The crammed centre of Messier 22This is the center of the globular cluster Messier 22 as seen by the Hubble Space Telescope. Globular clusters are more-or-less spherical collections of densely packed stars; they are relics of the early years of the Universe with ages of in the range of 12 to 13 billion years. The Universe is only 13.8 billion years old.

M22 is one of about 150 globular clusters in the Milky Way, and it is also one of the closest to Earth, only about 10,000 light-years away. The cluster has a diameter of about 70 light-years and appears to take up a patch of sky the size of the full Moon. However, the light from the stars in the cluster is not very bright because it is dimmed by dust and gas between the solar system and the cluster.

M22 in particular has some fascinating features: six planet-sized objects that are not orbiting a star have been detected in the cluster…

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