Cepheid variable Concepts

Day We Found the Universe

by Marcia Bartusiak · 6 Apr 2009 · 412pp · 122,952 words

painstaking examination of the Small Magellanic Cloud, she came to notice a special group of variable stars, sixteen in number. They were later identified as Cepheid variables, stars that are thousands of times more luminous than our Sun. Their name was derived from one of the first and brightest discovered, δ Cephei

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and the shape of the curve (sharp rise and slow decline), Hubble now comprehended that he had captured that elusive and rare celestial beast—a Cepheid variable, a star seven thousand times brighter than our Sun. But it appeared so dim—the barest smudge on his photographic plate—that Hubble knew it

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hundred thousand times dimmer than the faintest stars visible to the unaided eye. The photographic plate of Andromeda (M31) on which Edwin Hubble identified a Cepheid variable star, mistaken at first for a nova, in a spiral nebula—the first step in Hubble's opening up the universe (Courtesy of the Observatories

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polite niceties or inquiries of health. He got straight to the point. “Dear Shapley:—You will be interested to hear that I have found a Cepheid variable in the Andromeda Nebula (M31). I have followed the nebula this season as closely as the weather permitted and in the last five months have

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-luminosity curve.” Hubble was undeterred by Shapley's caveats and continued his searches at a brisk clip. His discovery spurred him to find even more Cepheid variables, in both Andromeda and other spiral nebulae. But cautious as ever, he made no public announcement. Not yet. Just a week after sending off his

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time that Hubble forged his industrious partnership with Humason, each taking on a specific task to get the overall job done. While Hubble searched for Cepheid variables to determine the distances to a sample of galaxies, his colleague focused on getting the redshift data to figure out the galaxies' velocities (if that

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some 6 million light-years away. He accomplished this feat by establishing a ladder of measurements, one rung leading to the next. First he used Cepheid variables, his most reliable yardstick, to directly obtain the distances to six relatively nearby galaxies; then he judged the magnitude of the brightest stars in those

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. 200 numbering each nova and variable: HUB, Box 1, Hubble Addenda. 202 “Dear Shapley:—You will be interested to hear that I have found a Cepheid variable in the Andromeda Nebula”: HUA, Hubble to Shapley, February 19, 1924. 203 figuring out early on, soon after he arrived at Mount Wilson, that they

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Clusters.” Astrophysical Journal 48: 154-81. ——. 1918c. “Studies Based on the Colors and Magnitudes in Stellar Clusters. Eighth Paper: The Luminosities and Distances of 139 Cepheid Variables.” Astrophysical Journal 48: 279-94. ——. 1918d. “Globular Clusters and the Structure of the Galactic System.” Publications of the Astronomical Society of the Pacific 30: 42

Big Bang

by Simon Singh · 1 Jan 2004 · 492pp · 149,259 words

that was causing the variation. They decided that Eta Aquilae and Delta Cephei belonged to a new class of variable star, which we now call Cepheid variables, or simply Cepheids. Some Cepheids are very subtle, such as Polaris, the North Star, which is our closest Cepheid. William Shakespeare was completely unaware of

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always indicates north, its luminosity varies and it grows slightly brighter and dimmer roughly every four nights. Today we know what goes on inside a Cepheid variable star, what causes its asymmetric variability and what makes it different from other stars. Most stars are in a state of stable equilibrium, which essentially

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, and the air in the balloon cools, the air pressure inside the balloon decreases and the balloon contracts to find a new equilibrium state. However, Cepheid variable stars are not in a stable equilibrium, but fluctuate. When a Cepheid is relatively cool, it is unable to counteract the gravitational force, which will

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.’ In a career lasting just a few years, Goodricke had made an outstanding contribution to astronomy. Although he did not realise it, his discovery of Cepheid variables would prove pivotal to the Great Debate and to the development of cosmology. Over the next century, Cepheid spotters would discover thirty-three stars with

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her ‘a variable-star fiend’. Of the various types of variable star, Leavitt developed a particular passion for Cepheids. After months spent measuring and cataloguing Cepheid variables, she yearned to gain some understanding of what determined the rhythm of their fluctuations. In an effort to solve the mystery she turned her attention

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to the only two firm pieces of information available for any Cepheid variable: its period of variation and its brightness. Ideally, she wanted to see whether there was any relationship between period and brightness – perhaps brighter stars might

