The Hubble Space Telescope might be 24 years old, but it’s still making discoveries that are changing the way we see and understand our universe. Hubble’s latest feat was to image one of the faintest, smallest, and oldest galaxies astronomers have ever seen.
The galaxy’s light took 13 billion light years to reach Earth, and astronomers estimate that it formed when our universe was only 500 million years old. Although 500 million years is long time for us, it is minuscule compared to the age of our universe, 13.8 billion years.
Astronomers know of only about ten other galaxies that formed so soon after the Big Bang. This newly discovered galaxy, however, is significantly smaller and fainter than the others.
They were able to find it due to gravity’s crazy ability to bend light. Researchers aimed Hubble at the three massive galaxy clusters, shown in the boxes in this image. Galaxy clusters are the most massive regions in the universe, and their gravitational pull is so great that it can noticably bend light.
As a result, we can see objects located behind these galaxy clusters because the light from the objects, that would not otherwise reach Earth, is bent toward us by these clusters. Moreover, the object is magnified in the process, and the team used this to their advantage to estimate the galaxy’s distance, size, and behaviour.
“This object is a unique example of what is suspected to be an abundant, underlying population of small and faint galaxies at about 500 million years after the Big Bang,” study researcher Adi Zitrin of the California Institute of Technology said in a statement.
“The discovery is telling us that galaxies as faint as this one exist, and we should continue looking for them and even fainter objects so that we can understand how galaxies, and the universe, have evolved over time,” Zitrin said.
The international team of astronomers who conducted the study estimate that this distant galaxy is about 850 light-years across. Our galaxy, the Milky Way is about 100 times longer.
Although the galaxy is small, it’s actually cooking up stars at an impressive rate for its size. The Milky Way produces about one star every year. This galaxy produces one star every three years, but for a galaxy that is 100 times smaller, that is extremely efficient, the team said.
Measuring the star formation rate in these very distant galaxies is important for figuring out why we see what we do in the universe. For much of the first 100 billion years of the lifetime of the universe, light from the first stars was constantly being absorbed by cold hydrogen gas permeating space. As a result, the universe was foggy.
It’s hard to tell when radiation began warming the hydrogen gas that clouded the universe, but astronomers estimate it happened between 150 million to one billion years after the Big Bang. It’s also hard to know what created this heat, but some think it was these early stars forming in distant galaxies that Hubble is probing.
As a result of this warming, which experts call ionization, the particles in the hydrogen gas no longer blocked the visible light from stars, making the universe transparent. Below is an animation simulating what this may have looked like:
This is why we can see so far back into time today and, ultimately, why the science field of astronomy exists in the first place.
“We tend to assume that galaxies ionized the universe with their ultraviolet light. But we do not see enough galaxies or light that could do that,” Zitrin said in the released statement. “So we need to look at fainter and fainter galaxies,” to learn how the universe evolved in its earliest days.
This study includes one of the most accurate distance estimates to a distant galaxy ever made. For more information on the technique they used and how they did it, check out their paper, which was published in the journal Astrophysical Journal Letters on Sept. 4.
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