Astronomers have discovered that a strange dwarf galaxy that has been hidden for years in our cosmic neighborhood seems to belong to the early universe, although it was formed more recently.
The tiny galaxy measuring just 1,200 light-years in diameter was given the nickname ‘Peekaboo’ because it was hidden in the bright glare of a fast-moving foreground star and only appeared 50 years ago. at 100 years old.
The dwarf galaxy, officially named HIPASS J1131–31, is located about 22 million light-years from Earth in the constellation Hydra. Its strange appearance was confirmed using the Hubble Space Telescope after it appeared in observations from other space and ground-based telescopes.
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The galaxy’s deceptively ancient appearance comes from having a low abundance of elements heavier than hydrogen and helium, the lightest and oldest elements in the universe. Astronomers describe these heavier elements as “metals” and are usually found in much more distant places; thus, the first galaxies which are generally described as “extremely metal-poor”.
As such, HIPASS J1131–31 represents the closest example of a galaxy formed by processes that existed primarily throughout the universe soon after the Big Bang.
“Discovering the Peekaboo galaxy is like discovering a direct window into the past, allowing us to study its extreme environment and stars in a level of detail unattainable in the distant, early universe,” co-author of the Space Telescope Science Institute study and astronomer Gagandeep Anand said in a statement (opens in a new tab).
During the first era of the universe, almost everything in the cosmos was composed of hydrogen and helium (opens in a new tab). These light elements formed shortly after the Big Bang when the universe expanded and cooled enough to allow electrons and protons to bond and form the first atoms and therefore the first chemical elements.
These elements formed the first stars, which over their lifetime forged heavier elements. When this first generation of extremely metal-poor stars reached the end of their lives and exploded, they spread these heavy elements throughout the universe to become the building blocks for the next generation of stars.
As this process repeated itself throughout cosmic history, each subsequent generation of stars became increasingly enriched with heavy elements and created the metal-rich universe we see today. in our cosmic neighborhood today.
Those heavier building blocks forged in earlier stars – specifically carbon, oxygen, iron and calcium – would also become the building blocks of life.
Although ancient and distant galaxies are metal-poor by default, other examples of extremely metal-poor galaxies have already been discovered closer to the Milky Way, our galaxy.
Peekaboo stands out from these galaxies because it appears to lack an older stellar population of old and therefore metal-poor stars. Additionally, at about 20 light-years from Earth, Peekaboo is much closer than other young, metal-poor galaxies that are twice as far away.
First discovered two decades ago by research co-author Professor Bärbel Koribalski in data collected as part of the HI Parkes All Sky Survey, the dwarf galaxy HIPASS J1131–31 did not immediately presented as something special to astronomers. It took far-ultraviolet observations by NASA’s now-defunct Galaxy Evolution Explorer (GALEX) space mission to reveal Peekaboo’s nature as a strange, compact blue dwarf galaxy.
“At first we didn’t realize how special this little galaxy was,” Koribalski said. “Now, with combined data from the Hubble Space Telescope, the Large South African Telescope (SALT) and others, we know that the Peekaboo Galaxy is one of the most metal-poor galaxies ever detected.”
Hubble was able to resolve about 60 stars in the dwarf galaxy, all of which appear to be no more than a few billion years old. Astronomers then used SALT to uncover the metal-poor nature of Peekaboo, revealing it as one of the youngest and least chemically enriched galaxies ever detected in the local universe.
As the local universe had over 13 billion years to evolve, the metal-poor nature of Peekaboo makes it extremely unusual and astronomers still have a lot to learn about this dwarf galaxy.
To enhance the snapshot of HIPASS J1131–31 collected by Hubble Observations, which was part of the Every Known Near Galaxy Survey, astronomers will now use the James Webb Space Telescope to observe the galaxy alongside Hubble.
Hopefully this will reveal more about its population of stars and their richness in metals.
“Due to Peekaboo’s proximity to us, we can make detailed observations, opening up the possibility of seeing an environment resembling the early universe in unprecedented detail,” Anand concluded.
The team’s research has been accepted for publication in the Monthly Notices of the Royal Astronomical Society.
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