Published: Sun, March 12, 2017
Science | By Boyd Webster

Scientists observe one of the universe's earliest galaxies

Scientists observe one of the universe's earliest galaxies

The presence of oxygen in this distant galaxy gives us a hint to when and how the first galaxies formed and what caused the cosmic "reionization". Galaxy A2744_YD4 is the farthest galaxy ever observed by astronomers. The researchers conducted follow-up observations with the Very Large Telescope's X-shooter instrument, which splits light apart into its different wavelengths.

An global astronomy team has made the earliest known discovery of oxygen in the universe - more than 13 billion years, or just 600 million years after the Big Bang. "The detection of so much dust indicates early supernovae must have already polluted this galaxy", says lead scientist Nicolas Laporte in a press release.

A2744_YD4's cosmological "timestamp", as given by its redshift, falls within the estimated age range for the Epoch of Reionization, which occurred somewhere around a redshift of 10, when the universe was about 400 million years old. New observations of this galaxy done using ALMA, shown in red, reveal that it is rich in ancient stardust.

ALMA (ESO/NAOJ/NRAO), NASA, ESA, ESO and D. Coe (STScI)/J. The chemical elements in these grains are created inside stars, and they are scattered across the cosmos when these stars die. "Today, this dust is plentiful and is a key building block in the formation of stars, planets and complex molecules; but in the early Universe - before the first generations of stars died out - it was scarce". This is due in part to a gravitational effect from a large cluster of galaxies between us and A2744_YD4 that bends the light from the distant galaxy and acts as a giant magnifying lens.

These distant discoveries can tell scientists a great deal about how stars formed in the early universe.

The ALMA observations also detected the glowing emission of ionized oxygen from A2744_YD4.

Scientists have been studying interstellar dust in the earliest, most distant galaxy seen by ALMA, finding the most distant detection of oxygen in the universe and gaining new insight to the formation of stars in the early universe.

"Determining the timing of this "cosmic dawn" is one of the holy grails of modern astronomy, and it can be indirectly probed through the study of early interstellar dust", ESO said.

Galaxy A2744_YD4 appears to hold enough of this stardust to make 6 million suns, while the mass of the galaxy's stars add up to 2 billion times the mass of the sun. They noticed how stars were forming at a rate of 20 solar masses per year. Far beyond this cluster is the faint, young galaxy A2744_YD4.

As a result, "we are witnessing this galaxy shortly after its formation", according to co-author Richard Ellis of the European Southern Observatory and University College London.

It reached its current observable form after only 200 million years.

The young galaxy's stardust is a valuable clue for the researchers and serves as a treasure trove of information in studying the time frame and period of the first supernovae and the time when stars lit up the whole universe.

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