Black holes occur when a massive star dies and collapses with enough gravity that nothing, not even light, can escape from it.

Black holes can absorb the surrounding mass and grow – eventually turning into supermassive black holes that can lie at the center of galaxies.

Now a team of Indian astronomers believe they’ve found a black hole spinning at a rate that’s close to the maximum possible speed it can go.

They first noticed it from X-rays that were picked up by India’s first ever dedicated astronomy satellite, called AstroSat.

Black holes are characterised by spin and mass(Getty)

The X-rays were coming from a binary star system called 4U 1630-47 that contains the black hole, which is about 10 times the mass of our sun. As gas, dust and other matter were absorbed by the spinning black hole, the research team figured out it was spinning fast enough to suck up all the space around it.

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‘As black holes get created, mass and spin rate are two properties that characterise them,’ Sudip Bhattacharyya of TIFR, and principal investigator of Astrosat’s Soft X-ray Telescope (SXT), told Hindustan Times.

‘Mass can be measured more easily as it has a long-range effect because of gravity as the black hole gets created,’ he added.

According to Einstein’s theory of relativity, a rapidly spinning black hole makes space itself rotate.

Caption: Black hole. Computer artwork representing a black hole against a starfield. (Getty)

This effect, coupled with gas spiraling toward the black hole, can produce a rotating, tightly wound vertical tower of magnetic field that flings a large fraction of the inflowing gas away from the vicinity of the black hole in an energetic, high-speed jet.

And the team believe this particular black hole is spinning almost as fast as it’s possible to do so.

Including the black hole discovered by the AstroSat, there are only five black holes that have accurately measured high spin rates.

Even if you’re not taking spin rates into account, this black hole is one of only 20 others that have been spotted in the Milky Way galaxy.

Caption: This artwork shows a star being distorted by its close passage to a supermassive black hole at the centre of a galaxy. (Getty)

‘Measurements, especially of the spin rate are very difficult to make, and can be done only by high-quality X-ray observations in the correct state of the binary stellar system, in which the black hole is a gobbling matter from its companion star,’ said the lead author Mayukh Pahari.

The research, which was a joint effort between the USA and India, has been accepted for publication in The Astrophysical Journal.</s>India's first astronomy dedicated satellite, AstroSat, together with NASA's Chandra X-ray Observatory, helped scientists find an 'extremely exotic' black hole spinning close to the maximum possible rate. The black hole exists in the binary star system 4U 1630-47 and obviously cannot be directly seen, because nothing, not even light, can escape from a region around it, thus justifying the name of the object.

The gravity of such a collapsing core is so strong that its entire mass is crushed into a point, according to the research accepted for publication in The Astrophysical Journal.

Mass and spin classify a black hole

Relatively smaller black holes are exotic end states of massive stellar cores, said astronomers led by the Tata Institute of Fundamental Research (TIFR) in Mumbai.

Surprisingly, astronomical black holes are the simplest known objects in the universe, because they can be fully characterised by only two properties, mass and spin rate.

Therefore, measurements of these two properties are uniquely important to probe some extreme aspects of the universe and the fundamental physics related to them, researchers said.

"The scientific measurement of the spin rate of the black hole, an extremely exotic but the simplest object of the universe, comes out to be close to the maximum possible value," Sudip Bhattacharyya, the Associate Professor at TIFR and the Principal Investigator of the AstroSat Soft X-ray Telescope (SXT), told PTI.

"This is generally very important to probe some extreme aspects of the universe and the fundamental physics (for example, the theory of gravitation) related to them," said Bhattacharyya.

"Such measurements, especially of the spin rate, are very difficult to make, and can be done only by high-quality X-ray observations in the correct state of the binary stellar system, in which the black hole is gobbling matter from its companion star," said Mayukh Pahari, who started this work at TIFR, before joining the University of Southampton in the UK.

