Science.-One in five distant galaxies are still hidden from telescopes

11-23-2021 With the help of the giant ALMA radio telescopes (Atacama Large Milimeter Array) in the Atacama desert of Chile, the two invisible galaxies suddenly appeared. RESEARCH AND TECHNOLOGY POLICY NASA


Astronomers at the Cosmic Dawn Center at the University of Copenhagen have discovered two previously invisible galaxies in the more distant universe.

The light from these two invisible galaxies, which have been named REBELS-12-2 and REBELS-29-2, has traveled around 13 billion years to reach us.

Their discovery suggests that up to one in five galaxies this far away remain hidden from our telescopes, camouflaged by cosmic dust. The new knowledge changes perceptions of the evolution of our universe since the Big Bang.

The two galaxies have been invisible to the optical lens of the Hubble Space Telescope. But with the help of the giant ALMA (Atacama Large Milimeter Array) radio telescopes in the Atacama Desert of Chile, which can capture radio waves emitted from the coldest and darkest depths of the universe, the two invisible galaxies suddenly appeared.

“We were looking at a sample of very distant galaxies, which we already knew existed from the Hubble Space Telescope. And then we noticed that two of them had a neighbor that we didn’t expect to be there at all. Since both the neighboring galaxies are surrounded by dust, part of their light is blocked, making them invisible to Hubble, “Associate Professor Pascal Oesch of the Cosmic Dawn Center of the Niels Bohr Institute explains in a statement.

The new discovery, published in Nature, suggests that the early universe contains many more galaxies than previously assumed. They simply hide behind the dust that consists of tiny particles of stars. However, they can now be detected thanks to the highly sensitive ALMA telescope and the method used by the researchers.

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By comparing these new galaxies with previously known sources in the early universe, roughly 13 billion years ago, the researchers estimate that between 10 and 20 percent of such early galaxies may still remain hidden behind curtains of cosmic dust.

“Our discovery shows that up to one in five of the first galaxies may have been missing from our map of the heavens. Before we can begin to understand when and how galaxies in the Universe formed, we first need proper accounting,” he says Pascal Oesch.

To help with that task, the Webb telescope – to be launched in late December – will look even more deeply at the universe and contribute new insights into its origins. This, among many other things, will help Cosmic Dawn researchers at the Niels Bohr Institute see through cosmic dust.

“The next step is to identify the galaxies that we miss, because there are many more than we think. That is where the James Webb telescope will be a big step forward. It will be much more sensitive than Hubble and will be able to investigate longer wavelengths. , which should allow us to see these hidden galaxies with ease, “says Pascal Oesch.

“We are trying to piece together the great puzzle about the formation of the universe and answer the most basic question: ‘Where is all this coming from?’ The invisible galaxies that we have discovered in the early universe are some of the first building blocks of the mature galaxies that we see around us in the Universe today. So that’s where it all started, “he added.

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