Astronomers are particularly enamored with Andromeda XXXV, a recently discovered dwarf galaxy. Located only 3 million light-years away, this relatively small galaxy packs a punch with its small stature and varying dimness. This dwarf galaxy revolves around the massive main Andromeda galaxy. Incredible as it may seem, it is the smallest and faintest galaxy ever detected, with an estimated mass of only about 20,000 solar masses. Even with its small size, Andromeda XXXV’s unique features have presented an intriguing look into how galaxies change and grow over time.
The dwarf galaxy's ability to form stars for several billion years, only ceasing about 10 billion years ago, defies prior expectations. It’s one of a handful of other dwarf galaxies that orbit Andromeda. These galaxies have somehow defied the brutal environment of the universe’s infancy.
A Galaxy Defying Expectations
Astronomers were stunned to discover that Andromeda XXXV, even though it was small and limited in size, was still a valuable and operating galaxy. It went on to form stars until roughly 6 billion years ago. This calls into question the long-held assumption that such small galaxies were unable to hold onto their gas or form stars in the extreme environmental conditions that pervaded the early universe.
"We thought they were basically all going to be fried because the entire universe turned into a vat of boiling oil," said Bell.
This find demonstrates that the processes shaping galaxy formation and evolution are much more complex than we once thought. Andromeda XXXV surprises all by its survival and vigorous star-forming prowess. It upends the long-held paradigm that smaller, lower mass galaxies rapidly lose their gas and cease star-forming activity.
"We thought that it would completely lose its gas, but apparently that doesn't happen, because this thing is about 20,000 solar masses and yet it was forming stars just fine for a few extra billion years," added Bell.
Implications for Galaxy Formation Theories
Andromeda XXXV and similar, more distant satellite galaxies have long fascinated us. Why wasn’t theirs completely gutted of every gas possible? This never-before-seen phenomenon indicates that there are underlying mechanisms at work here that haven’t been completely grasped by astronomers.
"These are fully functional galaxies, but they're about a millionth of the size of the Milky Way," Bell remarked.
The unexpected finding has led scientists to reevaluate previously formed models of galactic evolution. Remarkably, these small galaxies never stop making new stars, even in adverse environments. This unanticipated capacity demonstrates that the universe’s heating influences are a lot more challenging than we thought.
"It is also still true that the universe did heat up; we're just learning the consequences are more complicated than we thought," Bell explained.
The Mystery of Andromeda XXXV
Andromeda XXXV’s long duration of star formation is an open question. How it managed not to get “fried” by the extreme conditions of the early universe is a mystery that upends our current understanding. The collection of tiny galaxies orbiting Andromeda, including Andromeda XXXV, suggests that some force might have pushed these galaxies into their current positions.
As tiny as the dwarf galaxy is, its past record of star formation is grand. It matches up with other, closer by, small satellite galaxies, which continued to build stars until only a few billion years past. The unique characteristics of Andromeda XXXV provide astronomers with a valuable opportunity to study the complexities of galactic evolution further.
