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What is Pulsar?pulsar_web.jpgPulsars.jpg

A pulsar (pulsating star) is a highly magnetized, rotating neutron star that emits a beam of electromagnetic radiation. This radiation can only be observed when the beam of emission is pointing toward the Earth, much the way a lighthouse can only be seen when the light is pointed in the direction of an observer, and is responsible for the pulsed appearance of emission. Neutron stars are very dense, and have short, regular rotational periods. This produces a very precise interval between pulses that range from roughly milliseconds to seconds for an individual pulsar. The precise periods of pulsars makes them useful tools. Observations of a pulsar in a binary neutron star system were used to indirectly confirm the existence of gravitational radiation.

The first pulsar was observed on November 28, 1967, by Jocelyn Bell Burnell and Antony Hewish. The observed emission from the pulsar was pulses separated by 1.33 seconds, originated from the same location on the sky, and kept to sidereal time. In looking for explanations for the pulses, the short period of the pulses eliminated most astrophysical sources of radiation, such as stars, and since the pulses followed sidereal time, it could not be man-made radio frequency interference. When observations with another telescope confirmed the emission, it eliminated any sort of instrumental effects. At this point, Burnell notes of herself and Hewish that "we did not really believe that we had picked up signals from another civilization, but obviously the idea had crossed our minds and we had no proof that it was an entirely natural radio emission. It is an interesting problem—if one thinks one may have detected life elsewhere in the universe, how does one announce the results responsibly?" Even so, they nicknamed the signal LGM-1, for "little green men." It was not until a second pulsating source was discovered in a different part of the sky that the "LGM hypothesis" was entirely abandoned.

The events leading to the formation of a pulsar begin when the core of a massive star is compressed during a supernova, which collapses into a neutron star. The neutron star retains most of its angular momentum, and since it has only a tiny fraction of its progenitor's radius (and therefore its moment of inertia is sharply reduced), it is formed with very high rotation speed. A beam of radiation is emitted along the magnetic axis of the pulsar, which spins along with the rotation of the neutron star. The magnetic axis of the pulsar determines the direction of the electromagnetic beam, with the magnetic axis not necessarily being the same as its rotational axis. This misalignment causes the beam to be seen once for every rotation of the neutron star, which leads to the "pulsed" nature of its appearance. The beam originates from the rotational energy of the neutron star, which generates an electrical field from the movement of the very strong magnetic field, resulting in the acceleration of protons and electrons on the star surface and the creation of an electromagnetic beam emanating from the poles of the magnetic field. This rotation slows down over time as electromagnetic power is emitted. When a pulsar's spin period slows down sufficiently, the radio pulsar mechanism is believed to turn off (the so-called "death line"). This turn-off seems to take place after about 10–100 million years, which means of all the neutron stars in the 13.6 billion year age of the universe, around 99% no longer pulsate. The longest known pulsar period is 8.51 seconds. Though this very general picture of pulsars is mostly accepted, Werner Becker of the Max Planck Institute for Extraterrestrial Physics said in 2006, "The theory of how pulsars emit their radiation is still in its infancy, even after nearly forty years of work.

This is what we do at SVHS:

  • See below for Research Posters, pictures, and links.

  • SVHS students are contributing authors in a published paper in the Astrophysical Journal. The article is entitled, "The Pulsar Search Collaboratory: Discovery and Timing of Five New Pulsars."

  • Click on the following link to see this article: Astrophysical Journal - February 2013

  • SVHS students and teacher, Jeff Chaffins, are featured in the documentary in production, "Little Green Men," by award-winning director Sara Kolberg.

  • Click on the following link to see the trailer released in July 2013: "Little Green Men" Documentary Trailer


Links

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Summer 2009: Kristen, Jennifer, Aaron, Sam, and Mr. Chaffins at NRAO Green Bank.
Pulsar Search Collaboratory
PSC Database
350 MHz Driftscan Data
Green Bank Observatory
NRAO
NRAO - Green Bank
Nanograv
Cosmic Search Magazine - "Little Green Men, White Dwarfs or Pulsars?"
SETI
SkyNet Robotic Telescope Network


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2012 Capstone Presentation at WVU: Mr. McCloud, Jacob, Trevor, Shaun, Mr. Chaffins


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David discovers pulsar J2136-1612 !!
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2012 Summer Institute: Shaun and Abby at the NRAO, Green Bank, WV.

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Summer Institute 2011: Mr. Chaffins, Kris, Allie, David, Diana, Jacob, Zach, Erin, Mr. McCloud

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Abby Chaffins  - Capstone Poster 2013.jpg
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RFI Poster.jpg
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See also: