"In a letter written in 1924, who wrote ""You will be interested to hear that I have found a Cepheid variable in the Andromeda Nebula"" and transformed our view of the universe forever?"
"formation. American astronomer Edwin Hubble included M31 (then known as the Andromeda Nebula) in his groundbreaking 1923 research on galaxies. Using the 100-inch Hooker Telescope at Mount Wilson Observatory in California, he observed Cepheid variable stars in M31 during a search for novae, allowing him to determine their distance by using the stars as standard candles. The distance he found was far greater than the size of the Milky Way, which led him to the conclusion that many similar objects were ""island universes"" on their own. Hubble originally estimated that the Andromeda Galaxy was 900,000 light-years away, but Ernst Öpik's"
"was coming to a climax. Mount Wilson astronomer Harlow Shapley championed the model of a cosmos made up of the Milky Way star system only; while Heber D. Curtis argued for the idea that spiral nebulae were star systems in their own right as island universes. This difference of ideas came to a climax with the organization of the Great Debate on 26 April 1920 at the meeting of the U.S. National Academy of Sciences in Washington, D.C. The debate was resolved when Edwin Hubble detected Cepheid Variables in the Andromeda galaxy in 1923 and 1924. Their distance established spiral"
"wife and continued on a modified diet and work schedule. He died of cerebral thrombosis (a spontaneous blood clot in his brain) on September 28, 1953, in San Marino, California. No funeral was held for him, and his wife never revealed his burial site. Edwin Hubble's arrival at Mount Wilson Observatory, California in 1919 coincided roughly with the completion of the Hooker Telescope, then the world's largest. At that time, the prevailing view of the cosmos was that the universe consisted entirely of the Milky Way Galaxy. Using the Hooker Telescope at Mt. Wilson, Hubble identified Cepheid variables (a kind"
"a type of nebula existing within our own galaxy, was the subject of the Great Debate of 1920, between Heber Curtis of Lick Observatory and Harlow Shapley of Mt. Wilson Observatory. Beginning in 1923, Edwin Hubble observed Cepheid variables in several spiral nebulae, including the so-called ""Andromeda Nebula"", proving that they are, in fact, entire galaxies outside our own. The term ""spiral nebula"" has since fallen into disuse. The Milky Way was once considered an ordinary spiral galaxy. Astronomers first began to suspect that the Milky Way is a barred spiral galaxy in the 1960s. Their suspicions were confirmed by"
"(systems of orbiting bodies that are themselves orbiting in a larger system, ""ad infinitum"") in a fractal way such that the Universe has a negligibly small overall density; such a cosmological model had also been proposed earlier in 1761 by Johann Heinrich Lambert. A significant astronomical advance of the 18th century was the realization by Thomas Wright, Immanuel Kant and others of nebulae. In 1919, when Hooker Telescope was completed, the prevailing view still was that the Universe consisted entirely of the Milky Way Galaxy. Using the Hooker Telescope, Edwin Hubble identified Cepheid variables in several spiral nebulae and in"
"University-based Harlow Shapley. Despite the opposition, Hubble, then a thirty-five-year-old scientist, had his findings first published in ""The New York Times"" on , 1924, then presented them to other astronomers at the January 1, 1925 meeting of the American Astronomical Society. Hubble's results for Andromeda were not formally published in a peer-reviewed scientific journal until 1929. Hubble's findings fundamentally changed the scientific view of the universe. Supporters state that Hubble's discovery of nebulae outside of our galaxy helped pave the way for future astronomers. Although some of his more renowned colleagues simply scoffed at his results, Hubble ended up publishing"
"center of the Andromeda galaxy for the first time. These observations led him to define distinct ""populations"" for stars (Population I and Population II). The same observations led him to discover that there are two types of Cepheid variable stars. Using this discovery he recalculated the size of the known universe, doubling the previous calculation made by Hubble in 1929. He announced this finding to considerable astonishment at the 1952 meeting of the International Astronomical Union in Rome. Together with Fritz Zwicky, he identified supernovae as a new category of astronomical objects. Zwicky and he also proposed the existence of"
"Universe. To support his claim that the Great Andromeda Nebula is an external galaxy, Curtis noted the appearance of dark lanes resembling the dust clouds in the Milky Way, as well as the significant Doppler shift. In 1922, the Estonian astronomer Ernst Öpik gave a distance determination that supported the theory that the Andromeda Nebula is indeed a distant extra-galactic object. Using the new 100 inch Mt. Wilson telescope, Edwin Hubble was able to resolve the outer parts of some spiral nebulae as collections of individual stars and identified some Cepheid variables, thus allowing him to estimate the distance to"
