Messier 22, also known as NGC 6656, is one of the most glorious globular clusters in the northern sky, a huge starswarm 10,000 light years away that can be seen with the naked eye under dark sky conditions. Discovered by the German amateur astronomer Abraham Ihle in 1665, the cluster was added to Charles Messier’s catalog 99 years later in 1764. Packed with some of the oldest stars in the known universe, M22 hosts at least two stellar mass black holes (discovered by the Very Large Array) and six free-flying planet-size bodies (discovered by the Hubble Space Telescope) that are not orbiting stars. It also is one of just four globular clusters known to host a planetary nebula (discovered by the IRAS spacecraft). This infrared and visible light image, captured by the Hubble Space Telescope, shows the crowded heart of M22 where thousands of suns glitter like diamonds on back velvet. Click on the image below for a zoomed-in view.
This NASA/ESA Hubble Space Telescope image reveals the vibrant core of the galaxy NGC 3125, approximately 50 million light-years away. Discovered by John Herschel in 1835, NGC 3125 is a great example of a starburst galaxy — a galaxy in which unusually high numbers of new stars are forming, springing to life within intensely hot clouds of gas.
Globular clusters offer some of the most spectacular sights in the night sky. These ornate spheres contain hundreds of thousands of stars, and reside in the outskirts of galaxies. The Milky Way contains over 150 such clusters — and the example shown in this NASA/ESA Hubble Space Telescope image, named NGC 362, is one of the most unusual ones.