An international team of astronomers has revealed the chemical composition of 350,000 stars in the Milky Way as part of an unprecedented sky-scanning project which could reveal the Sun's lost siblings.
This is the first major data release from the Galactic Archaeology survey, known as GALAH, which was launched in 2013 in a bid to provide new insights into the formation and evolution of the Milky Way.
In total, GALAH will investigate more than one million stars using the HERMES spectrograph—an instrument at the Australian Astronomical Observatory's 3.9-meter Anglo-Australian Telescope in New South Wales. HERMES measures the different colors of light coming from stars in order to determine the proportions of chemical elements that they contain.
"This survey allows us to trace the ancestry of stars, showing astronomers how the Universe went from having only hydrogen and helium—just after the Big Bang—to being filled with all the elements we have here on Earth that are necessary for life," Martin Asplund, from the Australian National University's (ANU) Research School of Astronomy and Astrophysics, who led the analysis of the survey data, said in a statement.
When complete, the dataset could help astronomers to find our galaxy's original star clusters— including the one that gave birth to our Sun and its siblings before they were separated. Every star is born in a group, or cluster, of thousands of stars. And every star in the Sun's birth cluster will have the same chemical composition, meaning that astronomers will be able to trace these lost siblings by analyzing their stellar "DNA".
"Measuring each chemical element abundance to get the stellar DNA for so many stars is an enormous challenge, but that's exactly what we have done so this is a fantastic scientific achievement," Asplund said.
Analysis of the data from HERMES was carried out with the help of a set of machine-learning algorithms known as The Cannon, which has been trained to recognize patterns in the light information gathered from the stars.
"The Cannon is named for Annie Jump Cannon, a pioneering American astronomer who classified the spectra of around 350,000 stars by eye over several decades a century ago—our code analyses that many stars in far greater detail in less than a day," Ly Duong from ANU, who was part of the team that developed the code, said in a statement.
A set of 11 scientific papers describing various aspects of the GALAH data release have been submitted for publication in the journals Monthly Notices of the Royal Astronomical Society and the Astronomy & Astrophysics.
