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Johns Hopkins UniversityArts and Sciences Magazine

Research Briefs

A New Hubble Constant

Whatever dark energy is, explanations for it have less wiggle room following a Hubble Space Telescope observation that has refined the measurement of the universe's present expansion rate to a precision where the error is smaller than 5 percent. The new value for the expansion rate, known as the Hubble constant, is 74.2 kilometers per second per megaparsec. The results match closely an earlier measurement gleaned from Hubble, but they are now more than twice as precise.

The Hubble measurement, conducted by a team led by physics and astronomy professor Adam Riess, uses a number of refinements to streamline and strengthen the construction of a cosmic "distance ladder," a billion light-years in length, that astronomers use to determine the universe's rate of expansion.

The new technique used Hubble observations of pulsating stars called Cepheid variables to bridge rungs in this ladder and eliminate the systematic errors that are almost unavoidably introduced when comparing measurements from different telescopes.

"It's like measuring a building with a long tape measure instead of moving a yardstick end over end," Riess says. "You avoid compounding the little errors you make every time you move the yardstick. The higher the building, the greater the error."

This new, more precise value of the Hubble constant was used to test and constrain the properties of dark energy—the form of energy that produces a repulsive force in space—that is causing the expansion rate of the universe to accelerate.

"If you put in a box all the ways that dark energy might differ from the cosmological constant, that box would be three times smaller," Riess says. "That's progress, but we still have a long way to go to pin down the nature of dark energy."

Sheridan Libraries Awarded $20 Million
NSF Grant for “Data Curation”

The university's Sheridan Libraries have been awarded $20 million from the National Science Foundation (NSF) to build a data research infrastructure for the management of the ever-increasing amounts of digital information created for teaching and research. The five-year award, announced in early October, was one of two for what is being called "data curation."

The project, known as the Data Conservancy, involves individuals from several institutions, with Johns Hopkins University serving as the lead and Sayeed Choudhury, Hodson Director of the Digital Research and Curation Center and associate dean of university libraries, as the principal investigator. Seven Johns Hopkins faculty members are associated with the Data Conservancy, including Physics and Astronomy's Alexander Szalay and Earth and Planetary Sciences' Bruce Marsh and Katalin Szlavecz.

Beginning with the life, earth, and social sciences, project members will develop a framework to more fully understand data practices currently in use and arrive at a model for curation that allows ease of access both within and across disciplines.

"Science and engineering research and education are increasingly digital and data-intensive, which means that new management structures and technologies will be critical to accommodate the diversity, size, and complexity of current and future data sets and streams," says Choudhury. "Our ultimate goal is to support new ways of inquiry and learning."

The Data Conservancy grant represents one of the first awards related to the Institute of Data Intensive Engineering and Science (IDIES), a collaboration among Arts and Sciences, Engineering, and the libraries.

HST ACS/WFC Image of NGC 3021 /NASA, ESA, and A. Riess (STScI/JHU)