Quasar Absorption

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Quasar Absorption

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  Last updated September 26, 2017 at 3:30 pm

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Quasar light travels to Earth through the gas around some intervening galaxies. The light emitted by the quasar 10 billion years ago travels through the ever-expanding universe, shown by the quasar and our own Galaxy, the Milky Way, moving apart throughout the animation. This 10 billion year old light is only being observed by our best telescopes on Earth today. The light encountered the gas around the distant galaxies around 8.5 billion years ago, well before the Earth even existed. Such galaxies are typically too faint to be seen directly – their starlight is not bright enough for even our best telescopes to observe – but they imprint a characteristic pattern of absorption lines into the spectrum of the quasar light. This is shown by the dark lines appearing in the rainbow of colours. The expansion of the universe stretches the wavelength of the light as it travels to Earth, so the whole quasar spectrum shifts towards redder colours, but the distinctive pattern of absorption lines from the galaxy remains. From this pattern the strength of electromagnetism in the distant galaxy can be measured as it was 8.5 billion years ago. Animation credit James Josephides for Swinburne University of Technology. Read more



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