A star with a complicated past

Embracing a rejected star.

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Located about 440 light-years from Earth, Zeta Ophiuchi is a hot star with a complicated past. The star is 20 times more massive than the Sun, likely being ejected from its birthplace by a powerful stellar explosion.

According to earlier measurements, Zeta Ophiuchi was expelled at a speed of around 100,000 miles per hour when its close orbiting partner was obliterated in a supernova explosion over a million years ago.

A new look by NASA’s Chandra X-ray Observatory helps tell more of the story of this runaway star. This new composite image shows the magnificent shock wave (red and green) created by matter blowing away from the star’s surface and slamming into gas in its path. The shock wave was created by matter blowing away from the star’s surface and slamming into gas in its path. According to Chandra data, the star is surrounded by a bubble of X-ray emission (blue) that was created by gas that had been heated to tens of millions of degrees by the shock wave.

A team of astronomers from the Dublin Institute for Advanced Studies in Ireland created the first comprehensive computer simulations of the shock wave. They have started examining how well the models fit the data from observations using X-ray, optical, infrared, and radio wavelengths.

The three distinct computer models all predicted a fainter X-ray emission than what was observed. The bubble of X-ray emission is brightest near the star, whereas two of the three computer models predict the X-ray emission should be brighter near the shock wave.

In the future, scientists are planning to test more complicated models with additional physics — including the effects of turbulence and particle acceleration. They aim to see whether the agreement with X-ray data will improve.

Journal Reference:

  1. Thermal emission from bow shocks. II. 3D magnetohydrodynamic models of zeta Ophiuchi. S. Green, J. Mackey, P. Kavanagh, T. J. Haworth, M. Moutzouri, V. V. Gvaramadze. Astronomy and Astrophysics. DOI: 10.1051/0004-6361/202243531