The Cosmic radio burst caught red-handed

A schematic illustration of CSIRO’s Parkes radio telescope receiving the polarised signal from the new ‘fast radio burst’. Credit: Swinburne Astronomy Productions.

Pasadena, CA— Fast radio bursts are quick, bright flashes of radio waves from an unknown source in space. They are a mysterious phenomenon that last only a few milliseconds, and until now they have not been observed in real time. An international team of astronomers, including three from the Carnegie Observatories, has for the first time observed a fast radio burst happening live. Their work is published in Monthly Notices of the Royal Astronomical Society.

There is a great deal of scientific interest in fast radio bursts, particularly in uncovering their origin.

“These events are one of the biggest mysteries in the Universe” noted Carnegie Observatories' Acting Director John Mulchaey. “Until now, astronomers were not able to catch one of these events in the act.”

Only seven fast radio bursts have previously been discovered, since the first one found in 2007. All were found retroactively by combing through data from the Parkes radio telescope in eastern Australia and the Arecibo telescope in Puerto Rico.

“These bursts were generally discovered weeks or months or even more than a decade after they happened! We’re the first to catch one in real time,” said Emily Petroff, a PhD candidate from Swinburne University of Technology in Melbourne, Australia and lead author of the publication.
Swinburne is a member institution of the ARC Centre of Excellence for All-sky Astrophysics (CAASTRO).

In order to observe the fast radio burst in real time, the team mobilized 12 telescopes around the world and in space, including Carnegie’s Magellan and Swope telescopes. Each telescope followed-up on the original burst observation at different wavelengths.

Measurements of the interaction between previously detected fast radio burst’s flashes and the free electrons their signals encountered in space as they traveled to reach us had previously indicated that the bursts likely originated far outside of our galaxy. But the idea was controversial.

The team’s data indicates that the burst originated up to 5.5 billion light years away. This means that the sources of theses bursts are extremely bright and could perhaps be used as a cosmological tool for measuring and understanding our universe once we come to understand them better.

“Together, our observations allowed the team to rule out some of the previously proposed sources for the bursts, including nearby supernovae,” explained Carnegie’s Mansi Kasliwal who was on the team along with Mulchaey and colleague Yue Shen. “Short gamma-ray bursts are still a possibility, as are distant magnetic neutron stars called magnetars, but not long gamma ray bursts.”

Gamma ray bursts are high-energy explosions that form some of the brightest celestial events. Long bursts can signify energy released during a supernova and are followed by an afterglow, which emits lower wavelength radiation than the original explosion.

Another interesting piece of information the team was able to gather about the burst is its polarization. The orientation of the radio waves indicates that the burst likely originated near or passed through a magnetic field, information that can help narrow down potential sources going forward.

“As we continue to search for the source of fast radio bursts, Carnegie is well positioned to make big strides in the field,” Mulchaey said. “Quick access to big telescopes like Magellan may be the key to solving this mystery.”

Caption: A schematic illustration of CSIRO’s Parkes radio telescope receiving the polarised signal from the new fast radio burst. Image is credited to Swinburne Astronomy Productions.

