1610
Galileo uses his small, crude home built telescope to examine the
night skies over seventeenth century Padua, Italy and discovers
that our home galaxy, The Milky Way, is composed of millions of
stars. Galileo also finds, but is unable to resolve, a number of
patches of glowing light, later termed the nebulae, (from the Latin
word for "mist").
1781
The comet hunter Charles Messier, publishes a catalogue of 103
of these nebulae, to try and reduce the chance of himself, and other
observers, mistaking them for comets.
1755
Immanuel Kant publishes, anonymously, his "General
History of Nature and Theory of the Heavens", which proposed
although some nebulae were probably associated with stars in our
galaxy, the spiral or oval shaped nebulae were separate Galaxies
located at enormous distances from our own. Throughout the nineteenth
century, however, most observers still felt that all nebulae were
gas or dust in our own stellar system.
1802
William Wollaston, an English physicist, develops the spectroscope
and the German optician, Joseph von Fraunhofer, finds that the spectrum
of the Sun was interrupted by hundreds of black lines, indicating
the present of identifiable elements.
1770-1810
The English astronomer William Hershel, observers many more nebulae
using his 48 inch reflecting telescope. Herschel discovered the
planet Uranus during his "review of the heavens",
using a smaller telescope, also of his own construction. He later
used his "40 foot" telescope, with a
mirror diameter of 49 inches, to discover two new satellites of
Saturn, now known as Mimas and Enceladus. The first large reflector
built by the third Earl of Rosse utilized a mounting based on Herschel's
design. Herschel realized the Milky Way could be thought of as a
flattened disc, although he thought the Sun was near the centre
of the Galaxy, rather than its current estimated position of 30,000
light-years from the centre.
1839
Lord Rosse uses the 36 inch telescope to obtain hints that clumps
of stars existed within otherwise fuzzy masses of gas.
1850
Using his new 72 inch new telescope Lord Rosse was able to write,
regarding the nebulae:"We thus observe, that
with each successive increase of optical power, the structure has
become more complicated. That such a system should exist, without
internal movement, seems to be in the highest degree improbable.......The
nebulae itself however, is pretty well studded with stars"
1864
William Huggins, from his home in London, uses a spectroscope on
the nebulae and obtains results that support Kant's theory
1898
The American, Henrietta Swan Leavitt, discovers the period-luminosity
relationship, through the study of Cephid variables, allowing estimations
of the distance of cosmic objects.
1918-1919
Harlow Shapley, using the above relationship, determines the distances
of many globular clusters, estimating the diameter of the Galaxy
as 250,000 light years.
1922
Edwin Hubble suggests that a distinction between "galactic"
and "non-galactic" nebulae existed, but,
as with the third Earl of Rosse 70 years previously, he was anxious
to obtain more evidence before he could be fully convinced of his
(correct) theory.
1927
Hubble, after using the 100 inch reflector in California, publishes
"A relation between Distance and Radial Velocity
Among Extra-Galactic Nebulae", in which he first tentatively
discussed the possible expansion of the universe.
1934
Hubble takes a photograph showing as many galaxies as foreground
stars.
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1620
Birr town, castle and surrounding grounds acquired by Laurence
Parsons, area renamed Parsonstown
1800
William Parsons, Lord Oxmantown, born 17th of June
1822
William graduates from Oxford College with a first class Mathematics
degree.
1823
Lord Oxmantown enters the House of Lords as MP for King's County
(Offaly).
1824
William joins the Royal Astronomical Society
1827
Baron Oxmantown (William Parsons) commences experiments in telescope
making
1828
Baron Oxmantown builds first machine for grinding and polishing
metal mirrors and publishes first results of his experiments
1831
William (Lord Oxmantown), joins the Royal Society.
1834
William retires from politics to pursue full time his scientific
and engineering interests.
1836
Lord Oxmantown marries Mary Field, a wealthy heiress from Yorkshire.
1839
3-Foot telescope built, British astronomers Robinson and South
invited to test this telescope
1841
Baron Oxmantown becomes third Earl of Rosse
1842
72 inch mirror successfully cast (on 13th April)
1843-1844
Observatory and tube for large mirror built
1845
First light of 72 inch telescope (on 15th February), discovery
of the first spiral nebulae, M51
1845-1848
Irish Potato famine, telescope virtually unused, William becomes
President of the Royal Society
1850
Lord Rosse casts 15 inch mirror for Armagh Observatory reflecting
telescope
1852
British Astronomical Association's lunar committee meets in Birr
1862
William (Lord Rosse) becomes Chancellor of Dublin University
1867
Death of the third Earl (on 31st October) , first observational
paper published by the fourth Earl
1868
The fourth Earl uses the 36 inch telescope to measure the heat
of the Moon
1869
Clock-drive fitted to 72 inch telescope
1878
J.L.E. Dreyer leaves Birr and so finishes the main work of the
72 inch telescope
1889
Catalogue of Drawings of the planet Jupiter, mainly using the
Birr 36 inch telescope, published in Dublin
1872-1874
72 inch used to measure satellites of Uranus, 36 inch telescope
mounted equatorially
1908
Death of the fourth Earl (on 30th August), 72 inch reflector dismantled
1925
Staircase and wooden supports of the 72 inch reflector demolished
due to decay
1968
Centenary Exhibition Lecture (Delivered by Patrick Moore)
1970-1980
Museum and extensions to exhibition rooms set up in castle grounds
1994-1999
Restoration of 72 inch telescope and completion of National Historic
Science Centre
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