What is extragalactic astronomy?
The dawn of extragalactic astronomy was in 1917, when the American astronomer Heber Curtis watched the star Nova in M31, a formal name for what was then called the great Andromed Nebula. At that time, it was assumed that spiral nebulae, such as Andromeda, lies in our own galaxy, with a size only a few times larger than in our solar system and distance of less than 50,000 light -years. They thought the Milky Way galaxy was the whole universe.
After observing the Nova in M31, Curtis searched the photographic record and noticed 11 other Novae in the region. If the M31 was just star nebulae, why was there so much novae and why were these characteristically weaker than other Novae? The justification of the observations that these Novae were about 10 sizes weaker than the Novae, which is known to be in our own galaxy, Curtis said that the Nebula of the Great Andromeda was actually a "island universe" different from the Milky Railway and located 500,000 Lights.Cesta. AstronoAt first they did not accept his hypothesis and began a scientific debate.
In 1920, Harlow Shapey, another American astronomer, called on Curtis to discuss important astronomical issues of that time, including whether the spiral nebulae, such as Andromeda, was really outside our own galaxy. Many fellow citizens watched the debate, but the final results were inconclusive. Only in 1925, when Edwin Hubble (after which the Hubble Space Telescope is named) published observations from a 100 -inch binoculars, then the largest in the world, discovered Cepheid Variable Stars in Andromeda Nebula and used them to measure its distance, which were 2.5 million lights. The era of extragalactic astronomy and Andromed Nebula was renamed Andromed Galaxy.
Over the past 80 years, the extractical astronomy has an active area of research. By measuring the relative speed of galaxies using their opticalThe signature was found that all galaxies move apart and the entire universe is expanding. In 1998, Ia Supernova observation even indicated that expansion was accelerating. Cosmologists now think that it is likely that the universe will end up with the "death of heat", where accelerating expansion causes all the matter to disperse and freeze.
An important episode of extragalactic astronomy is the discovery and investigation of yeast, quasi-star radio sources. It was known that these bright point sources were very light and very distant, among the farthest objects that are up to 13 billion light -years. Although Kvasars were first observed in the 1950s, only in the 1970s. The scientific consensus of the nature of the yeast began to appear: they were active galactic cores, consisting of supermassive black holes suction of several solar materials for centuries of material and release a huge amount of radiation in this process. Were created formal models that described itY, and one of the greatest mysteries in extragalactic astronomy has been resolved.
Today, scientists have been photographed and classified by millions of galaxies, sometimes even by helping the public (as in Galaxyzoo). Galaxies are either spiral or elliptical. It is estimated that there are about one hundred billion galaxies in an observable universe. Interestingly, it is approximately the same as the number of neurons in the human brain.