";s:4:"text";s:6742:"However, other than our own Milky Way, there are only three other galaxies that we can see as fuzzy images without a telescope.
Were they gas clouds located within our Milky Way galaxy, or were they vast groups of stars located far beyond our galaxy?In 1919, American astronomer Edwin Hubble tackled the question. It winds behind the dust, gas and stars of our own galaxy, the Milky Way, from the constellation Perseus in the Northern Hemisphere to the constellation Apus in the far south. Both of these are around 160,000 light-years away.
Beyond the Milky Way …
Using the new 100-inch reflector at Mt. Astronomers no longer thought our galaxy was the entire universe. If, on the other hand, they were remote, far beyond the edge of the Galaxy, they could be other star systems containing billions of stars.To determine what the nebulae are, astronomers had to find a way of measuring the distances to at least some of them. For the first time, the images revealed faint stars in the nebula.Hubble now knew the Andromeda nebula was a collection of stars, but how far away was it? The Andromeda nebula was really the Andromeda galaxy. Astronomers have discovered that there is a vast wall across the southern border of the local cosmos.
Although a few others had glimpsed pieces of the puzzle, it was Hubble who put it all together and showed that an understanding of the large-scale structure of the universe was feasible.His work brought Hubble much renown and many medals, awards, and honorary degrees. In the early 1900s, astronomers were debating the makeup of spiral nebulae — cloudy, spiral-shaped objects found throughout the night sky. “We’d have to anticipate that our view of the filament is clipped; that it extends beyond our survey horizon.”And yet the South Pole Wall is nearby in cosmological terms. 1924: Astronomer Edwin Hubble announces that the spiral nebula Andromeda is actually a galaxy and that the Milky Way is just one of many galaxies in the universe.
It was the beginning of something big.“We now see the Great Attractor as the downtown region of the supercluster that we live in — an overall entity that our team has called the Laniakea Supercluster,” Dr. Tully said. Here were reliable indicators that Hubble could use to measure the distances to the nebulae using the technique pioneered by Henrietta Leavitt (see the chapter on No one in human history had ever measured a distance so great. Astronomers have long known that the brightest part of the Milky Way, the pancake-shaped disk of stars that houses the sun, is some 120,000 light-years across (SN: 8/1/19). 1930 — Robert Trumpler uses open cluster observations to quantify the absorption of light by interstellar dust in the galactic plane ; this absorption had plagued earlier models of the Milky Way,
All objects that were not sharp points of light were given the same name, As early as the eighteenth century, the philosopher Immanuel Kant (1724–1804) suggested that some of the nebulae might be distant systems of stars (other Milky Ways), but the evidence to support this suggestion was beyond the capabilities of the telescopes of that time.By the early twentieth century, some nebulae had been correctly identified as star clusters, and others (such as the Orion Nebula) as gaseous nebulae. “The South Pole Wall also contributes but, again, only in part,” he added, listing more local galaxy clusters and voids.
Astronomers estimate that the age of the Universe is 13.7 billion years old.
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