It was an important task of the very first stars in the universe. They were formed from primordial elements created by the Big Bang, so they did not contain metals. Their task was to synthesize the first metals and spread them throughout the nearby universe.
JWST has made some progress in its search for the earliest galaxies in the universe, the Universe Today. Can you be as successful in your search for the first stars?
Finding the first galaxies in the universe is an extremely difficult task, but it is also one of the main motivations for building the JWST. The light from these ancient objects shifts into the infrared range, which the telescope excels at detecting. With deep light observations in this range, the space telescope found some of the earliest galaxies.
However, the first stars are much older than the first galaxies. The first stars formed roughly 50 to 100 million years after the Big Bang, and their light eventually ended the dark ages of the universe. According to astrophysicists, these stars could have masses of up to 1000 solar masses.
The new study a Monthly Notices of the Royal Astronomical Society is published in the journal The lead author is Erik Zackrisson from the Department of Physics and Astronomy at Uppsala University in Sweden.
Due to the lack of effective coolants and the fragmentation of chemically unenriched gas, the resulting metal-free, i.e. population III, stars in these early epochs are presumably extremely large, typically 10-1000 solar masses.
To see these early, massive stars, JWST will need the help of gravitational lensing. “Gravitational lensing can make individual high-mass stars detectable, and a number of extremely magnified stars have been detected in recent years,” the authors explain. In the observed cases, the light needed more than 12.7 billion light years to reach us.
Gravitational lensing takes advantage of situations where a massive object, such as a galaxy cluster, is between us and an object we want to observe. As the light from the target passes through the object in the foreground, called a gravitational lens, the light is magnified. This makes an otherwise invisible object visible.
The first stars are at about z=20 in terms of redshift, and Webb should be able to see this light if it can take advantage of gravitational lensing. If this is successful, the high-powered telescope could provide evidence of a period of the early universe that we have so far mostly understood from theory: the Epoch of Reionization (EoR).
During the EoR, the universe was dominated by a dense, hazy nebula of hydrogen gas. When the first stars formed, their ultraviolet light reionized the gas and allowed light to propagate. This is a critical step in the life of the universe, so finding the ancient Pop III stars responsible is an important goal.
These first stars are also impressive in other ways. They were massive, millions of times brighter than the Sun, and very short-lived. They either exploded as supernovae or collapsed into black holes. Those that became black holes swallowed gas and other stars and became the first quasars in the universe. Astrophysicists believe that these quasars grew through accretion and mergers to become supermassive black holes anchored at the centers of galaxies like our Milky Way.
Those that exploded as supernovae played an equally important role. Elements heavier than hydrogen and helium were forged, and when they exploded, these metals were scattered into space. The stars that formed later also contained some of these metals, and rocky bodies were also formed from the metals. The III. before population supernovae, rocky planets did not exist, and life was certainly not possible. So these huge, ancient stars helped create everything we see around us today.
If JWST is successful, there won’t be any pretty pictures of these stellar progenitors. Instead, it will be data. Untangling the data and determining whether it contains III. population stars, a complex task. This effort will push the space telescope and the scientists working with it to the limit.
If Webb can find some of these stars, the pioneering telescope will be even more successful. The instrument and the people who operate it methodically check off the boxes on the list of scientific goals.
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2023-12-22 17:06:31
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