Getting Sloshed

What looks like blue light and hot gas but isn’t? Credit: X-ray: NASA/CXC/BU/E.Blanton; Optical: ESO/VLT

 

Nov 29, 2012

Is hot gas sloshing in a gravitational wine glass—or is astrophysicists’ reasoning going in a circle?

A recent press release explains: “Like wine in a glass, vast clouds of hot gas are sloshing back and forth….” The blue image is assembled electronically from x-ray data and superimposed on the gold image from optical data. Astrophysicists interpret the images in the light of preconceived ideas about gravity and gas. They see a small cluster of galaxies that “smashed into” a larger one, “sloshing” the gas in it. Off-center tidal forces pulled the gas first one way and then another, making it spiral around in the gravity well.

By photoshopping the x-ray data into a blue swash on the computer screen, the image looks a lot like what our eyes interpret as visual light. If it were visual light but with the energy bumped up to the x-ray level, the gas emitting it would need to have a temperature of 30 million degrees. “Gas” at that temperature should be fully ionized.

However, the “preconceptual” light in which it is interpreted requires it to remain un-ionized at that temperature. If the gas were ionized, it would be plasma. If it were plasma, it would be subject to the well-known effect of plasma cells that move relative to each other: They drive electric currents through each other.

Those currents would constrict into filaments in response to the Bennett pinch forces. The filaments would give rise to double layers, which in turn would accelerate electrons to high energies. The electrons would spiral in the magnetic fields generated by the currents and emit high-energy synchrotron radiation: x-rays.

Astrophysicists unacquainted with plasma would mistake the x-rays for thermal radiation and calculate a temperature from its energy. The temperature would be in the millions of degrees. But of course that temperature couldn’t cause ionization because, if it did, the hot gas would be plasma, and who knows where that could lead.

It’s best to restrict your attention to the wine swirling in your glass: Drink!

Mel Acheson

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