The letter that changed the universe

Views of a well-known pulsating star taken almost 90 years aside and a portrait of its galactic dwelling are proven on this picture assortment.
| Photo Credit: NASA Goddard Space Flight Center / flickr

You know that the Andromeda galaxy is the nearest giant galaxy to our personal Milky Way, don’t you? In case you didn’t, don’t be too onerous on your self. Just a century in the past, it was a hotly debated matter, even amongst astronomers. In truth, it was confirmed past doubt solely about 100 years in the past, in 1923-24.

Before that, astronomers used to consult with the Andromeda galaxy, often known as Messier 31, M31, or NGC 224, as the Andromeda nebula. In truth, all the many galaxies scattered by the sky have been known as spiral nebulae. Even although plenty of them, of various sizes, shapes, and orientations, have been seen in the evening sky, their nature remained a thriller and their distances have been unknown.

Island universes

The nature of spiral nebulae and the extent of the universe was a keenly contested matter. There have been two diverging theories that dominated the scene a little bit over 100 years in the past. While the outdated concept outlined the Milky Way as the universe that had all the spiral nebulae inside its boundaries, the new one noticed these different spirals as exterior particular person galaxies, known as “island universes.”

American scientist and astronomer Harlow Shapley of Mount Wilson Observatory was the important proponent of the former opinion based mostly on his conclusions from observations throughout the years 1914-17. American astronomer Hebert Doust Curtis of Lick Observatory, who had been finding out spiral nebulae for almost 10 years, was the central determine of the exterior galaxies view and believed that the Milky Way was one among many galaxies in an enormous universe. 

The Shapley-Curtis Debate

The two scientists confronted off in the Great Debate, additionally referred to as the Shapley-Curtis Debate, that was held at the Smithsonian Museum of Natural History on April 26, 1920. It was much less of a debate, nevertheless, as Shapley gave a secure lecture, and Curtis made his level with an intensive analysis presentation.

Even although the debate had no clear winner, the years that adopted offered one as one concept was proved to be proper. American astronomer Edwin Hubble was the one who made the discovery, and it put him onto higher issues.

Variable stars

In 1919, Hubble started working at Mount Wilson and used the 100-inch Hooker telescope, then the largest reflector in the world, and photographic plates to concentrate on spiral nebulae. He found a variable star –  a star whose brightness as seen from Earth adjustments with time – inside what was then known as the Andromeda nebula in October 1923. 

The star that Hubble had found, V1, was in truth a particular class of pulsating star. It was a Cepheid variable that can be utilized to measure giant cosmic distances reliably. Hubble’s assessments utilizing the star made it clear that Andromeda lies far past our personal Milky Way, thus proving that it needed to be one other galaxy.  

After spending a number of extra months peering at Andromeda, discovering one other Cepheid variable and plenty of extra novae (a kind of variable star), Hubble shot out a letter to Shapley on February 19, 1924. In this letter, Hubble advised Shapley about his discovery and its implications, whereas additionally together with a lightweight curve of V1. Shapley didn’t have to be advised twice that what he was studying was real, prompting him reportedly to inform a colleague, “Here is the letter that destroyed my universe.”

Expanding universe

By the finish of the yr, Hubble had discovered 36 variable stars in the Andromeda galaxy, 12 of which have been Cepheids. Using these, he was capable of place the galaxy at a distance of 900,000 mild years. Current improved measurements place the Andromeda galaxy roughly 2.5 million mild years away.

The discovery of V1, referred to typically as the star that changed the universe, helped Hubble uncover the reality about the universe. Hubble went on to find many extra galaxies past our personal. And with these discoveries, he was capable of decide that our universe is increasing.