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Galaxies are massive groups of billions of stars and other material all held together by gravity.
Observations from the Hubble Space Telescope and other ground-based equipment show that the first galaxies formed only about one billion years after the Big Bang, 13-14 billion years ago.
There are two leading theories to explain the formation of the first galaxies.
One states that galaxies were born when extensive clouds of gas collapsed under their own gravitational pull this allowed stars to form.
The other, which is gaining strength, states that that the young universe had small ‘lumps’ of matter which clumped together to form galaxies. The Hubble Space Telescope has photographed many of these lumps.
The galaxy formation process has not stopped and our Universe continues to evolve. Smaller galaxies are often ‘gobbled up’ by larger ones, this is known as galaxy merging. The Milky Way may contain the remains of several smaller galaxies, which it has swallowed in its lifetime.
Galaxy mergers happen quite often. The largest galaxies are giant ellipticals. The look like giant eggs or footballs and can be ten times the size of the Milky Way and contain over a trillion stars. These usually formed when two or more spiral galaxies merged.
Evidence to support the merger theory includes the large number of ellipticals in dense clusters of galaxies, where mergers must be common.
Mergers can take from few hundred million years to a few billion years to complete.
Observations from the Hubble Space Telescope and other ground-based equipment show that the first galaxies formed only about one billion years after the Big Bang, 13-14 billion years ago.
There are two leading theories to explain the formation of the first galaxies.
One states that galaxies were born when extensive clouds of gas collapsed under their own gravitational pull this allowed stars to form.
The other, which is gaining strength, states that that the young universe had small ‘lumps’ of matter which clumped together to form galaxies. The Hubble Space Telescope has photographed many of these lumps.
The galaxy formation process has not stopped and our Universe continues to evolve. Smaller galaxies are often ‘gobbled up’ by larger ones, this is known as galaxy merging. The Milky Way may contain the remains of several smaller galaxies, which it has swallowed in its lifetime.
Galaxy mergers happen quite often. The largest galaxies are giant ellipticals. The look like giant eggs or footballs and can be ten times the size of the Milky Way and contain over a trillion stars. These usually formed when two or more spiral galaxies merged.
Evidence to support the merger theory includes the large number of ellipticals in dense clusters of galaxies, where mergers must be common.
Mergers can take from few hundred million years to a few billion years to complete.