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New idea may crack enigma of the Crab Nebula’s ‘zebra’ pattern
LAWRENCE — A theoretical astrophysicist from the University of Kansas may have solved a nearly two-decade-old mystery over the origins of an unusual “zebra” pattern seen in high-frequency radio pulses from the Crab Nebula. Mikhail Medvedev’s findings have just been published in Physical Review Letters (PRL), among the most prestigious physics journals.
Watson Library Centennial time capsule to be displayed, archived
LAWRENCE — In closing KU Libraries’ fall lineup of programs and events marking the centennial of Watson Library, a time capsule’s contents will be displayed at a reception 3-4 p.m. Nov. 20 in Spencer Research Library’s North Gallery. The event serves as a celebratory transfer of the materials to University Archives.
New book aims to guide qualitative researchers looking to better understand the college student experience
LAWRENCE — A new book from a University of Kansas scholar aims to guide researchers conducting qualitative research to better study the college student experience, especially that of historically marginalized populations. “Conducting Qualitative Research on and with College Students: Practical Considerations and Examples” provides guidance and examples for conducting sound research that can advance both understanding and student success.
Full stories below.
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Contact: Brendan Lynch, KU News Service, 785-864-8855, [email protected], @BrendanMLynch
New idea may crack enigma of the Crab Nebula’s ‘zebra’ pattern
LAWRENCE — A theoretical astrophysicist from the University of Kansas may have solved a nearly two-decade-old mystery over the origins of an unusual “zebra” pattern seen in high-frequency radio pulses from the Crab Nebula.
His findings have just been published in Physical Review Letters (PRL), among the most prestigious physics journals.
The Crab Nebula features a neutron star at its center that has formed into a 12-mile-wide pulsar pinwheeling electromagnetic radiation across the cosmos.
“The emission, which resembles a lighthouse beam, repeatedly sweeps past Earth as the star rotates,” said lead author Mikhail Medvedev, professor of physics & astronomy at KU. “We observe this as a pulsed emission, usually with one or two pulses per rotation. The specific pulsar I’m discussing is known as the Crab Pulsar, located in the center of the Crab Nebula 6,000 light years away from us.”
The Crab Nebula is the remnant of a supernova that appeared in 1054.
“Historical records, including Chinese accounts, describe an unusually bright star appearing in the sky,” said the KU researcher.
But unlike any other known pulsar, Medvedev said the Crab Pulsar features a zebra pattern — unusual band spacing in the electromagnetic spectrum proportional to band frequencies, and other weird features like high polarization and stability.
“It’s very bright, across practically all wave bands,” he said. “This is the only object we know of that produces the zebra pattern, and it only appears in a single emission component from the Crab Pulsar. The main pulse is a broadband pulse, typical of most pulsars, with other broadband components common to neutron stars. However, the high-frequency interpulse is unique, ranging between 5 and 30 gigahertz — frequencies similar to those in a microwave oven.”
Since this pattern was discovered in a 2007 paper, the KU researcher said the pattern had proved “baffling” for investigators.
“Researchers proposed various emission mechanisms, but none have convincingly explained the observed patterns,” he said.
Using data from the Crab Pulsar, Medvedev established a method using wave optics to gauge the density of the pulsar’s plasma – the “gas” of charged particles (electrons and positrons) — using a fringe pattern found in the electromagnetic pulses.
“If you have a screen and an electromagnetic wave passes by, the wave doesn’t propagate straight through,” Medvedev said. “In geometrical optics, shadows cast by obstacles would extend indefinitely — if you’re in the shadow, there’s no light; outside of it, you see light. But wave optics introduces a different behavior — waves bend around obstacles and interfere with each other, creating a sequence of bright and dim fringes due to constructive and destructive interference.”
This well-known fringe pattern phenomenon is caused by consistent constructive interference but has different characteristics when radio waves propagate around a neutron star.