Also read | India launches its first satellite dedicated only for astronomy: All about it

Indian satellite AstroSat and its Soft X-ray Telescope (SXT)

AstroSat was launched in 2015 by the Indian Space Research Organisation (ISRO). It is the first dedicated astronomy satellite of India, and the SXT aboard AstroSat is the first Indian X-ray telescope.

"The SXT and the Large Area X-ray Proportional Counter (LAXPC) aboard the first dedicated Indian astronomy satellite AstroSat played a key role to measure the black hole spin rate, which was consistent with results from our contemporaneous Chandra satellite data," Mr Bhattacharyya added.

"From this first joint AstroSat-Chandra study of a black hole, that may lead to further such co-operations, we have found that the black hole in 4U 1630-47 spins very rapidly, with a rate not much less than the maximum possible rate, which makes it even more exotic," added Professor AR Rao of TIFR.

"In fact, apart from Japan, I believe, India is the first Asian country to build an X-ray Telescope (for example, China could not build such a telescope till now)," Bhattacharyya said.

He noted that this "first cooperation of India and US using AstroSat and Chandra satellites regarding black hole studies should open up ways for future such collaborations."

More about AstroSat

India's first astronomy dedicated satellite AstroSat is capable of making an observation in the ultraviolet, optical, low and high energy X-Rays wavebands at the same time. It comprises of five scientific instruments:

The UV Imaging Telescope

The Scanning Sky Monitor

The Cadmium-Zinc-Telluride Imager

The Soft X-ray Telescope, and

Three identical Large Area Xenon Proportional Counters

Tata Institute of Fundamental Research, Indian Institute of Astrophysics, Inter-University Centre for Astronomy and Astrophysics, and Raman Research Institute joined ISRO in the development of payload.

Two of the payloads were made in collaboration with Canadian Space Agency (CSA) and University of Leicester, UK.

Also read | 'Vampire' star caught feeding on bigger star by Astrosat

Interested in General Knowledge and Current Affairs? Click here to stay informed and know what is happening around the world with our G.K. and Current Affairs section.

To get more updates on Current Affairs, send in your query by mail to education.intoday@gmail.com</s>Indian space agency Tata Institute of Fundamental Research (TIFR) reported a black hole within the Milky Way is spinning so fast it is changing the face of space around it. The black hole, found in the binary star system called 4U 1630-47, was spotted thanks to the X-rays it was emitting by India's AstroSat and Nasa's Chandra X-Ray Observatory. Albert Einstein theorised in his famous theory of relativity that nothing can move faster than the speed of light – 670 million miles an hour (299,792,458 metres per second). However, the black hole, which was originally observed in 2016, is close to breaking this universal limit as it spirals at 90 percent of this speed.

The rapid movement of the black hole is causing gas, dust and other celestial debris to be sucked in by the entity at a more rapid pace than usual. However, this also meant it was spewing more materials out in the form of X-rays which made it easier to observed. Speaking to the Hindustan Times, Sudip Bhattacharyya of TIFR, and principal investigator of Astrosat's Soft X-ray Telescope (SXT), said of the results which will be published in next month’s Astrophysical Journal: “As black holes get created, mass and spin rate are two properties that characterise them. “Mass can be measured more easily as it has a long-range effect because of gravity as the black hole gets created.”

Only four black holes have been found to spin at such an extreme pace. The first was discovered in 2008 using NASA’s Chandra X-ray Observatory. Lead author Rodrigo Nemmen said at the time: "We think these monster black holes are spinning close to the limit set by Einstein's theory of relativity, which means that they can drag material around them at close to the speed of light.</s>Black holes, while fascinating, are hardly a new discovery - but a black hole spinning at one of the highest speeds ever, according to the Hindustan Times, is a completely different story - especially when there have only ever been four others like it.

In 2016, India's first dedicated astronomy satellite, the AstroSat, spotted a black hole in the binary star system called 4U 1630-47, which is bursting out X-rays that astronomers found unusual.

Those X-rays were caused by gas and dust falling into the black hole, which is about 10 times the mass of the Sun, and they revealed to researchers that the object is spinning very, very rapidly.

