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 on a specific question or field outside the scope of Earth. Astronomers observe astronomical objects, such as stars, planets, natural satellite, moons, comets and galaxy, galax ...

and

telescope A telescope is a device used to observe distant objects by their emission, Absorption (electromagnetic radiation), absorption, or Reflection (physics), reflection of electromagnetic radiation. Originally, it was an optical instrument using len ...

-maker.

Biography

Alvan Graham Clark was born in Fall River,

Massachusetts Massachusetts ( ; ), officially the Commonwealth of Massachusetts, is a U.S. state, state in the New England region of the Northeastern United States. It borders the Atlantic Ocean and the Gulf of Maine to its east, Connecticut and Rhode ...

, the son of

Alvan Clark Alvan Clark (March 8, 1804 – August 19, 1887) was an American astronomer and telescope maker. Biography Born in Ashfield, Massachusetts, Clark started as a portrait painter and engraver (c.1830s–1850s), and at the age of 40 became involved ...

, founder of

Alvan Clark & Sons Alvan Clark & Sons was an American maker of optics that became famous for crafting lenses for some of the largest refracting telescopes of the 19th and early 20th centuries. Founded in 1846 in Cambridgeport, Massachusetts, by Alvan Clark (1804& ...

. 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 Cambridgeport is one of the neighborhoods of Cambridge, Massachusetts. It is bounded by Massachusetts Avenue, the Charles River, the Grand Junction Railroad, and River Street. The neighborhood contains predominantly residential homes, many of ...

, Clark made the first ever observation of a

white dwarf A white dwarf is a Compact star, stellar core remnant composed mostly of electron-degenerate matter. A white dwarf is very density, dense: in an Earth sized volume, it packs a mass that is comparable to the Sun. No nuclear fusion takes place i ...

star. This discovery of

Sirius B Sirius is the brightest star in the night sky. Its name is derived from the Greek word (Latin script: ), meaning 'glowing' or 'scorching'. The star is designated Canis Majoris, Latinized to Alpha Canis Majoris, and abbre ...

, or affectionately "the Pup", proved an earlier hypotheses (

Friedrich Wilhelm 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 method ...

in 1844) that

Sirius Sirius is the brightest star in the night sky. Its name is derived from the Greek word (Latin script: ), meaning 'glowing' or 'scorching'. The star is designated Canis Majoris, Latinized to Alpha Canis Majoris, and abbr ...

, the brightest star in the night sky with an

apparent magnitude Apparent magnitude () is a measure of the Irradiance, brightness of a star, astronomical object or other celestial objects like artificial satellites. Its value depends on its intrinsic luminosity, its distance, and any extinction (astronomy), ...

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 Soc ...

Northwestern University Northwestern University (NU) is a Private university, private research university in Evanston, Illinois, United States. Established in 1851 to serve the historic Northwest Territory, it is the oldest University charter, chartered university in ...

Evanston, Illinois Evanston is a city in Cook County, Illinois, United States, situated on the North Shore (Chicago), North Shore along Lake Michigan. A suburb of Chicago, Evanston is north of Chicago Loop, downtown Chicago, bordered by Chicago to the south, Skok ...

, where it is still being used today. Alvan Graham Clark died in

Cambridge, Massachusetts Cambridge ( ) is a city in Middlesex County, Massachusetts, United States. It is a suburb in the Greater Boston metropolitan area, located directly across the Charles River from Boston. The city's population as of the 2020 United States census, ...

on June 9, 1897.

References

*
The Dearborn Telescope

* ttp://www.astro.northwestern.edu/Observatory/chronology2.html Northwestern University Astronomy and Astrophysics – History of Dearborn Observatory
Look 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

Biography

See also

References

External links