A team of astronomers from the University of California, Berkeley, has discovered what may be 21 neutron stars orbiting a sun-like star. The discovery, made using the W. M. Keck Observatory in Hawaii, is the largest number of neutron stars ever found in a single star system.

Neutron stars are the collapsed cores of massive stars that have exploded as supernovae. They are extremely dense, with a teaspoon of neutron star material weighing billions of tons. Neutron stars are also very hot, with surface temperatures of millions of degrees Celsius.

The newly discovered neutron stars are all located within a region of space about the size of our solar system. This suggests that they were all formed from the same supernova explosion. The astronomers estimate that the explosion occurred about 10 million years ago.

The discovery of so many neutron stars in a single star system is a mystery. Astronomers are not sure how the stars could have formed so close together. One possibility is that the supernova explosion was so powerful that it ejected a large amount of material, which then collapsed into neutron stars.

The discovery of the neutron stars is also important because it provides new insights into the evolution of massive stars. Astronomers believe that massive stars eventually explode as supernovae, and that the neutron stars that are left behind are the seeds of future black holes. The new discovery suggests that massive stars can produce more neutron stars than previously thought.

The astronomers plan to continue studying the neutron stars to learn more about their formation and evolution. They also hope to use the stars to search for gravitational waves, which are ripples in space-time that are predicted by Einstein's theory of general relativity.