Universe's First Stars Observed

The Spitzer Space Telescope is believed to have observed light from the earliest stars to have formed in the Universe, around 200 million years after the Big Bang. These first stars, usually referred to as Population III stars (from Walter Baade's original classification scheme) were around 100 times more massive than our Sun, and emitted the ultraviolet photons responsible for the reionization of the Universe. As a result of the expansion of the Universe, these photons are now visible in the infrared range, thereby making them observable by Spitzer. As Dr. John Mather, the senior project manager for the JWST, explains, "This deep observation was filled with familiar-looking stars and galaxies. We removed everything we knew - all the stars and galaxies both near and far. We were left with a picture of part of the sky with no stars or galaxies, but it still had this infrared glow with giant blobs that we think could be the glow from the very first stars."