A Dance Between Two Stars

An international team of scientists has found the brightest gamma-ray binary ever seen, and it’s the first to be seen outside the Milky Way galaxy. The team combined data from NASA’s Fermi Gamma-ray Space Telescope with those from other facilities and confirmed that what was once thought was just a high-mass X-ray binary (HMXB) was in fact, a gamma-ray binary system. Their findings have been published in The Astrophysical Journal.

The newly found gamma-ray binary, named LMC P3, was discovered in a small nearby galaxy called Large Magellanic Cloud (LMC), located 163,000 light years away.

Gamma-ray binaries are systems wherein there are two stars, one orbiting the other. One is usually a massive star and the other is either a black hole or a neutron star (an extremely magnetic star), and are very rare, with only five found in our galaxy to date. And so far, LMC P3 is the most luminous gamma-ray binary system ever found in terms of gamma rays, X-rays, radio waves and visible light.

"Fermi has detected only five of these systems in our own galaxy, so finding one so luminous and distant is quite exciting," NASA's Goddard Space Flight Center lead researcher Robin Corbet says. "Gamma-ray binaries are prized because the gamma-ray output changes significantly during each orbit and sometimes over longer time scales. This variation lets us study many of the emission processes common to other gamma-ray sources in unique detail."

Cosmic Death Rays

Having two extremely high-energy bodies within a system undoubtedly causes immense energy to be unleashed. On a regular day, the ozone layer protects us from gamma rays beaming around from outer space. However, gamma-ray bursts can wipe out life in an entire planet, if that planet happens to be in its beam direction. And some postulate that such an event did just that to Earth 450 million years ago.

Artist's concept of a ten-second gamma ray burst wiping out life on Earth. NASA.

It is estimated that gamma-ray binaries emit between 0.1 to over 100 gigaelectron-volts (GeV) of energy. According to the American Geophysical Union: “Alpha and Beta rays are easily stopped by paper, clothes and skin. Gamma Rays are the bad ones. It takes a few inches of lead or a few feet of concrete and dirt to slow or stop them. A detonating nuclear device will produce a LOT of gamma rays. Even if the blast doesn’t get you, the dose of radiation could be very high, and perhaps fatal.”

Such discoveries are incredibly humbling experiences. Even with all of our knowledge and technological achievements, we are still discovering new and exciting phenomena. This exemplifies the importance of scientific curiosity and exploration.

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