1755 - Drawing on Wright's
work, Immanuel
Kant conjectures that the galaxy is a rotating disk of stars held together
by gravity, and that
the nebulae are separate
such galaxies,
1845 - Lord Rosse discovers
a nebula with a distinct spiral shape
1918 - Harlow
Shapley demonstrates that globular clusters are arranged in an spheroid
or halo whose center is not the Earth,
decides, correctly, that its center is the center of the galaxy,
1920 - Harlow Shapley
and Heber Curtis debate whether or not the spiral nebulae lie within the
Milky Way,
1930 - Robert Trumpler
uses open cluster
observations to quantify the absorption
of light by interstellar
dust in the galactic plane; this absorption had plagued earlier models
of the Milky Way,
1943 - Carl Keenan Seyfert
identifies six spiral galaxies with unusually broad emission lines, named
Seyfert
galaxies,
1949 - J.G. Bolton, G.J.
Stanley, and O.B. Slee identify NGC
4486 (M87) and NGC 5128
as extragalactic radio sources,
1953 - Gerard de Vaucouleurs
discovers that the galaxies within approximately 200 million light years
of the Virgo
cluster are confined to a giant supercluster
disk,
1954 - Walter Baade and
Rudolph Minkowski identify the extragalactic optical counterpart of the
radio source Cygnus A,
1960 - Thomas Matthews
determines the radio position of 3C48 to within 5",
1960 - Allan Sandage
optically studies 3C48 and observes an unusual blue quasistellar object,
1962 - Cyril Hazard,
M.B. Mackey, and A.J. Shimmins use lunar occultations to determine a precise
position for the quasar3C273 and deduce that
it is a double source,
1963 - Maarten Schmidt
identifies the redshifted Balmer lines from the quasar 3C273
1973 - Jeremiah Ostriker
and James Peebles discover that the amount of visible matter in the disks
of typical spiral galaxies is not enough for Newtonian gravitation to keep
the disks from flying apart or drastically changing shape,
1974 - B.L. Fanaroff
and J.M. Riley distinguish between edge-darkened (FR I) and edge-brightened
(FR II) radio sources,
1976 - Sandra Faber and
Robert Jackson
discover the Faber-Jackson relation between the luminosity
of an elliptical galaxy and the velocity
dispersion in its center,
1977 - Brent Tully and
Richard Fisher discover the Tully-Fisher relation between the luminosity
of an isolated spiral galaxy and the velocity of the flat part of its rotation
curve,
1978 - Steve Gregory
and Laird Thompson describe the Coma supercluster,
1978 - Vera Rubin, Kent
Ford, N. Thonnard, and Albert Bosma measure the rotation curves of several
spiral galaxies and find significant deviations from what is predicted by
the Newtonian gravitation of visible stars,
1981 - Robert Kirshner,
August Oemler, Paul Schechter, and Stephen Shectman find evidence for a
giant void in Boötes
with a diameter of approximately 100 million light years,
1985 - Robert Antonucci
and J. Miller discover that the Seyfert II galaxy NGC 1068 has broad lines
which can only be seen in polarized
reflected light,
1987 - David Burstein,
Roger Davies, Alan Dressler, Sandra
Faber, Donald Lynden-Bell, R.J. Terlevich, and Gary Wegner claim that
a large group of galaxies within about 200 million light years of the Milky
Way are moving together towards the "Great
Attractor'' in the direction of the Hydra
and Centaurus,
1989 - Margaret Geller
and John Huchra discover the "Great Wall", a sheet of galaxies more than
500 million light years long and 200 million wide, but only 15 million light
years thick,
1990 - Michael Rowan-Robinson
and Tom Broadhurst discover that the IRAS galaxy F10214+4724 is the brightest
known object in the Universe.
