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The box-shaped opaque dust cloud at the center of our galaxy has long puzzled scientists, and observations that reveal a new detail about its composition deepen the mystery; It probably overturns what is known about how stars form.
The cloud, nicknamed “The Brick” for its visual impenetrability and rectangular appearance, was previously estimated to carry more than 100,000 times the mass of the sun. And according to researchers’ current understanding of star formation, such a dense droplet should produce massive new stars.
But it is not.
Brick is largely dormant. Recent observations using the James Webb Space Telescope did not reveal any hidden young stars.
New Webb data reveals that Brick is not just composed of gas. It’s also filled with much more frozen carbon monoxide than previously expected, according to a study published Monday in The Astrophysical Journal. And more ice is forming deep within the Brick.
The findings could have serious implications for how scientists analyze this region going forward. More carbon monoxide ice inside the Brick could significantly change the way researchers study and measure the dark clouds at the center of the Milky Way.
“We are now closer to understanding exactly what is happening in the Brick and where the mass is,” said University of Florida astronomer Adam Ginsburg, lead author of the study. “But with that we opened more questions than we closed.”
These questions include: Why and where does this carbon monoxide freeze into ice?
Other mysteries emerging from this region also remain unanswered: Why can’t we see new stars forming? Is the brick not as dense as scientists once believed? So what are the strange protrusions and filament-like features that appear in Brick?
“We still have a lot to investigate before we know for sure what is really going on,” Ginsburg said. “I would say we are in the hypothesis-forming stage, not the conclusion-drawing stage.”
What Webb revealed
Ginsburg and her fellow researchers, including University of Florida graduate students, first accessed these new Webb data in September 2022.
It was a very important moment. As the most powerful space telescope ever built, Webb could provide never-before-seen information about the Brick. But right from the start, Ginsburg and her team realized that the data needed a lot of work. The Webb telescope orients itself using a map and determines which direction it is pointing by reference to where it is relative to known stars.
The problem, Ginsburg said, is: “There are so many stars in the galactic center that it gets confusing.” So researchers had to spend months cleaning the data and orienting it so that it aligned correctly with existing sky maps.
Later, when they looked at Brick, they noticed that the images from Webb were coming out in the wrong color.
“All the stars were coming out a little too blue,” Ginsburg said, leading the researchers to wonder if there was something wrong with the data.
But it turned out that the problem was in their assumptions. Scientists didn’t expect there to be so much carbon monoxide ice there, and that’s what caused the color change, according to the study.
Dr., an assistant scientist at the National Radio Astronomy Observatory who was not involved in the study. Natalie Butterfield said learning about the existence of ice could have a broad ripple effect for any search for the center of the Milky Way.
Butterfield said his own research, which includes studying supernovae and radiation between star systems, could be changed forever by understanding the existence of this carbon monoxide ice. It could change scientists’ estimates of the mass of all clouds in the galactic center.
Why is carbon monoxide important?
There are a few confusing things about all this carbon monoxide ice. For example, the region is quite warm—about 60 Kelvin (minus 351.67 degrees Fahrenheit)—while carbon monoxide typically freezes at 20 Kelvin.
The dust inside the brick can be much colder than the gas, causing the carbon monoxide around the dust particles to solidify. Or, Ginsburg said, the water could be freezing and trapping carbon monoxide inside.
The answer is important.
All the ice in a region like the Brick could give scientists new information about our solar system, and even our home planet.
For example, the ice and water on Earth probably came here via comets. So where ice is found in the universe and how it forms can help researchers understand where these comets come from and how they accumulate the materials they deposit.
Where are the stars?
And there is a big mystery as to why there is a lack of star formation in the Brick.
Scientists already know that new stars are made of dust clouds and hydrogen molecules. But scientists can’t directly observe hydrogen molecules inside Brick or anywhere else in the universe because they can’t be seen with telescopes.
But scientists also know that for every hydrogen molecule there is probably a certain amount of carbon monoxide. And carbon monoxide is visible; so scientists can measure this as a proxy to determine how many hydrogen molecules are present in a given area.
Researchers have used this method to measure hydrogen molecules for 50 years, Ginsburg said.
But they always assumed that carbon monoxide was a gas, not solid ice, as the Webb data revealed. This finding opens a whole new can of worms, Ginsburg said.
Ginsburg stated that it is very important for researchers to understand what state (gas or solid) carbon monoxide is in in order to reach accurate answers.
Each new information about Brick and its structure better explains why this opaque cloud does not produce stars; although by most accounts it is one of the most active stellar nurseries in the galaxy.
“It’s really a natural place for new stars,” Ginsburg said. “But we didn’t find many; just a very, very small handful.”
There are some possible answers that Ginsburg and other researchers are looking forward to investigating: Perhaps the Brick is more dispersed, less compact, than scientists once thought. Or maybe he is still very young and the days when he will become a star are near.
Ginsburg and Butterfield said these are questions Webb can continue to help researchers answer.
“It’s just an impressive, impressive telescope,” Butterfield said. “I think this is just the first of many unique outcomes for the galactic center that will come out of JWST.”
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