Image credit: NASA, ESA, and C. Johnson (STScI); Image Processing: Gladys Kober

Key Takeaways

  1. Messier 19 (M19) is an elliptical globular star cluster first discovered by Charles Messier in 1764 and later identified by William Herschel in 1784.
  2. Located in the constellation Ophiuchus, M19 is one of the closest globular clusters to the center of the Milky Way, experiencing gravitational influence that has made it one of the most oblate clusters.
  3. Scientists are intrigued by M19’s peculiar horizontal branch gap, indicating differences in the way its stars are aging, possibly linked to helium abundance variations.
  4. Despite its distance of 28,000 light-years from Earth, M19 remains observable with telescopes, revealing its oblate shape and subtle blue tinge.
  5. The study of M19 provides valuable insights into galactic formation and the complex evolution of globular clusters.

In the 18th century, French astronomer Charles Messier stumbled upon a series of enigmatic “nebulous objects” while searching for comets. These discoveries led to the creation of the renowned Messier Catalog, a crucial milestone in deep-sky object research. Among these objects is Messier 19 (M19), an elliptical globular star cluster situated in the constellation Ophiuchus.

Unlike its spherical counterparts, M19 stands out due to its pronounced oblate shape, resulting from its close proximity to the Milky Way’s center. At a distance of about 28,000 light-years from Earth, this gravitationally bound cluster measures 140 light years in diameter and contains four RR Lyrae variable stars. However, what makes M19 truly intriguing is its horizontal branch gap, suggesting puzzling differences in the aging process of its stars. Researchers speculate that variations in helium abundance might hold the key to this mysterious phenomenon.

M19’s discovery and characterization have offered astronomers valuable insights into the formation and evolution of globular clusters. Despite its considerable distance, M19 remains an observable and captivating celestial object for astronomers armed with telescopes, showcasing its oblate nature and subtle blue hue. The study of Messier 19 continues to shed light on the vast complexities of our universe, further fueling our fascination with the wonders of deep space.

Read full article on Universe Today


The Messier 19 globular cluster, as viewed by the Two Micron All-Sky Survey (2MASS). Credit: 2MASS/


The Messier 19 globular cluster, relative to M4, M80 and Antares. Credit: Wikisky


The Messier 19 globular cluster, as imaged by the Hubble Space Telescope. Credit:NASA/STSc /HST/WikiSky


Messier 19 in Ophiuchus Date 23 June 2009 Source Own work Author Hewholooks


Credit: NASA, ESA


M19 by Fred Espenak


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