Zeta Ophiuchi has led an eventful life. It began as a typical large star, roughly twenty times the mass of the sun. It happily spent its days orbiting a large companion star until it exploded as a supernova about a million years ago. Zeta Ophiuchi was ejected by the explosion and is now speeding away through interstellar space.
Of course, the supernova also ejected the companion star’s outer layers, so instead of empty space, our brave star is speeding through the remnant gas as well. It’s complicated, as they say on Facebook. According to a recent study, this is great news for astronomers.
Zeta Ophiuchi is best known for her beautiful images like the one above. The star has created heated shock waves that glow in infrared to X-rays by ploughing through interstellar gas. The physics of these shock waves is extremely complicated. It is governed by magnetohydrodynamics, a set of mathematical equations that describe the behaviour of fluid gases and their surrounding magnetic fields. Modeling these equations is difficult enough, but when you add turbulent motion, such as shock waves, things become even more difficult. That is why Zeta Ophiuchi is so significant. We can compare our observations to computer simulations because we have such a good view of the shock wave.
The team created computer models to simulate the shock wave near Zeta Ophiuchi in this latest study. They then compared these models to infrared, visible, and X-ray observations. Their goal is to figure out which simulations are the most accurate so that the models can be improved.
Two of their three models predicted that the brightest region of X-ray emissions would be at the edge of the shock wave closest to the star, which is exactly what we see. However, all three models predicted that X-ray emissions should be fainter than what we observed, implying that none of the models is completely accurate. However, these models are difficult to execute well, and this work is a good starting point.
The X-ray brightness difference is most likely due to turbulent motion within the shock wave. The team intends to incorporate some of this turbulent motion into future models. They should be able to create a simulation that closely resembles this interstellar shock wave after several iterations.
Magnetohydrodynamics is a key component of many astrophysical processes, from solar flares to planet formation to the powerful black hole engines of quasars. Most of these interactions are obscured by distance or dust, so it’s fantastic that Zeta Ophiuchi can provide astronomers with a startling glimpse into this complex physics.