How far will Webb look?
One of the main goals of Webb is to detect some of the very first star formation in the Universe. This is thought to happen somewhere between redshift 15 and 30 (redshift explained below). At those redshifts, the Universe was only one or two percent of its current age. The Universe is now 13.7 billion years old, and these redshifts correspond to 100 to 250 million years after the Big Bang. The light from the first galaxies has traveled for about 13.5 billion years, over a distance of 13.5 billion light-years. • Will Webb see planets around other stars? The Webb will be able to detect the likely presence of planetary systems around nearby stars from their infrared radiation. It may even be able to see directly the reflected light of large planets – the size of Jupiter – orbiting around nearby stars. It will also be possible to see very young planets in formation, while they are still hot. Webb will have coronagraphic capability, which blocks out the light of the parent star of the plane
