PHOTOMETER

A tool that measure the intensity of a light. 

Before elements that were sensitive to electronic light, photometry was conducted by the estimation of the eye. The relative luminous flux, the perceived power of light, was compared to a standard source.  Photometers are still used today in modern cameras as they register the exposure in photography. 

(http://physics.kenyon.edu/EarlyApparatus/Optics/Photometer/Photometer.html)

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PHOTOMETRY

In astronomy, photometry is used to measure the brightness of stars and other celestial bodies (nebulae, galaxies, and planets). This practice, of course, started with the Ancient Greeks. Hipparchus divided the stars into classes of brightness: magnitudes. The faintest stars belonged to the sixth magnitude. In the early 19th century, Norman Robert Pogson suggested that there were equal steps in brightness, a constant ratio existed between the light energy received and the brightness of a particular magnitude. He created a formula to help refine and objectify the classification of a star’s magnitude. However, photography really changed the game in providing a nonsubjective way of measuring the brightness of stars. In the time of Silent Sky, photographic plates sensitive to violet and ultraviolet radiation rather than green and yellow wavelengths of the eye, led to the creation of two different scales for magnitude: a visual scale and a photographic scale. That being said, the photographic photometry still wasn’t completely flawless as the photo could not always accurately portray the complex size and density of the star. Starting in 1940s, photometry was even more revolutionized as the photographic detectors became photoelectric. Using photoelectric tubes, the magnitude of the faintest stars could be accurately and precisely measured. 

(https://www.britannica.com/topic/photometry-astronomy)

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DRAPER CATALOGUE

Refers to the Henry Draper Catalogue (HD), a record of the positions, magnitudes, and spectral types of stars in the sky. The catalogue was essentially a map of the sky. 

This catalogue launched the alphabetical system for stellar classification, classify stars by spectral type. This catalogue was named after astronomer, Henry Draper, and the project led by Edward Charles Pickering at the Harvard College Observatory. Most of the catalogue was compiled by Annie Jump Cannon and Antonia Caetana Maury. The first draft was released in 1890, listing 10, 351 stars. Other versions were released in sections from 1918 to 1924 culminating in a list of 225,300 stars. By 1949, the catalogue included 359,083. 

(https://www.britannica.com/topic/Henry-Draper-Catalogue)

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ASTROPHOTOGRAPHY

The study of astronomy whereby, at first, the technology of the daguerreotype (an early photographic process using an iodine-sensitized plate and a mercury vapor) to transfer images of a telescope to a photographic plate. 

At first the process was daunting because the plates were wet, required long exposure time, but could also dry out if the exposure went too long. Richard Maddox developed the dry plate method. However, the plates still weren’t as sensitive to light as they needed to be. In 1878, Charles Bennet furthered the process by developing the plates at 32 degrees Celsius, and this increased the plates sensitivity to light. 

 (https://www.smithsonianmag.com/history/the-women-who-mapped-the-universe-and-still-couldnt-get-any-respect-9287444/?no-ist)

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NEBULAE

The definition of nebula has changed as the science of astronomy has changed. Originally, during times before the telescope, nebula referred to objects in the sky which did not look like stars, point-like stars. We now identify these objects as open star clusters. “Nebula” refers to what is known as a “Deepsky Object.” It wasn’t until the technological advancements of spectroscopy and photography that distinguishing objects of the deepsky or nebula would occur. Today, “real” nebula are gas and dust clouds and now objects made up of stars are referred to as globular clusters and galaxies. There are three main classifications of nebulae based on spectroscopy: emission nebulae (emit light because the atoms of the nebulae are excited by radiation of stars involved), reflection nebulae (dust particles reflect light of nearby stars), and absorption nebulae or dark nebulae (the gases forming the nebulae absorb the light of background stars).

 (http://www.messier.seds.org/nebula.html)

Nebula means "mist, vapor, fog, smoke, exhalation” and figuratively refers to “darkness, obscurity.” The term was first coined in astronomy in 1730 referring to a “cloud patch in the night sky.” In 1802, German-born British astronomer, Sir William Herschel, hypothesized that nebulae were composed of stars and developed a theory on the life of stars. However, distinction between star clusters, distant galaxies, and cosmic gas clouds would not be officially made until the 1920s. 

(https://www.etymonline.com/word/nebula)

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NOVAE

From the Latin “new,” used to identify a new star in the sky, not previously known. 

A nova refers to the rapid increase in the brightness of a star. It is a “new” star because it is “new” in the sense that it was previously unseen. Novae are known for being cause by the reigniting of a dormant star. Apparently, sun-like stars shine by a nuclear fusion reaction, processing hydrogen into helium. When hydrogen, the fuel, is used up, the stars become smaller, shedding their outer shell. This new stage of the star is known as a “white dwarf.” Novae occur when the “white dwarf” begins attracting outside hydrogen gas and that hydrogen gas ignites a nuclear explosion on the surface of the star. 

