Astronomers Reach Beyond the Milky Way

Historically, observations of stars and galaxies have been limited by distance. But former graduate student Nhung Ho and current graduate student Luis Vargas in the laboratory of Professor Marla Geha are breaking barriers — developing detection techniques that will allow astronomers to observe systems outside the Milky Way.

Using the largest telescope in the world, the Keck Observatory, Ho and Vargas’ team was able to obtain readings from satellite dwarf galaxies of the Andromeda system, 780 kiloparsecs, or two million light years, away from earth. The ultimate goal is to understand galaxy evolution on a universal scale.

The technique Ho developed for these observations utilized spectral data and metallicity readings to determine the composition of the main stars in these various galaxies. By comparing the heavy metal and iron content in the stars of the system, the team was able to determine the timescales of evolution for parts of the galaxies’ lives. This work provides insight into the process of galaxy and star formation, as well as answers to how the Milky Way and our solar system came to be.

Galaxies in the Local Galactic Group include the Milky Way, Andromeda, and Triangular, as well as several dwarf galaxies. This study focused on dwarf galaxies near the Andromeda Galaxy. Image courtesy of Nhung Ho.

Ho and Vargas plan to continue research with these distant objects and to investigate individual chemical elements to yield better data. The biggest challenge the team faced when making their initial observations was collecting high-quality data, Ho said. Because of the large distances involved, the faint signals from these systems make spectroscopy quite difficult. “I am very fortunate to have access to the largest observatory in the world through Yale, as obtaining data with low natural variances would be much more difficult elsewhere,” Ho said.

Cover Image: The Keck Observatory in Mauna Kea, Hawaii is the largest observatory in the world. Yale’s partnership with Mauna Kea allowed the team to make observations with low variances. Image courtesy of Nhung Ho.