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the southern hemisphere, Leavitt had to rely on photographs taken at Harvard’s southern station at Arequipa in Peru. Leavitt managed to identify twenty-five Cepheid variables within the Small Magellanic Cloud. She did not know the distance from the Earth to the Small Magellanic Cloud, but she suspected that it was

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the luminosity of the Cepheid, the longer the period between the peaks in brightness. Leavitt was confident that this rule could be applied to any Cepheid variable star in the universe, and that her graph could be extended to include Cepheids with very long periods. This was a staggering result, pregnant with

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very similar period, then it must be 12 times as distant, because 122 = 144. Figure 45 These two graphs show Henrietta Leavitt’s observations of Cepheid variable stars in the Small Magellanic Cloud. Graph (a) is a plot of brightness (on the vertical axis) against period, measured in days (on the horizontal

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. They could prove that one Cepheid was, say, 12 times farther away than another, but that was all. If only the distance to just one Cepheid variable star could be found, then it would be possible to anchor Leavitt’s measurement scale and gauge the distance to every single Cepheid. The decisive

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’s Ejnar Hertzsprung. Together they used a combination of techniques, including parallax, to measure the distance to one Cepheid variable, which then transformed Leavitt’s research into the ultimate distance guide for the cosmos. Cepheid variables could act as a yardstick for the universe. In summary, an astronomer could now measure the distance to

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the lighthouse will be close to the village and the estimate will be fairly accurate. Similarly, an astronomer who works out the distance to a Cepheid variable also knows the rough distance to any other stars in its vicinity. The method is not foolproof, but it is effective in most cases. Professor

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was that two of the specks were indeed new novae. The even better news was that the third one was not a nova, but a Cepheid variable star. This third star had been recorded on some of the earlier plates but not on others, indicating its variability. Hubble had made the greatest

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7,000 times more luminous than the Sun. By comparing its absolute brightness and apparent brightness, Hubble deduced its distance. The result was staggering. The Cepheid variable star, and therefore the Andromeda Nebula which it inhabited, appeared to be roughly 900,000 light years from the Earth. The Milky Way was roughly

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October 1923 Hubble located three candidate novae in the Andromeda Nebula, each marked with an ‘N’. One of these novae turned out to be a Cepheid variable, a star that changes predictably in brightness, so the ‘N’ was crossed out and the star relabelled ‘VAR!’. Cepheids can be used to measure distance

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. Baade spent the war years studying a particular type of star known as an RR Lyrae star, a type of variable star similar to a Cepheid variable star. Williamina Fleming, who worked alongside Henrietta Leavitt at the Harvard Observatory, had shown that the variability of RR Lyrae stars could be used, like

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this way he could use the variability of RR Lyrae stars to measure the distance to Andromeda and cross-check earlier distance measurements based on Cepheid variables. In fact, Baade soon realised that the RR Lyrae stars in Andromeda were beyond the reach of the 100-inch Hooker Telescope, so he had

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and why the Andromeda Galaxy had been previously mismeasured. As explained in Chapter 3, the original measurement to the Andromeda Galaxy had been performed using Cepheid variable stars, which had become the basic yardstick for measuring intergalactic distances. Henrietta Leavitt had shown that Cepheids have the useful property that the time period

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were correct. Astronomers could not use the Cepheid yardstick technique for measuring the distance to the farthest galaxies because it had been impossible to detect Cepheid variable stars so far away. Instead, they were forced to adopt a completely different measuring technique, which relied on the reasonable assumption that the brightest star

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accepted model of the universe, according to which time and space emerged from a hot, dense, compact region between 10 and 20 billion years ago. Cepheid variable star A type of star whose brightness varies over a precise, regular period, usually between 1 and 100 days. The period of variation is directly

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planets from the Earth, which has a higher orbital speed around the Sun. RR Lyrae star A type of variable star less luminous than a Cepheid variable, and with a period between 9 and 17 hours. The inability to detect any RR Lyrae stars in the Andromeda Galaxy in the 1940s was

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, 73-5, 484-5; banned books 70, 74; endorses Big Bang 360-2, 364; Inquisition 39, 70, 73 Cavendish Laboratory 288 centrality, illusion of 272 Cepheid variable stars 199-201, 207-10, 211, 223-6, 224; distance scale 212-13, 225, 376-7, 381; magnitude 211; populations 376-7 Chadwick, James 295

