The latest in Ph-word: November 2020

Last month in science: huge amounts of matter and huge amounts of energy get accounted for. Also, selfies from another world.


A small mystery in space is that half of the matter that astronomers calculate to be in galaxies can’t be accounted for. (And it’s a “small” mystery because then there is dark matter, the vast majority of matter which we know exists but have no idea what form it takes. But this time this is not about it.)

There is a reasonable suspicion that this hidden matter actually lies between galaxies, in the form of gas filaments that extend from one to the other. You might actually remember another study from half a year ago which found serious hints of this being this case.

Now a new work supports this suspicion using a different method.

A research team at the Paris-Saclay University used two catalogs of celestial observations; one is about known intergalactic filaments (15 thousands of them) and the other is about X-rays in space. The X-rays mean that there is hot gas out there. Comparing the positions in the two catalogs, the researchers found that the unaccounted amount of matter seems indeed to make up the huge cosmic threads connecting galaxies. (Which makes the filaments kind of the Cayman islands of the universe, I guess.)


Borexino, an experiment at the italian Gran Sasso, seems to have just found where most of the energy of stars comes from.

Granted, it is already well known that stars create energy through fusion. Fusion might be cuisine and music, but it’s also the way of creating nuclear energy by combining smaller nuclei into larger ones (as opposed to fission, which breaks up nuclei and which is routinely used by humans).

But the most basic fusion in stars is suspected to happen in two different ways. They both combine hydrogen towards making helium, but their details are different.

One of them, called “proton-proton chain” is what the sun uses to provide 99% of its energy, and it is already well-studied through observations. The other one though, known as “carbon-nitrogen-oxygen cycle” had never been observed until now.

Now Borexino was able to detect it by looking at the neutrinos from the sun. Neutrinos are the subatomic particles infamous for passing through the whole earth without stopping; a tiny tiny percentage of them might stop though, when they happen to fall head-on on nuclei or electrons in atoms. This is what experiments like Borexino take advantage of, by putting detecting instruments inside huge volumes of heavy liquids and waiting for the head-on crashes.

Neutrinos are quite good for learning what happens inside the sun. The two fusion processes emit lots of them, with different characteristics in each case.

As implied, Borexino saw neutrinos from the “carbon-nitrogen-oxygen cycle”, and enough of them to say that it was observed for the first time. And although this fusion process gives off only 1% of the sun’s energy, it is the main process for energy production in stars that are heavier than 2.3 times the sun. This actually makes it the number one source of energy in the universe.


In the astro-cute news of the month, here is the latest selfie of Curiosity rover, roaming Mars since 2012. Curiosity makes for a meticulous influencer, as it took 59 shots and combined them for the perfect pic, also taking care of removing its selfie stick.

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