Jeff has a master's in engineering and has taught Earth science both domestically and internationally.
What are Neutron Stars?
A neutron star is composed almost entirely of neutrons, so let's first take a look at what a neutron is. Neutrons are found in the nuclei of every particle except hydrogen. A neutron is a fundamental particle of an atom, having approximately the same mass as a proton. It is located in the nucleus along with protons. A neutron has a mass equal to 1,838 electrons and a mass equal to 1.0014 protons.
In order for a neutron star to form, high temperatures and pressures are needed. Such pressures and temperatures only occur in the aftermath of a supernova during the collapse of massive stars. The resulting neutron star is composed almost entirely of neutrons. Neutron stars are some of the densest known objects in the universe, with a diameter roughly equal to an average city, but a mass equal to nearly 500,000 Earths or 2 suns.
In astronomy, large masses are usually measured in solar masses; one solar mass is equal to the mass of our sun (1.9891 x 10^30 kilograms). A typical neutron star has a mass between 1.3 and 2 solar masses. This means a neutron star can have twice the mass as our sun. For example, a neutron star named 1002.3825, discovered by Cornell University in the 4U region of the universe, was found to have a mass of 1.58 +/- 0.06 solar masses or 3.13 x 10^30 kilograms.
While the mass of neutron stars is almost beyond comprehension, the diameter is more within our normal range of measurement. The average range in diameter for a neutron star is only 10 - 20 kilometers. Going back to our example above, the neutron star 1002.3825 has a diameter of D = 18.22 +/- 0.80 km.
The density of neutron stars is, again, almost beyond comprehension. The density of a neutron star has a range of 8 x 10^13 g to 2 x 10^15 g per cubic centimeter. Although hard to believe, the density of a neutron star is about equal to the density of the nucleus of an atom.
The intense density of a neutron star means that the gravity on the surface is 2 x 10^11 - 3 x 10^12 times stronger than the gravity here on Earth. If a rocket ship were to try to escape the gravitational field of a neutron star, it would have to travel about 10,000 to 150,000 km per second, which is half the speed of light.
A neutron star is the result of the collapse of a star after a supernova explosion. The resulting neutron star is made up almost entirely of neutrons. Neutron stars are some of the most dense objects in the universe, having a mass up to two times our sun, but a diameter ranging only between 10 - 20 kilometers.
Neutron Star Quickview Table
|Origin||Aftermath of supernovas|
|Mass||1.3 to 2.0 solar masses|
|Radius||10 to 20 km|
|Density||8 x 10^13 g to 2 x 10^15 g per cubic centimeter|
|Gravity||2 x 10^11 - 3 x 10^12 times stronger than Earth's gravity|
|Example||Neutron star 1002.3825|
After finishing this lesson, students should be ready to:
- Define neutron stars and recall their origin
- Describe the mass, radius, density, and gravity of neutron stars
- Identify an example of a neutron star
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