This “giant flare” of high-energy radiation was detected by NASA and European satellites on December 27, 2004. ‘The event affected our atmosphere quite noticeably’ – Prof. David Eichler.The brightest and most powerful energy flash from beyond the solar system ever detected in the modern era was foreseen by an Israeli scientist.
This “giant flare” of high-energy radiation was detected by NASA and European satellites on December 27, 2004, and the details were revealed on Friday at a special press conference. This huge explosion by a neutron star called a magnetar, halfway across the galaxy – 50,000 light years from Earth – packed so much power that it briefly altered Earth’s upper atmosphere and emitted radio waves, which are still being recorded by radio telescopes around the world.
The event registered on instruments aboard 15 spacecraft, including NASA’s new Swift satellite, which was designed to record cosmic gamma rays. Astronomers said that it gave off more energy in 0.2 seconds than the sun does in 100,000 to 200,000 years.
Physicist Prof. David Eichler, the Joan and Robert Arnow Professor of Astrophysics at Ben-Gurion University of the Negev, predicted such an event in an article he wrote three years ago. Eichler published an article, “Waiting for the Big One: a new class of soft gamma-ray repeater outbursts?” that appears to describe and anticipate events such as the one that occurred on December 27th.
“The event affected our atmosphere quite noticeably and this was detected by instruments all over the globe,” Eichler told ISRAEL21c.
“At a distance of 50,000 light years, if it had been only a dozen light years away, its effects would have been far more drastic and we can calculate just how damaging it would have been to life on earth. Fortunately, there aren?t magnetars that we know of that are located this distance to earth,” said Eichler, whose achievement in predicting the event was noted in the story on the flare in the New York Times.
Because of his expertise in the area of theoretical astrophysics, NASA called on Eichler and his with BGU colleague Dr. Yuri Lyubarsky to join the effort to comprehend and process exactly what happened, and the Israeli scientists are part of the teams which are analyzing and explaining this important event. The teams will be publishing discovery papers in an upcoming issue of the scientific journal Nature.
In his 2002 article, published in Monthly Notices of the Royal Astronomical Society, Eichler had theorized about the possibility of “a supergiant version of the largest soft gamma-ray bursts that have thus far been observed.” In his conclusion, he anticipated that such an outburst would be about 100 times more powerful than the previously observed giant flares.
Indeed, the light from December’s giant flare was brightest in the gamma-ray energy range, a far more energetic realm of the spectrum than visible light or X-rays. The event was caused by an eruption on the surface of a known, exotic neutron star located about 50,000 light years from Earth in the constellation Sagittarius.
Scientists have previously discovered about a dozen such neutron stars – called magnetars – because of their incredibly high magnetic fields. Such stars were hypothesized to exist and their ultra-strong magnetic fields were observationally confirmed by Dr. Chryssa Kouveliotou of NASA Marshall Space Fight Center in 1998.
Kouveliotou and Eichler have since become research partners, studying magnetars for the past two years in research funded by a grant from the Israel-U.S. Binational Science Foundation, with Kouveliotou coordinating the observation and Eichler focusing on the theory.
The magnetic field around a magnetar is about 1,000 trillion gauss, strong enough to reshape atoms and even affect the properties of empty space. (Ordinary neutron stars typically measure a mere trillion gauss; and the Earth’s magnetic field is about 0.5 gauss). Four of these magnetars are also called soft gamma repeaters, or SGRs, because they flare up occasionally and release gamma rays flashes.
Remarkably, the recent event was 100 times brighter than the brightest among any similar “giant flares” that had been recorded previously, challenging scientists to find an explanation for the magnitude of the released energy. This fits together with what Eichler predicted three years ago.
“The well known principle on which the hypothesis was based, that magnetic fields are unstable when embedded in a movable medium,” he explains, “can be seen if you take two small magnets and align their magnetic fields. If held close together, they like to flip – one relative to the other – so that the total magnetic field energy is reduced.
“Applying this to highly magnetized stars, one imagines that large parts of the star can get realigned relative to each other by a sufficiently powerful magnetic field. If such a thing were to happen, a significant fraction of the total magnetic energy would be released in a single flare (as much of the magnetic field annihilated), and a comparably large amount of energy would be spent on rearranging the face of the star.”
The surface magnetic field indeed emerged from the Dec. 27 th flare with an entirely different profile.
Eichler received his B.A. and his PhD in physics from MIT, and was a faculty member at the University of Maryland, before joining BGU in 1983. He said he has always been drawn to the somewhat esoteric field of cosmology.
“The fun in astrophysics starts with a sense of wonder and then it becomes surprisingly relevant to daily life. But only after you learn what you learned out of curiosity,” he says. “As to whether astrophysics affects life on earth – 100 years ago, we would have said ‘no way.’”
But today, he notes, scientists are far more aware of how events on earth can be changed by heavenly events. For example, a leading theory regarding the extinction of the dinosaurs was that it was caused by an astral event such as a supernova.
The flare that occurred in December, he said, “was probably as bright or even brighter than a supernova in our own galaxy, with its energy was concentrated in gamma rays which is a penetrating and damaging form of radiation. At a closer distance, something like this might have done more damage to our atmosphere than even a supernova would have.”
The reason, he said was that “a supernova is at least 10,000 times as energetic as this event, but the energy does not all go into radiation. In this case, most of the energy was released and it was almost all radiation and it was released within several tenths of a second. So the impulsive effects on the planet were greater than that of a supernova.”
According to the New York Times report, the magnetar flare might help solve a cosmic mystery of gamma ray bursts, the prime mission of the Swift satellite. Bursts lasting for minutes are believed to be caused by the collisions of black holes – events that are even more violent than magnetar flares, which occur much farther away – but astronomers had been at a loss to explain shorter bursts lasting a couple of seconds or less.
Now they have at least a partial answer: some of the bursts are magnetar flares originating from other galaxies. More answers are expected as Swift observes more gamma ray bursts, and it is likely that when they do, Eichler will be called upon once more to help explain what has happened.