This image of the brown dwarf, Gliese 229b, was created using the Hubble Space Telescope. Compared to Jupiter, Gliese is about twice as large and 40 times as massive.
Click on image for full size
During the early 1900's, which is not very long ago, astronomers were
unaware that there were other galaxies outside our own Milky Way Galaxy
. When they
saw a small fuzzy patch in the sky through their telescopes, they
called it a nebula
examined closely, some of the nebulae had a spiral shape. So
astronomers at first called these "spiral nebulae". These nebulae
were all believed to be part of our Galaxy, our community of stars.
Edwin Hubble studied the "spiral nebulae" and found that they were
composed of stars. These nebulae were not nebulae at all, but other
communities of billions of stars held together by gravity - galaxies!
Suddenly, our universe was much bigger. We realized that our Galaxy
was just one of many billions of galaxies in the universe.
Hubble studied galaxies for a very long time, and after seeing many,
many galaxies, he realized that he could put them into groups based on
their shape: spirals, ellipticals, or irregulars. His work helped
us to understand that the appearance of galaxies depends on our point
of view, and on what's happening in the galaxies.
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