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NGC 6441 is a 13-billion-year-old collection of galaxies existing in the southern constellation of Scorpius, and is by far one of the largest and most luminous globular clusters in our regional galaxy. This vibrant cluster, one of 150 catalogued in the Milky Way, was initially discovered by Scottish astronomer James Dunlop (1793-1848) on May 13, 1826.
Dunlop was a renowned stargazer and in 1822 became the first person to observe the reappearance of Encke's comet — only the second incidence of a verified predicted return of a comet after the confirmation of Halley's Comet in 1758.
Hubble's dense composite image is formed using a range of filtered images of different wavelengths captured by Hubble’s Wide Field Camera 3 (WFC3) and Advanced Camera for Surveys (ACS), all drawn from the ultraviolet and optical bands of the full spectrum. Colors depicted are portrayed by assigning various hues to each monochromatic image snapped using individual filters.
NGC 6441 is a fertile starfield that is home to at least four millisecond pulsars, two of which are in binary star systems. It also hosts a rare planetary nebula called JaFu 2, one of only four planetary nebulae seen to reside in Milky Way globular clusters.
Hubble astronomers admit that the precise number of stars in such a concentrated cluster is hard to pin down, but have estimated that all together, its collection of stars weigh approximately 1.6 million times the mass of the Sun.
NASA/ESA's flagship low-Earth-orbit telescope is celebrating its 30th anniversary this year, having first been launched via the space shuttle Discovery (STS-31) on April 24, 1990, then successfully deployed into orbit the next day. For three decades, it has provided a window into the heavens by photographing galactic objects and celestial bodies while delivering a reliable, long-term space research facility for all aspects of optical astronomy.
The Hubble is named after astronomer Edwin Powell Hubble (1889–1953), a pioneering scientist who made some of the most relevant discoveries in the history of modern astronomy, including the novel idea of multiple galaxies existing in the Milky Way, and the determination in 1929 that the more distant a galaxy is from Earth, the faster it appears to move away.