Édouard Jean-Marie Stephan
Encyclopedia
Édouard Jean-Marie Stephan (August 31, 1837 – December 31, 1923) was a French
astronomer
. His surname is sometimes spelled Stéphan in some literature, but this is apparently erroneous.
He was born in St Pezenne and attended the École Normale Superieur, and graduated at the top of his class in 1862.
He was the director of the Marseille Observatory
from 1864 to 1907 (until 1872 he was subordinate to Urbain le Verrier). In the early part of his career there, he had limited opportunities to do observations because he was preoccupied with improving the observatory. He discovered the asteroid
89 Julia
in 1866. In 1867 he used the new telescope to observe a transit
of Mercury
.
Between 1870 and 1875, Edouard Stephan systematically studied nebulae
, precisely recording their positions and discovering many new ones. His goal was to enable the exact measurement of stellar proper motions by creating a reference system of fixed objects.
In 1873 Stephan was the first person to attempt to measure the angular diameter
of a star
using interferometry
, converting the 80 cm telescope at Marseille Observatory into an interferometer. He did this by obscuring the reflector with a mask containing two vertical slits.
Te star he chose to perform this experiment was Sirius
. He did not succeed in resolving any stellar disks, but by 1874 had obtained an upper limit to stellar diameters of 0.158".
He discovered the galaxy NGC 6027
in 1882 using the 80 cm reflector.
Among others, he discovered Stephan's Quintet
, also known as "Arp 319", a group of five galaxies
. Stephan made this discovery with the first telescope equipped with a reflection coated mirror.
His name is associated with the periodic comet
38P/Stephan-Oterma
, although Jérôme Coggia
saw it first.
France
The French Republic , The French Republic , The French Republic , (commonly known as France , is a unitary semi-presidential republic in Western Europe with several overseas territories and islands located on other continents and in the Indian, Pacific, and Atlantic oceans. Metropolitan France...
astronomer
Astronomer
An astronomer is a scientist who studies celestial bodies such as planets, stars and galaxies.Historically, astronomy was more concerned with the classification and description of phenomena in the sky, while astrophysics attempted to explain these phenomena and the differences between them using...
. His surname is sometimes spelled Stéphan in some literature, but this is apparently erroneous.
He was born in St Pezenne and attended the École Normale Superieur, and graduated at the top of his class in 1862.
He was the director of the Marseille Observatory
Marseille Observatory
Marseille Observatory or Observatoire de Marseille is an astronomical observatory run by the University of Provence. It is located near Marseille, France. In its first incarnation, it was the discovery site of a group of galaxies known as Stephan's Quintet or Hickson 92, discovered by Édouard...
from 1864 to 1907 (until 1872 he was subordinate to Urbain le Verrier). In the early part of his career there, he had limited opportunities to do observations because he was preoccupied with improving the observatory. He discovered 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...
89 Julia
89 Julia
89 Julia is a large main-belt asteroid. It was discovered by French astronomer Édouard Stephan on August 6, 1866. It was first of his two asteroid discoveries; the other was 91 Aegina. It is believed to be named after Saint Julia of Corsica. A stellar occultation by Julia was observed on December...
in 1866. In 1867 he used the new telescope to observe a transit
Astronomical transit
The term transit or astronomical transit has three meanings in astronomy:* A transit is the astronomical event that occurs when one celestial body appears to move across the face of another celestial body, hiding a small part of it, as seen by an observer at some particular vantage point...
of Mercury
Mercury (planet)
Mercury is the innermost and smallest planet in the Solar System, orbiting the Sun once every 87.969 Earth days. The orbit of Mercury has the highest eccentricity of all the Solar System planets, and it has the smallest axial tilt. It completes three rotations about its axis for every two orbits...
.
Between 1870 and 1875, Edouard Stephan systematically studied nebulae
Nebula
A nebula is an interstellar cloud of dust, hydrogen gas, helium gas and other ionized gases...
, precisely recording their positions and discovering many new ones. His goal was to enable the exact measurement of stellar proper motions by creating a reference system of fixed objects.
In 1873 Stephan was the first person to attempt to measure the angular diameter
Angular diameter
The angular diameter or apparent size of an object as seen from a given position is the “visual diameter” of the object measured as an angle. In the vision sciences it is called the visual angle. The visual diameter is the diameter of the perspective projection of the object on a plane through its...
of a star
Star
A star is a massive, luminous sphere of plasma held together by gravity. At the end of its lifetime, a star can also contain a proportion of degenerate matter. The nearest star to Earth is the Sun, which is the source of most of the energy on Earth...
using interferometry
Interferometry
Interferometry refers to a family of techniques in which electromagnetic waves are superimposed in order to extract information about the waves. An instrument used to interfere waves is called an interferometer. Interferometry is an important investigative technique in the fields of astronomy,...
, converting the 80 cm telescope at Marseille Observatory into an interferometer. He did this by obscuring the reflector with a mask containing two vertical slits.
Te star he chose to perform this experiment was Sirius
Sirius
Sirius is the brightest star in the night sky. With a visual apparent magnitude of −1.46, it is almost twice as bright as Canopus, the next brightest star. The name "Sirius" is derived from the Ancient Greek: Seirios . The star has the Bayer designation Alpha Canis Majoris...
. He did not succeed in resolving any stellar disks, but by 1874 had obtained an upper limit to stellar diameters of 0.158".
He discovered the galaxy NGC 6027
NGC 6027
NGC 6027 is a Lenticular galaxy that is the brightest member of Seyfert's Sextet, a compact group of galaxies. Edouard Stephan discovered the galaxy in 1882.- See also :* NGC 6027a* NGC 6027b* NGC 6027c* NGC 6027d* NGC 6027e* Seyfert's Sextet...
in 1882 using the 80 cm reflector.
Among others, he discovered Stephan's Quintet
Stephan's Quintet
Stephan's Quintet in the constellation Pegasus is a visual grouping of five galaxies of which four form the first compact galaxy group ever discovered. The group was discovered by Édouard Stephan in 1877 at Marseilles Observatory....
, also known as "Arp 319", a group of five 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...
. Stephan made this discovery with the first telescope equipped with a reflection coated mirror.
His name is associated with the periodic 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...
38P/Stephan-Oterma
38P/Stephan-Oterma
38P/Stephan–Oterma is a periodic comet discovered in January 1867, by Jerome Coggia at Marseilles Observatory, France.-Orbit:It has perihelion near the orbit of Mars and has aphelion near the orbit of Uranus...
, although Jérôme Coggia
Jérôme Eugène Coggia
Jérôme Eugène Coggia was a 19th-century French astronomer.Working in Marseille, he discovered a number of comets, including the bright "Coggia's Comet" . The periodic comet 27P/Crommelin was previously called "Comet Pons-Coggia-Winnecke-Forbes". In 1916 he was awarded the Lalande Prize of the...
saw it first.
| 89 Julia 89 Julia 89 Julia is a large main-belt asteroid. It was discovered by French astronomer Édouard Stephan on August 6, 1866. It was first of his two asteroid discoveries; the other was 91 Aegina. It is believed to be named after Saint Julia of Corsica. A stellar occultation by Julia was observed on December... |
August 6, 1866 |
| 91 Aegina 91 Aegina 91 Aegina is a large main-belt asteroid. Its surface coloring is very dark and the asteroid has probably a primitive carbonaceous composition. It was discovered by a French astronomer Édouard Jean-Marie Stephan on November 4, 1866. It was his second and final asteroid discovery. The first was 89... |
November 4, 1866 |