"Sandage was a graduate student assistant to cosmologist Edwin Hubble. He continued Hubble's research program after Hubble died in 1953. In 1952 Baade surprised his fellow astronomers by announcing (at the 1952 Conference of the International Astronomical Union, in Rome) his determination of two separate populations of Cepheid variable stars in the Andromeda Galaxy, resulted in a doubling of the estimated age of the universe (from 1.8 to 3.6 billion years). Hubble had posited the earlier value; he had considered only the weaker Population II Cepheid variables as standard candles. After Baade's pronouncements, Sandage showed that astronomers' previous assumption, that"
"for graduate work, where he studied under Henry Norris Russell and used the period-luminosity relation for Cepheid variable stars (discovered by Henrietta Swan Leavitt) to determine distances to globular clusters. He was instrumental in moving astronomy away from the idea that Cepheids were spectroscopic binaries, and toward the concept that they were pulsators. He realized that the Milky Way Galaxy was far larger than previously believed, and that the Sun's place in the galaxy was in a nondescript location. This discovery by Shapley is a part of the Copernican principle, according to which the Earth is not at the center"
"Zhevakin identified ionized helium as a likely valve for the engine. Cepheid variable A Cepheid variable () is a type of star that pulsates radially, varying in both diameter and temperature and producing changes in brightness with a well-defined stable period and amplitude. A strong direct relationship between a Cepheid variable's luminosity and pulsation period established Cepheids as important indicators of cosmic benchmarks for scaling galactic and extragalactic distances. This robust characteristic of classical Cepheids was discovered in 1908 by Henrietta Swan Leavitt after studying thousands of variable stars in the Magellanic Clouds. This discovery allows one to know the"
"Edwin Hubble Edwin Powell Hubble (November 20, 1889 – September 28, 1953) was an American astronomer. He played a crucial role in establishing the fields of extragalactic astronomy and observational cosmology and is regarded as one of the most important astronomers of all time. Hubble discovered that many objects previously thought to be clouds of dust and gas and classified as ""nebulae"" were actually galaxies beyond the Milky Way. He used the strong direct relationship between a classical Cepheid variable's luminosity and pulsation period (discovered in 1908 by Henrietta Swan Leavitt) for scaling galactic and extragalactic distances. Hubble provided evidence"
"in the Milky Way, as well as the significant Doppler shift. The controversy was conclusively settled by Edwin Hubble in the early 1920s using the Mount Wilson observatory Hooker telescope. With the light-gathering power of this new telescope, he was able to produce astronomical photographs that resolved the outer parts of some spiral nebulae as collections of individual stars. He was also able to identify some Cepheid variables that he could use as a benchmark to estimate the distance to the nebulae. He found that the Andromeda Nebula is 275,000 parsecs from the Sun, far too distant to be part"
"Pickering thought she would make a significant discovery—one that would eventually change astronomy."" The period–luminosity relationship for Cepheids, now known as ""Leavitt's law"" made them those stars the first ""standard candle"" in astronomy, allowing scientists to compute the distances to galaxies too remote for stellar parallax observations to be useful. One year after Leavitt reported her results, Ejnar Hertzsprung determined the distance of several Cepheids in the Milky Way and that, with this calibration, the distance to any Cepheid could be accurately determined. Cepheids were soon detected in other galaxies, such as Andromeda (notably by Edwin Hubble in 1923–24), and"
"Cepheid variable A Cepheid variable () is a type of star that pulsates radially, varying in both diameter and temperature and producing changes in brightness with a well-defined stable period and amplitude. A strong direct relationship between a Cepheid variable's luminosity and pulsation period established Cepheids as important indicators of cosmic benchmarks for scaling galactic and extragalactic distances. This robust characteristic of classical Cepheids was discovered in 1908 by Henrietta Swan Leavitt after studying thousands of variable stars in the Magellanic Clouds. This discovery allows one to know the true luminosity of a Cepheid by simply observing its pulsation period."
