Astroboffins peering back in time with Hubble find stars may have been flickering into life even earlier than thought

We need to look further to glimpse Population III fireballs – where's that James Webb Telescope?

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European astronomers, using data from the veteran Hubble Space Telescope, have suggested the formation of the first stars and galaxies in the early universe happened earlier than thought.

The NASA and ESA space telescope is capable of peering back into the early history of the universe and, with the aid of advanced boffinry, make observations to within 500 million years of the "Big Bang."

A team led by ESA's Rachana Bhatawdekar set out to study the first generation of stars in the early universe using data from the Hubble as well as NASA's Spitzer spacecraft and the ground-based (and imaginatively named) Very Large Telescope of the European Southern Observatory.

Studying the cluster MACS J0416, which was one of six galaxy clusters examined using the HST's Wide Field Camera 3 and Advanced Camera for Survey between 2012 and 2017, the team failed to find any evidence of first-generation Population III stars.

Population III, Cell block Universe

Population III stars are those formed from the primordial material that emerged as a result of the "Big Bang" and are made only of hydrogen, helium and lithium. Other heavier elements were produced later, in the cores of these stars.

The stars of the Milky Way with a high heavy-element content, such as the Sun, are classified as Population I. Older stars with a lower heavy-element content are classed as Population II.

Not finding a trace of Population III objects in the 500 million to 1 billion year period after the "Big Bang" is surprising, and gives boffins yet another area for further research when the James Webb Telescope is finally launched.

Hubble was able to make such deep observations through use of a gravitational lens effect, where the mass of foreground galaxies bends and magnifies light to allow objects far fainter to be observed. The team led by Bhatawdekar developed a process to strip away the light of the foreground galaxies to reveal fainter galaxies at a distance corresponding to when the universe was less than a billion years old.

"These results have profound astrophysical consequences," said Bhatawdekar, "as they show that galaxies must have formed much earlier than we thought."

It also means that stars and galaxies were forming further back than is currently possible to observe with Hubble. ®


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