The Astronomical Society of the red Sea of Arabia, ASRA is pleased to publish, for the first time, some parts from an article written in the respectful Astronomy Magazine, the world's best seller astronomy magazine.
The title of the article is : 100 years of astronomical discoveries.
The complete article was published in the September 2016 issue of the magazine.
THE ARTICLE.
One thing has become clear about our readers, you love history. You certainly delight in the recent discoveries made by the Hubble space telescope, but you are also fascinated by how that intricate piece of machinery came to be.
Indeed, since the magazine began in 1973, we have run numerous historical accounts of hard scientific subjects, such as the expanding universe, spectroscopy, Halley's Comet, galaxy classification, celestial motion, and Pluto.
As you will see, more happens as decades pass and knowledge and technology advance. In fact, the entries covering the first decade are so few that they all fit into a sidebar within the 1910s pages. But "few" does not mean unimportant or uninteresting- just ask Einstein !!
We know you will enjoy reliving many of the great discoveries, achievements and breakthroughs that occurred from the 20th century's down all the way to the present.
THE FIRST DECADE THE 1900s.
1904
German astronomer Johannes Franz Hartman discovers the interstellar medium.
(In astronomy, the interstellar medium (ISM) is the matter that exists in the space between the star systems in a galaxy. This matter includes gas in ionic, atomic, and molecular form, as well as dust and cosmic rays. It fills interstellar space and blends smoothly into the surrounding intergalactic space.)
1905
Albert Einstein describes the photoelectric effect, introducing the concept of photons for the first time.
Albert Einstein publishes "On the electrodynamics of moving bodies" in which he outlines special relativity.
1906
German astronomer Max Wolf discovers "588 Achilles", the first identified Trojan asteroid.
(Trojan asteroids are asteroids orbiting the sun inside the orbit of Jupiter.)
1908
Something, likely a small asteroid or comet, exploded in the air above a forest along the stony Tunguska river in Russia on June 30. Levels some 80 million trees.
The 60 inches (1.5m) Hale telescope sees first light atop Mount Wilson, California. It was at the time the largest operational telescope in the world.
American astronomer George Ellery Hale discovers magnetic fields in sunspots.
1909
Swedish astronomer Karl Bohlin proposed the idea that the sun is not in the center of the Milky Way Galaxy.
THE SECOND DECADE THE 1910s.
1910
The great January Comet of 1910, perhaps the 20th century's brightest comet reaches perihelion on January 17, it is brighter than Halley's Comet, which appears on May the same year.
(Halley's Comet returns to the night sky.)
On April 20, Halley's Comet reaches perihelion (its closest approach to the sun) and on May 20, it comes nearest to the Earth at approximately 22.5 million kilometers away. Because of the favorable geometry, the Comet blazes in the night sky at nearly magnitude 0.
For years afterward, people reminisce about seeing Halley's Comet. But many of those memories, however, probably recall instead the first bright Comet visible that year, an object often called the Great Daylight Comet. That visitor, also known as Comet 1910 A1 or the great January Comet was brighter than planet Venus at its peak and was visible even during daylight hours around its perihelion passes on January 17.
Halley's Comet is famous for a number of reasons. It was the first comet who return was predicted. Observations of it stretch back at least to 240 BC. And it is the only short period Comet (one whose orbit takes less than 200 years) visible without optical aid. It returned in 1986, and will return in the not too distant future, with its next perihelion on July 2061.
1912
American astronomer Vesto M. Slipher takes the first spectrogram of the Andromeda Galaxy (M31) known back then then as Andromeda Nebula. It reveals a Doppler shift, the first such recorded, indicating it is moving toward us.
1914
In May, American astronomer Vesto M. Slipher discovers that spiral galaxies rotates. (known back then as spiral nebulae).
(Our place in the galaxy.)
In 1914, American astronomer Harlow Shapley begins studying star's globular clusters to try to accurately measure their distances. He determines that the sun is not at the center of the Milky Way. In fact when he plots the position of 93 globular clusters, he sees they form a spherical distribution centered on a spot in the constellation Sagittarius between 25,000 and 30,000 light years from earth. That means the Sun lies 27,200 light years (the current best value) from the Milky Way's core.
1915
Scottish astronomer Robert Innes discovers Proxima Centauri (Alfa Centauri) the nearest star to the Sun.
American astronomer Walter Sydney Adams determines that Sirius B is a white dwarf star, the first ever found.
(Einstein Hammers out his theories.)
German mathematician and physicist Albert Einstein published the special theory of relativity in 1905, but that theory didn't include the effect of gravity. So for the next 10 years, Einstein labored to combine gravity with special relativity theory. Finally, in November 1915, Einstein presents what other physicist later call his 10 field equations within the general theory of gravitation better known as the general theory of relativity.
These equations describe how gravity works throughout the universe as a result of space-time curvature due to mass and energy. When the mass creating the gravity is small and the velocity is low (nowhere near the speed of light), Einstein's theory act justly like Isaac Newton's law of gravitation. But when the mass is large or fast moving, it distorts space time itself.
It took quite a while for most researchers to accept the general theory of relativity. But the first confirmation doesn't take long. Einstein demonstrates how the general theory of relativity account for a slight variation in Mercury's orbit (of only 43 arc second per century) that Newton's law of gravity could not explain. Previously, this discrepancy gave rise to the mistaken belief in a planet inside Mercury's orbit named Vulcan.
