Mysterious rare five-hour space explosion explained

The X-ray image from the Swift X-ray Telescope of the gamma-ray burst GRB 130925. 

The white object in the center is the gamma-ray burst. 

The large diffuse region to the right is a cluster of galaxies. 

The other objects are X-ray-emitting celestial objects, most likely supermassive black holes at the centers of distant galaxies. 

The full image is approximately the size of the full moon. 

Credit: Phil Evans/ University of Leicester

Next week in St. Petersburg, Russia, scientists on an international team that includes Penn State University astronomers will present a paper that provides a simple explanation for mysterious ultra-long gamma-ray bursts, a very rare form of the most powerful explosions in the universe.

"The recent discovery of ultra-long gamma-ray bursts raised questions about whether some new physics is required to explain them, but our work suggests a much simpler explanation," said David Burrows, a Penn State professor of astronomy and astrophysics.

"Our analysis reveals that these rare gamma-ray bursts, which can last for hours, can be explained as standard explosions occurring in a region with a low density of matter that is located behind a cloud of dust when viewed from Earth."

Dick Willingale, an astronomer at the University of Leicester and a co-author of the study, said, "Not only is this result significant scientifically, but it shows the importance of international collaborations to build observatories, and of sharing information between those observatories."

Burrows is the lead scientist for the X-Ray Telescope on board the Swift satellite, one of two space observatories that the scientists used to collect data from the gamma-ray burst named GRB 130925A, which they observed last year while the energy from its explosion streamed toward Earth for more than five hours.

Swift is a NASA-led collaboration with Penn State in the United States, the University of Leicester and University College-London in the United Kingdom, and the Italian space agency and Brera Observatory in Italy.

The scientists also observed the ultra-long gamma-ray burst with the US/Russian satellite Konus-Wind.

"We could not have reached our conclusions without the Swift and Konus teams working together," Willingale said.

Burrows said it is not surprising that some gamma-ray bursts occur in a low-density region, nor is it surprising when one occurs behind a dust cloud.

"Our analysis of the observations from the two observatories shows that these two conditions existing simultaneously can explain our observations of the ultra-long gamma-ray burst GRB 130925A," Burrows said.

"One reason that these results are satisfying is that scientists generally prefer to find the simplest explanations for mysterious phenomena," he said.

VLBI Network: Trio of Huge Black Holes in Distant Galaxy's Core

Two closely orbiting black holes in a galaxy about 4.2 billion light-years from Earth emit wavy jets while the third black hole in the trio is more distant, emitting linear jets. 

Research shows these kinds of systems are more common than originally believed. Image released June 25, 2014.

Credit: : © Roger Deane (large image); NASA Goddard (inset bottom left; modified from original)

Scientists have just discovered a distant galaxy with not one but three supermassive black holes at its core.

The new finding suggests that tight-knit groups of these giant black holes are far more common than previously thought, and it potentially reveals a new way to easily detect them, researchers say.

Supermassive black holes millions to billions of times the mass of the sun are thought to lurk at the hearts of virtually every large galaxy in the universe.

Most galaxies have just one supermassive black hole at their center. However, galaxies evolve through merging, and merged galaxies can sometimes possess multiple supermassive black holes.

Astronomers observed a galaxy with the alphabet soup name of SDSS J150243.09+111557.3, which they suspected might have a pair of supermassive black holes.

It lies about 4.2 billion light-years away from Earth, about "one-third of the way across the universe," said lead study author Roger Deane, a radio astronomer at the University of Cape Town in South Africa.

To investigate this galaxy, the scientists combined the signals from large radio antennas separated by up to 6,200 miles (10,000 kilometers), a technique called Very Long Baseline Interferometry (VLBI).

Using the European VLBI Network, the researchers could see details 50 times finer than is possible with the Hubble Space Telescope.

The astronomers unexpectedly discovered that the galaxy was actually not home to two supermassive black holes, but three.

Two of the black holes in this trio are very close together, which previously made them look like one black hole.



"All three of the black holes have masses around 100 million times that of the sun," Deane told reporters.

