Science

Vast Cosmic Bubble Around the Sun Identified as Source of Baby Stars

Astronomers have known since the 1970s that our Sun lies at the center of a wide cavity within the hot gas that fills the gaps between stars in the Milky Way. But the origins of this ever-growing void, known as the local bubble, and its relationship to our star-studded neighbours, have remained elusive.

Now, using new data from the European Space Agency’s Gaia space telescope, scientists have revealed that the bubble’s origin and growth were the result of a series of 15 supernovae – powerful explosions of collapsing stars – over the past 14 million years, each of which is a star-forming region and young star. Within 500 light-years of Earth sits on the surface of the Local Bubble.

When stars die, the resulting explosions emit shock waves that travel outward, sweeping across and collecting interstellar material such as gas and cosmic dust. Eventually, enough gas accumulates, condenses, and cools at the edge of this shock wave to start the birth of stars.

The local bubble is the result of these shock waves, as are stellar nurseries that envelop its outer shell.

said Kathryn Zucker, an astronomer with the Harvard-Smithsonian Center for Astrophysics and lead author of a study on the new findings, published Wednesday in the journal Nature.

“Imagine it’s like an icebreaker, at the edge of the crust there’s a sharp edge of accreted interstellar matter that basically hosts all of these star-forming regions,” she said.

How was the local bubble formed?

Powerful supernovae begin to explode, creating a cavity of very thin hot gas in space called the local bubble.

The sun’s path takes her into the expanding bubble. As the bubble expands, dense regions of cold gas that could generate stars gather on its surface.

Today, many young stars are sitting on the surface of the bubble, but they have not formed inside it.

Approximately. 1000 light years

Source: Space Telescope Science Institute with

Center for Astrophysics, Harvard and Smithsonian University

OG GD425 1bcba0 355PX 20220111183231

How was the local bubble formed?

Powerful supernovae begin to explode, creating a cavity of very thin hot gas in space called the local bubble.

The sun’s path takes her into the expanding bubble. As the bubble expands, dense regions of cold gas that could generate stars gather on its surface.

Today, many young stars are sitting on the surface of the bubble, but they have not formed inside it.

Approximately. 1000 light years

Source: Space Telescope Science Institute with

Center for Astrophysics, Harvard and Smithsonian University

OG GD425 1bcba0 300PX 20220111183231

How was the local bubble formed?

Powerful supernovae begin to explode, creating a cavity of very thin hot gas in space called the local bubble.

The path of the sun takes her forever-

Bubble expansion. As the bubble expands, dense regions of cold gas that could generate stars gather on its surface.

undefined

How was the local bubble formed?

Powerful supernovae begin to explode, creating a cavity of very thin hot gas in space called the local bubble.

The path of the sun takes her forever-

Bubble expansion. As the bubble expands, dense regions of cold gas that could generate stars gather on its surface.

Today, many young stars are sitting on the surface of the bubble, but they have not formed inside it.

Approximately. 1000 light years

Source: Space Telescope Science Institute with

The Astrophysical Center, Harvard

and Smithsonian

Gaia, launched in 2013, has helped astronomers map the location and movement of stars in these regions with unprecedented accuracy over the past two years. By combining this data with models of supernova behavior, Dr. Zucker’s team can trace where these stars were located millions of years in the past, and calculate how many supernovae were required for the local bubble to grow to its current size – with these star-forming regions embedded in its surface.

They created an animation that reconstructs the rate at which a bubble expands, and when those explosions began.

“We found that there is a huge group of stars located in the middle of where we think the bubble began to form 14 million years ago,” said Dr. Zucker.

“This study is a perfect illustration of what the European Space Agency’s Gaia space observatory allows,” said Rosen Lalmint, a researcher who studies the solar environment at the Paris Observatory who was not involved in the study. for the Milky Way.

The study found seven known star-forming regions, or molecular clouds, located on the local bubble’s crust — including Corona Australis, which lies within the constellation of the same name. Dr. Zucker said the young stars here are “going their way” and pushing away from the bubble’s center as the cavity expands.

Share your thoughts

Does this discovery help you understand our galaxy better or raise more questions about it? Join the conversation below.

She added that most stars, including the Sun, are at least a billion years old, but the stars in these clouds are less than about 10 million years old. The study suggests that these clouds, and the supernovae they helped create, occurred in at least four batches, each approximately 4 million years apart starting at 14 million years ago.

“It would have been a series of interconnected supernova explosions, it wouldn’t be like, ‘Boom, boom, boom’ steadily,” said study co-author Alyssa Goodman, professor of astronomy at Harvard University.

This is because stars form in clusters, and those of similar mass in these clusters all live roughly the same amount of time before the explosion.

Dr. Zucker said the local bubble was still growing, even though its expansion speed had fallen to 14,400 miles per hour — at its peak, the vacuum expanded 15 times faster than that.

“Most of the gravity injected into this expansion happened thousands of years ago,” when the most massive star in our galaxy morphed into a supernova, she said, adding that the bubble would eventually run out of steam.

It’s just by chance that the Sun and our solar system are currently sitting at the heart of this void — over the past five million years, our star’s path through the galaxy has led it to what the study authors believe is the center of the bubble.

The sun won’t stay there forever, Dr. Zucker said, adding, “In about 8 million years we should be out of the bubble.”

“But in the future, we may be in another bubble,” she said.

The entire structure of the interstellar medium may be bubbling, and stars may form at the junction of these bubbles as things are smashed together.


– Alyssa Goodman, professor of astronomy at Harvard University

In a study conducted in September 2021, a team led by Dr. Zucker and Dr. Goodman identified a similar cavity in the Milky Way. They assume that such bubbles are scattered throughout our galaxy, as well as other galaxies in the universe.

“We actually think that when supernovae explode in the interstellar medium, they all create bubbles,” said Dr. Goodman. “The entire structure of the interstellar medium may be bubbling, and stars may form at the intersection of these bubbles as things are smashed together.”

write to Aylin Woodward at Aylin.Woodward@wsj.com

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