posted October 11, 2010

NSF Grant Continues Support of Research into Pulsars Title

Featuring distances so vast and detailed calculations so precise and complex that they each in their way seem to approach the infinite, the astronomical research conducted by Dr. Peter Gonthier of the Hope College physics faculty provides a stellar learning opportunity for the students who work with him.

Gonthier, working in collaboration with Hope students, has been studying the rotating stars known as pulsars for nearly 20 years.  His research is currently supported by three federal grants - two from NASA, the second of which he received this summer; and a third, awarded this fall, through the "Research in Undergraduate Institutions" program of the National Science Foundation (NSF-RUI).

He is engaged by the opportunity to address fundamental questions about how the universe works, but - like his colleagues throughout the division of the natural and applied sciences at Hope--he is particularly driven by providing a chance for students to learn how science works by involving them in the process.  Students are regularly co-researchers with him, working on campus during the school year and summer as well as at NASA's Goddard Space Flight Center in Greenbelt, Md., for a number of weeks each summer; making presentations at professional conferences; and even earning co-author status on publications.

The research itself matters as scientific inquiry - hence the multiple competitive federal grants that Gonthier has received through the years - but it's the opportunity for undergraduate-level students to participate that he feels especially stands out at Hope.  It's a trait that he notes explains not only in his discipline of physics, but across the natural and applied sciences.

"Basically, anybody that wants to do research can do research at Hope, and that's what makes it unique," he said.

Gonthier's background is in experimental nuclear physics, but he became interested in pulsars during a 1991 sabbatical in Germany.  He has pursued a variety of research questions related to them in the years since, with his current projects - conducted with colleagues at NASA and other institutions - focusing on how they work and developing computer models to further aid in understanding them.

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.

Gonthier's newest funding from the NSF, a three-year, $124,103 grant that will provide support through August of 2013, has been awarded collaboratively to Hope as well as Goddard and Rice University.  The research leads at both other institutions - Dr. Alice Harding of Goddard and Dr. Matthew Baring of Rice University - are each scientists with whom he and his students have worked on other projects.  In fact, one of his former student researchers, 2007 graduate Sarah Story, now a graduate student working with Baring at Rice, will benefit from the portion of the new grant awarded to Rice University.

Gonthier is currently working with Hope juniors Caleb Billman of New Ringgold, Pa., and Caitlin Taylor of Kalamazoo, both of whom have been conducting research with him since last year.  Through the newest NSF award, they are continuing, in collaboration with Harding, to develop and refine computer models to reflect the behavior and even predict the presence of gamma-ray pulsars, drawing upon the new data made available since the 2008 launch of the Fermi Gamma-Ray Space Telescope.  With Baring's team at Rice, they are studying the characteristics of magnetars, a variety of pulsar that has an intensely high magnetic field - the highest in the universe, according to Gonthier.

The work involves scale that is simultaneously unimaginably enormous and microscopically small.  For example, one of the stars being studied in the Hope-Rice project is located about 200,000 light years away - some one million trillion miles.  Conversely, in conducting its investigations the team is considering the way that tiny particles called photons in the form of X rays emitted from the hot surface of the stars and extremely rapidly moving electrons interact, boosting the photons to even higher energies.  The interaction is called inverse Compton scattering to reflect the relationship as the particles essentially bounce off from one another.  In Compton scattering, photons, lose energy that they transfer to the electrons with which they connect; in inverse Compton scattering, the photons instead gain energy from the electrons.  The interactions in the case of the magnetars, Gonthier and his fellow researchers believe, are distinctive.

"What we want to do is develop some very clear analytics for the scientific community to use," Gonthier said.

"There's a resonance in the scattering process, and this resonance has not been properly taken into account," he said.  "Basically, we are trying to improve our understanding of the resonance scattering process by developing an accurate, exact description of the process."

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.

Gonthier said that the pulsars that produce radio waves remain the best known - some 1,880 have been recorded - because their emissions are detectable from earth by their radio waves.  The gamma radiation, in contrast, requires space-based instruments to discover because earth's atmosphere blocks it.  Some pulsars emit gamma radiation but no radio waves, which means that they've been harder to find.

He noted that the highly sensitive Fermi telescope has made a significant difference in the discovery and study of gamma-ray pulsars.  Where Fermi's predecessor had discovered seven to eight gamma-ray pulsars during its entire nine-year life, Fermi found about 60 in its first year.  At the same time, other instruments are able to detect pulsars of other radiation types.

"Fermi has opened up a new and very exciting field of astrophysics that is fertile ground for students to explore," Gonthier said.