(http://curious.astro.cornell.edu/physics/78-the-universe/stars-and-star-clusters/general-questions/352-what-is-a-nova-beginner)

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COMPUTER

“one who calculates,” “‘calculating machine’ (of any type).” 

(https://www.etymonline.com/word/computer)

The Harvard Computers: More than eighty women from 1877-1919 worked for Edward Charles Pickering in the Harvard Observatory in order to competently analyze the vast volume of data entering the observatory. They were known as Pickering’s Harem. That being said, Pickering was actually a progressive male educator and thinker who sought to expand the role of women in the sciences. He was also progressive in his study of astronomy as he advocated the study of astrophotography in mapping the night sky. However, he still used the women to classify rather than truly observe. He limited their scope of work thereby continuing the cultural assumption that women were only made for clerical, secretarial duties. 

(https://www.smithsonianmag.com/history/the-women-who-mapped-the-universe-and-still-couldnt-get-any-respect-9287444/?no-ist)

A Timeline of the Harvard Computers/Photographic Observatory Plates: https://platestacks.cfa.harvard.edu/about-collection

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ANNIE CANNON’S STAR CLASSIFICATION

Unfortunately, Annie Jump Cannon’s star classification is more commonly and widely known as the Harvard System of Spectral Classification. Annie Cannon simplified the system of stellar classification ranking the stars as O, B, A, F, G, K, or M> O stars were the hottest and M were the coolest. Our sun is a G star. This system is still used today and is captured in the saying “Oh! Be A Fine Girl—Kiss Me!” She was able to classify the spectra of over 350,000 stars and could classify a star within three seconds. Between 1918 and 1924, her classification and work was included in nine volumes of the Henry Draper Catalogue. Today, the system is still used but applied to the modern Morgan-Keenan spectral classification which uses OBAFGKM but also subdivides a star into classes of luminosity to more accurately define and classify the star. 

(https://www.space.com/34707-annie-jump-cannon-biography.html)

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THE GREAT REFRACTOR

This telescope was installed in the Harvard College Observatory in 1847. The construction of this first-class observatory was sparked by a great comet in  March 1843 that caused public excitement for astronomy. 94 donors contributed funds for the observatory totaling $25,730. The first observation of the Great Refractor was the moon. For the first thirty years, the telescope  was used to determine stellar positions and for the visual observation of planets, variable stars, comets, and nebulae. One of the first photographs of a double star occurred because of the Great Refractor using a wet-plate collodion process in 1857. In 1877, Edward C. Pickering became the fourth director of the observatory and would employ the Great Refractor for photometry. 

(https://www.cfa.harvard.edu/hco/grref.html)

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STAR SPANKING

Apparently, Henrietta Levitt actually invented the fly spanker. Before the fly spanker, the brightness of stars were estimated by eye. Thus, measurements fluctuated by the brightness of other nearby stars and the eyes of the astronomer. The fly spanker was a piece of photographic plate with a wire handle. Using this tool, the computers could compare the stars on the image with the well-established brightness of the fly spanker. This helped provide a standard for brightness measure. The plates are very thin and fragile. There are over an estimated 500,000 plates. 

(https://starmappers.wordpress.com/2017/04/16/notebooks-and-fly-spankers/)

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SMALL MAGELLANIC CLOUDS

The SMC is most visible from the Southern Hemisphere as it is about 20 degrees from the South Celestial pole. Because it is invisible to the Northeastern hemisphere (Europe), Western knowledge of the SMC did not occur until Ferdinand Magellan’s circumnavigation of the world 1519-1522; hence, the name of the “clouds.” The SMC is import to astronomy because Henrietta Leavitt discovered “period luminosity” relationship while analyzing this cluster of stars. This would eventually lead to astronomers’ ability to gauge the distance of star clusters and nearby galaxies. 

(http://earthsky.org/clusters-nebulae-galaxies/the-small-magellanic-cloud)

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CEPHEID STARS

Stars which brighten and dim periodically also known as Cepheid Variables. 

They are cosmic yardsticks reaching out a few tens of millions of light years from us. They are cosmic benchmarks in mapping the universe  In 1912, Hernrietta Leavitt noticed that 25 stars in the SMC would brighten and dim periodically. She measured the timing of the fluctuations in brightness for the stars and determined that a brighter Cepheid had a longer period. She found that this period of brightening and dimming was regular and that once you found that period, you could determine the actual brightness. Her work with the Cepheid stars helped astronomers to infer distances of stars and galaxies. 