"by Jan Oort.) Baade also discovered that there were two types of Cepheid variables, which resulted in a doubling of the distance estimate to Andromeda, as well as the remainder of the Universe. In 1950, radio emission from the Andromeda Galaxy was detected by Hanbury Brown and Cyril Hazard at Jodrell Bank Observatory. The first radio maps of the galaxy were made in the 1950s by John Baldwin and collaborators at the Cambridge Radio Astronomy Group. The core of the Andromeda Galaxy is called 2C 56 in the 2C radio astronomy catalog. In 2009, the first planet may have been"
"Milky Way was the entire universe (spanning over 100,000 lightyears or 30 kiloparsec across) and that all of the observed ""nebulae"" (currently known as galaxies) resided within this region. On the other hand, Curtis argued that the Milky way was much smaller and that the observed nebulae were in fact galaxies similar to our own Milky Way. This debate was not settled until late 1923 when the astronomer Edwin Hubble measured the distance to M31 (currently known as the Andromeda galaxy) using Cepheid Variable stars. By measuring the period of these stars, Hubble was able to estimate their intrinsic luminosity"
"principal distinguishing feature among different spectra. This led to re-ordering of the ABC types by temperature instead of hydrogen absorption-line strength. Due to Cannon's work, most of the then-existing classes of stars were thrown out as redundant. Afterward, astronomy was left with the seven primary classes recognized today, in order: O, B, A, F, G, K, M; that has since been extended. Henrietta Swan Leavitt first published her study of variable stars in 1908. This discovery became known as the ""period-luminosity relationship"" of Cepheid variables. Our picture of the universe was changed forever, largely because of Leavitt's discovery. The accomplishments"
"possible solutions to the equations of general relativity, and each solution implies a possible ultimate fate of the universe. Alexander Friedmann proposed several solutions in 1922, as did Georges Lemaître in 1927. In some of these solutions, the universe has been expanding from an initial singularity which was, essentially, the Big Bang. In 1931, Edwin Hubble published his conclusion, based on his observations of Cepheid variable stars in distant galaxies, that the universe was expanding. From then on, the ""beginning"" of the universe and its possible ""end"" have been the subjects of serious scientific investigation. In 1927, Georges Lemaître set"
"astronomy career he made a number of notable contributions. He observed the variation of star movements based on their distance from the core of a galaxy. He also found that there were globular clusters in the galaxy orbiting in a retrograde direction. He also discovered an important error in the period-luminosity law of Cepheid variables, that had resulted in a significant underestimation of the size of the universe. In 1936 he established the Institute d'Astrophysique in Paris. He became the director of this facility and remained at this post for the rest of his life. During World War II he"
"represented the entire Universe or was merely one of numerous galaxies in the Universe. In 1929, Hubble and Milton L. Humason formulated what is now known as Hubble's Law by combining Cepheid distances to several galaxies with Vesto Slipher's measurements of the speed at which those galaxies recede from us. They discovered that the Universe is expanding (see the expansion of the Universe). However, the expansion of the Universe was posited several years before by Georges Lemaître. In the mid 20th century, significant problems with the astronomical distance scale were resolved by dividing the Cepheids into different classes with very"
"the fundamental and first overtone, occasionally the second overtone. A very small number pulsate in three modes, or an unusual combination of modes including higher overtones. On September 10, 1784, Edward Pigott detected the variability of Eta Aquilae, the first known representative of the class of classical Cepheid variables. However, the eponymous star for classical Cepheids is Delta Cephei, discovered to be variable by John Goodricke a few months later. A relationship between the period and luminosity for classical Cepheids was discovered in 1908 by Henrietta Swan Leavitt in an investigation of thousands of variable stars in the Magellanic Clouds."
"He showed that the star 61 Cygni had a parallax of just 0.31 arcseconds (compared to the modern value of 0.287″). This corresponds to a distance of over 10 light years. In 1917, Heber Curtis noted that novae in spiral nebulae were, on average, 10 magnitudes fainter than galactic novae, suggesting that the former are 100 times further away. The distance to the Andromeda Galaxy was determined in 1923 by American astronomer Edwin Hubble by measuring the brightness of cepheid variables in that galaxy, a new technique discovered by Henrietta Leavitt. This established that the Andromeda galaxy, and by extension"
"Henrietta Hill Swope Henrietta Hill Swope (October 26, 1902 – November 24, 1980) was an American astronomer who studied variable stars. In particular, she measured the period-luminosity relation for Cepheid stars, which are bright variable stars whose periods of variability relate directly to their intrinsic luminosities. Their measured periods can therefore be related to their distances and used to measure the size of the Milky Way and distances to other galaxies. She was the daughter of Gerard Swope, and niece of Herbert Bayard Swope. Her father went to MIT and was an engineer. He worked for General Electric, eventually rising"
