Astronomers have found that the earliest stars formed only 250 million years after the Big Bang. The discovery also breaks the record for finding the most distant known source of oxygen.

Scientists looking at these stars are transported to a time when the universe was only 500 million years old.

Shortly After The Big Bang

An international team of researchers from the University College London and Osaka Sangyo University in Japan published a paper in the journal Nature showing that stars in the MACS1149-JD1 galaxy formed 250 million years after the Big Bang

Scientists used the Atacama Large Millimetre/Submillimetre Array (ALMA) and the European Southern Observatory's Very Large Telescope (VLT) to find the stars, which were 13.28 billion light-years away. Observations of the stars at that distance would show scientists what the universe looked like when it was at 3.5 percent its current age.

The stars that researchers observed were already mature stars, leading them to conclude that there may have been stars before this point. Oxygen is created inside of stars and it is released as a gas cloud when those stars die. This presence of oxygen in MACS1149-JD1 shows that earlier stars had formed and died.

Researchers were able to detect the ionized oxygen from a signal whose infrared light was stretched into microwave wavelengths by the expansion of the universe. They found that MACS1149-JD1 is the most distant known galaxy.

ALMA has been used previously to break the record for the most distant known galaxy. It did so twice in 2016, finding galaxies 13.1 billion light-years away and 13.2 billion light-years away.

Scientists determined that the galaxy formed 250 million years after the Big Bang by using infrared data taken by the Hubble Space Telescope and the Spitzer Space Telescope. They used the observed brightness along with a model that times the onset of star formation. This determined that the galaxy was formed 250 million years after the Big Bang.

Researchers are still trying to determine when the first stars were formed after the Big Bang.

Cosmic Dawn

Astronomers call the time when galaxies first emerged out of total darkness as cosmic dawn. With every new observation, scientists believe that they're coming closer to seeing when the first stars were born.

In February, astronomers detected a radio signal that comes from 180 million years after the Big Bang. At the time of this discovery, the oldest stars that had been observed came 400 million years after the Big Bang. It is difficult for scientists to observe older stars because until about 500 million years after the Big Bang, the universe was saturated with neutral hydrogen atoms which can block light easily.

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