Astronomers find stars forming just 250 million years after Big Bang

  • Astronomers find stars forming just 250 million years after Big Bang

Astronomers find stars forming just 250 million years after Big Bang

Using the giant ALMA telescope in Chile, researchers were able to observe the distant galaxy MACS1149-JD1 when it was just 550 million years old, a time when it contained stars that were about 300 million years old.

The discovery shows that stars in the galaxy - called MACS1149-JD1 - formed at an unexpectedly early stage in the age of the Universe and the new observations break the team's own record for detecting the most distant known source of oxygen.

Scientists believe that the Universe's first stars formed in regions of very dense matter, although understanding of that process is still limited.

Although the presence of galaxies at this epoch is not necessarily surprising, the detection of oxygen in MACS1149-JD1 indicates a more remarkable conclusion. However, numerous heavier elements we take for granted today (such as carbon and oxygen) did not exist before the first stars.

The ionised oxygen from stars in MACS1149-JD1 therefore means that there must have been an even earlier generations of stars before these ones. Although we are seeing it now, the gas glow from this far-off galaxy was likely emitted 500 million years after the universe was first formed.

The findings appear in the latest issue of Nature journal.

An global team of researchers from 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.

Based on the wavelength of the light, stretched from infrared to microwave by the expansion of the Universe, the team ascertained that the galaxy is 13.28 billion light-years away.

Dr Laporte independently confirmed the inferred distance of 13.28 billion light years by detecting emissions of hydrogen using the VLT [1].

This discovery also represents the most distant galaxy ever observed by the observatories that studied it; ESO's Very Large Telescope (VLT) and the Atacama Large Millimeter/submillimeter Array (ALMA) - an array that has already set the record for detecting the most distant oxygen several times before. 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. The oxygen is the furthest sign of this important gas ever detected, and studying it could help us finally discover when the first starlight emerged in the darkness that followed the Big Bang.

The Universe's very early years are notoriously hard to study.

The team then reconstructed the star formation history in the galaxy using infrared data taken with the NASA/ESA Hubble Space Telescope and NASA's Spitzer Space Telescope. The observed brightness of the galaxy is well explained by a model where the onset of star formation corresponds to a time only 250 million years after the Universe began.

"The mature stellar population in MACS1149-JD1 implies that stars were forming back to even earlier times, beyond what we can now see with our telescopes", said Laporte.

"Determining when cosmic dawn occurred is akin to the "Holy Grail" of cosmology and galaxy formation", said Richard Ellis, an astrophysicist at University College London and co-author on the paper. MACS1149-JD1 is the most distant galaxy with a precise distance measurement. There is renewed optimism we are getting closer and closer to witnessing directly the birth of starlight.

The Atacama Large Millimeter/submillimeter Array (ALMA), an global astronomy facility, is a partnership of the European Organisation for Astronomical Research in the Southern Hemisphere (ESO), the U.S. National Science Foundation (NSF) and the National Institutes of Natural Sciences (NINS) of Japan in cooperation with the Republic of Chile.