A workshop project of high school students has discovered a pulsar in one of only a handful of double neutron star systems known, this one with the widest orbit around its companion of any found to date.
The students discovered the pulsar in data collected by the National Science Foundation's Robert C. Byrd Green Bank Telescope in West Virginia.
They were participating in an NSF-sponsored workshop, the Pulsar Search Collaboratory, which involves students searching through telescope data for the unique signature of a pulsar. Students often spend weeks and months looking 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.
Pulsars are the dense remains of massive stars after they've exploded as supernovas, and as they spin rapidly they send out beams of radio waves like a lighthouse beacon.
If those beams sweep past the Earth as the pulsar spins, the waves can be detected by radio telescopes like the 100-meter Green Bank instrument, the world's largest fully steerable radio telescope. It is located in the National Radio Quiet Zone, which helps protect the very sensitive telescope from unwanted radio interference.
Astronomers following up on the student discovery determined the new pulsar is part of a binary system, like about 10 percent of known pulsars.
However, most pulsars orbit white dwarf star companions or a star like our sun; only a rare few are in obit around another neutron star.
Cecilia McGough, a student at Strasburg High School in Virginia, and De'Shang Ray, a student at Paul Laurence Dunbar High School in Baltimore, Md., discovered the new pulsar, dubbed PSR J1930-1852, during a 2012 pulsar search workshop, according to a study on the discovery and its implications to be published in the Astrophysical Journal.
"Pulsars are some of the most extreme objects in the universe," says study lead author Joe Swiggum, a graduate student in physics and astronomy at West Virginia University. "The students' discovery shows one of these objects in a really unique set of circumstances."
Optical telescopes were pointed in the direction of the pulsar, but found no visible companion such as a white dwarf or a normal star like our sun.
"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," Swiggum says.
Timing the pulsar's pulses led the researchers to conclude the pair of neutron stars orbit each other at the largest separation ever seen in a double neutron star system.
The orbital path of the pulsar spans about 32 million miles and it circles around its companion every 45 days. "Its orbit is more than twice as large as that of any previously known double neutron star system," says Swiggum.