The Glass Universe: How the Ladies of the Harvard Observatory Took the Measure of the Stars

by Dava Sobel · 6 Dec 2016 · 442pp · 110,704 words

his conclusions. In a letter to Pickering on July 20, 1918, Shapley stated, “I believe the most important photometric work that can be done on Cepheid variables at the present time is a study of the Harvard plates of the Magellanic clouds. Probably Miss Leavitt’s many other problems have interrupted and

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objects throughout the whole galactic system, the structure of the clouds—all these problems will benefit directly or indirectly from a further knowledge of the Cepheid variables.” • • • THE MEMBERS OF THE AAVSO, those devoted observers of the long-period variables, met in November 1918 at the Harvard College Observatory. They had been

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Edwin Hubble, a former colleague of his at Mount Wilson. “Dear Shapley,” it began. “You will be interested to hear that I have found a Cepheid variable in the Andromeda Nebula.” Few announcements could have rattled Shapley more than this one. The Andromeda Nebula, dimly visible to the naked eye, was the

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did not participate in the classification effort, but her pursuit of variable stars and her discovery of the relationship between period and brightness among the Cepheid variables has had an equal, if not greater, impact on progress in astronomy. Once calibrated and applied to the problem of measuring distances across space, Miss

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Radcliffe. Harlow Shapley (November 2, 1885–October 20, 1972), the fifth director, from 1921 to 1952, added graduate education to the observatory’s mission. Using Cepheid variables and the period-luminosity relation, he showed the Sun to be far from the center of the Milky Way, contrary to previous belief. Martha Betz

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surface, becoming a red giant M star. Other changes will ultimately render it a nonluminous “white dwarf.” CHAPTER TEN: The Pickering Fellows The study of Cepheid variables affected areas of astrophysics beyond cosmic distances. Attempts by Arthur Stanley Eddington and others to explain what factors would make a star pulsate led, eventually

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, 257, 260 Carnegie, Andrew, 105–7, 116, 117 Carnegie, Louise Whitfield, 116–18 Carnegie, Margaret, 117 Carnegie Institution grant, 105–6, 113 Carpenter, Alta, 171 Cepheid variables, 160, 170–71, 281, 296 Hubble’s discoveries, 204–5 Miss Leavitt’s work, 160, 170, 261–62 Mrs. Payne-Gaposchkin’s work, 251 Mrs

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, 84 cleveite gas, 68 clusters and cluster variables, 92, 111, 275, 281, 285 Trumpler’s work, 227–28 types, 282, 283 See also Bailey, Solon; Cepheid variables; Sawyer, Helen; Shapley, Harlow; variable star entries Clymer, William, 78 Colorado, Pickering brothers’ trip to, 29 Columbian Exposition (Chicago, 1893), 53, 54–55 comets and

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, 139–40, 141–45, 157–58 meetings of, 134–40, 156–58 interstellar light absorption, 127, 222, 227–28, 297 intrinsic variables, 251 See also Cepheid variables; variable star entries island universes, 151, 184, 190, 204–6, 233, 282 See also galaxies; nebulae Jamaica, William Pickering in, 155, 183, 191, 210 Jewett

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, Joseph, 254 Mackie, Joan, 171 Magellanic Clouds, 150–51, 153, 282 variable star discoveries in, 114–15, 125, 130–31, 149–53, 276 See also Cepheid variables magnitude (of stars), 11, 282 interstellar light absorption and, 222, 227–28 and spectral type, 277, 278 stellar distances and, 127, 128–29, 152–53

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volunteer observer program, 13–14, 42–43, 110, 148–50, 171 after World War II, 254, 255 See also American Association of Variable Star Observers; Cepheid variables; Harvard Photometry; specific stars, observers, and analysts variable stars: Chandler’s catalogues, 60, 111 Harvard catalogue, 97, 111 in Magellanic Clouds, 114–15, 125, 130

Coming of Age in the Milky Way

by Timothy Ferris · 30 Jun 1988 · 661pp · 169,298 words

to study variable stars as well. The knowledge he gained in this somewhat backhanded way came in handy, for a class of variable stars—the Cepheid variables—were to provide astronomy with a means of measuring distances across interstellar space and even intergalactic. Thanks to the Cepheids, Shapley was to earn a

