Detected giant star system acting as a cosmic particle accelerator

The researchers found that two blue giant stars emit a stellar wind that helps subatomic particles accelerate and generate intense gamma-ray radiation.

Simulate the activity of the star system Eta Carinae. (Video: HESS).

With a dedicated telescope in Namibia, the team led by Germany's Electron Synchrotron Research Center (DESY) demonstrated that a binary star system is the source of high-energy gamma radiation in the universe. The Eta Carinae star system 7,500 light-years from Earth in the Carina constellation produces gamma rays that carry up to 400 gigaelectronvolt (GeV), 100 billion times the energy of visible light. Researchers Stefan Ohm, Eva Leser and Matthias Fubling in DESY publish their findings in the journal Astronomy and Astrophysics.

Eta Carinae is a binary star system consisting of two blue giant stars , whose masses are 100 and 30 times the mass of the Sun, respectively. The two stars orbit around each other for a period of 5.5 years in elliptical orbit. Their distances are constantly changing, perhaps almost from the Sun to Mars or as far as the distance between the Sun and Uranus.

Both stars shoot solid winds containing charged particles into space at supersonic speeds. In the process, every 5,000 years, the larger star loses the mass equivalent to the Sun. The smaller star produces stellar winds at 11 million kilometers per hour. A shock front is formed where two stellar winds collide, heating matter in the wind to extreme temperatures. When it reaches 50 million degrees Celsius, matter emits light in the X-ray range. However, the particles in the stellar wind are not hot enough to emit gamma radiation.

Location of the constellation Eta Carinae.

According to Ohm, director of the X-ray observatory High Energy Stereoscopic System (HESS) in DESY, the shock zone is often where subatomic particles accelerate due to the strong electromagnetic field. When particles accelerate fast enough, they can emit gamma radiation. In fact, NASA's Fermi satellite and AGILE of the Italian Space Agency (ASI), each detected gamma rays with energies of up to 10 GeV from Eta Carinae in 2009.

Satellite data indicates that Eta Carinae can generate gamma radiation stronger than 100 GeV. HESS has successfully detected gamma radiation of 400 GeV when the two blue giants came close in 2014 and 2015. This makes the binary star the first example of a source of high-energy gamma radiation from va. touch between star winds.

"The shock tip region of the two stellar winds is like a natural particle accelerator for cosmic rays," the team said. With the new generation gamen-ray observatory Cherenkov Telescope Array (CTA) being built in the Chilean highlands, scientists hope to explore the event in more detail and explore more sources of gamma rays.