A paper published by Nature reports the discovery of a mysterious dust-filled galaxy that shouldn`t be there in the first place. The little galaxy is located in the cluster Abell 1689 and has been found by a team of international team of astronomers.
The discovery of the star-forming galaxy A1689-zD1 reveals that galactic dust may be able to accumulate much faster that it was thought until now. The problem is that the tiny galaxy dates from 700 million years after the Big Bang, but it is extremely dusty for something this young and small.
“The galaxy is highly evolved: it has a large stellar mass and is heavily enriched in dust, with a dust-to-gas ratio close to that of the Milky Way”
the authors of the study said.
But what is uncommon about this dusty galaxy? In the beginning of the Universe, the stars consisted mostly of lightweight hydrogen and helium. An expert on galaxy formation with the University of Arizona, Daniel Marone, was surprised by the amount of dust this galaxy appears to have. He said that, even if dust is a key ingredient in the planet formation process, the early universe had no dust at all. Stars died, generally in supernovae, by explosion. The stardust resulted from the explosion spread across the cosmos, seeding it with heavy elements and formed new stars, that would eventually die and spread even more stardust, to create more heavy elements, incorporated in other stars. But this was a slow process, and it took a long time for a great amount of dust to appear. That`s why the galaxies formed within several hundred millions of years after the Big Bang, the early galaxies, should not be dusty.
The discovery of A1689-zD1 contradicts the general belief. It is only 700 million years old, but contains dust in an amount that rivals the Milky Way, which is 13 billion years old. This lays bare that such evolved galaxies may have appeared much earlier than scientists thought.
The Nature paper’s lead author, Darach Watson, who is a researcher at the Dark Cosmology Centre at the University of Copenhagen, used the Very Large Telescope located in Chile`s Atacama Desert to observe a cluster of galaxies named Abell 1689. Watson said that the cluster’s gravity magnified A1689-zD1 by a factor of nine. This allowed him and his colleagues to measure the galaxy`s distance from Earth, so they could find out the moment when the light began travelling in our direction.
Watson had to call another colleague, since the VLT cannot detect stardust but only starlight. His colleague who was using the dust-sensitive ALMA(Atacama Large Millimeter/submillimeter Array) radio telescope. „She had a look and bingo!”,
Astronomers look back in time by studying extremely distant space objects. Surveys on such cosmic structures show how things used to look like in the past. For example, if you take a picture of the sun right now, the image would reveal how the sun looked like 8 minutes ago, because it took 8 minutes for the light to reach Earth. Thus, if you have a picture of a much farther object, the snapshot will show you the reality of a different time, maybe millions of years in the past.
“Although the exact origin of galactic dust remains obscure, our findings indicate that its production occurs very rapidly, within only 500 million years of the beginning of star formation in the universe — a very short cosmological time frame, given that most stars live for billions of years”,
Scientists estimate that our knowledge of the early universe is going to improve in the years to come. With the new generation of optical telescopes under construction, new stunning discoveries regarding the beginning of the Universe will be made soon.
Image Source: National Geographic
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