From Planets to Black Holes: Tracing the History of the Universe

By Gail Zasowski and Joel Brownstein

Department of Physics and Astronomy, University of Utah

Humans have carefully observed and tracked objects in the night sky since before recorded history. In the absence of light pollution, there are about 10,000 stars visible to the naked human eye, only about 5,000 at one time, of course, the Earth being famously opaque to optical light. When the telescope was developed in the early 1600s, we learned that there were far more things in the sky than our simple eyes can see; as instruments were developed that could detect light in other parts of the electromagnetic spectrum, we realized that there were objects and energy patterns in the sky that we could never see with our eyes, no matter how sensitive. And the Universe is not static, binary stars whip around each other, black holes flare brightly as they gobble up gas, and galaxies merge in billion-year-long collisions. How do we observe and analyze all these patterns to understand the nature of the Universe?

Enter astronomical surveys, and in particular, the newly-launched fifth generation of the Sloan Digital Sky Survey (SDSS). The first four generations of SDSS were each, in their own way, ground-breaking in terms of scientific goals and methods, and the new SDSS-V continues that tradition. As the data storage and processing hub of the survey, the University of Utah plays a very important role in the discoveries that will arise from SDSS-V’s massive data trove throughout the 2020s. SDSS-V is a spectroscopic survey, which means it collects high-resolution spectra of objects rather than taking images (see figure). With spectra, astronomers can infer (among other properties) the line-of-sight velocity, temperature, and composition of a star; the redshift, average age and stellar motions of a chunk of galaxy; the density and composition of intergalactic gas clouds; and the density and temperature of expanding supernova remnants. In many cases, the changes in these properties over time is even more exciting -- e.g., the change in density and temperature of a supernova remnant (which happens over scales of hours and days) tells us how the explosion material and energy is being deposited back into the interstellar gas and dust. Another key part of SDSS-V looks closer to home, collect- ing data for more than 5 million stars in our own Milky Way Galaxy and in a handful of our smaller galactic neighbors. These spectra are analyzed to get the stars’ temperatures, compositions, surface gravities, and line-of-sight velocities, which can be used to infer distances, ages, and orbit within the galaxy. By mapping these properties across the Milky Way, for example, ages and chemical compositions, we will learn an enormous amount about when, where, and how the Milky Way formed its stars. 

For more information, see our Fall 2020 newsletter, here.

System Status

Cluster Utilization