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is measure its apparent magnitude and then apply the formula that brightness decreases by the square of the distance. If, for instance, we have two Cepheid variables with the same period, we may assume that they have about the same absolute magnitude. If the apparent magnitude of one is four times that

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interference of an intervening interstellar cloud) that the dimmer star is twice as far away. The relationship between the periodicity and the absolute magnitude of Cepheid variable stars was discovered in 1912 by Henrietta Swan Leavitt, one of a number of women hired at meager wages to work as “computers” in the

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must result from genuine differences in their absolute magnitudes and not from the effect of differing distances. Thanks to this happy circumstance, Leavitt in studying Cepheid variable stars in the Magellanic Clouds was able to notice a correlation between their brightness and their period of variability—the brighter the Cepheid, the longer

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enthusiasm. Using the big sixty-inch Mount Wilson telescope, he photographed globular star clusters—spectacular assemblages of hundreds of thousands to millions of stars —identified Cepheid variable stars in each of them, then employed the Cepheids to calibrate the distances of the clusters. “The results are continual pleasure,” he wrote the astronomer

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the Milky Way galaxy previously had been reckoned—by various investigators, Shapley among them—at some fifteen to twenty thousand light-years. Now, with his Cepheid variable work in hand, Shapley concluded that the correct figure was three hundred thousand light-years—more than ten times larger than the dimensions entertained by

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of interstellar gas and dust dim the images of distant stars, making them appear farther away than they really are. Moreover, he assumed that the Cepheid variable stars he observed in globular clusters were essentially identical to those Henrietta Leavitt had found in the Magellanic Clouds; actually, as Walter Baade and other

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’s photographic plate really were stars, however, was open to contention; Shapley dismissed them as curds in a Laplacian nebula. Here, again, Henrietta Leavitt’s Cepheid variable stars provided the needed mileposts. Cepheids are bright enough to be discernible across intergalactic distances. Using the new one-hundred-inch telescope at Mount Wilson

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laconic note containing one of the most momentous findings in the history of science: “You will be interested to hear that I have found a Cepheid variable in the Andromeda Nebula.”13 Hubble deduced that Andromeda lies about one million light-years away, an estimate half the distance of later ones but

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of literature I have seen for a long time.”14 Later he complained that Hubble had given him insufficient credit for his priority in using Cepheid variables to chart distances. But the game was over. Hubble’s paper announcing that he had found Cepheids in spirals—read (in his Olympian absence) at

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Mount Wilson on the spiral nebulae, but he worked fast: Only five years later he was able to write Harlow Shapley that he had found Cepheid variable stars in the spirals, establishing that they are galaxies and making it possible to estimate their distances. Five years after that, in 1929, he was

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as staff members at a university where their sex barred them from attending classes or earning a degree. (Henrietta Leavitt, the pioneer researcher of the Cepheid variable stars that were to prove so useful to Shapley and Hubble, was a Harvard computer.) The computers were charged with examining the plates and entering

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most telling liability, the time-scale problem. Owing to a number of errors, chief among them an inadequate understanding of the absolute magnitude of the Cepheid variable stars employed as intergalactic distance indicators, Hubble and Humason had severely underestimated the dimensions of the expanding universe—and, therefore, its age as well. Hubble

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its repair by a space shuttle team three years later, made observations that substantially clarified our vision of the cosmos. Astronomers using it to chart Cepheid variable stars and other useful distance-measuring landmarks were able to refine their estimates of the cosmic expansion rate, with the result that the universe now

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to the scientific world view. See chance, determinism. Centauras A. Giant elliptical galaxy, located between the Local Group and the center of the Virgo Supercluster. Cepheid variable. A pulsating variable star whose periodicity—i.e., the time it takes to vary in brightness—is directly related to its absolute magnitude. This correlation

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aspects of wave-like behavior. Pauli exclusion principle. See exclusion principle. Period-luminosity function. The relationship between the absolute magnitude and period of variability of Cepheid variable stars. Phase transition. An abrupt change in the equilibrium state of a system, as evoked by the cooling of the early universe as it expanded

