The 1,000-light-year-wide cosmic bubble around Earth

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The last such supernova took place about 2 million years ago, according to Zucker’s research — a finding that matches nicely with the previously reported deposition of cosmic iron in the Earth’s crust.

Zucker presented her team’s work virtually this week at a drastically scaled-back gathering of the American Astronomical Society, which was to have met in-person in Salt Lake City. The ongoing COVID-19 pandemic upended those plans.

Zucker told Astronomy that while there are “tens of millions of ‘old’ stars [those that are more than 14 million years old] inside the Local Bubble,” there are “on the order of thousands of ‘young’ stars … on its surface that have been birthed by the supernovae.” 

It just happens that the Sun and our solar system currently sit inside this bubble. According to the team, the Sun rolled into the Local Bubble about 5 million years ago — but it likely sat in other bubbles at other times.

“This work is most useful for providing the ‘big picture’ context for star and planet formation,” Zucker says. “One takeaway that might have been missed is that this study is really the tip of the iceberg. The Local Bubble is just the first bubble whose history we have mapped out — it’s the easiest one to understand first, since it’s the bubble in which our Sun currently resides. However, we have clues that not just single superbubbles, but the interactions of many superbubbles, are driving the formation of young stars near our Sun.”

Zucker compares the process to plowing snow. If one or more superbubbles is “piling up gas in the same region of space … we should get even more enhanced star formation at those intersecting surfaces.” And, in fact, one such bubble, called Perseus-Taurus, is interacting with our Local Bubble “at the site of the Taurus molecular cloud” — home to known protoplanetary disks.

The European Space Agency’s Gaia star-mapping mission was crucial in providing the precise data needed to discover the star-formation nuances of the Local Bubble — what Zucker has been calling an “origin story.”

Luckily, you don’t need access to high-end data to connect to this work. “The two clusters of stars that hosted the supernovae are still around and they are about 15 to 16 million years old,” says Zucker. “They currently lie near the edge of the Local Bubble’s shell.” (At the time, the supernovae were getting underway, these clusters were in the thick of the action.) 

You can point your telescope toward those local star-forming regions. One is in Taurus, the other is in Ophiuchus, home of the Ophiuchus Nebula. Looking into those areas gives you a chance to bear witness to the history and continuance of star birth in our Local Bubble. 

Interested readers can also find cool data visualizations and more information at the team’s dedicated website.

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