“A typical diffraction pattern would produce evenly spaced fringes if we just had a neutron star as a shield,” the KU researcher said. “But here, the neutron star’s magnetic field generates charged particles constituting a dense plasma, which varies with distance from the star. As a radio wave propagates through the plasma, it passes through dilute areas but is reflected by dense plasma. This reflection varies by frequency: Low frequencies reflect at large radii, casting a bigger shadow, while high frequencies create smaller shadows, resulting in different fringe spacing.”
In this way, Medvedev determined the Crab Pulsar’s plasma matter causes diffraction in the electromagnetic pulses responsible for the neutron star’s singular zebra pattern.
“This model is the first one capable of measuring those parameters,” Medvedev said. “By analyzing the fringes, we can deduce the density and distribution of plasma in the magnetosphere. It’s incredible because these observations allow us to convert fringe measurements into a density distribution of the plasma, essentially creating an image or performing tomography of the neutron star’s magnetosphere.”
Next, Medvedev said his theory can be tested with collection of more data from the Crab Pulsar and fine-tuned by factoring in its powerful and strange gravitational and polarization effects. The new understanding of how a plasma matter alters a pulsar’s signal will change how astrophysicists understand other pulsars.
“The Crab Pulsar is somewhat unique — it’s relatively young by astronomical standards, only about a thousand years old, and highly energetic,” he said. “But it’s not alone; we know of hundreds of pulsars, with over a dozen that are also young. Known binary pulsars, which were used to test Einstein’s general relativity theory, can also be explored with the proposed method. This research can indeed broaden our understanding and observation techniques for pulsars, particularly young, energetic ones.”
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Contact: Kevin McCarty, KU Libraries, 785-864-6428, [email protected], @KULibraries
Watson Library Centennial time capsule to be displayed, archived
LAWRENCE — KU Libraries’ archivists and conservators specialize in making historical materials accessible to the researchers of today — but with the creation of a Watson Library Centennial time capsule, they hope to speak directly to KU students and scholars of the future.
In closing the libraries’ fall lineup of programs and events marking the centennial of Watson Library, the time capsule’s contents will be displayed at a reception 3-4 p.m. Nov. 20 in Spencer Research Library’s North Gallery. The event serves as a celebratory transfer of the materials to University Archives. Later, those items will be housed in a specially selected archival box that will be tucked within the shelves of the library.
“Spencer is almost a time capsule you can open every day,” said Beth Whittaker, director of the Spencer library. “Our collections are full of primary sources that offer direct perspectives through documents or artifacts from the people who experienced places, times or events firsthand. Holding the time capsule at Spencer feels like a perfect fit.”
Spencer Research Library houses a wide range of unique and historical materials including medieval manuscripts, rare maps, personal letters and diaries, scrapbooks from the beginnings of the university and ephemera from everyday life. KU Libraries work to ensure every item on Spencer’s shelves is accessible as part of special collections and university archives, but unlike those thousands of items, the Centennial time capsule won’t be accessed or opened for 100 years.
KU Libraries conservators Whitney Baker and Angela Andres will house and arrange the materials with an eye on offering Jayhawks in 100 years a glimpse into the life and culture of today.
“A successful time capsule project includes an archival storage container, a safe storage area and carefully chosen contents,” said Baker, head of conservation services. “We hope to ensure that the items included in the time capsule will be in fine condition in 100 years.”
The materials included in the time capsule have been gathered throughout the fall semester as celebrations of the Watson centennial occurred in various modes. Contributions from students, university departments and library supporters were compiled by the libraries’ Board of Advocates and Office of Communications and Advancement.
“As we planned to celebrate Watson’s 100-year anniversary, our team found it fascinating to dive into the University Archives and piece together the stories of KU’s campus and library back in 1924,” said Christy McWard, executive director of KU Libraries Office of Communications & Advancement. “By creating a time capsule of sorts, we hope that in another 100 years, the university’s future students, librarians and leaders will be able to look into this relatively small box and discover a slice of campus life in 2024.”