"universe. In 1764, Charles Messier cataloged Andromeda as object M31 and incorrectly credited Marius as the discoverer despite it being visible to the naked eye. In 1785, the astronomer William Herschel noted a faint reddish hue in the core region of Andromeda. He believed Andromeda to be the nearest of all the ""great nebulae"", and based on the color and magnitude of the nebula, he incorrectly guessed that it is no more than 2,000 times the distance of Sirius. In 1850, William Parsons, 3rd Earl of Rosse, saw and made the first drawing of Andromeda's spiral structure. In 1864, William"
"stars in different exposures. While doing this, she discovered that some stars have the same brightness no matter the distance. This discovery led to her developing a direct way to calculate a star's distance from earth using the period of Cepheid variable stars and their intrinsic brightness. This discovery, in turn, led to the modern understanding of the true size of the universe, and Cepheid variables are still an essential tool for the measurement of cosmological distance. Sadly, Leavitt does not receive as much credit as she deserves. Pickering published her work with his name on it. The legacy she"
"were Cepheids) of this galaxy. He also surveyed the galaxy's stars distribution down to magnitude 19.4. He provided spectral characteristics, luminosities and dimensions for the five brightest ""diffuse nebulae"" (giant H II regions) that included the Bubble Nebula and the Ring Nebula. He also computed the absolute magnitude of the entire galaxy. Hubble's detection of eleven Cepheid variable stars was a milestone in astronomy. Utilizing the Cepheid Period-Luminosity relationship, Hubble determined a distance of more than 700,000 light-years. This was the first system beyond the Magellanic Clouds to have its distance accurately determined. (Hubble continued this process with the Andromeda"
"nebulae well beyond the edge of the Milky Way. Subsequent modelling of the universe explored the possibility that the cosmological constant, introduced by Einstein in his 1917 paper, may result in an expanding universe, depending on its value. Thus the Big Bang model was proposed by the Belgian priest Georges Lemaître in 1927 which was subsequently corroborated by Edwin Hubble's discovery of the red shift in 1929 and later by the discovery of the cosmic microwave background radiation by Arno Penzias and Robert Woodrow Wilson in 1964. These findings were a first step to rule out some of many alternative"
"progress in science through the story of Leavitt. Robert Burleigh wrote the biography ""Look Up!: Henrietta Leavitt, Pioneering Woman Astronomer"" for a younger audience. It is written for four to eight year olds. Henrietta Swan Leavitt Henrietta Swan Leavitt (; July 4, 1868 – December 12, 1921) was an American astronomer. A graduate of Radcliffe College, she worked at the Harvard College Observatory as a ""computer"", tasked with examining photographic plates in order to measure and catalog the brightness of stars. This work led her to discover the relation between the luminosity and the period of Cepheid variables. Though she"
"of star that is used as a means to determine the distance from the galaxy – see also standard candle) in several spiral nebulae, including the Andromeda Nebula and Triangulum. His observations, made in 1922–1923, proved conclusively that these nebulae were much too distant to be part of the Milky Way and were, in fact, entire galaxies outside our own, suspected by researchers at least as early as 1755 when Immanuel Kant's General History of Nature and Theory of the Heavens appeared. This idea had been opposed by many in the astronomy establishment of the time, in particular by Harvard"
"Henry Norris Russell publishes a diagram that shows this relationship. Although astronomers agree that the diagram shows the sequence in which stars evolve, they argue about which way the sequence progresses. Arthur Eddington finally settles the controversy in 1924. Williamina Fleming publishes her discovery of White dwarf stars. Henrietta Swan Leavitt discovers the period-luminosity relation for cepheid variables, whereas the brightness of a star is proportional to its luminosity oscillation period. It opened a whole new branch of possibilities of measuring distances on the universe, and this discover was the base for the work done by Edwin Hubble on extragalactic"
"limits imposed by the difficulty in measuring the minuscule parallaxes associated with objects beyond our galaxy meant that astronomers had to look for alternative ways to measure cosmic distances. To this end, a standard candle measurement for Cepheid variables was discovered by Henrietta Swan Leavitt in 1908 which would provide Edwin Hubble with the rung on the cosmic distance ladder he would need to determine the distance to spiral nebula. Hubble used the 100-inch Hooker Telescope at Mount Wilson Observatory to identify individual stars in those galaxies, and determine the distance to the galaxies by isolating individual Cepheids. This firmly"
"creation of matter in the universe. In his book ""Astronomy and Cosmology"" (1928) he stated: ""The type of conjecture which presents itself, somewhat insistently, is that the centers of the nebulae are of the nature 'singular points' at which matter is poured into our universe from some other, and entirely extraneous spatial dimension, so that, to a denizen of our universe, they appear as points at which matter is being continually created."" This theory fell out of favour when the 1965 discovery of the cosmic microwave background was widely interpreted as the tell-tale signature of the Big Bang. His scientific"