Quasars are the most distant distinct objects that astronomers have been able to directly detect.
Because of their intrinsic brightness, the most distant quasars are seen at a time when the universe was one tenth its present age, roughly a billion years after the Big Bang . However, astronomers believe that some objects must have formed earlier than quasars, because the ambient gas in the universe is observed to be ionized at a relatively early time, presumably due to ionizing radiation from a population of early objects. Since ionized gas can interact with cosmic microwave background photons, MAP observations may help to elucidate the nature of the ionized gas and the objects that caused the ionization. Since light travels at a finite speed, distant objects are seen as they existed in the past. We see the Sun not as it is now, but how it was eight minutes ago.