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Explanation: Messier 15 is a 13 billion year old relic of the early formative years of our galaxy, one of about 170 globular star clusters that still roam the halo of the Milky Way. About 200 light-years in diameter, it lies about 35,000 light years away toward the constellation Pegasus. But this realistic looking view of the ancient globular star cluster is not a photograph. Instead it's an animated gif image constructed from remarkably precise individual measurements of star positions, brightness, and color. The astronomically rich data set used was made by the sky-scanning Gaia satellite which also determined parallax distances for 1.3 billion Milky Way stars. In the animated gif, twinkling stars are M15's identified RR Lyrae stars. Plentiful in M15, RR Lyrae stars are evolved pulsating variable stars whose brightness and pulsation period, typically less than a day, are related.
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NASA Official: Jay Norris. Specific rights apply.
A service of: LHEA at NASA / GSFC
& Michigan Tech. U.
Based on Astronomy Picture
Of the Day
Publications with keywords: M 15 - globular cluster
Publications with words: M 15 - globular cluster
See also:
- APOD: 2025 December 28 Á NGC 1898: Globular Cluster in the Large Magellanic Cloud
- APOD: 2025 November 26 Á Globular Cluster M15 Deep Field
- APOD: 2025 September 5 Á 47 Tucanae: Globular Star Cluster
- APOD: 2025 August 14 Á M13: The Great Globular Cluster in Hercules
- APOD: 2025 July 26 Á Globular Cluster Omega Centauri
- NGC6366 vs 47 Ophiuchi
- Messier 2