Mystery Cosmic Radio Pulse Leaves Magnetic Clue
Somewhere out there in the darkest depths of our universe, something is generating mysterious eruptions of energy that are being detected as fast radio bursts -- and astronomers are close to working out what they are.
Somewhere out there in the darkest depths of our universe, something is generating mysterious eruptions of energy that are being detected as fast radio bursts - otherwise known as FRBs.
Since these weird phenomena were first discovered nearly a decade ago, astronomers have been at a loss to explain what they could be. Everything from the exotic (aliens?!) to the "mundane" (supernovas, boo) have been cited as possible culprits. Now, by painstakingly analyzing the signal of one of these pulses, astronomers may be on the trail to finally working out what the heck is rumbling the cosmos.
FRBs last only a fraction of a second but pack a hell of an energetic punch. Because they are so transient, however, they're not easy to record. They flash, and they're gone. Also, as they have often traveled vast distances, their signals are stretched and blurred out. According to a Carnegie Mellon University press release, though only a few have been detected, astronomers think the universe sees tens of thousands of these pulses every single day, but to see one you need to be looking at the right place at the right time.
After analyzing hundreds of hours of data from the National Science Foundation's (NSF) Green Bank Telescope (GBT) in West Virginia, researchers stumbled across the most detailed signature of a FRB recorded to date. From this signal, they were able to gain a measure on its magnetic "fingerprint" to reveal the environment it must have been spawned.
"We now know that the energy from this FRB passed through a dense, magnetized region shortly after it formed," said astronomer Kiyoshi Masui, of the University of British Columbia and the Canadian Institute for Advanced Research. "This significantly narrows down the source's environment and type of event that triggered the burst."
What's dense and extremely magnetized? Supernovas and star forming regions. But exactly where did this FRB originate? So far, the detected FRBs have originated in random parts of the sky; there appears to be no pattern, and this particular FRB was no different. But the one thing that set this event apart - dubbed "FRB 110523″ - is the detail held in its signal. Now the detective work could begin.
Finding FRB 110523 was no easy task; the researchers had to scan through 40 terabytes of radio data looking for the split-second pulses. They found 6,000 candidate FRBs in the data, but the vast majority were of too low a quality for analysis or confirmation. Another problem is that, after travelling potentially billions of light-years to reach Earth, these pulses become smeared or blurred, an effect known as "dispersion delay." This has the effect of blending FRBs into the radio data, hiding it from view. The researchers therefore had to create a computer algorithm to track down these smeared-out pulses.
"Hidden within an incredibly massive dataset, we found a very peculiar signal, one that matched all the known characteristics of a Fast Radio Burst, but with a tantalizing extra polarization element that we simply have never seen before," said Jeffrey Peterson, a faculty member in Carnegie Mellon's McWilliams Center for Cosmology.
Until now, only 15 FRBs have been definitively identified, all of which fell within the 1.2-1.5 GHz frequency range. FRB 110523 has a lower frequency, falling within the 700-900 MHz range.
"I feel extremely lucky to have identified the 16th (FRB)," said Hsiu-Hsien Lin, also from Carnegie Mellon, who made the identification of FRB 110523. "Not only is this the first FRB in this frequency range, our FRB has provided us with a great deal of information that help us to better understand this astrophysical phenomenon."
This particular signal appeared like a diamond in the rough. Not only was its signal clear, it also held a polarization fingerprint (called Faraday rotation, a corkscrew-like twist in electromagnetic radiation) from where it was born.
"This tells us something about the magnetic field that the burst traveled through on its way to us, giving a hint about the burst's environment," said Masui. "It also gives the theorists a bit more to work with when they come up with explanations for these bursts."
Measurements of the dispersion delay of FRB 110523 revealed the source of the signal was 6 billion light-years away (it was therefore triggered 6 billion years ago, when the universe was a little over half the age it is now), but additional analysis revealed the size of the source region - it came from another galaxy. But that's not all.
Even more information was gleaned from the pulse's dispersion delay; it revealed the signal passed through two distinct regions of ionized gas. One of these regions was very close to the source (within the source's galaxy) and most likely "a nebula surrounding the source or the environment near the center of a galaxy."
"Taken together, these remarkable data reveal more about an FRB than we have ever seen before and give us important constraints on these mysterious events," said Masui. "We also have an exciting new tool to search through otherwise overwhelming archival data to uncover more examples and get closer to truly understanding their nature."
