Renown 18th century astronomer Charles Messier described this 9th entry in his famous astronomical catalog as “Nebula, without star, in the right leg of Ophiuchus …”. But Messier 9 (M9) does have stars, known to modern astronomers as a globular cluster of over 300,000 stars within a diameter of about 90 light-years. It lies some 25,000 light-years distant, near the central bulge of our Milky Way galaxy.

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Explanation: Renown 18th century astronomer Charles Messier described this 9th entry ^[4] in his famous astronomical catalog as “Nebula, without star, in the right leg of Ophiuchus …”. But Messier 9 (M9) ^[5] does have stars, known to modern astronomers as a globular cluster ^[6] of over 300,000 stars within a diameter of about 90 light-years. It lies some 25,000 light-years distant ^[7], near the central bulge of our Milky Way galaxy. This Hubble Space Telescope close-up ^[8] resolves the dense swarm of stars across the cluster’s central 25 light-years. At least twice the age of the Sun and deficient in heavy elements, the cluster stars have colors corresponding to their temperatures ^[9], redder stars are cooler, bluer stars are hotter. Many of the cluster’s cool red giant ^[10] stars show a yellowish tint in the sharp Hubble view.