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contained in their tiny nuclei. Time: 1912 Noteworthy Events: Henrietta Swan Leavitt discovers a correlation between the absolute magnitude and the period of variability of Cepheid variable stars, opening the door to their use as intergalactic distance indicators. Time: 1913 Noteworthy Events: Niels Bohr develops theory of atomic structure, in which electrons

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in 1905 can be explained as being due to the rotation of the Milky Way galaxy. Noteworthy Events: Edwin Hubble announces that he has identified Cepheid variable stars in the Andromeda galaxy, confirming that it is a galaxy of stars rather than a gaseous nebula and making it possible to measure its

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radio radiation emitted by interstellar clouds. Time: 1952 Noteworthy Events: Baade clears up serious discrepancies in the cosmic distance scale when he finds that the Cepheid variable stars used in measuring intergalactic distances actually come in two varieties, with different magnitude-periodicity relationships, Time: 1953 Noteworthy Events: Murray Gell-Mann proposes a

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, Giovanni, 130, 134, 153 Catastrophism, 224–225, 227, 228, 229 Causation doctrine (origin of the universe), 350–351 Celestial harmony, Pythagorean doctrine of, 75–77 Cepheid variable stars, 169, 170, 172, 173, 208, 274, 390 CERN accelerator, 319, 320–321, 322, 325–326, 336, 347, 352–353 Chamberlin, Thomas Chrowder, 255, 256

Origin Story: A Big History of Everything

by David Christian · 21 May 2018 · 334pp · 100,201 words

, a Harvard Observatory astronomer, found a way to measure the distance to remote stars and nebulae using a particular type of star known as a Cepheid variable, a star whose brightness varies with great regularity (the polestar is a Cepheid). She found a simple correlation between the frequency of the variations and

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Milky Way. In 1923, Hubble used one of the world’s most powerful telescopes, at the Mount Wilson Observatory in Los Angeles, to show that Cepheid variables in what was then known as the Andromeda nebula were so far away that they could not be in our own galaxy. This proved what

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, not just our own. Hubble made an even more astonishing discovery as he began to measure the distance to large numbers of distant objects using Cepheid variables. In 1929, he demonstrated that almost all galaxies appeared to be moving away from us and that the most remote objects seemed to have the

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1940s, Walter Baade, working at the Mount Wilson Observatory in LA (the same observatory at which Hubble had worked), showed there were two types of Cepheid variable stars, and they yielded different estimates of distance. Baade’s revised calculations suggested that the big bang might have happened more than 10 billion years

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it is, and that means you can estimate its true distance. Type 1a supernovas allow astronomers to estimate distances hundreds of times farther away than Cepheid variables. Stars more than about seven times the mass of our sun will also end their lives spectacularly in another type of explosion, known as a

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the history of planet Earth, from 4 billion years ago to 2.5 billion years ago. astronomical standard candle: An astronomical object such as a Cepheid variable or a type 1a supernova whose distance can be determined, allowing it to be used to measure the distances to other objects. atom: Smallest particle

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: A molecule (usually a protein) that facilitates particular chemical reactions by lowering the required activation energy without the molecule itself being changed by the reaction. Cepheid variable: A star whose brightness varies in a regular pattern. There are two main types, and because the rate of variation is related to their intrinsic

A Short History of Nearly Everything

by Bill Bryson · 5 May 2003 · 654pp · 204,260 words

practical that it is still in use today. Leavitt's contribution was even more profound. She noticed that a type of star known as a Cepheid variable (after the constellation Cepheus, where it first was identified) pulsated with a regular rhythm—a kind of stellar heartbeat. Cepheids are quite rare, but at

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the only thing constant about the Hubble constant has been the amount of disagreement over what value to give it. In 1956, astronomers discovered that Cepheid variables were more variable than they had thought; they came in two varieties, not one. This allowed them to rework their calculations and come up with

Wonders of the Universe

by Brian Cox and Andrew Cohen · 12 Jul 2011

Hubble was using what was then the world’s most powerful telescope at the Mount Wilson Observatory in Pasadena, California, to observe stars called Cepheid variables. These Cepheid variables are stars whose brightness varies regularly over a period of days or months, and they are astonishingly useful to astronomers because the period of their

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brightening and dimming is directly related to their intrinsic brightness. In other words, it is a simple matter to work out exactly how bright a Cepheid variable star actually is just by watching it brighten and dim for a few months. If you know how bright something really is, then measure how

