Chamberlin-Moulton planetesimal hypothesis
Encyclopedia
The Chamberlin–Moulton planetesimal hypothesis was proposed in 1905 by geologist Thomas Chrowder Chamberlin and astronomer Forest Ray Moulton
to describe the formation of the solar system
. It was proposed as a replacement for the Laplacian
version of the nebular hypothesis that had prevailed since the 19th century.
The theory was based on the idea that a star passed close enough to the sun early in its life to cause tidal bulges to form on its surface, which along with the internal process that leads to solar prominence
s, caused material to be ejected repeatedly from the sun. Due to the gravitational effects of the passing star, two spiral-like arms would have extended from the sun, and while most of the material would have fallen back, part of it would remain in orbit. This orbiting material would cool and condense into numerous small bodies that they termed planetesimal
s and a few larger protoplanet
s. Their theory proposed that as these objects collided over time, the planets and their moons were built up, with comet
s and asteroid
s being the leftover debris. The "spiral nebulae" photographed at Lick Observatory
were thought to possibly be views of other suns undergoing this process. These nebulae are now known to be galaxies
rather than developing solar systems.
In 1917, James Hopwood Jeans
argued that only a very close approach of a second star was necessary to eject material, instead of requiring solar prominences. In 1939, Lyman Spitzer
showed that a column of material drawn out from the sun would dissipate rather than condense. By this time the theory had mostly fallen out of favor, and in the 1940s, the work of Henry Norris Russell
showed that if the solar material had been pulled away from the sun with the force necessary to account for the angular momentum of Jupiter, the material would have continued out of the solar system entirely.
Though the Chamberlin–Moulton hypothesis is no longer accepted, the idea of planetesimals remains in modern theory.
Forest Ray Moulton
Forest Ray Moulton was an American astronomer.He was born in Le Roy, Michigan, and was educated at Albion College. After graduating in 1894 , he performed his graduate studies at the University of Chicago and gained a Ph.D. in 1899...
to describe the formation of the 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...
. It was proposed as a replacement for the Laplacian
Pierre-Simon Laplace
Pierre-Simon, marquis de Laplace was a French mathematician and astronomer whose work was pivotal to the development of mathematical astronomy and statistics. He summarized and extended the work of his predecessors in his five volume Mécanique Céleste...
version of the nebular hypothesis that had prevailed since the 19th century.
The theory was based on the idea that a star passed close enough to the sun early in its life to cause tidal bulges to form on its surface, which along with the internal process that leads to solar prominence
Solar prominence
A prominence is a large, bright feature extending outward from the Sun's surface, often in a loop shape. Prominences are anchored to the Sun's surface in the photosphere, and extend outwards into the Sun's corona...
s, caused material to be ejected repeatedly from the sun. Due to the gravitational effects of the passing star, two spiral-like arms would have extended from the sun, and while most of the material would have fallen back, part of it would remain in orbit. This orbiting material would cool and condense into numerous small bodies that they termed planetesimal
Planetesimal
Planetesimals are solid objects thought to exist in protoplanetary disks and in debris disks.A widely accepted theory of planet formation, the so-called planetesimal hypothesis of Viktor Safronov, states that planets form out of cosmic dust grains that collide and stick to form larger and larger...
s and a few larger protoplanet
Protoplanet
Protoplanets are large planetary embryos that originate within protoplanetary discs and have undergone internal melting to produce differentiated interiors. They are believed to form out of kilometer-sized planetesimals that attract each other gravitationally and collide...
s. Their theory proposed that as these objects collided over time, the planets and their moons were built up, with 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 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 being the leftover debris. The "spiral nebulae" photographed at Lick Observatory
Lick Observatory
The Lick Observatory is an astronomical observatory, owned and operated by the University of California. It is situated on the summit of Mount Hamilton, in the Diablo Range just east of San Jose, California, USA...
were thought to possibly be views of other suns undergoing this process. These nebulae are now known to be galaxies
Galaxy
A galaxy is a massive, gravitationally bound system that consists of stars and stellar remnants, an interstellar medium of gas and dust, and an important but poorly understood component tentatively dubbed dark matter. The word galaxy is derived from the Greek galaxias , literally "milky", a...
rather than developing solar systems.
In 1917, James Hopwood Jeans
James Hopwood Jeans
Sir James Hopwood Jeans OM FRS MA DSc ScD LLD was an English physicist, astronomer and mathematician.-Background:...
argued that only a very close approach of a second star was necessary to eject material, instead of requiring solar prominences. In 1939, Lyman Spitzer
Lyman Spitzer
Lyman Strong Spitzer, Jr. was an American theoretical physicist and astronomer best known for his research in star formation, plasma physics, and in 1946, for conceiving the idea of telescopes operating in outer space...
showed that a column of material drawn out from the sun would dissipate rather than condense. By this time the theory had mostly fallen out of favor, and in the 1940s, the work of Henry Norris Russell
Henry Norris Russell
Henry Norris Russell was an American astronomer who, along with Ejnar Hertzsprung, developed the Hertzsprung–Russell diagram . In 1923, working with Frederick Saunders, he developed Russell–Saunders coupling which is also known as LS coupling.-Biography:Russell was born in 1877 in Oyster Bay, New...
showed that if the solar material had been pulled away from the sun with the force necessary to account for the angular momentum of Jupiter, the material would have continued out of the solar system entirely.
Though the Chamberlin–Moulton hypothesis is no longer accepted, the idea of planetesimals remains in modern theory.