Alvan Graham Clark (July 10, 1832 – June 9, 1897) was an American
astronomer
An astronomer is a scientist in the field of astronomy who focuses their studies on a specific question or field outside the scope of Earth. They observe astronomical objects such as stars, planets, moons, comets and galaxies – in either o ...
and
telescope
A telescope is a device used to observe distant objects by their emission, absorption, or reflection of electromagnetic radiation. Originally meaning only an optical instrument using lenses, curved mirrors, or a combination of both to obse ...
-maker.
Biography
Alvan Graham Clark was born in
Fall River
Fall River is a city in Bristol County, Massachusetts, United States. The City of Fall River's population was 94,000 at the 2020 United States Census, making it the tenth-largest city in the state.
Located along the eastern shore of Mount H ...
,
, the son of
Alvan Clark
Alvan Clark (March 8, 1804 – August 19, 1887), born in Ashfield, Massachusetts, the descendant of a Cape Cod whaling family of English ancestry, was an American astronomer and telescope maker.
Biography
He started as a portrait painter and engra ...
, founder of
Alvan Clark & Sons.
On January 31, 1862, while testing a new aperture
great refractor
Great refractor refers to a large telescope with a lens, usually the largest refractor at an observatory with an equatorial mount. The preeminence and success of this style in observational astronomy defines an era in modern telescopy in the 19t ...
telescope in
Cambridgeport,
, Clark made the first ever observation of a
white dwarf
A white dwarf is a stellar core remnant composed mostly of electron-degenerate matter. A white dwarf is very dense: its mass is comparable to the Sun's, while its volume is comparable to the Earth's. A white dwarf's faint luminosity comes ...
star. This discovery of
Sirius B
Sirius is the brightest star in the night sky. Its name is derived from the Greek word , or , meaning 'glowing' or 'scorching'. The star is designated α Canis Majoris, Latinized to Alpha Canis Majoris, and abbreviated Alpha CM ...
, or affectionately "the Pup", proved an earlier hypotheses (
Friedrich Bessel
Friedrich Wilhelm Bessel (; 22 July 1784 – 17 March 1846) was a German astronomer, mathematician, physicist, and geodesist. He was the first astronomer who determined reliable values for the distance from the sun to another star by the met ...
in 1844) that
Sirius
Sirius is the brightest star in the night sky. Its name is derived from the Greek word , or , meaning 'glowing' or 'scorching'. The star is designated α Canis Majoris, Latinized to Alpha Canis Majoris, and abbreviated Alpha CMa ...
, the brightest star in the night sky with an
apparent magnitude
Apparent magnitude () is a measure of the brightness of a star or other astronomical object observed from Earth. An object's apparent magnitude depends on its intrinsic luminosity, its distance from Earth, and any extinction of the object's li ...
of −1.46, had an unseen companion disturbing its motion. Clark used the largest refracting telescope lens in existence at the time, and the largest telescope in the United States, to observe the magnitude 8 companion.
Clark's 18.5 inch refracting telescope was then delivered to his customer, the landmark
Dearborn Observatory
The Dearborn Observatory is an astronomical observatory located on the Evanston campus of Northwestern University. The observatory was originally constructed in 1888, through an agreement between the university and the Chicago Astronomical Socie ...
of
Northwestern University
Northwestern University is a private research university in Evanston, Illinois. Founded in 1851, Northwestern is the oldest chartered university in Illinois and is ranked among the most prestigious academic institutions in the world.
Chart ...
in
Evanston, Illinois
Evanston ( ) is a city, suburb of Chicago. Located in Cook County, Illinois, Cook County, Illinois, United States, it is situated on the North Shore (Chicago), North Shore along Lake Michigan. Evanston is north of Chicago Loop, Downtown Chicago, ...
, where it is still being used today.
Alvan Graham Clark died in
Cambridge, Massachusetts
Cambridge ( ) is a city in Middlesex County, Massachusetts, United States. As part of the Greater Boston, Boston metropolitan area, the cities population of the 2020 United States Census, 2020 U.S. census was 118,403, making it the fourth most ...
on June 9, 1897.
See also
*
List of astronomical instrument makers
The following is a list of astronomical instrument makers, along with lifespan and country of work, if available.
A
B
C
D
E
F
G
H
I
J
K
L
M
N
O
P
Q
R
S
T
U
V ...
References
*
The Dearborn Telescope*
ttp://www.astro.northwestern.edu/Observatory/chronology2.html Northwestern University Astronomy and Astrophysics – History of Dearborn ObservatoryLook south to see winter's brightest constellations
External links
Portraits of Alvan Graham Clark from the Lick Observatory Records Digital Archive, UC Santa Cruz Library's Digital Collections
{{DEFAULTSORT:Clark, Alvan Graham
1832 births
1897 deaths
American astronomers
People from Fall River, Massachusetts