General relativity also predicts exactly how much light bends around a massive object. To test this part of the theory, English physicist and astronomer Arthur Eddington captures images of the Sun during a total solar eclipse on May 1919. He sees that shifts in the position of stars near the sun because of the sun's gravity change by the precise amount given by Einstein's general theory of relativity. Little measurements confirm the results.
General relativity also predicts the existence of gravitational waves which are ripples in the fabric of space itself caused by collisions between very massive objects like neutrons stars and black holes. In 2016, one hundred years later, astronomers detected theses gravitational waves.
1916
German brilliant physicist, astronomer and mathematician Karl Schwarzschild solve Einstein's general relativity field equations and drive the size of the event horizon of a non rotating black hole. Schwarzschild accomplished this while serving in the German army during World War I in the Russian front. He died the same year age 43.
American astronomer Edward Emerson Barnard discovers the star with the largest known proper motion (the apparent angular motion of a star across the sky with respect to more distant stars), therefore called Barnard's Star.
1917
American astronomer Ritchey Curtis discovers the first nova and the first supernova in an object other than the Milky Way, in what we now know as galaxy NGC 6946. Eight supernovae have been spotted since then, given the galaxy its nickname the Fireworks Galaxy.
Carnegie observatories astronomers unknowingly record evidence of an exoplanet system around van Maanen's Star, a white dwarf, though no one recognizes it until 2016.
1918
Nova Aquilae 1918 peak at magnitude -0.5 , becoming the brightest nova witnessed since the invention of the telescope.
1919
The International Astronomical Union is founded.
THE THIRD DECADE THE 1920s.
1920
The New York Times magazine publishes the editorial "A severe Strain on Credulity" on January 13, which cast serious doubts on Robert Goddard's ideas for rocket travel. The newspaper would publish a correction and an apology on July 17, 1969, The day after Apollo 11 launched toward the Moon.
Astronomers directly measure the diameter of the red supergiant Betelgeuse (Alfa Orionis).
1921
A major geomagnetic storm occurs on Earth due to a coronal mass ejection from the Sun from May 13 to 15. Telegraph systems are severely damaged as a result.
Albert Einstein wins the Nobel prize in physics for his discovery and explanation of the photoelectric effect (not for the theory of relativity).
1922
A 20 ton meteorite lands in a field near blackstone, Virginia, USA creating a 500 square foot hole (46 square meters).
Canadian astronomer john Stanley Plaskett discovers what will become known as Plaskett's star, a binary system more than 100 times as massive as the sun.
1923
The first planetarium opens to the public in the Deutsches Museum in Munich Germany.
(Most Nebulae are Galaxies).
Edwin Hubble, working for the Carnegie Institution of Washington, takes a photographic plate of the Andromeda Nebula (M31) using the 100 inch (2.5 meters) Hooker Telescope at Mount Wilson observatory in California. The astronomer careful scrutiny of this and other photographic plates of M31 he takes around this date lead to an insight. Instead of being a nova (an old star rapidly shedding its outer layers), one point brightens and dims, revealing itself to be a Cepheid Variable (a star whose period is related to its brightness. Calculating its distance, Hubble finds the Andromeda Nebula, as it is known at the time, cannot possibly lie within our own galaxy. After this epiphany, Hubble takes his pen to the plate, crosses out the "N" (representing Nova) and scribbles "VAR" ( Variable). The universe as we know it is suddenly much much larger.
1924
English astronomer Arthur Eddington proposes the mass - luminosity relationship (stars with more mass are more luminous).
1925
Cecilia Payne Gaposchkin a female astronomer submits a doctoral thesis hypothesizing that hydrogen and helium are the main constituents of stars.
Carnegie observatory astronomers photographed Pluto, but do not realize it until some years later.
1926
American engineer and physicist Robert Goddard launches the first liquid propellant rocket in Auburn, Massachusetts.
1927
Comet Skjellerup - Maristany is visible for one month, shining yellow due to sodium content.
(The beginning of the Big Bang.)
Belgian astronomer Georges Lemaitre notes that if the universe is expanding, its motion should allow observers to trace it back in time to a single point. His revolutionary theory, which he calls "the hypothesis of the primeval atom" (and within which he introduces the concept of the "Cosmic Egg") meet a lot of skepticism. More than 20 years later, on a 1949 BBC radio broadcast, English astronomer Fred Hoyle, an ardent opponent of Lemaitre's theory, coins a sarcastic term for it that persists to this day : the Big Bang.
1928
The International Astronomical Union formalizes the constellation boundaries. This marks regions of the sky that fall under constellations, rather than relaying on the formation itself.
1929
(Hubble constant is first proposed).
Hubble's law explains two astronomical observations :
1) Galaxies farther than approximately 30 million light years away show a redshift indicating that the universe is expanding.
2) A proportional relationship exists such that the more distant a galaxy lies, the faster it moves away from earth.
Although astronomers call this Hubble's law, the first person to propose it was the Belgian astronomer Georges Lemaitre in 1927. Lemaitre also estimated the universe's rate of expansion. Edwin Hubble gets into the act in 1929 by using observational evidence to confirm the law, and by calculating a more accurate value for the relationship between a galaxy's distance and its recessional speed. Astronomers christen this number "Hubble constant."
Usually researchers use kilometers per second per megaparsec (1 Mpc = 32.6 million light years) as the unit of measure for the Hubble constant, and today most researchers indicates a value of 70 km/ sec/ Mpc. So , as an example, if a certain galaxy lies 50 megaparsec away , another galaxy 51 Mpc distant would move 70 km/sec faster. A galaxy 52 Mpc away would move 140 km/sec faster, and so on.
To be continued in part (2).
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