Astronomy experts note that when the universe was about 3 billion years old, it experienced the most prolific star birth in its long history. However the Hubble Space Telescope and the Atacama Large Millimeter / Submillimeter Array (ALMA) located in northern Chile, in the Atacama Desert, observed cosmic objects from that period and found true rarities: six galaxies of the early universe, massive and “dead”. Despite belonging to a time with a lot of activity, these galaxies ran out of cold hydrogen, the fuel with which stars are created.
Those galaxies are believed to have expanded since then, not through the creation of stars but by merging with other smaller pairs and gas.
Hubble and ALMA found these strange galaxies increasing their capabilities, by taking advantage of a “natural lensOf space that is created by massive galaxy clusters in the foreground. As explained by scientists in the study published in the journal Nature, the gravity of these clusters stretches and amplifies the light of the background galaxies, allowing researchers to use them as “magnifying glasses” and thus study their characteristics in detail.
“At that time in our universe, all galaxies should be forming many stars. It is the time of maximum formation ”, commented astronomer Kate Whitaker, lead author of the study. “By using strong gravitational lenses like natural telescopes, we can find the distant, most massive galaxies and the first to stop star formation,” Whitaker added.
As NASA, one of the main responsible for the Hubble project, notes, approximately 11,000 million years later, in the current universe, “these previously compact galaxies are believed to have evolved to be larger, but they are still dead in terms of any new star formation ”.
The six galaxies found had short lives, creating their stars in a short time. According to the US space agency, the reason why star formation abruptly ceased (that is, the loss of cold hydrogen) is a puzzle.
Whitaker establishes some hypotheses in this regard. “Did a supermassive black hole create in the center of the galaxy and heat up all the gas? If so, the gas might still be there, but it would be hot now. Or it could have been kicked out and is now preventing it from accumulating back into the galaxy. Or did the galaxy just use it all up and the supply was cut off? These are some of the open questions that we will continue to explore with new observations in the future, ”said the specialist.
The Hubble Space Telescope is an international cooperation project between NASA and the European Space Agency (ESA).