The cluster Messier 9 includes thousands of stars swarming in a spherical cloud about 25,000 light-years from Earth. The object can’t be seen with the naked eye.
It was discovered in 1764by French astronomer Charles Messier, the scientist could only resolve it as a faint smudge that he classified as a nebula (“cloud” in Latin). Only in the 18th century astronomers, most notably William Herschel, began to spot stars within the cluster.
The Hubble Space Telescope (HST) was carried into orbit by a Space Shuttle in 1990 and remains in operation. A 2.4 meter aperture telescope in low Earth orbit, Hubble’s four main instruments observe in the near ultraviolet, visible, and near infrared. The telescope is named after the astronomer Edwin Hubble.
The device was built by the United States space agency NASA, with contributions from the European Space Agency, and is operated by the Space Telescope Science Institute.
The HST is one of NASA’s Great Observatories, along with the Compton Gamma Ray Observatory, the Chandra X-ray Observatory, and the Spitzer Space Telescope.
Messier 9 is a roughly spherical swarm of stars that lies around 25 000 light-years from Earth, near the centre of the Milky Way, so close that the gravitational forces from the galactic centre pull it slightly out of shape, writes Informatives.
Globular clusters are thought to be one of the oldest stars in our galaxy, born when the Universe was just a small fraction of its current age. The stars of Messier 9 are twice older and also have a markedly different composition, and are enriched with far fewer heavier elements than the Sun.
Experts claim, the elements quite crucial to life on Earth, like oxygen and carbon, and the iron that makes up our planet’s core, are very scarce in Messier 9 and clusters like it.
The reason for it that the Universe’s heavier elements were formed in the cores of stars, and in supernova explosions. When the stars of Messier 9 formed, there were far smaller quantities of these elements in existence, writes Science Daily.
The contrast between Messier’s equipment and modern technologies which are used by astronomers is unbelievable. Hubble’s image, the highest resolution image yet made of Messier 9, is able to resolve every single stars, situated right into the crowded centre of the cluster.
Over 250 000 of them are neatly focused on the detector of Hubble’s Advanced Camera for Surveys, in an image which covers an area no bigger than the size of the head of a pin held at arm’s length. As well as showing the individual stars, Hubble’s image clearly differentiates colors of the stars.
It’s well-known fact that a star’s color directly depends on its temperature – counter-intuitively, perhaps, the redder it is, the cooler it is; and the bluer it is, the hotter.
The wide range of stellar temperatures here is clearly displayed by the broad palette of colors visible in Hubble’s image of Messier 9.
Messier 9′s neighbourhood is interesting as well, and is marked by two vast and dark nebulae. These pitch-black clouds of interstellar dust are known as Barnard 259 (to the south-east of Messier 9) and Barnard 64 (to the west), and are clearly visible in wide-field images of the cluster.