When was galaxies discovered

Slipher had found that many of the spiral nebulae were moving at enormous velocities, far faster than those of any known stars, and that the spirals were mostly traveling away from us. To Slipher, those peculiar velocities provided convincing evidence that they must be independent systems, driven by unknown mechanisms at work far outside our Milky Way. But Slipher lacked the necessary resources to prove his interpretation. What he needed was a giant telescope like the one Hubble was piloting on Mt Wilson.

This is where our story kicks into high gear. In , another important piece of the puzzle fell into place. That year, Swedish astronomer Knut Lundmark observed what he believed were individual stars in the arms of the spiral nebula M Shortly after, John Duncan at Mount Wilson spotted dots of light that grew fainter and brighter in the same nebula.

Could these be variable stars, similar to ones in the Milky Way but far dimmer owing to their enormous distance? Sensing the answer was at hand, Hubble stepped up his efforts. The effort paid off with highly detailed, long-exposure images of the Andromeda nebula. The mottled light of the nebula began to resolve itself into a multitude of luminous points, looking not like a smear of gas but like a vast hive of stars. This type of star grows brighter and dimmer in a regular and predictable way, with its intrinsic luminosity directly related to its period of variation.

Simply by timing the day cycle of this star as it slowly flickered, Hubble could deduce its distance. His estimate was , light years—less than half the modern estimate, but a shockingly large number at the time.

That distance placed Andromeda, one of the brightest and presumably closest of the spiral nebulae, vastly outside the bounds of the Milky Way. In principle, the Great Debate was settled then and there. Spiral nebulae were other galaxies, and our Milky Way was just one outpost within a staggeringly vast universe. And yet, still the story was far from over. Ever cautious, Hubble pressed on for more and better evidence. By the following February, he had uncovered a possible second Cepheid in Andromeda, Cepheid variables in M33, and possibly in three other nebulae as well.

Now that there could be no doubt, he wrote to his arch-rival Harlow Shapley — a leading proponent of the idea that the spiral nebula were small and nearby — to needle him with the news. Payne-Gaposchkin was another pivotal figure in modern astrophysics; by remarkable coincidence, her pioneering work on stellar spectra was completed on … January 1, !

Despite his obvious excitement at the Andromeda findings, Hubble was still reluctant to publish his results. For all his surface confidence, he was terribly concerned about making a grand pronouncement prematurely. Every time he walked down from the summit to attend the formal 5 P. Not all of them accepted the existence of other galaxies. Vain and intensely aware of his reputation, Hubble worried that he might end up looking the fool. Adriaan van Maanen, a playful and well-liked Dutch astronomer at Mt Wilson, was in fact still vigorously arguing in the other direction.

He was convinced that he had observed some of the spiral nebulae rotating, which was possible only if they were relatively small and nearby. Hubble found it unsettling to have a doubter in his own midst and held back until he was utterly sure of his results. Van Maanen never figured out where he went wrong and refused to admit his mistake.

As a result, the first public announcement of his astronomical breakthrough was a small story that ran in The New York Times on November 23, Edwin Hubble established some of the most important ideas in the study of galaxies. The pull of astronomy eventually proved too strong to resist, and so Hubble went back to the University of Chicago for graduate work. Just as he was about to finish his degree and accept an offer to work at the soon-to be completed 2.

Ripened by experience, energetic, disciplined, and a skillful observer, Hubble soon established some of the most important ideas in modern astronomy. He showed that other galaxies existed, classified them on the basis of their shapes, found a pattern to their motion and thus put the notion of an expanding universe on a firm observational footing , and began a lifelong program to study the distribution of galaxies in the universe.

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. As he became better known he was the first astronomer to appear on the cover of Time magazine , he and his wife enjoyed and cultivated friendships with movie stars and writers in Southern California.

It was fitting that observations with the Hubble Space Telescope and his foundational work on expansion of the universe contributed to the Nobel Prize in Physics, given for the discovery that the expansion of the universe is accelerating a topic we will expand upon in the chapter on The Big Bang.

Faint star clusters, clouds of glowing gas, and galaxies all appeared as faint patches of light or nebulae in the telescopes available at the beginning of the twentieth century. It was only when Hubble measured the distance to the Andromeda galaxy using cepheid variables with the giant 2. Skip to main content.

Search for:. Key concepts and summary Faint star clusters, clouds of glowing gas, and galaxies all appeared as faint patches of light or nebulae in the telescopes available at the beginning of the twentieth century. Licenses and Attributions. He earned a Ph. After serving in World War I and rising to the rank of major, he got bored with law and returned to astronomy. He trained the powerful new inch telescope at Mount Wilson in Southern California on spiral nebulae.

These fuzzy patches of light in the sky were generally thought to be clouds of gas or dust within our galaxy, which was presumed to include everything in the universe except the Magellanic Clouds. Some nebulae seemed to contain a few stars, but nothing like the multitudes of the Milky Way. Hubble not only found a number of stars in Andromeda, he found Cepheid variable stars. These stars vary from bright to dim, and a very smart Harvard computationist named Henrietta Leavitt had discovered in that you could measure distance with them.

Given the brightness of the star and its period — the length of time it takes to go from bright to dim and back again — you could determine how far away it is. Hubble used Leavitt's formula to calculate that Andromeda was approximately , light years away.