In fact, according to NASA this particular black hole is spinning very close to the limit set by Albert Einstein's theory of relativity, according to Rodrigo Nemmen, the lead author on the research paper. That means it is spinning close to the speed of light.

Currently, scientists only have two ways of measuring black holes - either by their mass or by their spin rate. A spin rate can be anywhere between 0 and 1: this black hole was spinning at the rate of 0.9.

Einstein's theory further implies that if a black hole is spinning that fast, then it is capable of making space itself rotate.

In fact, if the conditions around black holes are hypothesised to be correct, then the high spin rate coupled with the gaseous elements entering the black hole and high temperatures, could be the key to understanding how galaxies are formed.

Including the black hole discovered by the AstroSat, there are only five black holes that have accurately measured high spin rates. Even if you're not taking spin rates into account, this black hole is one of only 20 others that have been spotted in the Milky Way galaxy.

The Indian Space Research Organisation's (ISRO) AstroSat along with the National Aeronautics and Space Administration's (NASA) Chandra X-Ray Observatory have confirmed the speed of the spinning black hole.

The study was conducted by researchers from multiple institutions led by the Tata Institute of Fundamental Research (TIFR) and has been accepted for publication in The Astrophysical Journal.

This article was originally published by Business Insider.</s>An international team of astronomers has confirmed the discovery of a black hole which spins very close to the limit set by Albert Einstein's theory of relativity, which means that it spins close to the speed of light, according to Business Insider.

The black hole was first tracked in the binary stellar system 4U 1630−47 in 2016 by the Indian Space Research Organization (ISRO)'s AstroSat, in coordination with the National Aeronautics and Space Administration (NASA)'s Chandra X-ray Observatory.

READ MORE: Astronomers Capture Black Hole Devouring Cosmic Doughnut for First Time

Researchers then used the X-ray data from AstroSat and Chandra to calculate that the black hole is spinning a rate of 0.9, which is close to the celestial object's maximum possible rate of 1.

In this context, Business Insider quoted Rodrigo Nemmen, one of the lead authors of the research, as saying that Einstein's theory of relativity "further implies that if a black hole is spinning that fast, then it is capable of making space itself rotate."

READ MORE: Astronomers Discover Monster Black Hole the Size of 20 Billion Suns

Astronomers said that the discovery of the black hole, which is only one of five having an accurately measured high spin rate, may contribute greatly to uncovering the truth about the origin of the Universe.</s>One of the fastest black holes ever seen is spinning so fast it is moving space itself.

X-rays from a star system within the Milky Way revealed the presence of the black hole.

Analysis of these high-energy waves revealed the black hole has a mass ten times greater than that of our sun and is rotating close to the speed of light.

There have only ever been four other black holes found to be spinning at such a speed.

This intergalactic speed limit of 670 million miles an hour (299,792,458 metres per second) was first proposed by Albert Einstein via his famed theory of relativity.

X-rays from the distant binary star system 4U 1630-47 revealed the black hole's existence when they were detected by India's AstroSat and Nasa's Chandra X-Ray Observatory.

These observations, first taken in 2016, have revealed that the black hole is moving at 90 per cent of the maximum spin rate.

Rapid movement caused gas, dust and other celestial debris to be absorbed by the black hole's enormous gravity.

Analysis from the researchers discovered this was happening as a result of the black hole spinning fast enough to suck up matter in the nearby vicinity.

'As black holes get created, mass and spin rate are two properties that characterise them,' Sudip Bhattacharyya of Tata Institute of Fundamental Research, and principal investigator of Astrosat's Soft X-ray Telescope (SXT), told Hindustan Times.

'Mass can be measured more easily as it has a long-range effect because of gravity as the black hole gets created,' he added.

This black hole is also believed to be one of only 20 in the Milky Way.

The speed of the black hole has been confirmed by both the US and India, who collaborate don the research project which is due to be published in The Astrophysical Journal.</s>A massive black hole is spinning so fast that it tests the limits of Einstein's theory of relativity and may rotate space around itself, according to a joint study by India's AstroSat and NASA's Chandra X-Ray Observatory.

