Cosmic Rays From Massive Star System May Reach Earth: NASA

Cosmic Rays From Massive Star System May Reach Earth


The most luminous and massive stellar system, Eta Carinae, within 10,000 light-years, is accelerating particles to high energies, some of which may reach the earth as cosmic rays, suggests a new study.  The researchers used data from NASA’s NuSTAR space telescope. The study was published in the journal Nature Astronomy.

An astrophysicist and lead author of the study, Kenji Hamaguchi at NASA’s Goddard Space Flight Centre said, “We know the blast waves of exploded stars can accelerate cosmic ray particles to speeds comparable to that of light, an incredible energy boost,” and further added, “Similar processes must occur in other extreme environments. Our analysis indicates Eta Carinae is one of them.

Astronomers know that cosmic rays with energies greater than one billion electron volts (eV) come to us from beyond our solar system. But because these particles, electrons, protons and atomic nuclei, all carry an electrical charge, they veer off course whenever they encounter magnetic fields. This scrambles their paths and masks their origins.

Eta Carinae, located about 7,500 light-years away in the southern constellation of Carina, is famous for a 19th-century outburst that briefly made it the second-brightest star in the sky. This event also ejected a massive hourglass-shaped nebula, but the cause of the eruption remains poorly understood.

The system contains a pair of massive stars whose eccentric orbits bring them unusually close every 5.5 years. The stars contain 90 and 30 times the mass of our Sun and pass 225 million km apart at their closest approach, about the average distance separating Mars and the Sun. NuSTAR detects a source emitting X-rays above 30,000 eV, some three times higher than can be explained by shock waves in the colliding winds.

Using both archival and newly take data, the team examined NuSTAR observations acquired between March 2014 and June 2016, along with lower-energy X-ray observations from the ESA (European Space Agency’s) XMM-Newton satellite over the same period.

The principal investigator of NuSTAR, Fiona Harrison said “We’ve known for some time that the region around Eta Carinae is the source of energetic emission in high-energy X-rays and gamma rays” and further added, “But until NuSTAR was able to pinpoint the radiation, show it comes from the binary and study its properties in detail, the origin was mysterious.”