NASA has released a brilliant photo taken by the NASA/ESA Hubble Space Telescope of the globular cluster Messier 55.
This Hubble image shows a portion of Messier 55, a globular cluster located some 20,000 light-years away in the constellation of Sagittarius. Image credit: NASA / ESA / A. Sarajedini, Florida Atlantic University / M. Libralato, STScI, ESA & JWST / Gladys Kober.
Globular clusters are densely packed, spherical collections of hundreds of thousands or even millions of stars.
They are among the oldest known objects in the Universe and are preferentially associated with the oldest components of galaxies.
Our own Milky Way Galaxy hosts at least 150 such objects and a few more are likely to exist hidden behind the Galaxy’s thick disk.
One of these clusters, Messier 55, resides approximately 20,000 light-years away from Earth in the constellation of Sagittarius.
Otherwise known as M55 and NGC 6809, the object contains an estimated 100,000 stars with 55 variable stars whose brightness changes.
It has a diameter of about 100 light-years and a mass of 270,000 solar masses.
Messier 55 was discovered by the French astronomer Nicolas Louis de Lacaille in 1752 while observing from what today is South Africa.
“Messier 55 was originally spotted in 1752 by Nicolas Louis de Lacaille in what is now South Africa, but it took until 1778 for the French astronomer Charles Messier to catalog it,” Hubble astronomers said.
“This is because, while Messier 55 is large and reasonably bright, it is lacking a dense core and many of its stars are quite faint, making it hard to observe in non-optimal conditions.”
“For northern observers M55 sits low in the sky, so the view is hampered by a thicker layer of atmosphere, as well as water vapor and light pollution.”
“This hindered Messier’s view from his Paris observatory.”
“When he cataloged it, Messier noted that ‘its light is even and does not appear to contain any star’.”
Though this Hubble image shows just a portion of Messier 55, the cluster as a whole appears spherical because the stars’ intense gravitational attraction pulls them together.
“Hubble’s clear view above Earth’s atmosphere resolves individual stars in this cluster,” the astronomers said.
“Ground-based telescopes can also resolve individual stars in Messier 55, but fewer stars are visible.”
“Even in skies with low light pollution, viewed through binoculars, the cluster will only appear as a round hazy patch.”
“Small telescopes can begin to resolve individual stars in Messier 55, while larger aperture telescopes will pick out low magnitude stars easily.”
Source : Breaking Science News