“What can’t you see but can measure?” “” Not to smell, but to feel? »No, this is not a puzzle for a children’s party. This is one of the most confusing things in modern astronomy – dark matter.
Dark matter is “something” – a particle, most astronomers think, but it can also be something completely unexpected – that you can’t see or feel. But that you can measure. For example, in galaxies that spin so fast that the stars would normally sway, like the chairs on a merry-go-round with cables breaking. Dark matter holds things together in practice. Because the stars can still sense the gravity of this invisible dark matter. It is as if the cables of your whirligig are very thick, so that they do not break.
So far, all the galaxies that astronomers have studied need dark matter to exist. Until an international group of astronomers in 2019 discovered six galaxies with little or no dark matter.
‘Impossible! Go and measure again, ”was the consensus of the astronomical world. You will see that you are still measuring dark matter. But after another forty hours and even more precise measurements, the conclusion is again: we have found a galaxy without dark matter.
The researchers write that in an article to appear soon in the review Monthly notices from the Royal Astronomical Society. The galaxy in question has the esoteric name AGC 114905 and is located about 250 million light years from us. It’s called an ultra-diffuse galaxy – “ultra-diffuse” because it is about the size of the Milky Way, but contains a thousand times fewer stars.
In their research, the researchers dug into the rotation of the galaxy and examined whether they needed dark matter to support the metaphorical cables. It didn’t seem to be the case. The gravity of all visible matter in the system is enough to hold it together.
It’s weird. According to all standard theories about how the universe works, the mysterious elements should be there. What could happen? The researchers have no idea.
A measurement error, perhaps? Possible, but also other researchers have you ever seen galaxies? with less dark matter than expected. So there is definitely something strange going on.
Or maybe, just maybe, dark matter doesn’t exist at all. Is it an illusion, something that springs from a cave of physics as yet misunderstood? It’s not obvious from all of the evidence, but in science you have to be open to all options.
“What later turned out not to exist, but was named by physicists?” It wouldn’t be the first time physicists had to move a previously mysterious phenomenon to the rejected ideas section.
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