The VERITAS experiment measured gamma rays coming from the Crab Pulsar at such large energies that they cannot be explained by current scientific models of how pulsars behave, the researchers said.
The results, published today in the journal Science, outline the first observation of photons from a pulsar system with energies greater than 100 billion electron volts -- more than 50 billion times higher than visible light from the sun.
"This is the highest energy pulsar system ever detected," said Rene Ong, a UCLA professor of physics and astronomy and spokesperson for the VERITAS collaboration. "It is a completely new and surprising phenomenon for pulsars."
Data were acquired for 107 hours over the course of three years by VERITAS's ground-based gamma ray observatory, which is part of southern Arizona's Whipple Observatory, a facility managed by the Harvard–Smithsonian Center for Astrophysics. VERITAS (Very Energetic Radiation Imaging Telescope Array System) observes gamma rays using a network of four telescopes, each 12 meters in diameter.
Ong noted that all previous observations of pulsars indicated that the radiation cuts off at the high energies the team observed.
"It means the radiation we detect must be a new component that was completely unexpected," he said.
Gamma rays, the most energetic type of electromagnetic radiation, cannot be directed by lenses or bounced off mirrors like ordinary visible light, Ong said. Because the rays are invisible to the human eye, the only way telescopes on Earth can detect them is by observing the path they take as they are absorbed in the planet's atmosphere.
Gamma rays are ejected from the Crab Pulsar, and they smash into Earth's atmosphere, causing "the electromagnetic equivalent of a sonic boom," Ong said. This collision creates a shower of visible light more than 6 miles above the ground that is recorded by VERITAS.
"The atmosphere is an integral part of our measurement system, which makes VERITAS different from conventional telescopes," Ong said.
One of the most widely studied astronomical objects in the northern hemisphere, the Crab Nebula, which is some 6,500 light-years from Earth, was formed when a massive star exploded in a supernova event that was observed on Earth in the year 1054. While it is most typical for pulsars to be ejected from the stellar wreckage during a supernova, in the case of the Crab system, the pulsar remained at its center, producing radiation that covers the entire electromagnetic spectrum, Ong said.
He calls the Crab system the "Rosetta Stone of astronomy," because astronomers and astrophysicists have observed this object at every conceivable wavelength of light.
"The Crab Pulsar is considered among the best understood systems in all of astronomy, yet here we have found something totally new," he said. "It is astronomy in a completely new light; we are seeing phenomena that you just can't explore with optical light or X-rays, or even low-energy gamma rays."
The Crab Pulsar is a highly magnetized neutron star with a surface magnetic field a trillion times stronger than that of the Earth. The star spins at the dizzying rate of about 30 times a second and emits gamma rays through "curvature radiation," an effect that creates a lighthouse-like beacon that winks on when the beam faces the Earth and off when the star pivots away.
Light detected by the VERITAS experiment cannot be explained by curvature radiation, however, and likely comes from regions well outside the high–magnetic field region close to the neutron star, Ong said. While such energetic gamma rays have been observed elsewhere in the galaxy, the actual mechanism of how they are created in a pulsar is not fully understood.
"The pulse duration of the radiation we see is almost three times shorter than that seen at other gamma ray energies," he said. "This was very surprising and means this new radiation is probably coming from a different physical region of the star's outer magnetosphere."
The VERITAS experiment looks for radiation emanating from celestial objects such as pulsars, active galaxies, the center of the Milky Way and supermassive black holes. It has collected data for nearly 1,000 hours every year since it began operating in 2007.
"We are trying to understand processes out in the cosmos that can create particles at these extreme energies, beyond what can be produced here on Earth," Ong said. "We are also very interested in seeing if these processes indicate some sort of new physics."
Ong hopes his research may shed some light on the mystery of cosmic rays.
"We are bombarded by high-energy particles from all over the cosmos that reach unimaginable energies," he said. "These cosmic rays are an important energy source in our galaxy, yet we have no clue where they are coming from.
"This measurement indirectly gives us clues to the highest energies in the cosmos, telling us about particles and energies that we can't generate here on Earth but that nature's accelerators are able to create for us."
Ong is currently helping to plan the next-generation ground-based gamma ray observatory, called the Cherenkov Telescope Array (CTA). Covering more than one-half square mile with dozens of telescopes, the CTA will be 10 times more sensitive than VERITAS, allowing radiation from fainter and more distant objects to be accurately resolved.
The 95 co-authors of the Science paper on the Crab Pulsar include scientists from 26 institutions in five countries who are part of the VERITAS collaboration. UCLA co-authors include Vladimir Vassiliev, an associate professor of physics and astronomy; Pratik Majumdar, a postdoctoral scholar in physics and astronomy; and Timothy Arlen, a graduate student.
This research is supported by the U.S. Department of Energy, the U.S. National Science Foundation, the Smithsonian Institution, the National Sciences and Engineering Research Council of Canada, the U.K.'s Science and Technology Facilities Council, and the Science Foundation Ireland.
UCLA is California's largest university, with an enrollment of nearly 38,000 undergraduate and graduate students. The UCLA College of Letters and Science and the university's 11 professional schools feature renowned faculty and offer 337 degree programs and majors. UCLA is a national and international leader in the breadth and quality of its academic, research, health care, cultural, continuing education and athletic programs. Six alumni and five faculty have been awarded the Nobel Prize.
For more news, visit the UCLA Newsroom and follow us on Twitter.
Stuart Wolpert | EurekAlert!
Hubble sees Neptune's mysterious shrinking storm
16.02.2018 | NASA/Goddard Space Flight Center
Supermassive black hole model predicts characteristic light signals at cusp of collision
15.02.2018 | Rochester Institute of Technology
Breakthrough provides a new concept of the design of molecular motors, sensors and electricity generators at nanoscale
Researchers from the Institute of Organic Chemistry and Biochemistry of the CAS (IOCB Prague), Institute of Physics of the CAS (IP CAS) and Palacký University...
For photographers and scientists, lenses are lifesavers. They reflect and refract light, making possible the imaging systems that drive discovery through the microscope and preserve history through cameras.
But today's glass-based lenses are bulky and resist miniaturization. Next-generation technologies, such as ultrathin cameras or tiny microscopes, require...
Scientists from the University of Zurich have succeeded for the first time in tracking individual stem cells and their neuronal progeny over months within the intact adult brain. This study sheds light on how new neurons are produced throughout life.
The generation of new nerve cells was once thought to taper off at the end of embryonic development. However, recent research has shown that the adult brain...
Theoretical physicists propose to use negative interference to control heat flow in quantum devices. Study published in Physical Review Letters
Quantum computer parts are sensitive and need to be cooled to very low temperatures. Their tiny size makes them particularly susceptible to a temperature...
Let’s say the armrest is broken in your vintage car. As things stand, you would need a lot of luck and persistence to find the right spare part. But in the world of Industrie 4.0 and production with batch sizes of one, you can simply scan the armrest and print it out. This is made possible by the first ever 3D scanner capable of working autonomously and in real time. The autonomous scanning system will be on display at the Hannover Messe Preview on February 6 and at the Hannover Messe proper from April 23 to 27, 2018 (Hall 6, Booth A30).
Part of the charm of vintage cars is that they stopped making them long ago, so it is special when you do see one out on the roads. If something breaks or...
15.02.2018 | Event News
13.02.2018 | Event News
12.02.2018 | Event News
16.02.2018 | Information Technology
16.02.2018 | Health and Medicine
16.02.2018 | Physics and Astronomy