A galaxy that has teased astronomers since they first detected a hint of its existence more than 20 years ago has finally emerged from hiding.
It’s called HIPASS J1131-31 or Peekaboo, and it’s located just 22 million light-years away. It was very difficult to see because it is so small and obscured by a bright star in the Milky Way almost directly in front of it.
Through a collaborative effort involving terrestrial and space telescopes, scientists have learned that tiny peekaboo is also very small and very close–offering a snapshot of galactic childhood.
“Discovering the Peekaboo galaxy is like discovering a direct window into the past, allowing us to study its harsh environment and stars at a level of detail unattainable in the distant, distant universe,” said astronomer Gagandeep Anand of the Space Telescope Science Institute. in Baltimore.
Given the absolute predominance of objects in the universe, it is very common for foreground objects to sit in front of distant objects. So when the H.I. Parkes All Sky Survey spotted the galaxy peeking in from behind the bright star TYC 7215-199-1 in the early 2000s, it wasn’t much of a surprise.
Ultraviolet observations have revealed that Peekaboo is what is known as a compact blue dwarf galaxy: a young galaxy bursting with formation of young stars, the brightest of which appear to be blue.
But the light and diffraction effects of TYC 7215-199-1 obscure the galaxy from clear view.
It might have been – except it turns out that the star was fast-moving, and the direction it’s moving is farther away from the galaxy. If we looked 100 years ago, we might not have seen the galaxy at all. Over the past two decades, this gap has continued to widen. Our space control technology has grown more and more.
So an international team led by astronomer Igor Karachentsev of the Russian Academy of Sciences visited Peekaboo to take a closer look. They used the Hubble Space Telescope for optical observations, the South African Large Telescope for optical spectra, and the Australia Telescope Integrated Array (ATCA) for radio observations.
Not only have these observations resolved about 60 individual stars in Peekaboo, but they have helped researchers determine what the stars are made of.
“At first, we didn’t realize how special this little galaxy was,” says astronomer Bärbel Korypalski of the Commonwealth Scientific and Industrial Research Organization (CSIRO) in Australia and the researcher who discovered the existence of HIPASS J1131-31.
“Now, with data gathered from the Hubble Space Telescope, the South African Large Telescope, and others, we know that the Peekaboo Galaxy is one of the most metal-poor galaxies ever discovered.”
All of the stars analyzed by Hubble appear to be less than a few billion years old, at most, which means that Peekaboo appears very young in the outline of the universe.
And Peekaboo has a surprisingly low abundance of the mineral. In general, low minerals indicate that the body was formed in the early universe; Fresher organisms contain a higher content of heavy elements.
This is because there weren’t a lot of metals in the very early universe. In the era after the Big Bang 13.8 billion years ago, the universe consisted mostly of hydrogen and helium. From these elements the first stars were formed, fusing hydrogen and helium into heavier elements, right down to iron.
Metals heavier than iron were formed in violent supernova explosions when stars died, and are dispersed into the universe where they can be combined to form new stars.
In addition to the number of young stars, the researchers have only faintly detected imprints of old stars, indicating that star formation in Peekaboo only began a few billion years ago.
This means that it could be an example of what the first generation of galaxies and the star clusters within them looked like.
It’s basically a time capsule and it’s practically right next door, cosmically speaking. Because the Hubble observations were not particularly detailed, the researchers hope to revisit the galaxy using JWST to make a more detailed catalog of its chemical composition.
“Because peekaboo is so close to us, we can make detailed observations, opening up the possibilities of seeing an environment similar to the early universe in unprecedented detail,” says Anand.
Search accepted Monthly Notices of the Royal Astronomical Society.
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