Some 3.9 billion years ago in the heart of a distant galaxy, the intense tidal pull of a monster black hole shredded a star that passed too close. When X-rays produced in this event first reached Earth on March 28, 2011, they were detected by NASA's Swift satellite, which notified astronomers around the world. Within days, scientists concluded that the outburst, now known as Swift J1644+57, represented both the tidal disruption of a star and the sudden flare-up of a previously inactive black hole.
Now astronomers using archival observations from Swift, the European Space Agency's (ESA) XMM-Newton observatory and the Japan-led Suzaku satellite have identified the reflections of X-ray flares erupting during the event. Led by Erin Kara, a postdoctoral researcher at NASA's Goddard Space Flight Center in Greenbelt, Maryland, and the University of Maryland, College Park (UMCP), the team has used these light echoes, or reverberations, to map the flow of gas near a newly awakened black hole for the first time.
"While we don't yet understand what causes X-ray flares near the black hole, we know that when one occurs we can detect its echo a couple of minutes later, once the light has reached and illuminated parts of the flow," Kara explained. "This technique, called X-ray reverberation mapping, has been previously used to explore stable disks around black holes, but this is the first time we've applied it to a newly formed disk produced by a tidal disruption."
Stellar debris falling toward a black hole collects into a rotating structure called an accretion disk. There the gas is compressed and heated to millions of degrees before it eventually spills over the black hole's event horizon, the point beyond which nothing can escape and astronomers cannot observe. The Swift J1644+57 accretion disk was thicker, more turbulent and more chaotic than stable disks, which have had time to settle down into an orderly routine. The researchers present the findings in a paper published online in the journal Nature on Wed., June 22.
One surprise from the study is that high-energy X-rays arise from the inner part of the disk. Astronomers had thought most of this emission originated from a narrow jet of particles accelerated to near the speed of light. In blazars, the most luminous galaxy class powered by supermassive black holes, jets produce most of the highest-energy emission.
"We do see a jet from Swift J1644, but the X-rays are coming from a compact region near the black hole at the base of a steep funnel of inflowing gas we're looking down into," said co-author Lixin Dai, a postdoctoral researcher at UMCP. "The gas producing the echoes is itself flowing outward along the surface of the funnel at speeds up to half the speed of light."
X-rays originating near the black hole excite iron ions in the whirling gas, causing them to fluoresce with a distinctive high-energy glow called iron K-line emission. As an X-ray flare brightens and fades, the gas follows in turn after a brief delay depending on its distance from the source.
"Direct light from the flare has different properties than its echo, and we can detect reverberations by monitoring how the brightness changes across different X-ray energies," said co-author Jon Miller, a professor of astronomy at the University of Michigan in Ann Arbor.
Swift J1644+57 is one of only three tidal disruptions that have produced high-energy X-rays, and to date it remains the only event caught at the peak of this emission. These star shredding episodes briefly activate black holes astronomers wouldn't otherwise know about. For every black hole now actively accreting gas and producing light, astronomers think nine others are dormant and dark. These quiescent black holes were active when the universe was younger, and they played an important role in how galaxies evolved. Tidal disruptions therefore offer a glimpse of the silent majority of supersized black holes.
"If we only look at active black holes, we might be getting a strongly biased sample," said team member Chris Reynolds, a professor of astronomy at UMCP. "It could be that these black holes all fit within some narrow range of spins and masses. So it’s important to study the entire population to make sure we’re not biased."
The researchers estimate the mass of the Swift J1644+57 black hole at about a million times that of the sun but did not measure its spin. With future improvements in understanding and modeling accretion flows, the team thinks it may be possible to do so.
ESA's XMM-Newton satellite was launched in December 1999 from Kourou, French Guiana. NASA funded elements of the XMM-Newton instrument package and provides the NASA Guest Observer Facility at Goddard, which supports use of the observatory by U.S. astronomers. Suzaku operated from July 2005 to August 2015 and was developed at the Japanese Institute of Space and Astronautical Science, which is part of the Japan Aerospace Exploration Agency, in collaboration with NASA and other Japanese and U.S. institutions.
NASA's Swift satellite was launched in November 2004 and is managed by Goddard. It is operated in collaboration with Penn State University in University Park, the Los Alamos National Laboratory in New Mexico, and Orbital Sciences Corp. in Dulles, Virginia, with international collaborators in the U.K., Italy, Germany and Japan.
By Francis Reddy
NASA's Goddard Space Flight Center, Greenbelt, Maryland #nasa #spaceexploration
Real-Life Good Will Hunting – Chinese Delivery Man Discovers Simpler Solution to Complex Math Problem
The Geneva-based nuclear research team have created what they hope to be ‘the worlds largest open source distribution cosmic ray telescope’… trying saying that after a couple of Friday, post-work tipples!
For those not in the know (of which I was one), a cosmic ray is a high-enery particle that travels to the earth from space, and the ray detector hopes to, well, detect them.
The team aim for homes all over the world to build their own detectors, sharing back the information with the aim of better understanding the activity of the rays on earth.
I'll hand over to Cosmic Pi co-founder Cosimo Cantini to explain in greater detail...
- US Department of StateSenior Foreign Service Officer, 1988 - present
- Hewlett-PackardDisc Memory Division, 1981 - 1983
- Jet Propulsion LaboratorySynthetic Aperture Radars, 1984 - 1985
- Boeing AerospaceSenior Engineer, 1985 - 1988
- California Institute of TechnologyBS Electrical Engineering
- Whitman CollegeBA Math/Physics
Ancient DNA study finds Phoenician from Carthage had European ancestry
A research team co-led by a scientist at New Zealand's University of Otago has sequenced the first complete mitochondrial genome of a 2500-y
CBS This Morning Video - Workers at the company built an innovative 3-D ...
Silicon Valley startup Carbon is preparing to launch an invention that could change how many industries do business. Workers at the company
ESP8266 Temperature and Humidity Web Server - Experiment
Not the Raspberry Pi Experiment as promised - But a Learning Experience! Since I just received a couple of ESP8266s I wanted to play with th
Sardauscan, the Sub-$30 DIY 3D Scanner — Open Source 3D Printable Files ...
The sooner that affordable 3D scanners are made available, the sooner the consumer side of the 3D printing market will expand. You see, curr
Killer Whales Spied from Drone's Eye View: Photos : DNews
For the first time, scientists have used an unmanned aerial vehicle to photograph killer whales from above.
The WIRED iPhone 6 Plus Review: Too Big to Fail, But Not to Bend | WIRED
Here's the best way to start an iPhone review: Goddamn do I love Android.
This Painstaking Recreation of Star Trek Redefines ‘Obsession’ | Underwi...
If Vic Mignogna bears a passing resemblance to James Tiberius Kirk, there's a reason for it: he's executive-producing (and directing, and st
Introduction to C language bitwise operators: " _BV " Macro (...cont)
/* The _BV() is a compiler macro defined as #define _BV( bit ) ( 1<<(bit) ) in which was included already indirectly through . It stands for
David Grayson's blog: Using I²C on the Raspberry Pi
Last night I succeeded in getting my Raspberry Pi to do some basic I²C (also known as I2C, TWI, or SMBus) communication. I had to look aroun