Other co-authors are: M. Bailes (Swinburne University of Technology and ARC Centre of Excellence for All-sky Astrophysics); E.D. Barr (Swinburne University of Technology and ARC Centre of Excellence for All-sky Astrophysics); B. R. Barsdell (Harvard-Smithsonian Center for Astrophysics); N. D. R. Bhat (ARC Centre of Excellence for All-sky Astrophysics and Curtin University) ; F. Bian (Australian National University); S. Burke-Spolaor (Caltech); M. Caleb(Australian National University, Swinburne University of Technology, ARC Centre of Excellence for All-sky Astrophysics); D. Champion (Max Planck Institut für Radioastronomie); P. Chandra (Tata Institute of Fundamental Research Pune University Campus); G. Da Costa (Australian National University); C. Delvaux (Max-Planck-Institut für extraterrestrische Physik); C. Flynn (Swinburne University of Technology and ARC Centre of Excellence for All-sky Astrophysics); N. Gehrels (NASA Goddard Space Flight Center); J. Greiner (Max-Planck-Institut für extraterrestrische Physik); A. Jameson (Swinburne University of Technology and ARC Centre of Excellence for All-sky Astrophysics); S. Johnston (CSIRO Astronomy & Space Science Australia Telescope National Facility); E. F. Keane (Swinburne University of Technology and ARC Centre of Excellence for All-sky Astrophysics); S. Keller (Australian National University); J. Kocz (Harvard-Smithsonian Center for Astrophysics and Jet Propulsion Laboratory, Caltech); M. Kramer (Max Planck Institut für Radioastronomie and University of Manchester) G. Leloudas (University of Copenhagen and Weizmann Institute of Science); D. Malesani (University of Copenhagen); C. Ng (Max Planck Institut für Radioastronomie); E. O. Ofek (Weizmann Institute of Science); D. A. Perley (Caltech); A. Possenti (Osservatorio Astronomico di Cagliari); B. P. Schmidt (Australian National University and ARC Centre of Excellence for All-sky Astrophysics); B. Stappers (University of Manchester); P. Tisserand (Australian National University and ARC Centre of Excellence for All-sky Astrophysics); W. van Straten (Swinburne University of Technology and ARC Centre of Excellence for All-sky Astrophysics ); and C. Wolf (Australian National University and ARC Centre of Excellence for All-sky Astrophysics).

The Parkes radio telescope and the Australia Telescope Compact Array are part of the Australia Telescope National Facility, which is funded by the Commonwealth of Australia for operation as a National Facility and managed by CSIRO. Parts of this research were conducted by the Australian Research Council Centre of Excellence for All-sky Astrophysics (CAASTRO). GMRT is run by the National Centre for Radio Astrophysics of the Tata Institute of Fundamental Research. Research with the ANU SkyMapper telescope is supported in part through an ARC Discovery Grant. Part of the funding for GROND was granted from a Leibniz-Prize. The Dark Cosmology Centre is supported by the Danish National Research council. Other support came from Curtin Research Fellowship;, EXTraS, funded from the European Union's Seventh Framework Programme for research, technological development and demonstration; Hubble Fellowships; a Carnegie-Princeton Fellowship; the Arye Dissentshik career development; the Willner Family Leadership Institute Ilan Gluzman (Secaucus, N.J.), the Israeli Ministry of Science; Israel Science Foundation; Minerv;, Weizmann-UK; the I-CORE Program of the Planning and Budgeting Committee.

The Carnegie Institution for Science (carnegiescience.edu) is a private, nonprofit organization headquartered in Washington, D.C., with six research departments throughout the U.S. Since its founding in 1902, the Carnegie Institution has been a pioneering force in basic scientific research. Carnegie scientists are leaders in plant biology, developmental biology, astronomy, materials science, global ecology, and Earth and planetary science.

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Source: Royal Astronomical Society

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Hubble goes high def to revisit the iconic ‘Pillars of Creation'

NASA's Hubble Space Telescope has revisited the famous Pillars of Creation, revealing a sharper and wider view of the structures in this visible-light image. Astronomers combined several Hubble exposures to assemble the wider view. The towering pillars are about 5 light-years tall. The dark, finger-like feature at bottom right may be a smaller version of the giant pillars. The new image was taken with Hubble's versatile and sharp-eyed Wide Field Camera 3. The pillars are bathed in the blistering ultraviolet light from a grouping of young, massive stars located off the top of the image. Streamers of gas can be seen bleeding off the pillars as the intense radiation heats and evaporates it into space. Denser regions of the pillars are shadowing material beneath them from the powerful radiation. Stars are being born deep inside the pillars, which are made of cold hydrogen gas laced with dust. The pillars are part of a small region of the Eagle Nebula, a vast star-forming region 6,500 light-years from Earth. The colors in the image highlight emission from several chemical elements. Oxygen emission is blue, sulfur is orange, and hydrogen and nitrogen are green. Credit: NASA, ESA, and the Hubble Heritage Team (STScI/AURA)

Although NASA's Hubble Space Telescope has taken many breathtaking images of the universe, one snapshot stands out from the rest: the iconic view of the so-called "Pillars of Creation." The jaw-dropping photo, taken in 1995, revealed never-before-seen details of three giant columns of cold gas bathed in the scorching ultraviolet light from a cluster of young, massive stars in a small region of the Eagle Nebula, or M16.

