Earth is inside a star-forming bubble, says new study

This bubble has a radius of 500 light years.

It is the result of at least 15 supernovae that have exploded since 14 million years ago.

Astronomers from the Harvard-Smithsonian Center for Astrophysics (CfA) and the Space Telescope Science Institute (STScI) have pieced together the evolutionary history of our galactic neighborhood.

Show how a chain of events that began 14 million years led to the creation of a vast bubble that is responsible for the formation of all the stars nearby young, as published in the journal ‘ Nature ‘.

“For the first time we can explain how nearby stars began to form ,” says astronomer and data visualization expert Catherine Zucker, who did the work as a fellow at the CfA.

The article’s central figure, a 3D space-time animation, reveals that all young stars and star-forming regions – within 500 light-years of Earth – lie on the surface of a giant bubble known as the Local Bubble . Although astronomers have known of its existence for decades, scientists can now see and understand its beginnings and its impact on the surrounding gas.

Supernovae that exploded 14 million years ago

Thanks to a set of new data and data science techniques, the space-time animation shows how a series of supernovae that first exploded 14 million years ago pushed interstellar gas outward, creating a structure in the shape of bubble with a surface ripe for star formation.

Currently, seven known star-forming regions or molecular clouds – dense regions in space where stars can form – sit on the bubble’s surface .

“We’ve calculated that about 15 supernovae have erupted over millions of years to form the Local Bubble we see today,” says Zucker, now a NASA Hubble Fellow at STScI .

The oddly shaped bubble is not dormant and continues to grow slowly, the astronomers note. “It’s moving at about 6 kilometers per second,” explains Zucker. “However, it has lost most of its oomph and has leveled off in terms of speed.”

The bubble’s rate of expansion , as well as the past and present trajectories of young stars forming on its surface, were deduced using data obtained by Gaia, a space observatory launched by the European Space Agency.

“This is an incredible detective story, driven by both data and theory,” says Harvard professor and astronomer at the Alyssa Goodman Center for Astrophysics, co-author of the study and founder of glue, the data visualization software that allowed the discovery.

“We can reconstruct the history of star formation around us using a wide variety of independent clues: models of supernovae, stellar motions, and exquisite new 3D maps of the material surrounding the Local Bubble ,” he continues.

“When the first supernovae that created the Local Bubble erupted , our Sun was a long way from the action,” adds co-author João Alves, a professor at the University of Vienna (Austria). “But about five million years ago, the Sun’s path through the galaxy took it right inside the bubble, and now the Sun is – luckily – almost right in the center of the bubble.”

Today, when humans observe space from close to the Sun, they have a front row seat to the star formation process that occurs around the surface of the bubble.

Astronomers first proposed that superbubbles were ubiquitous in the Milky Way almost 50 years ago . “Now we have proof, and what are the chances that we’re right in the middle of one of these things?” Goodman wonders. Statistically, it is very unlikely that the Sun is centered on a giant bubble if such bubbles are rare in our Milky Way, he explains.

Goodman compares the discovery to a Milky Way galaxy that resembles Swiss cheese with lots of holes, where the holes in the cheese are blown out by supernovae, and new stars in the cheese can form around the holes created by dying stars .

Next, the team, which includes co-author and Harvard doctoral student Michael Foley, plans to map more interstellar bubbles to get a full 3D view of their locations, shapes, and sizes. Mapping the bubbles and their relationship to one another will allow astronomers to understand the role that dying stars play in the birth of new ones and in the structure and evolution of galaxies like the Milky Way.