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bright it looks to you, you can work out how far away it is. Edwin Hubble’s research project was simply to search for Cepheid variables in the sky and measure their distance from Earth. During his observations, he discovered two remarkable things: firstly, he quickly determined that the

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Cepheid variables he found in the so-called spiral nebulae (which at the time were thought to be clouds of glowing gas within the Milky Way) were

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plotting a graph of the redshift of the light from the distant galaxies against their distance, which he had calculated from his observations of the Cepheid variables. To his great surprise, Hubble noticed that his graph was approximately a straight line. This is because the further away a galaxy is, the greater

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the Universe began with a big bang around fourteen billion years ago. All this was deduced in the 1920s simply by capturing the light from Cepheid variable stars and distant galaxies. The Big Bang is difficult to visualise; it is easy to think of it as a vast explosion that flung matter

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Carina Nebula 74–5, 74–5 Cassini, Giovanni 40, 164 Cassiopeia (constellation) 48, 48, 49 Cat’s Eye Nebula 125, 125 Cavafy, C.P. 10 Cepheid variables 60, 65 centrifuge 174–5 CERN, Geneva 12, 78, 79, 106 Chaco Canyon Great Houses, New Mexico 177, 177, 178–9, 178–9 Chandra X

The Milky Way: An Autobiography of Our Galaxy

by Moiya McTier · 14 Aug 2022 · 194pp · 63,798 words

apparent brightness of some distant object, they can calculate how far away that object is. The two standard candles your astronomers use most often are Cepheid variable stars and RR Lyrae stars. They work the same way, but Cepheids are brighter than RR Lyrae because they evolve from much more massive stars

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you humans ever miss an opportunity to try to put yourselves at the center of everything? A young rebel named Harlow Shapley had been using Cepheid variables (thanks to Henrietta Leavitt) to map globular clusters in my halo. Globular clusters are just what your astronomers call collections of gas, dust, and up

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call it the Great Debate, and I was flattered. Around the same time as the debate, Edwin Hubble, a newly minted astronomy PhD, was using Cepheid variables to determine the distances to dim nebulae. In 1924, he ended the debate once and for all when he found that the variable stars in

Models. Behaving. Badly.: Why Confusing Illusion With Reality Can Lead to Disaster, on Wall Street and in Life

by Emanuel Derman · 13 Oct 2011 · 240pp · 60,660 words

universe. The distance to a galaxy is also an unspoken kind of analytic continuation. One of the ways galactic distances are measured is by observing Cepheid variables, stars whose visible brightness varies. Their true luminosities (“luminosity” is the technical term for their light output, or brightness) have been found to pulsate in

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R away radiates out over a sphere of surface 4πR2 , the apparent luminosity decreases with distance inversely proportional to R2 . When you look at a Cepheid variable in a distant galaxy through a telescope, you see its apparent luminosity, but the frequency of the pulsation tells you its absolute luminosity. From the

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perfect calibration Cape Flats Development Association (South Africa) Capital Asset Pricing Model (CAPM) capitalism caricatures: models as cash. See currency/cash Cauchy, Augustin-Louis causes Cepheid variable stars chalazion chaver (comrade) Chekhov, Anton chemistry: electromagnetic theory and Chesterton, G. K. Chinese choice chromatography Churchill, Winston Coetzee, J. M. coin tossing Coleridge, Samuel

Zero: The Biography of a Dangerous Idea

by Charles Seife · 31 Aug 2000 · 233pp · 62,563 words

gas inside our galaxy. In the 1920s that all changed, thanks to an American astronomer named Edwin Hubble. A special type of star, called a Cepheid variable, had a property that allowed Hubble to measure the distance to faraway objects. Cepheid stars pulsate, getting brighter and dimmer in a very predictable way

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Bruno, Giordano calculus calendars Egyptian Mayan Cantor, Georg cardinal numbers Cartesian coordinates Casimir, Hendrick B. G. Casimir effect Cavalieri, Bonaventura century, arguments over start of Cepheid variables Chandogya Upanishad Chandrasekhar, Subrahmanyan Charles, Jacques-Alexandre Christianity see also God Churchill, Winston, proof that he is a carrot cipher circle Cohen, Paul complex numbers