Stars Are Held Together By

Star Clusters

A Mutual Bail

Artist rendering of an open star cluster

Some of the stars in the universe are part of multiple star systems known as star clusters. Nigh appear to be part of a binary system where two stars orbit a common heart of gravity. A few are even office of a triple star system. But some stars are besides part of a larger group. They tin can exist found together in associations known as star clusters. Star clusters are groupings of stars held together by a common gravitational bond. They vary greatly in size and shape besides as the number of stars. They also vary in age from just thousands of years to billions of years old. Gravity is the force that binds these catholic swarms together. Star clusters are among the about spectacular objects in the sky. Many of these clusters can exist seen with the naked centre on a dark night. Astronomers have divided star clusters into two main types co-ordinate to their shape and number of stars. The tin all be classified as either open clusters or globular clusters.

Stellar Siblings

Hubble image of the Pleiades star cluster

Open up clusters are also chosen galactic clusters. They commonly contain somewhere between a dozen and a g stars. They are held together by common gravitational attraction and have a mutual eye of mass. Open up star clusters are composed of hot, relatively immature stars and tend to be institute within the spiral arms of our Galaxy galaxy. It is estimated that there are nigh twenty,000 open up star clusters in our galaxy. The reason open clusters are so young is because they don't concluding very long. Gravitational interactions between the stars and other objects volition crusade these clusters to eventually disperse over time. Open clusters are formed when several stars are formed at the aforementioned time from the same cloud of dust and gas. Our own Sun is part of an open up cluster than includes other nearby stars such as Alpha Centauri and Barnard'south star. All of these stars are believed to have formed from the same primordial nebula around 5 billion years agone. We know that the stars in open clusters are young because their spectrums indicate that an abundance of heavy elements. These elements are formed through many generations of star nativity and death. Over billions of years, this stellar bike produces star-forming clouds rich in heavy elements. Open up clusters are formed from clouds like these.

Primordial Stars

Unlike open clusters, globular clusters are much older and usually contain between ten thousand to a million stars, which are gravitationally spring in a tight concentration. The stars are normally packed into a spherical system with the highest density of stars occurs in the heart of the cluster. Globular clusters are found only outside our galaxy. They orbit around the galaxy's fundamental halo or bulge like a swarm of bees. Their concentration increases closet to the galaxy's eye. They orbit the galaxy in highly elliptical orbits, which have them far outside the Milky way. There are most 200 known globular clusters surrounding our galaxy. They have also been observed around many other galaxies every bit well. Spectroscopic studies testify that the stars inside these clusters are much lower in heavy elements than stars such as the Lord's day. This means that they must exist much older, because heavy elements are produced when stars end their lives in supernova explosions. Nigh globular clusters are believed to exist between 14 and 16 million years old. They are believed to have formed from the same primordial thing that initially formed the galaxies.

Observing Clusters

Globular Star Cluster

Some star clusters, such as the Pleiades, accept been known for some time. Others remained undiscovered until the invention of the telescope. Before that time, many of the globular clusters and smaller open clusters were visible only as fuzzy spots in the sky. Many were even mistaken for comets at 1 fourth dimension or some other. Charles Messier was ane of the first astronomers to discover and catalog star clusters along with other deep heaven objects. His catalog contains 51 of the brightest and largest star cluster in the night sky. Star cluster are amidst the easiest objects to find in the nighttime sky. Many open clusters, such equally the Pleiades and the Hyades, are large enough to be seen with the naked centre. Binoculars will reveal a wealth of globular clusters when pointed toward the centre of our galaxy nearly the constellation of Sagittarius. When seen through a telescope, globular clusters are arguably the most beautiful objects in the sky. Photographs exercise not do them justice. Atmospheric turbulence causes many of these photos to exist lacking in sharpness. But when observed through a telescope from a dark location, they can take on the look of silvery glitter on black velvet. Observing star clusters can be 1 of the most rewarding experiences in the astronomy hobby.