GREEN BANK, W. Va. -- A team of highly determined high school students, which included current Penn State University sophomore and Schreyer Honors College Scholar Cecilia McGough, has discovered a never-before-seen pulsar by painstakingly analyzing data from the National Science Foundation’s (NSF) Robert C. Byrd Green Bank Telescope (GBT). Further observations by astronomers using the GBT have revealed that this pulsar has the widest orbit of any around a neutron star and is part of only a handful of double neutron star systems.This impressive find will help astronomers better understand how binary neutron star systems form and evolve. Pulsars are rapidly spinning neutron stars, the super dense remains of massive stars that have exploded as supernovas. As a pulsar spins, lighthouse-like beams of radio waves, streaming from the poles of its powerful magnetic field, sweep through space. When one of these beams sweeps across the Earth, radio telescopes can capture the pulse of radio waves.This pulsar, which received the official designation PSR J1930-1852, was discovered in 2012 by McGough, then a student at Strasburg High School in Virginia, and De’Shang Ray, then a student at Paul Laurence Dunbar High School in Baltimore, Maryland. The two students were participating in a summer Pulsar Search Collaboratory (PSC) workshop, an NSF-funded educational outreach program that involves interested high school students in analyzing pulsar survey data collected by the GBT. Students often spend weeks and months poring over data plots, searching for the unique signature that identifies a pulsar. Those who identify strong pulsar candidates are invited to Green Bank to work with astronomers to confirm their discovery. McGough, now pursuing a degree in science in Penn State’s Eberly College of Science, will be a co-author on the scientific paper explaining this result and its implications, which has been accepted for publication in the Astrophysical Journal. Lead author is Joe Swiggum, a graduate student in physics and astronomy at West Virginia University in Morgantown.
“This experience taught me that you do not have to be an 'Einstein' to be good at science,” said McGough, who is majoring in astronomy and astrophysics and physics. “What you have to be is focused, passionate and dedicated to your work.”
About 10 percent of known pulsars are in binary systems; the vast majority of these are found orbiting ancient white dwarf companion stars. Only a rare few orbit other neutron stars or main sequence stars like our Sun. The reason for this paucity of double neutron star systems, astronomers believe, is the process by which pulsars and all neutron stars form. When a massive star goes supernova at the end of its normal life, the explosion can be a little one-sided, imparting a “kick” to the remaining stellar core. When this happens, the resulting neutron star is sent hurtling through space. These kicks—and the corresponding mass loss from a supernova explosion—mean that the chances of two such stars remaining gravitationally locked in the same system are remarkably slim.
Astronomers determined that this new pulsar is part of a binary system, based on the differences in its spin frequency (revolutions per second) between the original detection and follow-up observations. Optical telescope surveys of the same area of the sky, however, revealed no visible companion–which would have been clearly seen if it were a white dwarf star or main sequence star.
“Pulsars are some of the most extreme objects in the universe,” Swiggum said. “The students’ discovery shows one of these objects in a really unique set of circumstances. Given the lack of any visible signals and the careful review of the timing of the pulsar, we concluded that the most likely companion was another neutron star.”
Further analysis of the timing of the pulses indicates that the two neutron stars have the widest separation ever observed in a double neutron star system. "Some pulsars in double neutron star systems are so close to their companion that their orbital paths are comparable to the size of our sun and they make a full orbit in less than a day. The orbital path of J1930-1852 spans about 52 million kilometers, roughly the distance between Mercury and the Sun and it orbits its companion once every 45 days. “Its orbit is more than twice as large as that of any previously known double neutron star system,” said Swiggum. “The pulsar’s parameters give us valuable clues about how a system like this could have formed. Discoveries of outlier systems like J1930-1852 give us a clearer picture of the full range of possibilities in binary evolution.”Studies involving Pulsar Search Collaboratory discoveries are ongoing; as the PSC program continues, astronomers expect the 130 terabytes of data produced by the 17-million-pound GBT will likely reveal dozens of previously unknown pulsars. The Pulsar Search Collaboratory is a joint project between the National Radio Astronomy Observatory and West Virginia University. The goal is to give high school students experience doing real research. "As we look up into the sky and study the universe, we try to understand what’s out there,” said Ray, currently a student at the Community College of Baltimore County studying biology, engineering, and emergency medical services. “This experience has helped me to explore, to imagine, and to dream what could be and what we haven’t seen.”The 100-meter Green Bank Telescope is the world's largest fully steerable radio telescope. Its location in the National Radio Quiet Zone protects the incredibly sensitive telescope from unwanted radio interference, enabling it to perform unique observations.The National Radio Astronomy Observatory is a facility of the National Science Foundation, operated under cooperative agreement by Associated Universities, Inc.