Neutron stars are incredibly dense objects about 16 km across. Only their immense gravity keeps the matter they contain from exploding; if you brought a spoonful of a neutron star to Earth, the lack of gravity would cause it to expand rapidly. Credit: X-ray: NASA/CXC/UNAM/Ioffe/D. Page, P. Shternin et al; optical: NASA/STScI; illustration: NASA/CXC/M. Weiss
What would happen if a spoonful of a neutron star were brought to Earth?
Carolina Adams
Portland, Oregon
Before we can figure out what happens when our spoonful hits Earth, let's think about what's in our spoonful: a super-dense collection of neutrons.
TO neutron star It is the remnant of a massive star (bigger than 10 suns) that ran out of fuel, collapsed, exploded, and collapsed once more. Its protons and electrons fused to create neutrons under the pressure of the collapse. The only thing stopping neutrons from collapsing further is “neutron degeneracy pressure,” which prevents two neutrons from being in the same place at the same time.
The star also loses a lot of mass in the process, ending up with only about 1.5 times the mass of the Sun. But all that matter has been compressed into an object about 16 kilometres (10 miles) in diameter. A normal star of that mass would be more than 1.6 million kilometres (1 million miles) in diameter.
A spoonful of the Sun, depending on where you scoop it up, would weigh about 2 kilograms (5 pounds), the weight of an old laptop computer. A spoonful of a neutron star weighs more than 900 billion kilograms (1 billion tons), the weight of Mount Everest. So while you could lift a spoonful of the Sun, you can't lift a spoonful of a neutron star.
If we were only concerned about weight, putting a spoonful of neutron star on Earth's surface wouldn't affect our orbit or tides. It's like adding another mountain. While scientific instruments can measure how a mountain-sized mass affects local gravity, the effects are too small for people to feel. So unless you're standing right next to the spoonful, you wouldn't notice it.
However, it's not just the spoon's mass that we're concerned with. The neutron star's matter became as dense (and hot) as it was because it's underneath a lot of other mass crammed into a relatively small space. When we pick up our spoon and transport it to Earth, the rest of the star's mass (and the gravity associated with it) disappears. Inside a neutron star, neutron degeneracy pressure fights gravity, but without all that gravity, degeneracy pressure takes over!
Imagine you have a shaken can of soda. You know that the moment you open the lid, the pressure is gone and it explodes. When we bring our spoonful of neutron star to Earth, the gravity holding it together causes the lid to pop open and whatever is inside expands very rapidly. spoonful of neutron star If it were to suddenly appear on the surface of the Earth, it would cause a giant explosion and would probably vaporize a good part of our planet.
Valerie Mikles
National Oceanic and Atmospheric Administration Contractor,
Quality Assurance, IM Systems Group,
University Park, Marylandd
This article was first published in September 2018 issue of Astronomy.
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