New discoveries by the Hubble Space Telescope suggest that the first star in the early universe may have been much earlier than scientists initially thought, opening up new questions about the evolution of galaxies shortly after the Big Bang. The researchers expect the so-called Population III stars to be found in the latest Hubble observations, but they will return empty-handed.
Population III stars are thought to be the first stars to form in the new universe. They are made up of hydrogen, helium and lithium, which scientists believe are the only elements that existed after the Big Bang.
However, they play an important role in producing substances that we now take for granted. Before the early burning of the universe, their rich cores created heavier elements — including oxygen, nitrogen, carbon, and iron — but before that they were thought to have grown to a huge volume, perhaps a thousand times the size of our sun.
Their secret is what led a team of scientists led by the European Space Agency’s Rachana Bhatawdekar to try to find the Population III star using Hubble data. Using readings of the MACSJ0416 cluster and its parallel field, and combining Hubble data with further information from NASA’s Spitzer Space Telescope and the European Southern Observatory’s Ground Very Large Telescope, they can get a glimpse of what the universe looked like about 500 million to 1 billion years after the Big Bang.
It’s not easy, and Hubble took advantage of so-called gravitational lenses. Here, the clusters of galaxies closer are heavy enough to bend and amplify light. This, in turn, is a magnifying glass for objects farther behind them. Through these naturally occurring lenses, Hubble can see star evidence far beyond its protooptical system. However, to truly identify something meaningful from this data, the ESA team first needs to do something about it. They came up with a new technique to remove light from the brightest foreearth galaxies: although stars help by producing gravitational lensing, they also surpass the darker distant objects of interest to researchers.
However, they did not find the Population III star. In fact, “we found no evidence of these first-generation Population III stars in this cosmic time interval,” Bhatawdekar said. “These results have profound astrophysical consequences because they suggest that galaxies must have formed much earlier than we thought. This also strongly supports the idea that low-mass/weak galaxies in the early universe were responsible for reionization. “
Reionization is the process by which intergalactic mediums in the early universe were ionized by the first stars and galaxies. However, Bhatawdekar’s findings suggest that the process happened earlier—- in fact, the Hubble Space Telescope could not observe. Fortunately, Hubble’s successors are close at hand. The James Webb Space Telescope will be able to go deeper into the universe to track earlier events. It is scheduled for launch in 2021.