Giant telescope reveals star formation shortly after Big Bang
17 maj 2018
In an article in the journal Nature, an international research team reports how, using the giant ALMA and VLT telescopes, they discovered signatures of the elements oxygen and hydrogen from an extremely distant galaxy – so far away that its light has taken 13.3 billion years to reach us. The scientists can now draw conclusions about star formation further back in the Universe’s history than ever before.
By studying light sources at great distances in space, astronomers can learn more about the early development of the Universe and how the very first galaxies formed. It has taken billions of years for the light from the most distant galaxies to reach Earth, so they are seen as they appeared all those aeons ago, closer to the time of the Big Bang.
Observations of the galaxy MACS1149-JD1 were made using two different telescope arrays: the Atacama Large Millimeter/submillimeter Array (ALMA) and the Very Large Telescope (VLT), both in Chile’s Atacama Desert. There, the researchers succeeded in detecting light signatures from both oxygen and hydrogen. While hydrogen was already in place very soon after the Big Bang, oxygen was created when the first stars began to shine. The amount of oxygen in the MACS1149-JD1 galaxy reveals that by 13.3 billion years ago – corresponding to some 500 million years after the Big Bang – several generations of stars had already blazed into life and burnt out.
“Never before have measurements of chemical elements been achieved for a galaxy so early in the history of the Universe. However, by combining our observations with archive data from the Hubble Space Telescope and the Spitzer Space Telescope, we’ve actually been able to say something about how star formation in this galaxy took place even earlier: some 250 million years after the Big Bang. That’s never been done before either, so in a way this is a double record,” explains Erik Zackrisson, Associate Professor (docent) of Astronomy at Uppsala University and co-author of the article.
The research group consists of scientists from Japan, the UK, France, Sweden, the US, Chile and Germany. Their analysis shows that the galaxy must initially have formed stars at a tremendous rate, but that the star formation activity then subsided before later intensifying once more.
“It’s something you can see in computer simulations of early galaxies,” Zackrisson says. “A generation of stars are born, emit their light and then die in violent supernova explosions that heat up and blow away the gas that stars are formed from. That prevents further star formation for a while. But for a galaxy as massive as this, today’s galaxy simulations don’t predict such huge fluctuations in star formation activity as we see traces of here. It’s as if something were missing in today’s computer models of early galaxy formation. Perhaps we don’t understand the supernova explosions from the first stars well enough.”
The forthcoming James Webb Space Telescope, which will be launched into space in 2020, will make it possible to study many galaxies at the same distance as MACS1149-JD1 with considerably better data quality than today’s telescopes permit.
“Then I expect we’ll find out what really went on in the first galaxies,” Zackrisson says.
T. Hashimoto et al. (2018) The onset of star formation 250 million years after the Big Bang, Nature