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A cloud of opaque, box-shaped dust at the center of our galaxy has long perplexed scientists, and observations that reveal new details about its composition are deepening the mystery, possibly altering what is known about How do stars form.
The cloud, nicknamed “the Brick” for its visual impenetrability and rectangular appearance, was previously estimated to have more than 100,000 times the mass of the sun. And such dense mass should be producing massive new stars, according to researchers’ current understanding of star formation.
But is not.
The Brick is largely inactive. And the latest observations, made with the James Webb Space Telescope, revealed no hidden young stars.
Instead, Webb’s new data revealed that the Brick is not just made of gas. It’s also full of frozen carbon monoxide, much more than previously expected, according to a study published Monday in The Astrophysical Journal. And more ice is forming in the depths of the Brick.
The findings could have drastic implications for how scientists will analyze this region in the future. More carbon monoxide ice inside the Brick could dramatically change the way researchers study and measure dark clouds at the center of the Milky Way.
“We are (now) closer to understanding what exactly is happening in the Brick and where the mass is,” said astronomer Adam Ginsburg of the University of Florida, lead author of the study. “But we opened more questions than we closed with this.”
Among those questions: Why and where does this carbon monoxide freeze into ice?
Other mysteries hanging over this region also remain unanswered: Why can’t we see the formation of new stars? Isn’t the Brick as dense as scientists believed? And what are the strange ridge- and filament-like features that appear within the Brick?
“We have more to investigate before we can be really sure what’s going on,” Ginsburg said. “I would say that we are in the phase of forming hypotheses, not in drawing conclusions.”
What Webb revealed
Ginsburg and her fellow researchers, who included graduate students at the University of Florida, first obtained this new data from Webb in September 2022.
It was a crucial moment. As the most powerful space telescope ever built, Webb could offer never-before-seen information about the Brick. But from the beginning, Ginsburg and his team discovered that the data needed a lot of work. The Webb telescope orients itself using a map, determining which direction it points by referring to where it is in relation to known stars.
The problem was that “there are so many stars in the galactic center that it gets confused,” Ginsburg said. So the researchers had to spend months cleaning the data, orienting it so that it aligned correctly with existing sky maps.
Then, while looking at the Brick, they discovered that Webb’s pictures were the wrong color.
“All the stars came out too blue,” Ginsburg said, leading researchers to wonder if there was something wrong with the data.
But it turned out, he said, that the problem was with his assumptions. Scientists didn’t expect there to be so much carbon monoxide ice, and that was the cause of the color change, according to the study.
Learning about the ice’s existence could have broad knock-on effects for all kinds of research on the center of the Milky Way, said Dr. Natalie Butterfield, an assistant scientist at the National Radio Astronomy Observatory, who was not involved in the study.
Butterfield said his own research, which includes the study of supernovae and radiation between star systems, could be altered forever if the existence of this carbon monoxide ice is understood. He could change the way scientists estimate the mass of all the clouds in the galactic center.
Why carbon monoxide is important
There are several puzzling things about all this carbon monoxide ice. For example, the area is quite warm (around 60 Kelvin (minus 351.67 degrees Fahrenheit), while carbon monoxide generally freezes at 20 Kelvin.
It could be that the dust inside the brick is much colder than the gas, causing the carbon monoxide around the dust particles to turn solid. Or, Ginsburg said, it could be that the water is freezing, trapping carbon monoxide inside.
The answer matters.
All the ice in a region like Brick can give scientists new insight into our solar system, even our home planet.
The ice and water that exist on Earth, for example, probably arrived here via comets. So knowing where ice exists in the universe and how it forms can help researchers understand where these comets came from and how they collected the materials they deposited.
Where are the stars?
And then there is the great mystery of why there is a lack of star formation within the Brick.
Scientists already know that new stars form from clouds of dust and hydrogen molecules. But scientists can’t directly observe hydrogen molecules inside the Brick (or anywhere else in the universe) because they are invisible to telescopes.
However, scientists also know that for every molecule of hydrogen, there is probably a certain amount of carbon monoxide. And carbon monoxide is visible, so scientists can measure it as an indicator to identify how many hydrogen molecules are in a given area.
Researchers have been using this method to measure hydrogen molecules for 50 years, Ginsburg said.
But they have always assumed that carbon monoxide was gas, not solid ice, as Webb’s data revealed. This finding opens a whole new Pandora’s box, Ginsburg said.
Ginsburg noted that it is crucial for researchers to understand what state of matter carbon monoxide is in (gas or solid) to arrive at the right answers.
Each new knowledge about the Brick and its composition better informs why this opaque cloud is not producing stars, although by most opinions it should be one of the most active star nurseries in the galaxy.
“It’s a really natural place for new stars,” Ginsburg said. “But we haven’t found many, just a very, very small handful.”
There are some possible answers that Ginsburg and other researchers are eager to explore: Perhaps the Brick is more widespread (less compact) than scientists once thought. Or maybe he’s too young and his star-making days are ahead of him.
Those are questions, Ginsburg and Butterfield said, that Webb can continue to help researchers answer.
“It’s just an awesome, awesome telescope,” Butterfield said. “I believe this is just the first of many unique results that will emerge from JWST for the galactic center.”
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