Ernst Öpik
Encyclopedia
Ernst Julius Öpik was a noted Estonia
Estonia
Estonia , officially the Republic of Estonia , is a state in the Baltic region of Northern Europe. It is bordered to the north by the Gulf of Finland, to the west by the Baltic Sea, to the south by Latvia , and to the east by Lake Peipsi and the Russian Federation . Across the Baltic Sea lies...

n astronomer and astrophysicist who spent the second half of his career (1948–1981) at the Armagh Observatory
Armagh Observatory
Armagh Observatory is a modern astronomical research institute with a rich heritage, based in Armagh, Northern Ireland. Around 25 astronomers are actively studying stellar astrophysics, the Sun, Solar System astronomy, and the Earth's climate....

 in Northern Ireland
Northern Ireland
Northern Ireland is one of the four countries of the United Kingdom. Situated in the north-east of the island of Ireland, it shares a border with the Republic of Ireland to the south and west...

.

Education

Öpik was born in Kunda, Estonia. He went to University of Moscow to specialize in the study of minor bodies, such as asteroid
Asteroid
Asteroids are a class of small Solar System bodies in orbit around the Sun. They have also been called planetoids, especially the larger ones...

s, comet
Comet
A comet is an icy small Solar System body that, when close enough to the Sun, displays a visible coma and sometimes also a tail. These phenomena are both due to the effects of solar radiation and the solar wind upon the nucleus of the comet...

s, and meteor
METEOR
METEOR is a metric for the evaluation of machine translation output. The metric is based on the harmonic mean of unigram precision and recall, with recall weighted higher than precision...

s. He completed his doctorate at the University of Tartu
University of Tartu
The University of Tartu is a classical university in the city of Tartu, Estonia. University of Tartu is the national university of Estonia; it is the biggest and highest-ranked university in Estonia...

.

Astronomical work

In 1916 Öpik published article in Astrophysical Journal where he estimates the densities of visual binary stars. It is interesting to note that in his sample was ο2 Eridani, a white dwarf
White dwarf
A white dwarf, also called a degenerate dwarf, is a small star composed mostly of electron-degenerate matter. They are very dense; a white dwarf's mass is comparable to that of the Sun and its volume is comparable to that of the Earth. Its faint luminosity comes from the emission of stored...

 star. Öpik determined its density as 25000 times the density of the Sun but concluded that the result is impossible.

In 1922, Ernst Öpik published a paper where he estimated the distance of the Andromeda Galaxy
Andromeda Galaxy
The Andromeda Galaxy is a spiral galaxy approximately 2.5 million light-years from Earth in the constellation Andromeda. It is also known as Messier 31, M31, or NGC 224, and is often referred to as the Great Andromeda Nebula in older texts. Andromeda is the nearest spiral galaxy to the...

. Using a novel and simple astrophysical method, he determined the distance as 450 kpc. His result was in good accordance with other estimates of these days (100 to 1000 kpc) and were closer to recent estimates (778 kpc) than Hubble's result (275 kpc). His method is still widely used.

In 1922 he correctly predicted the frequency of crater
Impact crater
In the broadest sense, the term impact crater can be applied to any depression, natural or manmade, resulting from the high velocity impact of a projectile with a larger body...

s on Mars
Mars
Mars is the fourth planet from the Sun in the Solar System. The planet is named after the Roman god of war, Mars. It is often described as the "Red Planet", as the iron oxide prevalent on its surface gives it a reddish appearance...

 long before they were detected by space probe
Space probe
A robotic spacecraft is a spacecraft with no humans on board, that is usually under telerobotic control. A robotic spacecraft designed to make scientific research measurements is often called a space probe. Many space missions are more suited to telerobotic rather than crewed operation, due to...

s. In 1932 he postulated a theory concerning the origins of comets in our solar system
Solar System
The Solar System consists of the Sun and the astronomical objects gravitationally bound in orbit around it, all of which formed from the collapse of a giant molecular cloud approximately 4.6 billion years ago. The vast majority of the system's mass is in the Sun...

. He believed that they originated in a cloud orbiting far beyond the orbit of Pluto
Pluto
Pluto, formal designation 134340 Pluto, is the second-most-massive known dwarf planet in the Solar System and the tenth-most-massive body observed directly orbiting the Sun...

. This cloud is now known as the Oort cloud
Oort cloud
The Oort cloud , or the Öpik–Oort cloud , is a hypothesized spherical cloud of comets which may lie roughly 50,000 AU, or nearly a light-year, from the Sun. This places the cloud at nearly a quarter of the distance to Proxima Centauri, the nearest star to the Sun...

 or alternatively the Öpik-Oort Cloud in his honour. He also invented a rocking camera for the study of meteors. In 1951 he published a paper concerning the triple-alpha process
Triple-alpha process
The triple alpha process is a set of nuclear fusion reactions by which three helium-4 nuclei are transformed into carbon.Older stars start to accumulate helium produced by the proton–proton chain reaction and the carbon–nitrogen–oxygen cycle in their cores...

