camera 3, to look for infrared light in the Ultra Deep Field region. The ultraviolet light from galaxies in the early universe has been stretched by the expansion of space, transforming it into infrared light. Therefore, to see the early universe, we must look for infrared light.

The results were interesting not just because they involve the Ultra Deep Field ¡ª they also hint at what Webb¡¯s sensitive infrared vision might detect once it is launched.

Early on, some were nervous that Webb had been optimized to study a population of objects we didn¡¯t know for sure existed, even if they were predicted by models.

Now, thanks to Wide Field Camera 3, we can all breathe a sigh of relief. These galaxies are there and they are faint: the best possible outcome for Webb.

Wide Field Camera 3¡¯s observations of the Ultra Deep Field beat even the most optimistic expectations. In particular, they revealed a population of galaxies existing in the first billion years of the universe. A preliminary analysis suggests that these objects are rare and dim, possibly indicating that we are beginning to see the era when galaxies first form.

This is very good news for the James Webb Space Telescope. With its large mirror  ¡ª about seven times the area of Hubble¡¯s ¡ª and incredible infrared sensitivity, Webb will be able to study in greater detail this population of galaxies and measure their properties.