Astronomers have discovered a collection of tiny galaxies located roughly 3 million light-years away that includes the smallest and faintest galaxy ever seen.
This galaxy, designated Andromeda XXXV, and its compatriots orbiting our neighbor galaxy, Andromeda, could change how we think about cosmic evolution.
That's because dwarf galaxies this small should have been destroyed in the hotter and denser conditions of the early universe . Yet somehow, this tiny galaxy survived without being fried.
"These are fully functional galaxies, but they're about a millionth of the size of the Milky Way," team member and University of Michigan professor Eric Bell said in a statement. "It's like having a perfectly functional human being that's the size of a grain of rice."
Meet Andromeda XXXV
Dwarf galaxies themselves are nothing new to scientists. Our own galaxy, the Milky Way , is orbited by dozens of these satellite galaxies trapped within the grasp of its larger galactic neighbors.
Nevertheless, many aspects of dwarf galaxies remain mysteries to scientists. Due to their smaller size, these galaxies emit less light compared to larger ones, which makes them more difficult to observe and investigate from far away.
Although astronomers have managed to pinpoint numerous dwarf galaxies circling the Milky Way, discovering similar small galaxies around our luminous neighboring galaxies has proven extremely challenging. Thus, the dwarf galaxies of the Milky Way Have served as our sole source of knowledge regarding tiny galactic entities.
This task is somewhat less challenging around the closest major galaxy to the Milky Way, Andromeda. Other Dwarf galaxies have been observed near Andromeda. before, but these have been large and bright, thus simply confirming the information that astronomers had gathered about dwarf galaxies around the Milky Way.
To uncover these groundbreaking faint and diminutive dwarf galaxies, lead researcher Marcos Arias, an astronomer from the University of Michigan, along with his collaborators examined extensive astronomical databases. They were additionally granted observing time with powerful telescopes. Hubble Pawonation.comTelescope to aid their search.
This discovery showed that Andromeda XXXV is not just a satellite galaxy, but its size is also significant enough to alter our understanding of galactic evolution.
I found this quite astonishing," Bell stated. "Being the dimmest object detected in the area makes it particularly intriguing. However, it also turns out to be unexpectedly unusual in numerous aspects.
A cosmic murder mystery
A crucial element of galactic evolution is determining the duration of their star-forming periods The primary distinction appeared to lie with the Milky Way's dwarf galaxies compared to the less massive satellite galaxies orbiting Andromeda.
Arias noted that most of the Milky Way’s satellite galaxies contain predominantly old stellar populations, having ceased star formation approximately 10 billion years ago. However, she pointed out that some analogous satellites orbiting Andromeda were still forming stars as recently as 6 billion years ago, up until just a few billion years past.
Star formation requires a steady supply of gas and dust to collapse and birth stellar bodies. When that gas is gone, star formation halts, and the galaxy "dies."
Thus, Bell described the situation around these small galaxies as a "murder mystery." Did star formation end when dwarf galaxies' gas supplies petered out On their own, or when these gases were stripped away by gravitational forces from a massive galactic host?
For the Milky Way, it seems that the supply of gas needed for star formation naturally depleted over time. In contrast, for the smaller galaxies surrounding Andromeda, it looks like they were essentially “destroyed” by their larger host galaxy.
The lighting is somewhat dim, but it seems these galaxies either fell or were forced out of their positions. It appears they were pushed," Bell stated. "From this, we’ve gained new qualitative insights into how galaxies form.
What is particularly intriguing is the prolonged duration of star formation observed in Andromeda XXXV. To grasp this phenomenon, we must journey back in time to when the very first galaxies were formed.
Why isn't Andromeda XXXV a 'deep fried' galaxy?
The earliest epoch of the universe was marked by incredibly hot and dense conditions. This inflationary period, begun by the Big Bang , continued, and the universe dispersed and cooled. This allowed the first atoms of hydrogen to take shape, birthing the first stars, which gathered in the first galaxies.
These stars and galaxies blasted out energy as did the first feeding black holes reheating the cosmos. This signaled the death of very small galaxies, and scientists theorize this heat "cooked off" the gas needed for star formation in such collections of stars.
Nevertheless, Andromeda XXXV managed to survive!
Bell mentioned that we initially believed everything would be destroyed since the whole cosmos seemed like a giant cauldron of bubbling oil. We expected it to exhaust all its gas, but surprisingly, that wasn’t the case. This entity holds roughly 20,000 times the mass of our sun and continued producing new stars without issue for an additional couple of billion years.
The exact way Andromeda XXXV managed to avoid being destroyed remains an enigma.
“I don’t have a solution,” Bell stated. “The fact remains that the universe did experience warming; we’re merely discovering that the outcomes are far more complex than we initially believed.”
NASA and other Pawonation.comagencies are planning missions that could discover further dwarf galaxies around other large galaxies and help solve this mystery. But there's a good chance that the solution will open up new questions just as the discovery of Andromeda XXXV has.
"We still have a lot to discover," Arias said. "There are so many things that we still need to learn — even about what's near to us — in terms of galaxy formation, evolution, and structure before we can reverse engineer the history of the universe and understand how we came to be where we are today."
The team's research was published on Tuesday (March 11) in The Astrophysical Journal Letters.
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