How do galaxies evolve and what is dark energy?
The acceleration in the expansion of the Universe has been attributed to a mysterious dark energy. The SKA will investigate this expansion after the Big Bang by mapping the cosmic distribution of hydrogen. The map will track young galaxies and help identify the nature of dark energy.
Hydrogen is the most abundant element in the Universe and is the raw material from which stars form. Hydrogen atoms produce radio emission at a wavelength of 21 cm or a frequency of 1420 MHz. This emission was first discovered from the hydrogen gas clouds within our Milky Way Galaxy in the early 1950s. Since then, hydrogen gas has been found in tens of thousands of galaxies, most of which are relatively near to the Milky Way. Generally, astronomers find that spiral galaxies, like our Milky Way Galaxy, and irregular galaxies, like the Magellanic Clouds, often contain large amounts of hydrogen gas. These galaxies also form stars and astronomers believe that hydrogen gas provides the raw fuel for star formation.
The SKA will revolutionise our study of how galaxies form and transform their gas into stars by detecting hydrogen gas in as many as a billion galaxies, at distances much greater than is possible to detect today.
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