The black hole in question is roughly 10 times the mass of the Sun and one of only five with an accurately measured spin rate this fast, close to the speed of light.

India's first dedicated astronomy satellite, Astrosat, launched back in 2015, observed the frenetic pace of the black hole, with findings later confirmed by NASA’s Chandra X-Ray Observatory.

Scientists measure black holes in terms of their mass or their spin rate, which ranks on a scale of 0 to 1. This black hole, in the binary star system 4U 1630-47, has been clocked at a phenomenal rate of 0.9 - in other words, very close to the limit set by Einstein’s theory of relativity.

The incredible void might also provide the key to understanding how galaxies form.

Gas, dust and other mass from the 4U 1630-47 system’s star gets torn away and forms a disk around the black hole, reaching temperatures of over 10 million degrees Celsius and blasting out x-rays monitored and measured by the Chandra Observatory. The overall system generates more than 10,000 times the power emitted by our sun.

Think your friends would be interested? Share this story!</s>Roughly one billion light-years from Earth, a giant elliptical galaxy has been found to be an enthusiastic recycler - albeit not of plastic bottles. The supermassive black hole at its core is blasting cold molecular gas, which is then falling into the black hole, and feeding the cycle anew.

Such a phenomenon is known as a "fountain", a galactic means of recycling star-forming material; long theorised, it's never before been observed in its entirety.

Astronomers found this amazing scene in a galaxy at the heart of a cluster known as Abell 2597.

"This is possibly the first system in which we find clear evidence for both cold molecular gas inflow toward the black hole and outflow or uplift from the jets that the black hole launches," explained Grant Tremblay of the Harvard-Smithsonian Center for Astrophysics.

"The supermassive black hole at the centre of this giant galaxy acts like a mechanical pump in a fountain."

A black hole, of course, doesn't actually spew out material. As an active black hole "feeds", material forms an accretion disc of swirling material that falls into it, like water swirling down a drain. But not all the material ends up swallowed by the black hole.

Some of it is funnelled towards the poles, possibly via magnetic field lines, much like charged particles from solar wind travel along Earth's magnetic field lines to produce aurora.

But the dynamics of a black hole are different; instead of aurora, they produce powerful jets of plasma, travelling at near light-speed into space, blasted out from their polar region.

In the case of the supermassive black hole powering Abell 2597's brightest cluster galaxy (BCG), its jets blast cold molecular gas 9 kiloparsecs (30,000 light-years) into space.

This cold gas then rains back down into the reservoir that feeds into the black hole's accretion disc - a vast filamentary nebula, with a mass equivalent to around 3 billion Suns, spanning 30 kiloparsecs (100,000 light-years) across in the galaxy's centre.

Tremblay and his team first observed this rain back in 2016 using the Atacama Large Millimeter/submillimeter Array (ALMA). They observed molecules of carbon monoxide, some with temperatures as low as 13-23 Kelvin (-260 to -250 degrees Celsius, or -438 to -418 degrees Fahrenheit), falling towards the black hole.

Above: This composite image shows the cold infalling gas in yellow from ALMA data, and the hot outflowing gas in red from MUSE data.

Since then, the team connected it to earlier observations made using the MUSE instrument on the ESO's Very Large Telescope. It saw the warmer gas being blasted into space by the black hole's jets.

Follow-up observations using NASA's Chandra X-ray Observatory confirmed this connection - marking the first evidence that the outflow and inflow are part of the same process.

"This very, very hot gas can quickly cool, condense, and precipitate in much the same way that warm, humid air in Earth's atmosphere can spawn rain clouds and precipitation," Tremblay explained in 2016.

"The newly condensed clouds then rain in on the galaxy, fuelling star formation and feeding its supermassive black hole."

The result may only be the first time these two parts of the process have been put together, but it could be quite a common part of galactic evolution, the researchers believe. It could shed some light on star formation, the way black holes feed, and the overall life cycle of galaxies.

