Hubble and the expansion of the Universe

Hubble and the expansion of the Universe

Hubble was an important American scientist of the twentieth century, considered the father of observational cosmology.

Edwin Powell Hubble was born in Marshfield, Missouri, on November 20, 1889 and died in San Marino, California, on September 28, 1953. He was an astronomer and cosmologist who became famous for discovering that the Universe is expanding, and estimating his size and age

However, Hubble's contribution to knowledge of the universe is much broader and goes beyond the expansion of the universe, since its influence in astronomy and astrophysics touches many other fields.

He began his professional career studying jurisprudence in Chicago and Oxford, but also distinguished himself as an athlete and boxer. One of his first discoveries dates back to 1919, when he showed that inside our Galaxy there are hydrogen clouds that are made luminous by the existence of stars inside.

In 1923 he discovered the individual stars that constitute the nebula of the outer region of the Andromeda galaxy, and, thanks to the luminosity-distance relationship that characterizes these stars, he was able to demonstrate that Andromeda is not inside our Galaxy, but outside , and that is a star system completely similar to ours. Hubble also introduced a classification system of the Galaxies according to their structure.

In 1929 Hubble compared the distances he had calculated for different galaxies with the redshifts set by Slipher for the same galaxies. He discovered that the farther the galaxy was, the higher its recession speed.

This relationship is known as the law of redshifts or Hubble's law; determines that the speed of a galaxy is proportional to its distance. The relationship between the recession velocity of a galaxy and its distance is the Hubble constant. The value of this constant is estimated to be between 50 and 100 km / s per megaparsec (1 megaparsec equals 1 million parsecs), although the most recent data points to a value between 60 and 70 km / s per megaparsec

As it seems that galaxies recede in all directions from the Milky Way, one might think that our galaxy is the center of the Universe. However, this is not so. Imagine a globe with uniformly separated points. By inflating the balloon, an observer at one point on its surface would see how all other points move away from it, just as observers see all galaxies recede from the Milky Way.

The analogy also provides us with a simple explanation of Hubble's law: the Universe expands like a globe.

Before he died, Hubble also participated in the design of the mastodontic American telescope of Monte Palomar in California. In his honor, the Hubble Space Telescope is named after him.

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