Credit NAOJ
Researchers have uncovered evidence for our sun joining a mass migration of similar “twins” leaving the core regions of our galaxy, 4 to 6 billion years ago. The team created and studied an unprecedentedly accurate catalog of stars and their properties using data from the European Space Agency’s Gaia satellite. Their discovery sheds light on the evolution of our galaxy, particularly the development of the rotating bar-like structure at its center.
While archaeology on Earth studies the human past, galactic archaeology traces the vast journey of stars and galaxies. For example, scientists know that our sun was born around 4.6 billion years ago, more than 10,000 light years closer to the center of the Milky Way than we are today.
While studies of the composition of stars support this theory, this has long proven a conundrum for scientists. Observations reveal an enormous bar-like structure at our galactic center which creates a “corotation barrier,” which makes it difficult for stars to escape so far from the center.
So how did we get here? To answer this question, a team led by Assistant Professors Daisuke Taniguchi from Tokyo Metropolitan University and Takuji Tsujimoto from the National Astronomical Observatory of Japan have undertaken an unprecedentedly large study of solar “twins,” stars which have very similar temperature, surface gravity, and composition to our sun. The team has published their findings in two papers in Astronomy and Astrophysics.
They used data taken by the European Space Agency’s Gaia satellite mission, a daunting trove of observations from two billion stars and other objects. They created a catalog of 6,594 stellar “twins,” a collection around 30 times larger than previous surveys.
From this immense list, they were able to obtain the most accurate picture to date of the ages of these stars, carefully correcting for selection bias of stars which are easier to see.
Looking at the distribution of ages, they noticed a broad peak for stars around 4 to 6 billion years old: this includes our sun, and is evidence for similar stars of similar age, positioned around the same distance from the center of the galaxy.
This means that our sun is not at its current position by accident, but as part of a much larger stellar migration.
This discovery sheds light not only on the nature of our solar system, but the evolution of the galaxy itself. The corotation barrier created by the bar structure at the galactic center would not allow for such a mass event. However, the story changes if it was still being formed at the time. The ages of our stellar “twins” reveal not only when the mass escape occurred, but the time range over which the bar was formed.
The center of the galaxy is a far less hospitable environment for the evolution of life than outer regions. The team’s findings thus illuminate a key factor in how our solar system, and in turn our planet, found itself in a region of the galaxy where organisms could develop and evolve. https://www.eurekalert.org/news-releases/1119007
Recent Comments