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.
They show how a chain of events that began 14 million years ago led to the creation of a vast bubble that is nearby.
“For the first time we can explain how the formation of nearby stars began,” says astronomer and data visualization expert Catherine Zucker, who did the work during a fellowship 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, now scientists and its impact on the gas that surrounds it. The Earth and the Sun are within it.
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 –
“We have calculated that about 15 supernovae have exploded over millions of years to form the Local Bubble we see today.” says Zucker, who is 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 –explica sugar. However, he has lost most of his drive 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, says Harvard professor and astronomer at the Center for Astrophysics Alyssa Goodman, co-author of the study and founder of glue, the data visualization software that enabled the discovery.
“We can reconstruct the history of star formation around us using a wide variety of independent clues –continue-: models of supernovae, stellar motions, and exquisite new 3D maps of the material surrounding the Local Bubble.”
“When the first supernovae erupted to create the Local Bubble, our Sun was a long way from the action –adds co-author João Alves, professor at the University of Vienna (Austria)-. But about five million years ago, the Sun’s path through the galaxy brought it just inside the bubble, a”.
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 are right in the middle of one of these things?Goodman asks. 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 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 dying stars play in the birth of new ones and in the structure and evolution of galaxies like the Milky Way.