The research has been published in The Astrophysical Journal, and can be read on preprint resource arXiv.</s>(CNN) -- There was enough happening on Earth to keep us occupied this week, but don't forget to look up once in a while. Here's everything galactic you missed during Halloween and early voting.

Two historic NASA missions ran out of fuel this week: the 11-year Dawn mission to explore the two biggest objects in the asteroid belt and the nine-year Kepler Space Telescope mission that discovered thousands of exoplanets.

Although both mission conclusions were expected, it's sad to see them come to an end. Luckily, the data they provided will lead to discoveries for years to come. And neither is on a collision course with Earth. Dawn will orbit the dwarf planet Ceres for decades, and Kepler is 94 million miles away.

Farewell, brave voyagers, and thanks for all the science.

But let's give the Parker Solar Probe a hearty cheer for breaking a record and coming closer to the sun than any other spacecraft.

Despite our letter to the Mars Opportunity rover, it still hasn't awakened and responded to NASA's many messages since it became shrouded in a planet-encircling dust storm that began in May.

NASA will continue to send more messages, and scientists hope that increasing winds will knock the dust off of Oppy's solar panels.

Meanwhile, NASA's Hubble Space Telescope is back in business and making observations again.

A gyro, or device that measures the speed at which the spacecraft is turning, had failed. This meant Hubble couldn't turn and lock on to new targets. A backup gyro turned out to be no help when it malfunctioned as well.

The backup was recovered, so expect more gorgeous images from the famed space telescope.

NASA's Chandra X-ray Observatory, which also had a gyro issue recently, is also back up and running.

Speaking of Hubble, the space telescope captured an image called a bat shadow 1,300 light-years away in the stellar nursery known as the Serpens Nebula.

So what is it? A sun-like star, HBC 672, is surrounded by a big dusty debris ring. But Hubble can't see that ring. Instead, it's capturing the shadow of the ring created by the star's bright light. NASA scientists compared the large shadow to what happens when something small crosses in front of a flashlight beam.

"This is an analog of what the solar system looked like when it was only 1 or 2 million years old," explained Klaus Pontoppidan, an astronomer at the Space Telescope Science Institute. "For all we know, the solar system once created a shadow like this."

If you were in space, the last thing you'd want to get too close to is a black hole, the terrifyingly destructive and insatiable garbage disposals of the universe. Once you're near one, you're really past the point of no return.

Many astronomers assume that a supermassive black hole is at the center of the Milky Way, our galaxy. That's because they tend to lurk at the center of other galaxies, too.

But for the first time, material has been seen circling the drain, so to speak. The European Southern Observatory's GRAVITY instrument observed bright radiation flares around the disc belonging to Sagittarius A, this massive object at the galactic center.

"It's mind-boggling to actually witness material orbiting a massive black hole at 30% of the speed of light," said Oliver Pfuhl, a scientist at the Max Planck Institute for Extraterrestrial Physics.

It makes for a trippy image, too.

Have you ever wondered why there are so many stars in our galaxy? It turns out that the Milky Way's halo was gifted -- well, kind of.

Galaxies aren't exactly friendly neighbors in the universe. Instead, they tend to merge or cannibalize one another. The Milky Way is one of the largest galaxies, and astronomers are trying to figure out whether it grew after many small mergers or just a few large ones. Sometimes, the evidence of these mergers can be found using "galactic fossils" or just following an unusual stream of stars.

New data from the Gaia satellite mission, published this week, revealed that 10 billion years ago, the Milky Way merged with another large galaxy, Gaia-Enceladus. The stars from that galaxy make up most of the Milky Way's halo and helped shape its thick disk.

The stars donated by the merger stand out from the "native stars" of our galaxy because they're younger, the researchers said.

And in about 4 billion years, the Milky Way will collide with the neighboring gigantic Andromeda galaxy. So there's that to look forward to.

After two years of trekking through space for a date with an asteroid, NASA's OSIRIS-REx spacecraft is sending images of the primitive asteroid Bennu.

