Massive star system Eta Carinae is shooting cosmic rays at Earth

July 4 (UPI) — New observations by NASA’s NuSTAR space telescope suggest the super luminous star system Eta Carinae produces cosmic rays, some of which likely reach Earth.

Scientists have surmised that Eta Carinae, the brightest, most massive stellar system within 10,000 light-years of Earth, is capable of accelerating cosmic particles to speeds approaching the speed of light. Scientists also know that high-energy cosmic rays regularly collide with Earth’s magnetosphere. But because the paths of cosmic rays are scrambled by magnetic fields, tracing their origins is quite difficult.

Eta Carinae is a binary star system. The stars feature masses of 90 and 30 times the mass of the sun. Every 5.5 years, their eccentric orbits see the duo pass within 140 million miles of each other.

“Both of Eta Carinae’s stars drive powerful outflows called stellar winds,” Michael Corcoran, an astrophysicist at NASA’s Goddard Space Flight Center, said in a news release. “Where these winds clash changes during the orbital cycle, which produces a periodic signal in low-energy X-rays we’ve been tracking for more than two decades.”

NASA’s Fermi Gamma-ray Space Telescope has also observed a unique gamma ray signature emanating from the direction of Eta Carinae. However, the observations weren’t precise enough to confirm a link between the high-energy rays and the massive star system.

Enter NuSTAR, which can observe X-rays with higher energies than previous generations of X-ray telescopes. Using NuSTAR, researchers re-examined new and archival observations of Eta Carinae. The space telescopes revealed the low-energy X-rays originally spied by Fermi, but it also picked up high-energy X-rays produced by shock waves in the colliding winds. Some of the X-rays boasted energy exceeding 30,000 electron Volts. Visible light features energy ranging from 2 to 3 electron Volts.

The origin of these so-called hard X-rays varies with the orbits of the two massive stars, but the signatures of the outbursts match the gamma ray patterns first imaged by Fermi.

Scientists believe some of the particles accelerated to high energies by the colliding stellar winds likely escape the star system. A few likely reach Earth.

Researchers shared their conclusions this week in the journal Nature Astronomy.

“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,” said Fiona Harrison, the principal investigator of NuSTAR and a professor of astronomy at Caltech. “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.”


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