Peekaboo! A strange little galaxy gives a glimpse into the early history of the universe
Astronomers have discovered that a strange dwarf galaxy hidden for years in our cosmic neighbor looks like it belongs to the early universe, even though it formed recently.
The little one galaxy measuring just 1,200 light-years across, it earned the nickname “Peekaboo” because it was hidden in the bright glow of a fast-moving foreground star and appeared only 50 and 100 years ago.
The dwarf galaxy, officially named HIPASS J1131–31, is located about 22 million light-years from Earth in the constellation Hydra. His strange appearance was confirmed with the help of Hubble Space Telescope after appearing in observations from other space and ground-based telescopes.
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The galaxy’s artificially ancient appearance comes from the fact that it has a low abundance of elements heavier than hydrogen and helium, the lightest and earliest-formed elements in the universe. Astronomers describe these heavier elements as “metals” and they are usually found in much more distant places; hence, early galaxies that are usually described as “extremely metal-poor”.
As such, HIPASS J1131–31 represents the closest example of a galaxy formed by processes that existed primarily in the Universe shortly 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 at a level of detail unavailable in the distant, early universe,” study co-author and Space Telescope Science Institute astronomer , Gagandeep Anand, said in a statement (opens in new tab).
During the earliest era of the universe, almost everything in space consists of hydrogen and helium (opens in new tab). These light elements formed shortly after Big bang when the universe expanded and cooled enough to allow electrons and protons to bind together to form the first atoms and thus the first chemical elements.
These elements formed the first stars that forged heavier elements during their lifetime. When this first generation of extremely metal-poor stars reached the end of their lives and exploded, they spread these heavy elements throughout universe to become the building blocks of the next generation of stars.
As this process repeated itself throughout cosmic history, each successive generation of stars became increasingly enriched in heavy elements and created the metal-rich universe we see in our cosmic neighbor today.
These heavier building blocks forged in earlier stars—especially carbon, oxygen, iron, and calcium—would also become the building blocks of life.
Although early and distant galaxies are by default metal-poor, other examples of extremely metal-poor galaxies have previously been found closer to Milky Wayour galaxy.
Peekaboo stands out from these galaxies because it appears to lack an older stellar population of ancient and therefore metal-poor stars. Also, at only 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 study co-author Professor Barbel Koribalski in data collected in the HI Parkes All Sky Survey, the dwarf galaxy HIPASS J1131–31 did not immediately present itself as anything special to astronomers. Observations in far ultraviolet light from NASA’s now-defunct spacecraft are needed Galaxy Evolution Explorer (GALEX) mission to reveal the nature of Peekaboo as a strange compact blue dwarf galaxy.
“At first we didn’t realize how special this little galaxy was,” Koribalski said. “Now with the combined data from the Hubble Space Telescope, South African Large Telescope (SALT) and others, we know that the Peekaboo Galaxy is one of the most metal-poor galaxies ever discovered.”
Hubble was able to distinguish 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 discover the metal-poor nature of Peekaboo, revealing it to be one of the youngest and least chemically enriched galaxies ever discovered in the local universe.
Since the local universe has had over 13 billion years to evolve, Peekaboo’s metal-poor nature marks it as highly 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 that were part of the Every Known Nearby Galaxy Survey, astronomers will now use James Webb Space Telescope to observe the galaxy with Hubble.
Hopefully this will reveal more about its population of stars and how metal-enriched they are.
“Because of Peekaboo’s proximity to us, we can conduct detailed observations, opening up opportunities to see an environment resembling the early universe in unprecedented detail,” concluded Anand.
The team’s research has been accepted for publication in the Monthly Notices of the Royal Astronomical Society.
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