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TEHRAN, Jun 4 -Scientists have for the first time observed a coronal mass ejection, CME, on the surface of a distant star.
TEHRAN, Young Journalists Club (YJC) -Until now, astronomers had only observed coronal mass ejections emanating from our own sun, but data collected by NASA's Chandra X-ray Observatory revealed a powerful eruption exploding from the surface of HR 9024, a distant star.
While surveying Chandra data, astronomers identified an explosion of X-rays followed by a large burst of plasma.
"The technique we used is based on monitoring the velocity of plasmas during a stellar flare," Costanza Argiroffi, astronomer at the University of Palermo in Italy, said in a news release. "This is because, in analogy with the solar environment, it is expected that, during a flare, the plasma confined in the coronal loop where the flare takes place moves first upward, and then downwards reaching the lower layers of the stellar atmosphere. Moreover, there is also expected to be an additional motion, always directed upwards, due to the CME associated with the flare."
HR 9024 is a rotational variable star in the constellation Andromeda. It is located about 450 light-years from Earth. Scientists identified a flare with promising characteristics. The team of astronomers used Chandra's High-Energy Transmission Grating Spectrometer to measure the movement of plasma associated with the flare.
Their measurements clocked the movement of extremely hot stellar material -- measuring 18 to 45 million degrees Fahrenheit -- at 225,000 to 900,000 miles per hour. The plasma first rises into the stellar atmosphere and then dives back toward the star's surface.
"This result, never achieved before, confirms that our understanding of the main phenomena that occur in flares is solid," said Argiroffi. "We were not so confident that our predictions could match in such a way with observations, because our understanding of flares is based almost completely on observations of the solar environment, where the most extreme flares are even a hundred thousand times less intense in the X-radiation emitted."
Scientists published their observations this week in the journal Nature Astronomy.
"The most important point of our work, however, is another: we found, after the flare, that the coldest plasma -- at a temperature of 'only' seven million degrees Fahrenheit -- rose from the star, with a constant speed of about 185,000 miles per hour," said Argiroffi. "And these data are exactly what one would have expected for the CME associated with the flare."
While the new findings proved bigger, younger stars produce larger, more powerful stellar flares and CMEs, researchers were expecting to clock the looping plasma at higher speeds. The lower speeds suggest the electromagnetic fields of young, active stars are less efficient at propelling plasma into the atmosphere.
Source: UPI
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