News from the Center of Earth’s Galaxy

| August 1, 2013

The Karl G. Jansky Very Large Array

Whitney-Guion Professor of Physics Scott Hyman’s search continues even as he concludes a sabbatical year spent scouring the center of the Milky Way Galaxy. He is looking for transient radio emissions from astronomical sources such as neutron stars, extra-solar planets, supernovae, and, maybe, previously undiscovered types of objects. It has happened before.

Hyman received a College grant to fund two monthlong visits to the Expanded Very Large Array operations center in Socorro, N.M., as part of his research. He and his collaborators from the Naval Research Laboratory and other institutions make their observations by studying data collected from radio telescopes around the world, including the National Radio Astronomy Observatory’s EVLA and the Giant Metrewave Radio Telescope in India. They focus on low-frequency, wide-field imaging techniques that are more likely to detect transient sources than radio waves collected at higher frequencies.

In 2004, Hyman and several Sweet Briar students were part of a team that detected a new bursting transient source, which led to an article published in Nature. He hopes to make more such discoveries with help from student researchers.

In addition to his ongoing work, Hyman and his colleagues from the NRL and NRAO are monitoring a rare cosmic event through observations from the EVLA and GMRT. The giant black hole, known as Sagittarius A* (pronounced A-star), at the center of Earth’s galaxy is gobbling up a gas cloud speeding toward it. From observatories around the globe, scientists are watching as it devours what amounts to a snack for Sgr A*, which has a mass about 4 million times greater than our sun.

Early models predicted peak noshing will occur in September, but calculations vary, says Hyman, who cautions the event may be a dud from a radio emissions standpoint. In fact, some models suggest emissions peaked in February or March. Watchers could have missed weaker-than-expected activity, especially because it is taking place at the limits of what scientists can detect. Still, it is one of the most closely observed astronomical events to date, using the most sensitive telescopes ever built.

Image information: The Karl G. Jansky Very Large Array, about 50 miles from its operations center in Socorro, N.M., consists of 27 230-ton dish antennas that together comprise a single radio telescope system. Recent electronics and software upgrades “completely transformed the VLA into the EVLA,” with 10 times mores ensitivity, according to the NRAO, which operates the site. Image courtesy of NRAO/AUI and NRAO.

Category: On the Quad Summer 2013, Summer 2013