Behind the star TYC 7215-199-1 lay a cosmic secret. The bright light was hiding a small, yet exciting galaxy. The dwarf galaxy – which researchers have nicknamed ‘Peekaboo’ – has now come into view and the Hubble space telescope has snapped a pretty incredible picture (take that JWST).
A paper looking at the Peekaboo Galaxy (or HIPASS J1131-31 if it’s in trouble) in detail is to be published in the Monthly Notices of the Royal Astronomical Society.
“At first we did not realize how special this little galaxy is,” Professor Bärbel Koribalski, an astronomer at CSIRO said.
“Now with combined data from the Hubble Space Telescope, the Southern African Large Telescope (SALT), and others, we know that the Peekaboo Galaxy is one of the most metal-poor galaxies ever detected.”
The Australian Parkes radio telescope Murriyang was the first to discover the galaxy more than 20 years ago. The galaxy is around 22 million light years away from Earth.
A project called the HI Parkes All Sky Survey (HIPASS) back in late 90s and early 2000s was trying to map as many galaxies as possible.
“I was involved in the project nearly from the beginning and I was keen to catalogue all nearby galaxies and find gas clouds between galaxies,” Koribalski told Cosmos.
“Finding needles in a haystack is hard, so finding little – previously unknown – dwarf galaxies in the HIPASS cubes took a lot of work, but it paid off with the discovery of many hundreds of new galaxies.
“I found HIPASS J1131-31, the only dwarf galaxy to hide behind the glare of a bright foreground star.”
More recently, using SALT, the team discovered that the galaxy is one of the most extremely ‘metal-poor’ galaxies known. This isn’t just the metals we think of though. In astronomy, ‘metals’ refers to all elements heavier than hydrogen and helium.
“Uncovering 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 that is inaccessible in the distant, early universe,” said Space Telescope Science Institute astronomer Gagandeep Anand.
In the early universe, there was pretty much only hydrogen and helium, and heavier elements were forged in stars later on.
So how did this dwarf galaxy end up with so little metal? Even today the researchers aren’t sure.
“So, nearby dwarf galaxies tend to be metal-rich, but surprisingly HIPASS J1131-31 is extremely metal-poor – as if it is very old,” Koribalski told Cosmos.
“Now we wish to find out why, for example by obtaining deeper images with the JWST.”
Although there have been other extremely metal poor galaxies found in the local universe, Peekaboo is different in two ways. First, it’s located much closer – at least half the distance of the previously known similar galaxies. Secondly, it’s a metal poor galaxy without older stars around it. This new image was part of a snapshot survey program called ‘The Every Known Nearby Galaxy Survey’, which means that further work with Hubble and JWST could give us even more information about Peekaboo.
Originally published by Cosmos as Hubble snaps a tiny, ancient-looking galaxy hiding behind a star
Jacinta Bowler
Jacinta Bowler is a science journalist at Cosmos.
They were published in the Best Australian Science Writing 2023.
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