Dark matter asteroids (if any) can cause solar flares


A class X1.6 solar flare flashes in the middle of the sun on September 10, 2014.


Dark matter is proving to be a rather frustrating subject for physicists, cosmologists, and other outward-looking scientists. All dark matter data is gravitational data, and the lack of other evidence just draws a box on the particle map in which scientists scribbled, “Here be dark matter.”

Dark matter interacts so weakly with ordinary matter that when ordinary matter drunkenly screams at the particle bar of the universe, we simply don’t notice it. What we need is to give it a place to shine – to be in the spotlight and sing karaoke. It turns out that the interior of a star could be just that place.

Disappointing flashes in the dark

Most dark matter candidate proposals use the simplest possible extension of the Standard Model. These extensions allow theoretical physicists to estimate how such particles would interact with ordinary matter.

Based on these ideas, experimental physicists placed large tanks of xenon in the deepest, darkest holes they could find and surrounded the tanks with light detectors to look for evidence of rare events – dark matter colliding with ordinary matter. These are tightly controlled experiments where each flash of light is analyzed. The non-dark matter chain reactions that result in flashes of light are well known and controlled.

So far, however, nothing concrete has surfaced.

Because we don’t really know what dark matter is, theoretical physicists are now letting their imaginations run wild. They have created a zoo of possible dark matter particles. Extensions to the Standard Model allow for almost anything, so there are proposals for dark matter atoms, molecules, and even stars. Yes, there could be a completely invisible mirror universe holding our own universe together.

Exciting star flares

If it’s true that dark matter can form structures, dark matter asteroids are likely flying through the universe. Occasionally, dark matter asteroids collide with stars, and that’s when things get very exciting.

Dark matter in an asteroid interacting with real matter in a star essentially makes a unit (because stars are quite dense). Based on what we know about the universe and how galaxies form, dark matter asteroids must be moving very quickly.

“Fast” in this case means “faster than the speed of sound inside a star”. So when an asteroid hits a star, it creates a cylindrical shaped acoustic shock wave. The star acts as an acoustic lens—a star is less dense and directs acoustic rays toward the surface—so the shock wave is loosely focused around the asteroid’s entry point.

This process serves to intensify the shockwave in a local region rather than allowing it to spread. Then, as the shock wave approaches the surface, its speed (relative to the speed of sound) increases, increasing its effect on the stellar medium.

These two processes are sufficient to cause the star to emit a beam of X-rays, with an emission tail extending into visible light. In other words, there is a flash of light that is definitely visible to our observational instruments.

Solar flares are common

The researchers used the estimated dark matter density of a globular cluster called 47 Tuc to calculate how often flares induced by dark asteroids would be visible to the Hubble Space Telescope (if it had the right filters). Scientists concluded that a week of observation time should be enough to spot flares. Then they looked back at Hubble’s database and found that 47 Tuc had been the subject of a week-long observation – but with the wrong filter. Unsurprisingly, nothing was found.

In addition to Hubble, the researchers also considered a soon-to-be-deployed wide-field UV space telescope. In this case, the researchers suggest looking at K dwarfs (a series of relatively cold stars in the main sequence) that are local by astronomical standards. If dark matter asteroids do exist and behave as researchers have predicted, this telescope can’t help but spot the resulting flares. The same applies to all others, which are also designed to measure large parts of the sky in the ultraviolet.

Even our own sun would be subject to flares caused by dark asteroids. Researchers estimate that the Sun should collide with a small asteroid every year. The evidence – solar flares – may even already be in the observational records.


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