Mit researchers, including undergraduate students, have discovered three of the oldest stars in the Milky Way’s halo, which they believe were once part of small, primitive galaxies that were later absorbed by the larger Milky Way. These stars, named SASS stars, are estimated to have formed between 12 and 13 billion years ago, around the time of the very first galaxies in the universe. The researchers hope to find more such ancient stars in order to better understand the evolution of ultrafaint dwarf galaxies, which are thought to be among the universe’s first galaxies but are too distant and faint for detailed study.
The discoveries were made possible through a new course, “Observational Stellar Archaeology,” where students were tasked with analyzing star data collected by MIT professor Anna Frebel over the years. The students, including undergraduates Hillary Andales, Ananda Santos, and Casey Fienberg, used spectral analysis to determine the chemical composition of the stars and found that they had low abundances of elements such as strontium, barium, and iron compared to our own sun. This led them to conclude that the stars are extremely old, dating back to the early universe.
The researchers also analyzed the orbital patterns of the stars and found that they were moving in a retrograde motion, indicating that they were once part of smaller dwarf galaxies that were absorbed by the Milky Way at random angles. This unique motion, combined with their low chemical abundances, suggests that the stars are indeed ancient survivors of older galaxies that now call the Milky Way home. By studying more SASS stars with similar properties, the researchers hope to gain insight into the evolution of primitive dwarf galaxies and the formation of the Milky Way.
This research has been published in the Monthly Notices of the Royal Astronomical Society, and the team plans to continue searching for more ancient stars using their new methodology of identifying stars with low chemical abundances and tracking their orbital patterns for signs of retrograde motion. With over 400 billion stars in the Milky Way, they expect to find a significant number of the universe’s oldest stars using this approach. The team is excited to continue their work and unravel more mysteries of the universe’s cosmic family tree.
The students involved in this research learned how to characterize stars and analyze spectra during the course, providing them with valuable research experience at the forefront of astrophysics. By applying these techniques to previously unstudied stars, they were able to uncover the origins and age of the three ancient stars in the Milky Way’s halo. The team’s discoveries highlight the importance of hands-on research opportunities for undergraduate students in advancing our understanding of the universe’s history and evolution.
This groundbreaking research, led by a diverse team of researchers, showcases the collaborative and innovative spirit of MIT and highlights the potential for further discoveries in the field of astronomy. The researchers are eager to continue their search for ancient SASS stars and delve deeper into the mysteries of the universe’s earliest galaxies. With the support of the National Science Foundation, they aim to expand their research and uncover more secrets hidden within our cosmic neighborhood.