, describing the burning of helium-4 into carbon-12 in the cores of red giant stars. However, this achievement is often overlooked because Edwin Salpeter's paper on the same subject had already been published by the time Öpik's paper reached Britain and the United States.

In 1972, Öpik published a very important piece on the origin of the Moon by capture in the Irish Astronomical Journal. Vol. 10, pp. 190-238. He included breakup and re-assembly of rings into which the Moon was broken.

Yarkovsky Effect connection

The Yarkovsky Effect
Yarkovsky effect
The Yarkovsky effect is a force acting on a rotating body in space caused by the anisotropic emission of thermal photons, which carry momentum...

 was discovered by the Russian civil engineer Ivan Osipovich Yarkovsky
Ivan Osipovich Yarkovsky
Ivan Osipovich Yarkovsky was a Russian-Polish civil engineer. He worked for a Russian railway company and was obscure in his own time. Beginning in the 1970s, long after Yarkovsky's death, his work on the effects of thermal radiation on small objects in the solar system was developed into the...

 (1844–1902), who worked on scientific problems in his spare time. Writing in a pamphlet around the year 1900, Yarkovsky noted that the diurnal heating of a rotating object in space would cause it to experience a force that, while tiny, could lead to large long-term effects in the orbits of small bodies, especially meteoroids and small asteroids. Yarkovsky's remarkable insight would have been consigned to oblivion had it not been for Öpik, who read Yarkovsky's pamphlet sometime around 1909. Decades later, Öpik, recalling the pamphlet from memory, discussed the possible importance of the Yarkovsky Effect
Yarkovsky effect
The Yarkovsky effect is a force acting on a rotating body in space caused by the anisotropic emission of thermal photons, which carry momentum...

 for moving meteoroids about the solar system.

Exile

Öpik fled his native country in 1944 because the approaching Red Army
Red Army
The Workers' and Peasants' Red Army started out as the Soviet Union's revolutionary communist combat groups during the Russian Civil War of 1918-1922. It grew into the national army of the Soviet Union. By the 1930s the Red Army was among the largest armies in history.The "Red Army" name refers to...

 raised fear among Estonians. Living as a refugee in Germany, he became Estonian rector of the Baltic University
Baltic University
The Baltic University in Exile was established in the displaced persons camps in Germany to educate refugees from Estonia, Latvia and Lithuania in the aftermath of the Second World War....

 in Exile in the displaced persons camp
Displaced persons camp
A displaced persons camp or DP camp is a temporary facility for displaced persons coerced into forced migration. The term is mainly used for camps established after World War II in West Germany and in Austria, as well as in the United Kingdom, primarily for refugees from Eastern Europe and for the...

s. In 1948 he was offered a post in Armagh and remained there despite offers of lucrative jobs in America.

Awards

He won the Gold Medal of the Royal Astronomical Society
Gold Medal of the Royal Astronomical Society
-History:In the early years, more than one medal was often awarded in a year, but by 1833 only one medal was being awarded per year. This caused a problem when Neptune was discovered in 1846, because many felt an award should jointly be made to John Couch Adams and Urbain Le Verrier...

 in 1975 and the Bruce Medal
Bruce Medal
The Catherine Wolfe Bruce Gold Medal is awarded every year by the Astronomical Society of the Pacific for outstanding lifetime contributions to astronomy. It is named after Catherine Wolfe Bruce, an American patroness of astronomy, and was first awarded in 1898...

 in 1976.

Legacy

The asteroid
Asteroid
Asteroids are a class of small Solar System bodies in orbit around the Sun. They have also been called planetoids, especially the larger ones...

 2099 Öpik
2099 Öpik
2099 Öpik is a Mars crosser asteroid, named after Estonian astronomer Ernst Julius Öpik.-Orbital data:Epoch J2000.0*semimajor axis: 2.303 AU*perihelion 1.470 AU*aphelion 2.002 AU*eccentricity: 0.362*inclination of orbit: 26.957 degree...

 is named in his honour. His grandson, Lembit Öpik
Lembit Öpik
Lembit Öpik is a British Liberal Democrat politician. He was the Member of Parliament for the constituency of Montgomeryshire in Wales from 1997 until he lost his seat in the 2010 General Election...

, was formerly the Liberal Democrat Member of Parliament for Montgomeryshire
Montgomeryshire (UK Parliament constituency)
Montgomeryshire is a constituency represented in the House of Commons of the Parliament of the United Kingdom. Created in 1542, it elects one Member of Parliament , traditionally known as the knight of the shire, by the first-past-the-post system of election.The Montgomeryshire Welsh Assembly...

, and has some astronomical connection in that he is a noted supporter of searching for asteroids that may collide with the Earth.

The crater Öpik on the Martian
Mars
Mars is the fourth planet from the Sun in the Solar System. The planet is named after the Roman god of war, Mars. It is often described as the "Red Planet", as the iron oxide prevalent on its surface gives it a reddish appearance...

 moon Phobos
Phobos (moon)
Phobos is the larger and closer of the two natural satellites of Mars. Both moons were discovered in 1877. With a mean radius of , Phobos is 7.24 times as massive as Deimos...

 is also named for him.

External links

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