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Students Find Pulsar

Three high school students won first place in America's national Siemens-Westinghouse Science and Technology Competition in 2000 for their discovery of a spinning neutron star, or pulsar. Their unique access to data from NASA's Chandra X-ray Observatory allowed them to prove the existence of a pulsar that professionals had not been able to positively identify, despite extensive studies.

Christopher Clearfield, Charles Olbert, and Nikolas Williams, who all attend the North Carolina School of Science and Mathematics, were contracted to do research on the IC443 supernova remnant by Dr. Jonathan Keohane, a physics professor at the school. This was an extension of Keohane's earlier work studying the same remnant, in which he could not prove the existence of a pulsar because it had never been observed to pulse.

Still curious about the remnant, Keohane applied to NASA for observing time from the Chandra telescope and hired the three students to help with the research. Analyzing ten thousand seconds' worth of data, the students found a point source of X-rays and from this were able to show that the IC443 remnant was housing a pulsar.

"The experience of doing new and relevant science has been one of the most rewarding experiences I have ever had," said Olbert.

The students presented their findings at the Siemens-Westinghouse scholarship competition in Washington, D.C., where they won first place.

The students, from diverse regions of North Carolina, lived together over the summer to complete their analysis. They often called the Chandra support personnel at the Smithsonian Astrophysical Observatory for consultations on data analysis and calibration.

"The kids did all the real work," said Keohane. "I just provided data and funding and answered some questions."

The students first presented their work at a scientific meeting at the University of Maryland, wrote a scientific paper for the Astrophysical Journal, and survived several stages of the Siemens-Westinghouse contest before winning the finals on December 11, 2000.

Pulsars are named and known for their characteristic pulsing, so much so that their first observer, Jocelyn Bell, thought that the pulsing radio signals could be signs of extraterrestrial life and called them 'Little Green Men'. So how would it be possible to prove the existence of a pulsar like the one in IC443 that refuses to pulse? The answer is a standard one in science: better technology.

The new data obtained from Chandra, which can be used to create high-resolution pictures of stars and interstellar matter, showed clear evidence of a 30,000-year-old pulsar in the midst of the IC443 remnant. A pulsar is a spinning neutron star that forms from a supernova that implodes and then explodes. The implosion smashes together countless protons and electrons, creating an extremely dense, massive star composed entirely of neutrons. The 'kick' created when the star 'bounces' from the implosion to the explosion sets the new neutron star spinning away from the site of the supernova. It is this rapid revolution that causes the characteristic pulsing.

To do this, the team used an image processing program called AIPS, which smooths the edges of the pixels on the map. This smoothing creates a picture that we can actually look at and understand, unlike the photon maps. Radio-wave data was also used to help with image creation. Finally, the team did numerical guesswork to interpret the images. The pictures show a point source with lower energy X-rays and a comet-like tail with higher energy X-rays, direct evidence of a pulsar.

Clearfield, Olbert, and Williams attend the N.C. School of Science and Mathematics, a residential, state university-affiliated high school in Durham, N.C., for students with a high aptitude and interest in math and science. The students will share the Siemens-Westinghouse $100,000 scholarship award.

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Author: Kathryn Fromson

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