Though such butte-like features are common in star-forming regions, the M16 structures are by far the most photogenic and evocative. The Hubble image is so popular that it has appeared in movies and television shows, on tee-shirts and pillows, and even on a postage stamp.

And now, in celebration of its 25th anniversary, Hubble has revisited the famous pillars, providing astronomers with a sharper and wider view. As a bonus, the pillars have been photographed in near-infrared light, as well as visible light. The infrared view transforms the pillars into eerie, wispy silhouettes seen against a background of myriad stars. That's because the infrared light penetrates much of the gas and dust, except for the densest regions of the pillars. Newborn stars can be seen hidden away inside the pillars. The new images are being unveiled at the American Astronomical Society meeting in Seattle, Washington.

Although the original image was dubbed the Pillars of Creation, the new image hints that they are also pillars of destruction. "I'm impressed by how transitory these structures are. They are actively being ablated away before our very eyes. The ghostly bluish haze around the dense edges of the pillars is material getting heated up and evaporating away into space. We have caught these pillars at a very unique and short-lived moment in their evolution," explained Paul Scowen of Arizona State University in Tempe, who, with astronomer Jeff Hester, formerly of Arizona State University, led the original Hubble observations of the Eagle Nebula.

The infrared image shows that the very ends of the pillars are dense knots of gas and dust, and they shadow the gas below them, creating the long, column-like structures. The gas in between the pillars has long since been blown away by the ionizing winds from the central star cluster located above the pillars.

At the top edge of the left-hand pillar, a gaseous fragment has been heated up and is flying away from the structure, underscoring the violent nature of star-forming regions. "These pillars represent a very dynamic, active process," Scowen said. "The gas is not being passively heated up and gently wafting away into space. The gaseous pillars are actually getting ionized (a process by which electrons are stripped off of atoms) and heated up by radiation from the massive stars. And then they are being eroded by the stars' strong winds (barrage of charged particles), which are sandblasting away the tops of these pillars."

When Scowen and Hester used Hubble to make the initial observations of the Eagle Nebula in 1995, astronomers had seen the pillar-like structures in ground-based images, but not in detail. They knew that the physical processes are not unique to the Eagle Nebula because star birth takes place across the universe. But at a distance of just 6,500 light-years, M16 is the most dramatic nearby example, as the team soon realized.

As Scowen was piecing together the Hubble exposures of the Eagle, he was amazed at what he saw. "I called Jeff Hester on his phone and said, 'You need to get here now,'" Scowen recalled. "We laid the pictures out on the table, and we were just gushing because of all the incredible detail that we were seeing for the very first time."

The first features that jumped out at the team in 1995 were the streamers of gas seemingly floating away from the columns. Astronomers had previously debated what effect nearby massive stars would have on the surrounding gas in stellar nurseries. "There is only one thing that can light up a neighborhood like this: massive stars kicking out enough horsepower in ultraviolet light to ionize the gas clouds and make them glow," Scowen said. 

"Nebulous star-forming regions like M16 are the interstellar neon signs that say, 'We just made a bunch of massive stars here.' This was the first time we had directly seen observational evidence that the erosionary process, not only the radiation but the mechanical stripping away of the gas from the columns, was actually being seen."

By comparing the 1995 and 2014 pictures, astronomers also noticed a lengthening of a narrow jet-like feature that may have been ejected from a newly forming star. The jet looks like a stream of water from a garden hose. Over the intervening 19 years, this jet has stretched farther into space, across an additional 60 billion miles, at an estimated speed of about 450,000 miles per hour.

Our Sun probably formed in a similar turbulent star-forming region. There is evidence that the forming solar system was seasoned with radioactive shrapnel from a nearby supernova. That means that our Sun was formed as part of a cluster that included stars massive enough to produce powerful ionizing radiation, such as is seen in the Eagle Nebula. "That's the only way the nebula from which the Sun was born could have been exposed to a supernova that quickly, in the short period of time that represents, because supernovae only come from massive stars, and those stars only live a few tens of millions of years," Scowen explained. 

"What that means is when you look at the environment of the Eagle Nebula or other star-forming regions, you're looking at exactly the kind of nascent environment that our Sun formed in."

Source: Space Telescope Science Institute (STScI)

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