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Have we been wrong about how big neutron stars are this whole time?

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[♪ INTRO] Most human eyes can see a vast range of objects, from a single strand of hair between  our fingertips to stars lightyears away.

But with the help of tools like  particle accelerators and telescopes, we can detect tinier objects like neutrons and  larger celestial objects like other galaxies. These two ends of the size spectrum actually have more in common than you might think.

After all, we can find these tiny particles  just about everywhere in the universe, including in neutron stars. So some scientists are using particle accelerators to turn astrophysics on its  head by applying what they learn from neutrons in the smallest things on Earth to some of the most massive  things in the universe. A particle accelerator works by speeding  up neutrons, protons, and electrons, which make up atoms, to do  things like see how much energy they generate and figure out what they’re made of.

And researchers are constantly working  to improve particle acceleration. At the start of 2022, the new FRIB particle  accelerator opened for experimentation. This particle accelerator adds  to the toolbox that scientists can use to study tiny phenomena  with huge implications.

For example, by looking at the  properties of uncharged neutrons in specific molecules like  different variations of lead, researchers can come up with an idea  of how big that lead molecule is. And that can tell us a lot about  molecules and the things made of them. In one 2021 study, researchers  focused on a version of lead with 82 protons and 126 neutrons.

In this atom, neutrons are farther from the  center of the lead’s nucleus than its protons. This arrangement happens because there are way more neutrons than protons, and they don’t all fit in such close quarters. As the outermost particle  of these lead atoms’ nuclei, neutrons can give us an idea of  how big the lead molecule is.

But we can learn even more from the space where the protons stop and the neutrons start. There’s a layer of neutrons surrounding  the outermost layer of protons, acting as a neutron skin. And that neutron skin on the outside  of the nucleus is super thin.

But despite looking slim at first  glance, the researchers uncovered that it’s not as thin as they  had previously thought it was. In fact, it’s thicker than  they thought was even possible! This is making researchers rethink the  size limits of all sorts of things.

If we’ve been wrong about how  far a tiny atom can expand and how much space it takes up, then we might be wrong about the same  properties in giant neutron stars. See, neutron stars are the leftovers  from a collapsed massive star. In its collapse, all of the  star’s protons and electrons got crushed into neutrons.

So the resulting neutron stars are essentially  dense balls of neutrons in our sky. And those are no different from the neutrons that we can detect using particle accelerators. Now, these super-dense neutron stars are estimated to be 40% more massive than  our sun, but way smaller.

And given the error bars in  the recent lead experiment, this could still be an accurate  estimation for neutron star size. But the results from the lead  experiment suggest that neutron stars also could be way bigger than we thought. The difference of only a few quadrillionths  of an inch in the neutron skin could be a huge deal scaled  up to the astrophysics level.

And who knows, with new tools, researchers could find more data  supporting this thicker skin idea. So the researchers who conducted  this lead experiment plan to conduct follow-up experiments  using the FRIB particle accelerator. FRIB is the first-ever particle  accelerator to use a liquid lithium film to charge up heavy-ion beams using less power, making it super powerful.

That kind of power might be  just what researchers need to reduce uncertainty in their measurements and make better models for neutron stars. Using FRIB, scientists will be  able to investigate neutrons in lead and all sorts of other particles  to gain a better understanding of, you know, pretty much everything in the universe. Thank you to our patron, Naomi, for  suggesting that we look into FRIB.

If you would like to join our Patreon community, go to And if you’d like to display  your love of all things space, remember to check out this month’s  Pin of the Month, Deep Space 1! You can pre-order this snazzy  pin until the end of February, when orders will close and we’ll ship them out.

And then, it’ll be time for you to  keep an eye out for March’s pin! You can check out the link in  the description to learn more. Thanks for watching this episode of SciShow Space! [♪OUTRO ]