694 Ekard is a

minor planet According to the International Astronomical Union (IAU), a minor planet is an astronomical object in direct orbit around the Sun that is exclusively classified as neither a planet nor a comet. Before 2006, the IAU officially used the term ''minor ...

orbiting the

Sun The Sun is the star at the center of the Solar System. It is a nearly perfect ball of hot plasma, heated to incandescence by nuclear fusion reactions in its core. The Sun radiates this energy mainly as light, ultraviolet, and infrared radi ...

that was discovered by American astronomer

Joel Hastings Metcalf Joel Hastings Metcalf (January 4, 1866 – February 23, 1925) was an American astronomer, humanitarian and Minister (Christianity), minister. Reverend Metcalf graduated from Harvard Divinity School in 1892. He served as a Unitarianism, Unitarian ...

on November 7, 1909. The asteroid's name comes from the reverse spelling of

Drake University Drake University is a private university in Des Moines, Iowa. It offers undergraduate and graduate programs, including professional programs in business, law, and pharmacy. Drake's law school is among the 25 oldest in the United States. Hi ...

Des Moines, Iowa Des Moines () is the capital and the most populous city in the U.S. state of Iowa. It is also the county seat of Polk County. A small part of the city extends into Warren County. It was incorporated on September 22, 1851, as Fort Des Moines, ...

, where

Seth Barnes Nicholson Seth Barnes Nicholson (November 12, 1891 – July 2, 1963) was an American astronomer. He worked at the Lick observatory in California, and is known for discovering several moons of Jupiter in the 20th century. Nicholson was born in Springfield, ...

and his wife calculated its orbit. Photometric observations of this asteroid gave a

light curve In astronomy, a light curve is a graph of light intensity of a celestial object or region as a function of time, typically with the magnitude of light received on the y axis and with time on the x axis. The light is usually in a particular frequ ...

with a period of 5.925 hours and a brightness variation of 0.50 in

magnitude Magnitude may refer to: Mathematics *Euclidean vector, a quantity defined by both its magnitude and its direction *Magnitude (mathematics), the relative size of an object *Norm (mathematics), a term for the size or length of a vector *Order of ...

. Measurements of the

thermal inertia In thermodynamics, a material's thermal effusivity, thermal inertia or thermal responsivity is a measure of its ability to exchange thermal energy with its surroundings. It is defined as the square root of the product of the material's thermal co ...

of 694 Ekard give a value of around 100–140 J m⁻² K⁻¹ s^−1/2, compared to 50 for

lunar regolith Lunar soil is the fine fraction of the regolith found on the surface of the Moon. Its properties can differ significantly from those of terrestrial soil. The physical properties of lunar soil are primarily the result of mechanical disintegra ...

and 400 for coarse sand in an atmosphere. 13-cm radar observations of this asteroid from the

Arecibo Observatory The Arecibo Observatory, also known as the National Astronomy and Ionosphere Center (NAIC) and formerly known as the Arecibo Ionosphere Observatory, is an observatory in Barrio Esperanza, Arecibo, Puerto Rico owned by the US National Science F ...

between 1980 and 1985 were used to produce a diameter estimate of 101 km. Four separate stellar occultation events involving this asteroid were observed from multiple sites in 2009. The resulting chords matched a least squares equivalent diameter of .

References

External links

* * Background asteroids Ekard Ekard CP:-type asteroids (Tholen) 19091107 {{beltasteroid-stub