This Month in the History of Astronomy - May
- 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.
During WW I, de Sitter provided the only copies of Einstein's papers
on his new theory of relativity (general relativity) to the English
speaking world, via Arthur Eddington in Great Britain, who would be
instrumental in promoting and testing the theory at the May 29, 1919,
total solar eclipse (see below).
- 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
- 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
- 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
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