Eta Carinae may reach Earth

Eta Carinae’s great eruption in the 1840s created the Homunculus Nebula imaged here by the NASA  ESA Hubble Space Telescope. Now about a light-year long the expanding cloud contains enough material to make at least 10 copies of our Sun. Astronomers can

Eta Carinae’s great eruption in the 1840s created the Homunculus Nebula imaged here by the NASA ESA Hubble Space Telescope. Now about a light-year long the expanding cloud contains enough material to make at least 10 copies of our Sun. Astronomers can

The most luminous and massive stellar system within 10,000 light-years from Earth, Eta Carinae is accelerating cosmic ray particles at high speeds and perhaps some of these rays are reaching Earth. "Similar processes must occur in other extreme environments".

"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, as the particles carry electric charge, the magnetic field of the solar system and Earth deflects their path, leaving no sign to detect where they came from.

The massive stars of Eta Carinae orbit each other once every 5.5 years, when they come "unusually close" to one another, at a distance of about 140 million miles (225 million kilometers) - or roughly the same distance between Mars and the sun.

"Both of Eta Carinae's stars drive powerful outflows called stellar winds", Michael Corcoran, also from Goddard, said.

"Where these winds clash changes during the orbital cycle, which produces a periodic signal in low-energy X-rays we have been tracking for more than two decades", Corcoran said.

Kenji Hamaguchi, an astrophysicist at Goddard and the lead author of a new study, says a review of NuSTAR data and archived observations by the European Space Agency's XMM=Newton space telescope indicates Eta Carina is a likely source.

However, astronomers could not confirm the connection as Fermi's vision is not as sharp as X-ray telescopes.

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An artist's impression of the NuSTAR space telescope.

The team behind the new study examined both new and archival data acquired by NuSTAR between March 2014 and June 2016.

Low-energy, or soft, X-rays originate in gas at the interface of colliding stellar winds where temperatures can exceed 40 million degrees Celsius (79 million degrees Fahrenheit).

To solve the problem, the agency chose to employ its NuSTAR space telescope that can make highly-accurate X-ray detections. Visible light features energy ranging from 2 to 3 electron Volts.

To be specific, both the high powered X-rays detected by NuStar and the gamma rays detected by Fermi seemed to be emanating from a binary orbital period.

Focused NuSTAR observations show that the colliding winds of the massive binary eta Carinae accelerate particles to very high energies, adding to the cosmic ray flux of the Galaxy. Since its launch in 2012, it has been detecting X-rays above 30,000 electron volts. Before this, the origin of some unique X-rays and gamma rays detected on Earth was a mystery to experts. The best explanation for hard X-rays is electrons accelerated in violent shock waves along the boundary of the colliding stellar winds, suggesting that these stellar winds are more dramatic than expected. The system was first cataloged by the English astronomer Edmond Halley in 1677, as a star of fourth magnitude.

According to the latest observations, Eta Carinae stars emits cosmic radiations that can escape their system, while some of these X-ray and gamma-ray emissions can even reach Earth. "But until NuSTAR was able to pinpoint the radiation... the origin was mysterious".

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