The spacecraft and asteroid will have their official rendezvous in December. And then we'll have some photos with color filters on them. Can't wait to see the Instagram of that date.</s>On Aug. 17, 2017, Fermi detected the first light ever seen from a source of gravitational waves—ripples in space-time produced, in this event, by the merger of two superdense neutron stars. Just five weeks later, a single high-energy particle discovered by the National Science Foundation's (NSF) IceCube Neutrino Observatory was traced to a distant galaxy powered by a supermassive black hole thanks to a gamma-ray flare observed by Fermi.

"For millennia, light was our only source of information about the universe," said Julie McEnery, the Fermi project scientist at NASA's Goddard Space Flight Center in Greenbelt, Maryland. "The recent discoveries connect light, our best-known cosmic courier, to gravitational waves and particles like neutrinos—new messengers delivering different kinds of information that we're just beginning to explore."

The origins of these discoveries stretch back to cutting-edge research as long ago as 1887. That's when physicists Albert Michelson and Edward Morley conducted an experiment to detect a substance, called the aether, which was postulated as a medium that permitted light waves to travel through space. As their experiment showed and many since have confirmed, the aether doesn't exist. But the negative result proved to be one of the inspirations for Albert Einstein's 1905 special theory of relativity. He generalized this into a full-fledged theory of gravity in 1915, one that predicted the existence of gravitational waves.

A century later, on Sept. 14, 2015, the NSF's Laser Interferometer Gravitational-Wave Observatory (LIGO) detected these space-time vibrations for the first time as waves from the merger of two black holes reached Earth. In between came a steady stream of advances, including lasers, improved instrumentation and increasingly more powerful computers and software.

"Just as inventing the detector technologies has taken decades, so too has the theoretical and computational framework for analyzing and interpreting multimessenger observations," said Tyson Littenberg, the principal investigator of the LIGO research group at NASA's Marshall Space Flight Center in Huntsville, Alabama. "We went through countless simulations to test new ideas and improve on existing algorithms so that we were prepared to make the most out of the first observations, and that basic research and development work continues."

Until 2005, it wasn't even possible to simulate in detail what happens when a pair of orbiting black holes coalesce. The breakthrough came when separate teams at Goddard and the University of Texas at Brownsville independently developed new computational methods that overcame all previous hurdles. An accurate understanding of gravitational-wave signals was one important step in evolving techniques designed to rapidly detect and characterize them.

"Another fundamental development was the highly optimized analysis pipelines and information technology infrastructure that can compare the theoretical model with the data, recognize the presence of a signal, calculate the location of the source on the sky and format the information in a way that the rest of the astronomical community could use," explained Tito Dal Canton, a NASA Postdoctoral Program Fellow and a member of a LIGO research group at Goddard led by Jordan Camp.

Astronomers need to know about short-lived events as soon as possible so they can bring to bear a wide array of telescopes in space and on the ground. Back in 1993, scientists at Goddard and Marshall began developing an automated system for distributing the locations of gamma-ray bursts (GRBs)—distant, powerful explosions that typically last a minute or less—to astronomers around the world in real time. Located at Goddard and led by Principal Investigator Scott Barthelmy, the Gamma-ray Coordinates Network/Transient Astronomy Network now distributes alerts from many space missions as well as ground-based instruments like LIGO and IceCube.

The historical thread for neutrinos began with French physicist Henri Becquerel and his 1895 discovery of radioactivity. In 1930, after studying a radioactive process called beta decay, Wolfang Pauli suggested it likely involved a new subatomic particle, later dubbed the neutrino. We now know neutrinos possess little mass, travel almost as fast as light, come in three varieties and are among the most abundant particles in the universe. But because they don't readily interact with other matter, neutrinos weren't discovered until 1956.