Scientists had previously known of four triple black-hole systems. However, the closest pairs of black holes in those triplets are about 7,825 light-years apart.

In this newfound trio of supermassive black holes, the closest pair of black holes is only about 455 light-years apart, "a very close pair of black holes," Deane said, the second-closest pair of supermassive black holes known.

The researchers found this "tight pair" of black holes after searching only six candidate galaxies. This suggests that tight pairs of supermassive black holes "are far more common than previous observations have found," Deane said.

Knowing how often supermassive black holes merge is key to discovering how they might influence their galaxies, the researchers noted. Supermassive black holes can shape the evolution of their galaxies with blasts of energy given off by turbulent matter, which gets sucked toward the black holes.

Although tight pairs of supermassive black holes might previously have been difficult to tell apart, the researchers discovered that the pair they saw left a helical or corkscrew-like pattern in the large jets of radio waves they emitted.

This suggests that twisted jets may serve as easy-to-find signals of tight pairs without the need for extremely high-resolution telescopic observations, such as those from the European VLBI Network.

"The twisted radio jets associated with close pairs may be a very efficient way to find more of these systems that are even closer together," Deane said.

ILLUSTRIS: Astronomers create first realistic virtual universe

Move over, Matrix - astronomers have done you one better. They have created the first realistic virtual universe using a computer simulation called "Illustris."

Illustris can recreate 13 billion years of cosmic evolution in a cube 350 million light-years on a side with unprecedented resolution.

Mark Vogelsberger

"Until now, no single simulation was able to reproduce the universe on both large and small scales simultaneously," says lead author Mark Vogelsberger (MIT/Harvard-Smithsonian Center for Astrophysics), who conducted the work in collaboration with researchers at several institutions, including the Heidelberg Institute for Theoretical Studies in Germany.

These results are being reported in the May 8th issue of the journal Nature.

Previous attempts to simulate the universe were hampered by lack of computing power and the complexities of the underlying physics.

As a result those programs either were limited in resolution, or forced to focus on a small portion of the universe.

Earlier simulations also had trouble modeling complex feedback from star formation, supernova explosions, and supermassive black holes.

Illustris employs a sophisticated computer program to recreate the evolution of the universe in high fidelity. It includes both normal matter and dark matter using 12 billion 3-D "pixels," or resolution elements.

Large scale projection through the Illustris volume at z=0, centered on the most massive cluster, 15 Mpc/h deep. 

Shows dark matter density (left) transitioning to gas density (right). 

Credit: Illustris Collaboration

The team dedicated five years to developing the Illustris program.

The actual calculations took 3 months of "run time," using a total of 8,000 CPUs running in parallel.

If they had used an average desktop computer, the calculations would have taken more than 2,000 years to complete.

The computer simulation began a mere 12 million years after the Big Bang. When it reached the present day, astronomers counted more than 41,000 galaxies in the cube of simulated space.

Importantly, Illustris yielded a realistic mix of spiral galaxies like the Milky Way and football-shaped elliptical galaxies.

It also recreated large-scale structures like galaxy clusters and the bubbles and voids of the cosmic web. On the small scale, it accurately recreated the chemistries of individual galaxies.

Large scale projection through the Illustris volume at z=0, centered on the most massive cluster, 15 Mpc/h deep. 

Shows dark matter density overlaid with the gas velocity field. 

Credit: Illustris Collaboration

Since light travels at a fixed speed, the farther away astronomers look, the farther back in time they can see.

A galaxy one billion light-years away is seen as it was a billion years ago.

Telescopes like Hubble can give us views of the early universe by looking to greater distances.

However, astronomers can't use Hubble to follow the evolution of a single galaxy over time.

"Illustris is like a time machine. We can go forward and backward in time. We can pause the simulation and zoom into a single galaxy or galaxy cluster to see what's really going on," says co-author Shy Genel of the CfA.

The team is releasing a high-definition video, which morphs between different components of the simulation to highlight various layers (e.g. dark matter density, gas temperature, or chemistry).

They also are releasing several smaller videos and associated imagery online

More information: Paper: dx.doi.org/10.1038/nature13316