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This Month in the History of Astronomy - May

Birthdays

May 6, 1872 - Willem de Sitter, Dutch astronomer and mathematician, who worked at the Cape Observatory in South Africa and later became chair of astronomy at Leiden University for the last fifteen years of his life. He's chiefly remembered now for the de Sitter model of the universe (1917), an early solution to Einstein's equations of general relativity which is spatially flat, has no matter in it (zero density), but a positive cosmological constant, so it expands. Two years before his death he co-authored a paper with Einstein, creating what's called the Einstein-de Sitter universe (1932), in an attempt to combine all the observational data then known into a coherent model for the universe; this universe is also flat, but contained matter and therefore decelerated.
May 15, 1713 - Nicholas Louis de la Caille (or de Lacaille), French astronomer and mapmaker who demonstrated that the Earth bulged at the equator. From 1751 to 1753 he mapped the southern skies from The Cape of Good Hope and established the 14 "modern" constellations there.
May 17, 1835 - J. Norman Lockyer, discoverer of the element helium in 1868, while making visual spectroscopic studies of the sun (helios), when he attributed unknown absorption lines to the new element, not located on earth until 1891. It's the second simplest and most abundant element in the universe after hydrogen.
Sir Lockyer is also known as the Father of Archeoastronomy: he was among the first to propose that Stonehenge was an astronomical observatory and that the Egyptian pyramids and great medieval Christian cathedrals were built along important astronomical orientations.
May 22, 1920 - Tommy Gold, British cosmologist. Besides his work with Hoyle and others on the steady state theory, Gold is probably most famous now for raising the alarming possibility in the 1960's that the first lunar lander might sink into a deep, quicksand-like layer of lunar dust and immediately be lost.
May 25, 1865 - Pieter Zeeman, Dutch physicist who discovered the splitting of spectral lines by strong magnetic fields, an effect now named after him, though it was first predicted by his mentor Hendrik Lorentz, with whom he shared the 1902 Nobel Prize in Physics, only the second time it had ever been awarded. George Hale observed the Zeeman effect in sunspots in 1908, leading to the recognition that they are dark because magnetic fields are acting to impede motion of hot material into these regions, "bottling up" gas which cools by radiating away some of its initial heat content. Zeeman also helped discover the isotope of argon with mass number 38.
May 31, 1912 - Martin Schwarzschild, German-born American astrophysicist. The son of also famous astrophysicist Karl Schwarzschild (see Oct 9), Martin left Germany in 1936 and spent most of his post-WW II career at Princeton working in a multitude of areas relating to stellar structure and stellar evolution. His 1958 book on the subject was the standard text for the next 20+ years. After retirement he also contributed to the field of galaxy dynamics, building theoretical models of triaxial galaxies.

