Physics researchers at Hope College are participating in a NASA-funded collaborative project that is linking multiple teams in an international effort that could result in a giant leap in mankind's understanding a type of star.
Dr. Peter Gonthier, who is a professor of physics, and his student researchers are part of a NASA-based project that has been seeking to better understand how pulsars, which are highly compact collapsed stars, produce high-energy gamma rays. The team's project, "Particle Acceleration and High Energy Radiation from Pulsar Magnetospheres," has recently received a three-year, $459,043 grant--$76,866 of which will support work at Hope - from the NASA Astrophysics Theory Program.
"This grant is highly significant because it is mainstream and it has to compete with the big guns to get funded by NASA," said Dr. Moses Lee, who is dean for the natural and applied sciences and a professor of chemistry at Hope. "I am extremely proud of Pete and his collaborators."
The latest round of support follows an earlier three-year award to the project from the NASA Astrophysics Theory Program. While the overall focus on pulsars remains the same, recent developments in both the research and its supporting technology make the new phase particularly exciting, according to Gonthier.
"It's an extremely exciting grant because it's bringing two teams together that are experts in pulsar-magnetosphere physics," Gonthier said. "And this proposal, if our research is successful, will really leap us forward in our understanding of how pulsars generate these beams of gamma rays."
One group has been working to understand the acceleration mechanism that generates the gamma rays. Another has recently developed a new understanding of the electrodynamics of the stars' magnetospheres - the magnetized regions that surround all astronomical objects. Through the newest support, they will be merging their specializations together to try to understand the process more fully.
Added into the mix is the new Fermi Gamma Ray Space Telescope, launched into orbit in June 2008 and already contributing significant data. Gonthier noted that the new satellite-based telescope is about 30 times more sensitive than its predecessor, which provided data for nine years beginning in 1991. The previous telescope, for example, discovered seven to eight gamma pulsars during its entire nine-year life; Fermi found about 20 new pulsars in its first four months.
Gonthier noted that pulsars are extremely dense neutron stars which have the mass of one and a half of the earth's sun packed within a ball 16 miles in diameter. They rotate rapidly, completing a revolution in a range between once every 10 seconds and a thousand times a second. Highly magnetized, they shoot out a beam of radiation that, given the spinning, makes the star seem to pulse as the beam passes into view.
Pulsars were discovered in the 1960s, when scientists observed radio waves coming from them. The range of electromagnetic radiation, however, is much broader, covering also microwaves, infrared, visible light, ultraviolet light, x-rays and, at the highest end, gamma rays.
The overall research effort is headed by Dr. Alice Harding, who is on the staff of the Astrophysics Space Division of the NASA Goddard Space Flight Center in Greenbelt, Md. In addition to Gonthier, who has been conducting research with Harding since 1992, co-investigators or collaborators on the project include researchers from RiceUniversity, the Universities Space Research Association, the Academy of Athens in Greece and the CEA Saclay research center in France.
Gonthier and his students have been running simulations examining the development and behavior of pulsars, and have also been studying physical processes near the surface of the stars. Each year, they work not only on campus but also for four weeks during the summer at the NASA Goddard Space Flight Center itself. He is excited to have the opportunity to work with the new Fermi telescope data, which will be used to evaluate the accuracy of the simulations and to help the Hope researchers shape the computer models to even more accurately reflect the way the stars behave.
"It's a very exciting moment because of this new observatory," he said. "And Hope is up there with it, in a sense. We're connected."
Gonthier and his students have presented their work in scholarly journals and at major national and international conferences. For example, then-student Sarah Story participated in about eight conferences with Gonthier, including as the only undergraduate presenter during the first GLAST (Gamma-ray Large Area Space Telescope) Symposium in February 2007, and was lead author - writing with Gonthier--of an article published in "Astrophysics Journal." Story, who graduated in 2007, is now a graduate student in physics at Rice and working with Dr. Matthew G. Baring, part of the collaborative team. Gonthier will be among the presenters this summer, in the section on neutron stars, during the 27th General Assembly of the International Astronomical Union, meeting in Rio De Janeiro, Brazil in August.