What we have before our eyes is a bright star field, captured by the NASA/ESA Hubble Space Telescope’s Wide Field Camera 3 and the Advanced Camera for Surveys. What are we observing? The image contains the globular cluster ESO 520-21 (also known as Palomar 6), a closely packed collection of stars, which lies near the center of the Milky Way.
Palomar 6 or ESO 520-21 is located in the constellation Ophiuchus, near the celestial equator. Ophiuchus was precisely one of the 48 constellations that appeared in the writings of the 2nd-century Egyptian astronomer Ptolemy , which are among the 88 constellations officially recognized by the International Astronomical Union today.
But not all the constellations proposed by astronomers throughout history have survived: among the forgotten or obsolete constellations are Felis (the cat), Rangifer (the reindeer) and even Officina Typographica (the printing workshop).
clusters and stars
Globular clusters are among the oldest known objects in the universe and are relics of the earliest days of galaxy formation. They contain hundreds of thousands or perhaps a million stars and each galaxy is believed to have a population of globular clusters. Some, like our Milky Way, have a few hundred, while elliptical galaxies can have several thousand.
“Palomar 6, a densely packed and roughly spherical collection of stars, lies near the center of the Milky Way, where interstellar gas and dust absorb starlight and make observations more challenging,” the astronomers said. from Hubble. “This absorption by interstellar material affects some wavelengths of light more than others, changing the colors of astronomical objects and making them appear redder than they really are. We call this process ‘reddening’, and it makes it particularly difficult to determine the properties of globular clusters close to the galactic center.”
Reference: NASA / ESA / Hubble / R. Cohen.