Discoveries and other firsts

May 1, 1949 - Neptune's moon Nereid is discovered by Gerard Kuiper.
May 3, 1715 - The date of the total eclipse of the sun now called Halley's Eclipse, because he was the first to calculate in advance any eclipse's time and location with reasonably high precision. Due to inaccuracies in the ephemeris for the moon he used, Halley was off by 4 minutes in the timing and 20 miles in the exact track location. Halley himself viewed the eclipse from London.
May 5, 1933 - Karl Jansky's announcement of the discovery of mysterious radio "star noise" coming from the center of the Milky Way runs in the New York Times, which says "There is no indication of any kind ... that these galactic radio waves constitute some kind of interstellar signaling, or that they are the result of some form of intelligence striving for intra-galactic communication".
May 5, 1961 - Alan Shepard became the first American in "space" (as we now refer to that region above the sky), taking a 15 minute suborbital ride aboard the Mercury craft Freedom 7.
May 10, 1994 - Alan Clark and associates use a lunar limb occultation during an annular eclipse of the sun to measure profiles of spectral lines in the chromosphere formed by carbon monoxide.
May 12, 485 - Probable date of the first known conference of astronomers, at current day Copán, Honduras.
Mayan interest in eclipse prediction and refining their calendar likely started in earnest 150 years earlier, during the 14 year period from 331 to 344 (A.D.), when five solar eclipses were visible in the region of current day Mexico, Guatemala, and Central America -- a total eclipse (331), a partial eclipse (335), an annular eclipse (342), and two near-total eclipses (338, 344).
A decade after the meeting the region saw two partial solar eclipses only a month apart, with a lunar eclipse in between.
The Mayan's Sacred Round was 260 days long, so two of these (520 days) constituted almost exactly three eclipse half-years (173.31 days x 3 = 519.93 days), when the nodes of the moon's orbit (where it crosses the ecliptic) are aligned with the sun and an eclipse is possible if the moon is near enough to that position then.
May 12, 1706 - An Englishman vacationing in Switzerland reports a "reddish streak" along the rim of the sun right at the beginning of totality of a solar eclipse, making it the first mention of either prominences or the sun's chromosphere. Nine years later, Edmond Halley, observing a total eclipse in England, notes bright red prominences, as well as what would later be called Baily's Beads (see entry after next).
May 13, 1733 - Birger Wassenius is the first to report prominences visible to the unaided eye during a solar eclipse, but attributes them to the moon.
May 15, 1836 - Francis Baily's annular eclipse in Scotland, from whence the term Baily's Beads derives.
May 17, 1882 - Arthur Schuster photographs the first unknown comet ever discovered during a total solar eclipse. The sun-grazing comet has not been seen since, though with only one observation it wasn't possible to get a very good fix on its orbit.
May 18, 1910 - Halley's Comet transitted the Sun, but was not seen, leading to an upper limit of about 100 km on the size of its nucleus.
May 21, 1961 - President John F. Kenedy launches the country on a journey to the Moon in perhaps his grandest and most famous speech.
May 22, 1724 - The Italian/French astronomer Giacomo Filippo Maraldi concludes the corona is part of the sun because the moon traverses it during a total eclipse.
May 23, 1967 - A powerful solar flare simultaneously jams all three U.S. ballistic missile early warning system (BMEWS) radars, causing the Air Force's Strategic Air Command (SAC) to go on high alert and put nuclear armed bombers into the air -- before space weather specialists determine the cause was not the Soviet Union.
May 28, 1959 - First primates in space; rhesus monkeys Able and Baker complete a suborbital flight.
May 29, 1919 - Measurements made during a total eclipse of the Sun agree with predictions made on the basis of Einstein's General Relativity theory. This was G.R.'s first scientific test of a predictive nature. (The precession of the perihelion of Mercury was already well-known when G.R. accounted for it.) The curvature of spacetime due to the sun's mass, which we normally think of as gravity, slightly deflects or bends the light coming from stars beyond the Sun, causing their apparent position to be different from when they're not near the Sun on the celestial sphere.
Ignoring what radioastronomers can do nowadays, you can only observe stars near the sun's limb, where the effect is most pronounced -- though still only about an arc-second (1.75 max) -- during an eclipse. Interestingly, Newton's theory of light and gravitation also predicts an angular deflection, but the amount is only half that of G.R.
Moral: light travels along straight lines only in spacetime!
The eclipse occurred with the Hyades cluster in the background, providing numerous stars for the measurements. The actual results were announced Nov 6th by Dyson and Eddington before a joint meeting of the Royal Astronomical Society and the Royal Society.
May 31, 2010 - OPERA researchers observed the first tau neutrino candidate event in a muon neutrino beam, the first time a transformation in mixed neutrino states had been observed. This bears on the neutrino's mass (if any), which is important because the universe is filled with neutrinos so their combined mass (if any) could be important in how the universe evolves.

©2002-2017, Chris Wetherill. All rights reserved. Display here does NOT constitute or imply permission to copy, republish, or redistribute my work in any manner for any purpose without prior written permission.

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