ALMA Reveals Constituent of a Galaxy at 12.4 Billion Light-Years Away |
How and when did galaxies with hundreds of billions of stars form and evolve? The sun, which is the center of the solar system in which we live, is also only one of the countless stars contained within a galaxy. In brief, it can be said that we need to understand the evolution of galaxies to understand the world we live in.
One of the most effective methods of studying galaxy evolution is “element investigation.” In short, this involves investigating the chemical composition of galaxies. In astronomy, observing distant galaxies means investigating galaxies in the past universe. (This is because the velocity of electromagnetic waves such as visible light and radio wave, or the speed of light, is finite — approximately 0.3 million km per second. It takes time for the light to reach us and the light carries the information of celestial objects at the time when the light itself was emitted, then we can obtain the information of the past.) In fact, constituents of galaxies at various periods of the universe have been studied by visible light observations of distant galaxies using optical telescopes such as the Subaru Telescope.
However, galaxies in the phase of active star formation are covered in large amounts of dust which block visible light. Furthermore, for galaxy constituent investigation, it is necessary to observe very dark galaxies located at extreme distances. For these reasons, it has been difficult to investigate chemical composition of active star-forming galaxies at a great distance with visible light observations. continue reading