If you stare at the sky at night, you will see several thousand stars. However, this number is not so bad, because the Sun is located in a fairly quiet neighborhood about 26,000 light-years from the galactic center.
There are places in our universe where stars are very close together, namely in globular clusters and at the centers of galaxies. If you look around at such a constellation, you will see hundreds of times more stars.
Globular clusters are groups of stars that are bound together by gravity. In such a group there are hundreds of thousands of stars. About 150 globular clusters are known in our galaxy. This week’s space image is a stunning shot of the globular cluster NGC 1898. This globular cluster is not in the Milky Way, but in the Large Magellanic Cloud, one of the satellite galaxies of the Milky Way.
In these globular clusters, stars pile up together like herrings in a barrel. The density is one hundred to one thousand stars per cubic parsec. Converted: A parsec equals 3.32 cubic light years. The density near the Sun is only 0.1 stars per parsec.
Four million stars per parsec
Could it be more extreme? Yes, of course. The ancient globular cluster M15 contains approximately 100,000 stars, most of which are close to the center. The density in the center is four million stars per parsec, but that density is rapidly decreasing outward. Even the Hubble telescope is unable to separate the individual stars in the center of this cluster, while the globular cluster is only 37,000 light-years away. Now you might think that there are regular collisions at the center of this globular cluster, but that’s not so bad. Scientists believe that fewer than 1 in 10,000 stars have coalesced into globular clusters.
Density is higher in some centers of galaxies. This applies, for example, to the galaxy M32, one of the neighbors of the Andromeda galaxy. The density in the center is twenty million stars per cubic parsec. The distance between the stars is 0.008 light-years on average, or 500 times the distance from the Earth to the Sun. This is 12 times the distance from the Sun to Pluto.
Fun fact: The stars in M32 are too close to each other to ever get dark. Scientist Todd Lauer once calculated that the night sky in the middle of M32 could be compared in brightness to the twilights on Earth.
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