Cosmic dawn, the epoch given to the point in time when the first ever stars formed, may now just be in sight.
To look back in time to when the first ever stars formed in the Universe, we need ever more powerful telescopes to be able to detect the faintest of light. This electromagnetic radiation, that has travelled billions of light years across the universe, is stretched towards the red end of the spectrum – its wavelength is said to be red-shifted. A measurement of this redshift can tell us how far this light has travelled and thus what epoch in time it came from.
A team of scientists led by Takuya Hashimoto, from Osaka Sangyo University in Japan, have just observed the gravitationally lensed galaxy, MACS149-JDI, and confirmed it to be one of the farthest objects from Earth. Utilizing the Atacama Large Millimeter/Submillimeter Array (ALMA) and the European Southern Observatory’s Very Large Telescope (VLT), spectroscopic observations revealed an emission line of double ionized oxygen at a redshift of 9.1 – which corresponds to an age of 500 million years old.
However, although the detection of galaxies at this epoch is expected, what added intrigue to this confirmation was the detection of oxygen. According to the standard model oxygen is only created in stars which is then released into the gas clouds of their host galaxies. The presence of oxygen therefore indicates that a generation of stars must have already existed. To explore this further and look into the galactic history, infrared data was obtained with the Hubble Space Telescope and NASA Spitzer Space Telescope. The data revealed an observed brightness indicative of a galactic history with star formation beginning when the Universe was only 250 million years old.
This result brings us one step closer to determining when cosmic dawn occurred – which as stated by one of the authors, Professor Ellis of University College London, is the “Holy Grail” of cosmology and galaxy formation. When did the first stars form? When did galaxies form and how does this fit with a unified physics perspective? These are the questions we can begin to answer, especially with future telescopes, such as the James Webb Space Telescope, which will allow for even earlier epochs of exploration.