This voyage of discovery reminds me of the story behind the first detection of a pulsar in 1967. At the time, the periodic signal coming from the pulsar PSR B1919+21 was mysterious, so astronomers nicknamed it "LGM-1″ - a.k.a. "Little Green Men-1." The signal, however, was quickly identified as a rapidly-spinning neutron star generating powerful radio emissions as it rotated (creating pulses 1.34 seconds apart) and not evidence of an intelligent alien civilization (read the full story here).
Although the source of FRBs is not clear quite yet, it seems their mystery is slowly unraveling and the mechanism may lie deep inside the magnetic hearts of galaxies billions of light-years away.
Artist impression of a Fast Radio Burst reaching Earth.
March 13, 2013, marks 20 years since the W. M. Keck Observatory began taking observations of the cosmos. Located in arguably one of the most extreme and beautiful places on the planet -- atop Mauna Kea, Hawai'i, 13,803 ft (4,207 m) above sea level -- the twin Keck domes have observed everything from asteroids, planets, exoplanets to dying stars, distant galaxies and nebulae. Seen in this photograph, the Keck I and Keck II telescopes dazzle the skies with their adaptive optics lasers -- a system that helps cancel out the turbulence of the Earth's atmosphere, bringing science some of the clearest views attainable by a ground-based observatory.
To celebrate the last two decades of incredible science, Discovery News has assembled some of the most impressive imagery to come from Keck.
Starting very close to home, the Keck II captured this infrared image of asteroid 2005 YU55 as it flew past Earth on Nov. 8, 2011.
Deeper into the solar system, the Keck NIRC2 near-infrared camera captured this beautiful observation of the oddball Uranus on July 11-12, 2004. The planet's north pole is at 4 o'clock.
This is a mosaic false-color image of thermal heat emission from Saturn and its rings on Feb. 4, 2004, captured by the Keck I telescope at 17.65 micron wavelengths.
A nice image of Saturn with Keck I telescope with the near infrared camera (NIRC) on Nov. 6, 1998. This is a composite of images taken in Z and J bands (1.05 and 1.3 microns), with the color scaling adjusted so it looks like Saturn is supposed to look to the naked eye.
This is Saturn's giant moon Titan -- a composite of three infrared bands captured by the Near Infrared Camera-2 on the 10-meter Keck II telescope. It was taken by astronomer Antonin Bouchez on June 7, 2011.
Another multicolored look at Titan -- a near-infrared color composite image taken with the Keck II adaptive optics system. Titan's surface appears red, while haze layers at progressively higher altitudes in the atmosphere appear green and blue.
This image of Neptune and its largest Tritan was captured by Caltech astronomer Mike Brown in September 2011. It shows the wind-whipped clouds, thought to exceed 1,200 miles per hour along the equator.
A color composite image of Jupiter in the near infrared and its moon Io. The callout at right shows a closeup of the two red spots through a filter which looks deep in the cloud layer to see thermal radiation.
HR 8799: Three exoplanets orbiting a young star 140 light years away are captured using Keck Observatory's near-infrared adaptive optics. This was the first direct observation by a ground-based observatory of worlds orbiting another star (2008).
Now to the extremes -- an image of Stephan's Quintet, a small compact group of galaxies.
The Egg Nebula: This Protoplanetary nebula is reflecting light from a dying star that is shedding its outer layers in the final stages of its life.
This is WR 104, a dying star. Known as a Wolf Rayet star, this massive stellar object will end its life in the most dramatic way -- possibly as a gamma-ray burst. The spiral is caused by gases blasting from the star as it orbits with another massive star.
Narrow-field image of the center of the Milky Way. The arrow marks the location of radio source Sge A*, a supermassive black hole at the center of our galaxy.
A high resolution mid-infrared picture taken of the center of our Milky Way reveals details about dust swirling into the black hole that dominates the region.
A false-color image of a spiral galaxy in the constellation Camelopardalis.
A scintillating square-shaped nebula nestled in the vast sea of stars. Combining infrared data from the Hale Telescope at Palomar Observatory and the Keck II telescope, researchers characterized the remarkably symmetrical “Red Square” nebula.
Galaxy cluster Abell 2218 is acting as a powerful lens, magnifying all galaxies lying behind the cluster's core. The lensed galaxies are all stretched along the shear direction, and some of them are multiply imaged.
The central starburst region of the dwarf galaxy IC 10. In this composite color image, near infrared images obtained with the Keck II telescope have been combined with visible-light images taken with NASA’s Hubble Space Telescope.
Keck I (right) and Keck II (left) domes at Mauna Kea.
Keck I and Keck II aim their adaptive optics lasers at the galactic center.