Forum for Science, Industry and Business

NASA missions monitor a waking black hole

The outburst came from V404 Cygni, a binary system located about 8,000 light-years away that contains a black hole. Every couple of decades the black hole fires up in an outburst of high-energy light, becoming an X-ray nova. Until the Swift detection, it had been slumbering since 1989.

This is an artist's interpretation of Swift J1745-26, a newly discovered black hole with a flaring accretion disk. Downloadable: http://svs.gsfc.nasa.gov/cgi-bin/details.cgi?aid=11110

Credit: NASA SVS

An X-ray nova is a bright, short-lived X-ray source that reaches peak intensity in a few days and then fades out over a period of weeks or months. The outburst occurs when stored gas abruptly rushes toward a neutron star or black hole. By studying the patterns of the X-rays produced, astronomers can determine the kind of object at the heart of the eruption.

"Relative to the lifetime of space observatories, these black hole eruptions are quite rare," said Neil Gehrels, Swift's principal investigator at NASA's Goddard Space Flight Center in Greenbelt, Maryland. "So when we see one of them flare up, we try to throw everything we have at it, monitoring across the spectrum, from radio waves to gamma rays."

Astronomers classify this type of system as a low-mass X-ray binary. In V404 Cygni, a star slightly smaller than the sun orbits a black hole 10 times its mass in only 6.5 days. The close orbit and strong gravity of the black hole produce tidal forces that pull a stream of gas from its partner. The gas travels to a storage disk around the black hole and heats up to millions of degrees, producing a steady stream of X-rays as it falls inward.

But the disk flips between two dramatically different conditions. In its cooler state, the gas resists inward flow and just collects in the outer part of the disk like water behind a dam. Inevitably the build-up of gas overwhelms the dam, and a tsunami of hot bright gas rushes toward the black hole.

Astronomers relish the opportunity to collect simultaneous multiwavelength data on black hole binaries, especially one as close as V404 Cygni. In 1938 and 1956, astronomers caught V404 Cygni undergoing outbursts in visible light. During its eruption in 1989, the system was observed by Ginga, an X-ray satellite operated by Japan, and instruments aboard Russia's Mir space station.

"Right now, V404 Cygni shows exceptional variation at all wavelengths, offering us a rare chance to add to this unique data set," said Eleonora Troja, a Swift team member at Goddard.

Ongoing or planned satellite observations of the outburst involve NASA's Swift satellite, Chandra X-ray Observatory and Fermi Gamma-ray Space Telescope, as well as Japan's MAXI, the European Space Agency's INTEGRAL satellite, and the Italian Space Agency's AGILE gamma-ray mission. Ground-based facilities following the eruption include the 10.4-meter Gran Telescopio Canarias operated by Spain in the Canary Islands, the University of Leicester's 0.5-meter telescope in Oadby, U.K., the Nasu radio telescope at Waseda University in Japan, and amateur observatories.

V404 Cygni has flared many times since the eruption began, with activity ranging from minutes to hours. "It repeatedly becomes the brightest object in the X-ray sky -- up to 50 times brighter than the Crab Nebula, which is normally one of the brightest sources," said Erik Kuulkers, the INTEGRAL project scientist at ESA's European Space Astronomy Centre in Madrid. "It is definitely a 'once in a professional lifetime' opportunity."

In a single week, flares from V404 Cygni generated more than 70 "triggers" of the Gamma-ray Burst Monitor (GBM) aboard Fermi. This is more than five times the number of triggers seen from all objects in the sky in a typical week. The GBM triggers when it detects a gamma-ray flare, then it sends numerous emails containing increasingly refined information about the event to scientists on duty.

Every time the GBM recovered from one trigger, V404 Cygni set it off again, resulting in a torrent of emails. The event prompted David Yu, a GBM scientist at the Max Planck Institute of Extraterrestrial Physics in Garching, Germany, to comment on social media: "Achievement Unlocked: Mailbox spammed by a blackhole."

Lynn Chandler | EurekAlert!

Im Focus: Future electronic components to be printed like newspapers

A new manufacturing technique uses a process similar to newspaper printing to form smoother and more flexible metals for making ultrafast electronic devices.

The low-cost process, developed by Purdue University researchers, combines tools already used in industry for manufacturing metals on a large scale, but uses...

Im Focus: First evidence on the source of extragalactic particles

For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.

To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...

Im Focus: Magnetic vortices: Two independent magnetic skyrmion phases discovered in a single material

For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.

Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...

Im Focus: Breaking the bond: To take part or not?

Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.

A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...

Im Focus: New 2D Spectroscopy Methods

Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.

"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....