Reception attendees can view the materials and hear from KU libraries conservators and archivists about the process of preservation. For more about Watson Library’s 100-year history, visit the centennial webpage.
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Don’t miss new episodes of “When Experts Attack!,”
a KU News Service podcast hosted by Kansas Public Radio.
https://kansaspublicradio.org/podcast/when-experts-attack
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Contact: Mike Krings, KU News Service, 785-864-8860, [email protected], @MikeKrings
New book aims to guide qualitative researchers looking to better understand the college student experience
LAWRENCE — College students are among the most popular subjects and topics of research across academia, whether subjects in an undergraduate psychology experiment or the topic of an in-depth study by researchers looking to understand the college experience. A new book from a University of Kansas scholar aims to guide researchers conducting qualitative research to better study the college student experience, especially that of historically marginalized populations.
“Conducting Qualitative Research on and with College Students: Practical Considerations and Examples” by Antonio Duran of Arizona State University and Zak Foste, associate professor of educational leadership & policy studies at KU, provides guidance and examples for conducting sound research that can advance both understanding and student success.
Duran and Foste both specialize in qualitative research of the college student experience. Published by Routledge, the book covers considerations researchers should make when studying the growth, experience, development and challenges today’s diverse student population faces.
“Qualitative research is well suited for a host of questions related to the study of college students, including how they experience various transitions in their educational journeys, how they arrive at particular decisions or choices related to major or institution type, or how they come to understand and make sense of who they are and what they value in the world,” Foste said. “One of the benefits of qualitative research is that it can help illuminate the how and why behind many of our most desirable outcomes in postsecondary education. These approaches can illustrate how students experience and make meaning of important educational contexts and conditions.”
The authors were both students of Susan Jones, an influential researcher at Ohio State University and co-author of “Negotiating the Complexities of Qualitative Research in Higher Education: Fundamental Elements and Issues.” Jones wrote the foreword for Duran and Foste’s book, framing their new volume as a passing of the torch in qualitative college student research.
The new book provides technical guidelines on developing qualitative questions, issues related to sampling and participant recruitment, and how to write and present findings for audiences such as academic journals and practitioners who work with students. The book also guides researchers through considerations such as why qualitative research can be the proper approach, considering oneself and the relationship with college students involved in research and why qualitative research is more than just talking with people.
“We hope the reason people take up qualitative research is not just to theorize or engage in purely academic exercises, but to write in such a way that speaks to practitioners, faculty, administrators and policy makers directly responsible for student success. As we emphasize throughout the book, we believe this is especially important for students from those communities historically excluded from full participation in higher education,” Foste said.
“Conducting Qualitative Research” also provides examples of research that has successfully and effectively examined such topics and how new studies can draw inspiration and guidance from them. Ethical considerations researchers should make before and during research are also discussed throughout.
The book is written with novice researchers and graduate students looking to make a career in the field in mind but can also be a valuable resource for veteran scholars looking for new ideas.
“‘Conducting Qualitative Research on and with College Students’ should be required reading in every higher education program. The authors distill methodological texts, synthesize contemporary higher education research and offer practical examples of how to do qualitative research on college students. And they do this in an accessible, engaging manner. It’s a book I wish I had as a student but am happy to have as an instructor. Duran and Foste have offered a gift to the field of higher education,” said Antar Tichavakunda of the University of California, Santa Barbara.
There is a common refrain that scholars come to qualitative research because they are not good with numbers, a necessary component of quantitative research, or because they enjoy talking with people. While not discounting that, the authors hope to help show there is much more to experience in the line of inquiry.
“One of the hopes of our book is to say, ‘A meaningful study of college students is more than just talking to people,’” Foste said. “There are questions of meaning, experience and interpretation. We really want those new to the qualitative study of college students to think critically about what they are embracing and what such approaches can offer us in the way of improving our collective understanding of college students today.”
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