338
ERNST ÖPIK
1893–1985
Estonian astrophysicist Ernst
Öpik obtained his doctorate at the
University of Tartu, Estonia, where
he worked from 1921 to 1944,
specializing in the study of minor
objects such as asteroids, comets,
and meteors. In 1922, he estimated
the distance of the Andromeda
galaxy using a new method based
on the galaxy’s speed of rotation.
This method is still used today.
Öpik also suggested that comets
originated from a cloud beyond
Pluto, now known commonly as
the Oort cloud, but sometimes
referred to as the Öpik–Oort cloud.
As the Red Army approached
Estonia in 1944, Öpik fled into
exile, eventually settling in
Northern Ireland, where he took
a position at Armagh Observatory.
See also: The Oort cloud 206
CLYDE TOMBAUGH
1906–1997
In the late 1920s, the Lowell
Observatory in Arizona embarked
upon a systematic search for a
planet believed to be causing
perturbations to the orbit of
Uranus. To carry out the work, the
director Vesto Slipher hired the
young amateur astronomer Clyde
Tombaugh, who had impressed him
with drawings of Jupiter and Mars
made using a homemade telescope.
After 10 months examining
photographs, on February 18, 1930,
Tombaugh discovered an object
orbiting the sun beyond Neptune.
Named Pluto after the Roman god
of the underworld, it was initially
classified as the ninth planet, but
has since been demoted to the
status of dwarf planet. Following
his discovery, Tombaugh earned a
degree and pursued a career as
a professional astronomer.
See also: Spiral galaxies 156–61 ■
Studying Pluto 314–17VICTOR AMBARTSUMIAN
1908–1996Soviet–Armenian astronomer Victor
Ambartsumian was a founding
figure in the field of theoretical
astrophysics, contributing to
theories of star formation and
galactic evolution. He was one of
the first people to suggest that young
stars formed from protostars. In
1946, he organized the construction
of the Byurakan Observatory in
Armenia, where he was the director
until 1988. A popular lecturer with
a colorful and engaging style,
Ambartsumian served as the
president of the International
Astronomical Union from 1961–64,
and hosted several conferences on
the search for extraterrestrial life.
See also: Dense molecular clouds
200–01 ■ Inside giant molecular
clouds 276–79GROTE REBER
1911–2002In 1937, American radio engineer
Grote Reber built his own radio
telescope in his backyard after
hearing of Karl Jansky’s discovery
of galactic radio waves. Over
the next few years, Reber was
effectively the only radio astronomer
in the world, conducting the
first radio survey of the sky and
publishing his results in astronomy
and engineering journals. Reber’s
work was to form the basis for the
development of radio astronomyafter the end of World War II. To
conduct further radio investigations
in clear atmospheric conditions,
in 1954 Reber moved to Tasmania,
where he remained for the rest
of his life.
See also: Radio astronomy 179IOSIF SHKLOVSKY
1916–1985In 1962, Soviet astrophysicist
Iosif Shklovsky wrote a popular
book examining the possibility
of extraterrestrial life, which was
republished four years later in an
expanded edition, co-authored by
Carl Sagan, as Intelligent Life in
the Universe. In this later edition,
paragraphs by the two authors
are alternated with one another,
as Sagan provides a commentary
and expansion on Shklovsky’s
original points. Many of the latter’s
ideas were highly speculative,
including a suggestion that an
observed acceleration of Mars’s
moon Phobos was due to the fact
that it was a hollow artificial
structure, a monument to a long-
gone Martian civilization.
See also: Life on other planets
228–35MARTIN RYLE
1918–1984Like many pioneer radio
astronomers, Briton Martin Ryle
started his career developing radar
technology during World War II.
Subsequently, he joined the
Cavendish Radio Astronomy Group
in Cambridge, where he worked
alongside Antony Hewish and
Jocelyn Bell Burnell, developing
new techniques in radio astronomy
and producing a number of catalogsDIRECTORY