NASA’s NuSTAR mission proves superstar Eta Carinae shoots cosmic rays

A conclusive evidence that the high-energy emission indeed originates from non-thermal particles accelerated at colliding wind shocks.

Eta Carinae's great eruption in the 1840s created the billowing Homunculus Nebula, imaged here by Hubble. Now about a light-year long, the expanding cloud contains enough material to make at least 10 copies of our Sun. Astronomers cannot yet explain what caused this eruption. Credit: NASA, ESA, and the Hubble SM4 ERO Team
Eta Carinae's great eruption in the 1840s created the billowing Homunculus Nebula, imaged here by Hubble. Now about a light-year long, the expanding cloud contains enough material to make at least 10 copies of our Sun. Astronomers cannot yet explain what caused this eruption. Credit: NASA, ESA, and the Hubble SM4 ERO Team

Astronomers know that cosmic rays with energies more prominent than 1 billion electron volts (eV) come to us from beyond nearby planetary group. But since these particles — electrons, protons and atomic nuclei — all convey an electrical charge, they veer off course at whatever point they experience attractive fields. This scrambles their ways and veils 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.

A new study using data from NASA’s NuSTAR space telescope suggests that Eta Carinae, the most luminous and massive stellar system within 10,000 light-years, is accelerating particles to high energies — some of which may reach Earth as cosmic rays.

Eta Carinae shines in X-rays in this image from NASA's Chandra X-ray Observatory. The colors indicate different energies. Red spans 300 to 1,000 electron volts (eV), green ranges from 1,000 to 3,000 eV and blue covers 3,000 to 10,000 eV. For comparison, the energy of visible light is about 2 to 3 eV. NuSTAR observations (green contours) reveal a source of X-rays with energies some three times higher than Chandra detects. X-rays seen from the central point source arise from the binary’s stellar wind collision. The NuSTAR detection shows that shock waves in the wind collision zone accelerate charged particles like electrons and protons to near the speed of light. Some of these may reach Earth, where they will be detected as cosmic ray particles. X-rays scattered by debris ejected in Eta Carinae's famous 1840 eruption may produce the broader red emission. Credits: NASA/CXC and NASA/JPL-Caltech
Eta Carinae shines in X-rays in this image from NASA’s Chandra X-ray Observatory. The colors indicate different energies. Red spans 300 to 1,000 electron volts (eV), green ranges from 1,000 to 3,000 eV and blue covers 3,000 to 10,000 eV. For comparison, the energy of visible light is about 2 to 3 eV. NuSTAR observations (green contours) reveal a source of X-rays with energies some three times higher than Chandra detects. X-rays seen from the central point source arise from the binary’s stellar wind collision. The NuSTAR detection shows that shock waves in the wind collision zone accelerate charged particles like electrons and protons to near the speed of light. Some of these may reach Earth, where they will be detected as cosmic ray particles. X-rays scattered by debris ejected in Eta Carinae’s famous 1840 eruption may produce the broader red emission.
Credits: NASA/CXC and NASA/JPL-Caltech

Michael Corcoran, also at Goddard said, “Both of Eta Carinae’s stars drive powerful outflows called stellar winds. 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.”

Using Fermi Gamma-ray Space Telescope, astronomers additionally watch a change in gamma beams — light pressing much more vitality than X-beams — from a source toward Eta Carinae. Be that as it may, Fermi’s vision isn’t as sharp as X-beam telescopes, so stargazers couldn’t affirm the association.

To cross over any barrier between low-energy X-ray checking and Fermi observations, Hamaguchi, and his partners swung to NuSTAR. Propelled in 2012, NuSTAR can focus X-ray of considerably more prominent energy than any past telescope. Utilizing both recently taken and recorded information, the group analyzed NuSTAR observations obtained between March 2014 and June 2016, alongside bring down vitality X-ray perceptions from the European Space Agency’s XMM-Newton satellite over a similar period.

Eta Carinae’s low-energy, or soft, X-rays come from gas at the interface of the colliding stellar winds, where temperatures exceed 70 million degrees Fahrenheit (40 million degrees Celsius). But 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. For comparison, the energy of visible light ranges from about 2 to 3 eV.

The analysts say that the best clarification for both the hard X-ray and the gamma-ray emission is electrons accelerated in violent shock waves along the limit of the impacting stellar wind. The X-rays identified by NuSTAR and the gamma rays distinguished by Fermi emerge from starlight given a tremendous jolt of energy by communications with these electrons.

A portion of the superfast electrons, and in addition other accelerated particles, must escape the system and maybe some, in the end, wander to Earth, where they might be distinguished as cosmic rays.

Fiona Harrison, the principal investigator of NuSTAR and a professor of astronomy at Caltech in Pasadena, California 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. 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.”

The team’s analysis, presented in a paper published on Monday, July 2, in Nature Astronomy.