Massive 3-D universal map explores mysteries of space
A group of researchers led by Shirley Ho, a Carnegie Mellon assistant professor of physics, has made significant strides in analyzing a trillion-pixel, three-dimensional map of the universe. Ho and her team hope their results lead to a better understanding of the origins of the universe.
Ho is an active participant in the Sloan Digital Sky Survey (SDSS), a gigantic, multi-university effort for astrophysicists to map out areas of the universe. Based at Apache Point Observatory in New Mexico, the survey uses a 2.5-meter telescope, equipped with a large-format digital camera, to capture celestial bodies over 6 billion light years away.
According to SDSS’s website, the project’s most recent iteration — SDSS-III — is working to map out the Milky Way galaxy, search for extrasolar planets, and explore the mysteries of dark energy.
Just last year, the largest three-dimensional color map of the universe was unveiled as part of the Baryon Oscillation Spectrographic Survey, a branch of SDSS-III. It was this unique, trillion-pixel image that Ho and her team assessed. From the 1.5 million galaxies captured within the image, Ho and her team chose over 900,000 to analyze.
“We used multiple computing clusters,” Ho said. “One of them was in the National Energy Research Scientific Computing Center. It’s basically a national facility that’s for all kinds of research. We also used supercomputing facilities in Yale University.”
Ho said that the research is still very much a work in progress. “We haven’t started using the computing resources here [at Carnegie Mellon] yet, but we intend to,” Ho explained.
What numbers are these massive computing clusters crunching? Ho pointed to the Optimal Quadratic Estimator, a theorem-turned-algorithm that she and her team used on the map to estimate distances of celestial bodies from one another. The collection of distances was then transformed into a power spectrum — a set of data that essentially gave astrophysicists information about the distribution of matter throughout the universe.
Because of their work with such a massive data set, Ho and her colleagues are credited with forming the most accurate power spectrum calculation of the universe to date.
“The power spectrum tells you how fast the universe is expanding, and how much dark matter and neutrinos exist in the universe,” Ho said. “The power spectrum contains a wealth of information that could help explain what happened at the beginning of the universe and during the expansion of the universe.”
Power spectrums may also help unravel the secrets of dark energy, a hypothetical form of energy that opposes gravity by continuously pushing matter apart. While dark energy accounts for about 73 percent of the total mass-energy of the universe, scientists know very little about it. However, Ho is expecting this situation to change in the future as research continues.
Analyses of these large celestial maps also make it easier to observe important trends, including ones that may explain the origins of the universe. With these maps, astrophysicists are able to observe the distributions of galaxies and make inferences about the distributions of bodies in the early universe based on those structures. According to Ho, a scientific paper detailing these findings is in the works.
“We’re linking 13.6 billion years of history,” Ho said. “We’re going all the way back to the beginning.”
Ho is currently being assisted in this research by graduate students, though she had a few words to offer interested undergraduates.
“For projects like these, we’re looking actively for students to help,” Ho said. “A significant part of the collaboration consists of young people.... You don’t need to have multiple degrees to do this.”