The latest in Ph-word: March 2020

In last month’s news a black hole photobombs an asteroid, a hundred new mini planets are revealed and we still don’t know what dark matter is.

The axion craze

If the infamous dark matter consists of particles that we have actually already thought of, then axions are a very good candidate.

The previous seasons of The Dark Matter Candidate saw the hypothesized particles called WIMPs, initially the favourite for some of the judges, increasingly lose their popularity. Eventually with WIMPs insisting on not getting discovered axions started rising into prominence instead. And here we are at the current season, where Dark Matter Candidate news are taken over by the axion craze.

ADMX (Axion Dark Matter eXperiment) is the most seasoned judge of all. Being around for a quarter-century now, it has progressively cut down on the range of masses and properties that axions can possibly have. And in its latest round of results it concluded that if there are so many axions in the universe that they make up dark matter, then they can’t have the best set of properties that the theory hopes for.

And yet…

If dark matter consists of particles, then we are passing through clouds of them the whole time as earth moves within the galaxy. And if those particles are axions, then we don’t need to isolate our experiments in underground caves or put them in space in order to catch them: axions are predicted to give flashes of light when they pass through strong magnetic fields. And as of writing, several experiments around the world have set up their strong magnets and wait.

One of them, the CAPP-8TB (Center for Axion and Precision Physics 8 Tesla Big bore) is a new arrival among the Dark Matter Candidate judges, but last month it showed results that complemented those of ADMX. It had tuned itself to look for flashes from different possible masses that the axion might have (because, even though the best ones have been excluded, The Candidate could be a little different than we expect after all). Unfortunately it’s still empty-handed, but it’s also ready to look in more and more possible ranges.

So, yes, what all this means in practice is that our current best hopes for explaining the mystery of dark matter through particle physics hit the ground one after the other. But hey, in case you follow the science news and were curious as to why “axions” are mentioned more and more often lately, now you have your answer.

The asteroid and the hole

NASA’s OSIRIS-REx is a small spacecraft that a year ago reached asteroid Bennu and now studies it (while preparing to also land on it this summer). It has taken several great photos and last November even took Bennu’s pictures in X-rays to study how it reflects sunlight. Then, when scientists developed them, something amazing happened.

They saw that a black hole had photobombed Bennu.

During the X-ray observations, an unidentified object shined up. It turned out to be a black hole thirty thousand light years away that during those days devoured material from its “companion star”. Under its attraction the material spiraled, felt enormous friction, released a lot of energy, most of it in the X-ray spectrum, and made Bennu’s portraits priceless as a result.


Looking very very carefully at some other pictures taken from the DES (Dark Energy Survey) project, astronomers found 145 new mini-planets. The planetinos are all at least 100 kilometers across and found between 30 to 90 times as far as earth away from sun. For comparison, Pluto is found at 40 times this much away.

By the way, yes, Pluto is really not a planet-planet, but just look at how cool the kid is. It sits at the back of the solar system, has too-many-to-count not-really-a-planet friends (actually closer to seventy thousand), and even got itself a heart tattoo.

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