(https://starchild.gsfc.nasa.gov/docs/StarChild/questions/cepheids.html)

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THEORY OF RELATIVITY

In 1905, Albert Einstein created a theory based on two principles: the laws of physics appear the same to all observers and the speed of light is unchanging. He found that there is no fixed frame of reference in the universe. Therefore, everything moving is relative to everything else; hence, theory of relativity. However, this is special relativity because it only applies to special cases of frames of reference that are in constant, unchanging motion. In 1915, he published these findings as the general theory of relativity. He also found that mass and energy are different manifestations of the same thing ( E = mc2). Under the theory of relativity, space and time are also part of one continuum, the space-time continuum. The presence of mass distorts space-time and this is how we have come to understand the nature of gravity (two objects exert a force of attraction on one another): massive objects warp space and time creating a gravity well which is why planets move in ellipses as that is the path around the sun that is shortest and uses the least amount of energy.

His theory was based on empirical and skeptical philosopher, David Hume, who believed that scientific concepts must be based on experience and evidence, not just reason. He was the inspiration behind the concept that time does not exist separately from the movement of objects. 

His theory of relativity has been supported by the natural phenomena such as gravitational lensing (light around a massive object becomes bent by space and matter causing it to be a lens for the objects lying behind the massive object), the gradual change in the orbit of Mercury (due to the curvature of space and time around the sun, Mercury could possibly collide with Earth in a few billion years), gravitational redshift (the Doppler Effect: radiation and light waves, like sound waves, stretch based on their location relationship with an observer; like an alarm siren as the vehicle moves toward an observer, the sound waves are compressed, as the siren moves away, the siren sound is stretched out or redshifted). The theory of relativity supports Edwin Hubble’s assertion in 1928 that the Universe is expanding. 

(https://www.space.com/17661-theory-general-relativity.html)

For Margaret, some find that the theory of relativity supports the idea of a Creator. The theory of relativity shows that time is related to matter and space, and therefore, time, space, and matter constitute a continuum in which time cannot exist without space and matter. Thus, the uncaused first cause had to exist outside of space and time as the first cause would have brought space, matter, and time into being. This argument suggests that even the physical nature of time and space indicate the presence of a creator. Because the universe continues to unfurl and expand, energy continues to flow into a direction. This idea, as exhibited in the theory of relativity, states that if the universe were eternal, the energy of the universe would be evenly distributed and static. However, as the theory of relativity suggests, everything is moving. Therefore, time, though represented by eternity, is finite with a beginning and end, and space, though infinite in the universe must be fixed which means, for the sake of this argument, that the concepts of infinity and eternity can only apply to a Creator because the concept of the Creator is the only concept to transcend both infinity and eternity, space and time. 

(https://www.allaboutscience.org/theory-of-relativity.htm)

(http://www.einstein-website.de/z_biography/credo.html)

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STATISTICAL PARALLAX

 “the mean parallax of a group of stars, found by analyzing their peculiar motions”; the position of the stars seem to shift due to the background of distant objects. 

(http://www.oxfordreference.com/view/10.1093/oi/authority.20110803100529439) 

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HERTZSPRUNG

A Danish astronomer, Ejnar Hertzsprung, classified types of stars by relating color to their absolute brightness. This led to the creation of the Hertzsprung-Russell diagram of stellar types. He also created a luminosity scale for Cepheid variable stars, and this scale would help in measuring intergalactic distances. He determined that giant and dwarf stars must exist and that the correlation of brightness and color would help in the spectroscopic parallaxes of the stars (the estimated distances of these stars from Earth). 

(https://www.britannica.com/biography/Ejnar-Hertzsprung)

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ZERO POINT

 A term used in reference to apparent magnitude. 

The brighter the star, the lower the magnitude. The sun is about a -27 as it is the brightest object in our sky. Originally in the creation of Pogson’s scale, the zero point was defined by assigning a magnitude of 2 to Polaris. However, the brightness and magnitude of Polaris is variable, so now the zero point, reference star, is Vega. 

(https://web.archive.org/web/20080206074842/http://www.nso.edu/PR/answerbook/magnitude.html)

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HUBBLE

Using the foundation of Henrietta Leavitt’s work with Cepheid variables and period luminosity, Hubble managed to determine the distance to the Andromeda Galaxy, the nearest large galaxy to Earth, which is about 2.5 million light years. By discovering this, Edwin Hubble found that there were galaxies like our own in the universe. Hubble also helped in discovering that the universe was expanding by measuring the redshift of receding stars. 

(https://www.space.com/34708-henrietta-swan-leavitt-biography.html)

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