The NASA/ESA Hubble Space Telescope has captured a striking new photo of NGC 6440, which is found in the constellation of Sagittarius.
Globular clusters are systems of very ancient stars, gravitationally bound into a single structure about 100-200 light-years across.
They contain hundreds of thousands or perhaps a million stars. The large mass in the rich stellar center of a cluster pulls the stars inward to form a ball of stars.
The word globulus, from which these clusters take their name, is Latin for small sphere.
Globular clusters are among the oldest known objects in the Universe and are relics of the first epochs of galaxy formation.
It is thought that every galaxy has a population of globular clusters. Our Milky Way Galaxy hosts at least 150 such objects and a few more are likely to exist hidden behind the Galaxy’s thick disk.
The globular cluster NGC 6440 resides 8,470 parsecs (27,625 light-years) away from Earth in the constellation of Sagittarius.
Otherwise known as C 1746-203 or GCl 77, the cluster was discovered by the German-born British astronomer William Herschel on May 28, 1786.
NGC 6440 has an apparent magnitude of about 10, with a diameter of about 6 arcminutes.
“Globular clusters like NGC 6440 are roughly spherical, tightly packed collections of stars that live on the outskirts of galaxies,” Hubble astronomers said in a statement.
“They hold hundreds of thousands to millions of stars that average about one light-year apart, but they can be as close together as the size of our Solar System.”
“The Hubble data used to create this image came from five different Hubble observing programs, four of which focused on the properties of pulsars.”
“Pulsars are highly magnetized, rotating neutron stars emitting a beam of electromagnetic radiation from its magnetic poles.”
“To us, that beam appears as a short burst or pulse as the star rotates.”
“Pulsars spin extremely fast,” the researchers added.
“Astronomers have clocked the fastest pulsar at 716 rotations per second, but a pulsar could theoretically rotate as fast as 1,500 rotations per second before they slowly lose energy or break apart.”
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