The distant galaxy MACS1149-JD1, shown in the insert, seems as it was 13.3 billion years ago, just 500 million years after the Big Bang. Oxygen distribution detected by ALMA is shown in red.
Observations of the most distant galaxy ever identified revealed traces of oxygen from at least one of the previous generation of stars, a sign that star formation got an early start.
For the observation of the earliest stages of star formation, astronomers, combined with the power of a natural magnifying glass in space, by means of a process called gravitational lensing, with the human-built Atacama Large Millimeter/submillimeter Array ( ALMA ) and the European Space Agency’s Very Large Telescope ( VLT ) in Chile. Turning them in the direction of the galaxy MACS1149-JD1, they saw the guts of the first stars, in the form of oxygen.
“Most of the distant galaxies are very weak, but thanks to the gravitational lensing effect [light bending around an intervening galaxy], our goal was clear,” Takuya Hashimoto, an astronomer from Osaka Sangyo University and the National Astronomical Observatory of Japan, told Space.com. Hashimoto, the lead author of the new research, presented the results at the semi-annual winter meeting of the American Astronomical Society in Seattle in January.
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“This is one of the earliest star-formation events in the universe,” Hashimoto said.
The first generation
The first stars formed mostly from hydrogen, the element that dominated the universe just after the Big Bang. Like their descendants, these stars were element-making machines, building new elements into their heart as the temperature and the pressure increased. When these stars exploded after only a short lifespan, they scattered the newly-born elements in the space around them, so that the next generation of stars to take the gas and dust.
Hashimoto and his colleagues have pushed the boundaries of how far back in the ALMA can see. In 2016, a team led by Akio Inoue at Osaka Sangyo University in Japan used ALMA to find a signal of oxygen emitted 13.1 billion years ago. Just a few months later, Nicolas Laporte from University College London used the telescope to detect oxygen of 100 million years earlier. The two teams joined forces to find of oxygen in a galaxy 13.3 billion years ago, about 500 million years after the Big Bang.
The collaboration also revealed the VLT in the direction of the old galaxy, with the help of the telescope in the presence of a weaker signal of hydrogen, and to verify that the distance measured by ALMA. The researchers aim galaxy is the most distant galaxy ever seen with the instrument and the most distant galaxy that scientists have an accurate measure of distance, Hashimoto said.
Because the scientists determined that the debris after the exploded star, rather than the stars themselves, they were able to conclude that the star formation is started before they have observed in the young galaxy. Using observations from NASA’s Hubble and Spitzer space telescopes, the team developed a model of star formation that suggested the first generation of stars to form within a radius of 250 million years after the Big Bang.
After the Big Bang, the universe was thick with neutral hydrogen atoms, which do a good job of blocking the light. Hydrogen shrouded the early universe for the first 500 million years or so until, eventually, the radiation from the first stars split hydrogen atoms. But the first stars and galaxies are still a challenge to observe, because they are both silly and little.
Astronomers suspect that the first stars started within the first few hundred million years of the universe, and that galaxies quickly followed, but on the basis of Hashimoto’s, researchers are still not sure of the exact timeline. Have the stars shine individually and together as galaxies, or the galaxies formed in the first place, with the stars turning on the inside of them? Astronomers do not know it, but MACS1149-JD1 can help solve the mystery.
“Understanding the star-formation history of the universe is very important for the understanding of the physics of the universe,” Hashimoto said.
As powerful as they are, ALMA and the VLT would not be able to find the distant galaxy on their own. They needed to pair it with a natural magnifying glass. As the light travels through space, it can be bent by the gravity of massive objects in the way. In gravitational lensing, an effect predicted by Albert Einstein, these huge goals enlarge distant objects, allowing astronomers to catch a glimpse of things with their telescopes would not otherwise get.
By studying the light from the beginning of the milky way as it deflected around an older, more massive galaxy, and astronomers were able to peer much further into the universe than they would have done without magnification.
The team is still not ready with MACS1149-JD1. According to Hashimoto, the researchers are looking for signs of activity in the centre of the milky way that could indicate the presence of a black hole or a young quasar. If they find something, Hashimoto’s “very excited,” he said.
“That would then give us a hint of the first formation of a supermassive black hole in the universe,” he said.
The research was published in May in the journal Nature.
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Original article on Space.com.