Alexandra (

minor planet designation A formal minor-planet designation is, in its final form, a number–name combination given to a minor planet (asteroid, centaur, trans-Neptunian object and dwarf planet but not comet). Such designation always features a leading number (catalog o ...

: 54 Alexandra) is a

carbonaceous Carbon () is a chemical element with the symbol C and atomic number 6. It is nonmetallic and tetravalent—its atom making four electrons available to form covalent chemical bonds. It belongs to group 14 of the periodic table. Carbon makes up o ...

asteroid An asteroid is a minor planet of the Solar System#Inner solar system, inner Solar System. Sizes and shapes of asteroids vary significantly, ranging from 1-meter rocks to a dwarf planet almost 1000 km in diameter; they are rocky, metallic o ...

from the intermediate

asteroid belt The asteroid belt is a torus-shaped region in the Solar System, located roughly between the orbits of the planets Jupiter and Mars. It contains a great many solid, irregularly shaped bodies, of many sizes, but much smaller than planets, called ...

, approximately 155 kilometers in diameter. It was discovered by German-French astronomer

Hermann Goldschmidt Hermann Mayer Salomon Goldschmidt (June 17, 1802 – August 30 or September 10 1866) was a German-French astronomer and painter who spent much of his life in France. He started out as a painter, but after attending a lecture by the famous Fren ...

on 10 September 1858, and named after the German explorer

Alexander von Humboldt Friedrich Wilhelm Heinrich Alexander von Humboldt (14 September 17696 May 1859) was a German polymath, geographer, naturalist, explorer, and proponent of Romantic philosophy and science. He was the younger brother of the Prussian minister, ...

; it was the first asteroid to be named after a male.

Description

On May 17, 2005, this asteroid occulted a faint star (

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 ...

8.5) and the event was observed and timed in a number of locations within the

U.S. The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country primarily located in North America. It consists of 50 states, a federal district, five major unincorporated territor ...

and

Mexico Mexico ( Spanish: México), officially the United Mexican States, is a country in the southern portion of North America. It is bordered to the north by the United States; to the south and west by the Pacific Ocean; to the southeast by Guate ...

. As a result, a

silhouette A silhouette ( , ) is the image of a person, animal, object or scene represented as a solid shape of a single colour, usually black, with its edges matching the outline of the subject. The interior of a silhouette is featureless, and the silhou ...

profile was produced, yielding a roughly oval cross-section with dimensions of 160 × 135 km (± 1 km).D.W. Dunham, "Upcoming Asteroid Occultations", ''Sky & Telescope'', June, 2006, p. 63. The mass of the asteroid can be estimated based upon the mutually perturbing effects of other bodies, yielding an estimate of . Photometric observations of this asteroid during 1990–92 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 18.14 ± 0.04 hours and a brightness variation of 0.10 in

. Alexandra has been studied by

radar Radar is a detection system that uses radio waves to determine the distance ('' ranging''), angle, and radial velocity of objects relative to the site. It can be used to detect aircraft, ships, spacecraft, guided missiles, motor vehicles, w ...

. It was the namesake and largest member of the former Alexandra

asteroid family An asteroid family is a population of asteroids that share similar proper orbital elements, such as semimajor axis, eccentricity, and orbital inclination. The members of the families are thought to be fragments of past asteroid collisions. A ...

; a dynamic group of

C-type asteroid C-type (carbonaceous) asteroids are the most common variety, forming around 75% of known asteroids. They are volatile-rich and distinguished by a very low albedo because their composition includes a large amount of carbon, in addition to rocks ...

s that share similar

orbital elements Orbital elements are the parameters required to uniquely identify a specific orbit. In celestial mechanics these elements are considered in two-body systems using a Kepler orbit. There are many different ways to mathematically describe the same ...

. Other members included 70 Panopaea and

145 Adeona Adeona (minor planet designation: 145 Adeona) is a large asteroid from the intermediate asteroid belt, approximately in diameter. Its surface is very dark, and, based upon its classification as a C-type asteroid, is probably composed of primitiv ...

. 145 Adeona was subsequently assigned to the

Adeona family The Adeona or Adeonian family () is a large asteroid family that formed from the parent body 145 Adeona. Its spectral type is that of a carbonaceous C-type, with currently 2,236 asteroids identified as family members. Based upon simulation ...

, with Alexandra and Panopaea being dropped.

In Popular Culture

In the Swedish film Aniara (2018) it is mentioned that 54 Alexandra is the closest celestial body which the off-course and out-of-control spacecraft will approach before it leaves the Solar System.

References

External links

Lightcurve plot of 54 Alexandra
Palmer Divide Observatory, '' B. D. Warner'' (2008)
Asteroid Lightcurve Database (LCDB)
query form

)
Dictionary of Minor Planet Names
Google books

– Observatoire de Genève, Raoul Behrend

– Minor Planet Center * * {{DEFAULTSORT:Alexandra 000054 Discoveries by Hermann Goldschmidt Named minor planets 000054 000054 18580910