In 1912, Victor Hess discovered that charged particles, now called cosmic rays, continually enter Earth's atmosphere from every direction, which means space is filled with them. When cosmic rays strike air molecules, the collision produces a shower of particles—including neutrinos—that rains down through the atmosphere. Searching for astronomical neutrino sources meant placing experiments underground to reduce interference from cosmic rays and building very large detectors to tease out the weak signals of publicity-shy neutrinos.

Neutrinos produced by nuclear reactions inside the Sun's core were first detected in 1968 thanks to an experiment using 100,000 gallons of dry-cleaning fluid located deep in a South Dakota gold mine. Discovering the next astronomical neutrino source would take another 19 years. Supernova 1987A, a stellar explosion in a nearby galaxy, remains the brightest and closest supernova seen in over 400 years and is the first for which the original star could be identified on pre-explosion images. Theorists anticipated that neutrinos, which escape a collapsing star more readily than light, would be the first signal from a new supernova. And hours before 1987A's visible light arrived at Earth, experiments in Japan, the U.S. and Russia detected a brief burst of neutrinos, making the supernova the first source of neutrinos identified beyond the solar system.

On Aug. 17, 2017, gravitational waves from a neutron star merger produced a signal detected by the Laser Interferometer Gravitational-Wave Observatory (LIGO). The sound in this video represents the same frequencies as the combined stretching and squeezing caused by waves passing through the LIGO detectors at Hanford, Washington, and Livingston, Louisiana. Just 1.7 seconds later, a brief burst of gamma-rays — indicated by a ping — was seen by NASA's Fermi Gamma-ray Space Telescope. Credit: NASA's Goddard Space Flight Center, Caltech/MIT/LIGO Lab "If none of these experiments was operating at the time, the neutrino signal would have passed by unnoticed," said Francis Halzen, the principal investigator of IceCube, which is essentially a neutrino telescope build into a cubic kilometer of ice at the South Pole. "It isn't enough to develop the technology, refine theories or even construct a detector. We need to be making observations as often as we can for the best chance of catching brief, rare and scientifically interesting events. Both Fermi and IceCube are operating continuously, making uninterrupted observations of the sky."

The third historical thread belongs to gamma rays, the highest-energy form of light, discovered in 1900 by the French physicist Paul Villard. When a gamma ray of sufficient energy interacts with matter, it provides a perfect demonstration of Einstein's most famous equation, E=mc2, by instantly transforming into particles—an electron and its antimatter counterpart, a positron. Conversely, crash an electron and a positron together and a gamma ray results.

NASA's Explorer 11 satellite, launched in 1961, detected the first gamma rays in space. In 1963, the U.S. Air Force began launching a series of satellites as part of Project Vela. These increasingly sophisticated satellites were designed to verify compliance with an international treaty that banned nuclear weapons tests in space or in the atmosphere. But starting in July 1967, scientists became aware the Vela satellites were seeing brief gamma-ray events that were clearly unrelated to weapons tests.

These explosions were GRBs, an entirely new phenomenon now known to mark the death of certain types of massive stars or the merger of orbiting neutron stars. NASA further explored the gamma-ray sky with the Compton Gamma Ray Observatory, which operated from 1991 to 2000 and recorded thousands of GRBs. Starting in 1997, critical observations by the Italian-Dutch BeppoSAX satellite proved that GRBs were located far beyond our galaxy. Compton was succeeded by NASA's Neil Gehrels Swift Observatory in 2004 and Fermi in 2008, missions that continue exploring the high-energy sky and that follow up on LIGO and IceCube alerts.

"In the fields of observation, chance favors only the prepared mind," noted Louis Pasteur, the French chemist and microbiologist, in an 1854 lecture. Supported by decades of scientific discoveries and technological innovation, the burgeoning field of multimessenger astronomy is increasingly prepared for its next stroke of luck.

More information: For more about NASA's Fermi mission, visit www.nasa.gov/fermi
NASA's Chandra X-ray Observatory confirms earlier observations by Indian Space Research Organisation's Astrosat space observatory of a rotating black hole in the binary star system 4U1630-47, which is spinning close to the speed of light, one of the fastest ever observed.