The sun and thousands of its twins migrated across the Milky Way just in time
The sun and thousands of its twins migrated across the Milky Way just in time
The sun surrounded an enormous galactic migration wave to the Milky Way’s suburbs
The sun, and thousands of stars prefer it, migrated 10,000 light-years across the galaxy collectively to achieve their present positions.
Our sun was born 4.6 billion years in the past close to the crowded center of the Milky Way and then migrated roughly 10,000 light-years outward to the peaceable galactic suburbs it at present occupied. Now a pair of research printed at present in Astronomy and Astrophysics argue that the sun did not make this journey alone.
The telltale signal of the sun’s galactic journey is its chemical composition, says Tokyo Metropolitan University astronomer Daisuke Taniguchi, a co-author on each of the research. “Astronomers know that the sun’s birthplace lies closer to the galactic core than its current position,” Taniguchi explains. The Milky Way’s dense inner regions formed stars faster and accumulated heavy metals far quicker than the outer edges—and a star with the sun’s age and chemical components would not have been able to form at its present location. But to get there required crossing a dramatic border.
Observations of the Milky Way have revealed an enormous rotating barlike structure made of gas, dust and millions of stars slicing through our galactic center. This bar creates a distinct gravitational phenomenon known as the corotation barrier that prevents inner galaxy stars from migrating to the outskirts. Computer simulations suggest that only about 1 percent of stars born at the sun’s presumed original location could successfully breach this barrier to reach our current neighborhood within a 4.6-billion-year time frame. And yet Taniguchi and his colleagues discovered that thousands of “solar twin” stars with a mass and a metallic make-up just like these of the sun managed to take action.
On supporting science journalism
If you are having fun with this text, think about supporting our award-winning journalism by subscribing. By purchasing a subscription you are helping to ensure the future of impactful stories about the discoveries and ideas shaping our world today.
To catalog these stellar migrants, the researchers turned to the European Space Agency’s Gaia satellitean observatory tracking the positions, movements and wavelengths of light from more than two billion stars. The researchers dug up 6,594 solar twins within roughly 1,000 light-years of Earth.
When the scientists looked at the age distribution within their catalog, they saw two distinct peaks: one narrow spike of stars around two billion years old that likely formed locally and another broad, massive grouping of stars between six billion and four billion years old that included our sun—“a large population of stars that migrated from their birthplace to their current positions,” Taniguchi proposes.
Alice C. Quillen, a physicist and astronomer at the University of Rochester, who was not involved in Taniguchi’s study, warns that there’s a chance that the broad peak of solar twins might be an artifact generated by the way Taniguchi’s team collected this sample—a mere statistical illusion. “The sample is distance-limited, and most of it would be stars that make it into the solar neighborhood,” Quillen says. This factor could favor stars with more oblong orbits, which tend to be older, because younger stars with circular orbits wouldn’t have made it to our vicinity yet.
But Taniguchi says his team addressed this bias, finding no strong effect of age on the distribution of orbital shape in solar twins.
His team proposes that the corotation barrier did not stop a migration of the sun and its cohort because the barrier was not fully formed when it happened. In fact, Taniguchi suggests, the growing galactic bar could have pushed the migration forward instead of restricting it. The sun and thousands of its twins could have been propelled by the combined gravitational forces of the forming bar, the Milky Way’s spiral arm structure and most likely close passages of the neighboring Sagittarius dwarf galaxy.
Rosemary Wyse, an astrophysicist at Johns Hopkins University, who was not involved in the study, says that the researchers’ argument is persuasive but adds that (as the study authors note) the exact timescales remain uncertain. “The field of galaxy dynamics is itself dynamic,” she says.
It’s Time to Stand Up for Science
If you enjoyed this article, I’d like to ask for your support. Scientific American you have served as an advocate for science and industry for 180 years, and right now may be the most critical moment in that two-century history.
I’ve been to Scientific American subscriber since I was 12 years old, and it helped shape the way I look at the world. SciAm always educates and delights me, and inspires a sense of awe for our vast, beautiful universe. I hope it does that for you, too.
If you subscribe to Scientific Americanyou help ensure that our coverage is focused on meaningful research and discovery; that we have the resources to report on the decisions that threaten labs across the US; and that we support both budding and working scientists at a time when the value of science itself too often goes unrecognized.
In return, you get important information, captivating podcastsgood infographics, can’t-miss newslettersmust-watch movies, challenging gamesand the science world’s greatest writing and reporting. You may even gift someone a subscription.
There has by no means been a extra vital time for us to face up and present why science issues. I hope you will assist us in that mission.
