406 Erna, provisional designation , is a dark

asteroid An asteroid is a minor planet—an object larger than a meteoroid that is neither a planet nor an identified comet—that orbits within the Solar System#Inner Solar System, inner Solar System or is co-orbital with Jupiter (Trojan asteroids). As ...

of the background population in the outer regions of the

asteroid belt The asteroid belt is a torus-shaped region in the Solar System, centered on the Sun and roughly spanning the space between the orbits of the planets Jupiter and Mars. It contains a great many solid, irregularly shaped bodies called asteroids ...

, approximately 46 kilometers in diameter. It was discovered by French astronomer

Auguste Charlois Auguste Honoré Charlois (; November 26, 1864 – March 26, 1910) was a French astronomer who discovered 99 asteroids while working at the Nice Observatory in southeastern France. Asteroid discovery His first discovery was the asteroid 267 Tirz ...

Nice Observatory The Nice Observatory () is an astronomical observatory located in Nice, France on the summit of Mount Gros. The observatory was founded in 1879, by the banker Raphaël Bischoffsheim. The architect was Charles Garnier (architect), Charles Garnier, ...

on 22 August 1895. The asteroid was presumably named after Erna Bidschof, the granddaughter of

Johann Palisa Johann Palisa (6 December 1848 – 2 May 1925) was an Austrian astronomer, born in Troppau, Austrian Silesia, now Czech Republic. He was a prolific discoverer of asteroids, discovering 122 in all, from 136 Austria in 1874 to 1073 G ...

Orbit and classification

''Erna'' is a non-

family Family (from ) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). It forms the basis for social order. Ideally, families offer predictabili ...

asteroid from the main belt's background population. It orbits the Sun in the outer asteroid belt at a distance of 2.4–3.4 AU once every 4 years and 12 months (1,818 days). Its orbit has an

eccentricity Eccentricity or eccentric may refer to: * Eccentricity (behavior), odd behavior on the part of a person, as opposed to being "normal" Mathematics, science and technology Mathematics * Off-Centre (geometry), center, in geometry * Eccentricity (g ...

of 0.18 and an

inclination Orbital inclination measures the tilt of an object's orbit around a celestial body. It is expressed as the angle between a reference plane and the orbital plane or axis of direction of the orbiting object. For a satellite orbiting the Eart ...

of 4 ° with respect to the

ecliptic The ecliptic or ecliptic plane is the orbital plane of Earth's orbit, Earth around the Sun. It was a central concept in a number of ancient sciences, providing the framework for key measurements in astronomy, astrology and calendar-making. Fr ...

. The body's

observation arc In observational astronomy, the observation arc (or arc length) of a Solar System body is the time period between its earliest and latest observations, used for tracing the body's path. It is usually given in days or years. The term is mostly use ...

begins at the

United States Naval Observatory The United States Naval Observatory (USNO) is a scientific and military facility that produces geopositioning, navigation and timekeeping data for the United States Navy and the United States Department of Defense. Established in 1830 as the ...

in September 1905, more than 10 years after its official discovery observation at Nice.

Physical characteristics

In the Tholen classification, ''Erna'' is a dark and primitive

P-type asteroid P-type (primitive-type) asteroids have low albedo and a featureless reddish spectrum. It has been suggested that they have a composition of organic-rich silicates, carbon and anhydrous silicates, possibly with water ice in their interior. P-type ...

. It has also been characterized as such by polarimetric observations.

Rotation period

In October 2005, a rotational

lightcurve In astronomy, a light curve is a graph (discrete mathematics), graph of the Radiance, light intensity of a celestial object or region as a function of time, typically with the magnitude (astronomy), magnitude of light received on the ''y''-axis ...

of ''Erna'' was obtained from photometric observations by French and Italian astronomers Raymond Poncy (), Roberto Crippa (), Federico Manzini and

Silvano Casulli __NOTOC__ Vincenzo Silvano Casulli, usually known as Silvano Casulli (25 August 1944 – 24 July 2018

. Lightcurve analysis gave a well-defined

rotation period In astronomy, the rotation period or spin period of a celestial object (e.g., star, planet, moon, asteroid) has two definitions. The first one corresponds to the '' sidereal rotation period'' (or ''sidereal day''), i.e., the time that the objec ...

of 8.7893 hours with a brightness variation of 0.35

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 ...

(). Another lightcurve from the

Palomar Transient Factory The Palomar Transient Factory (PTF, obs. code: I41), was an astronomical survey using a wide-field survey camera designed to search for optical transient and variable sources such as variable stars, supernovae, asteroids and comets. The projec ...

in November 2010 gave a similar period of 8.790 hours with an amplitude of 0.35 magnitude ().

Spin axis

In 2013, an international study modeled a lightcurve from various data sources including the Uppsala Asteroid Photometric Catalogue and the Palomar Transient Factory survey. The modeling gave a concurring period of 8.79079 hours and determined two spin axis in

ecliptic coordinates In astronomy, the ecliptic coordinate system is a celestial coordinate system commonly used for representing the apparent positions, orbits, and pole orientations of Solar System objects. Because most planets (except Mercury) and many small So ...

(λ, β) of: (357.0°, −49.0°) and (161.0°, −60.0°).

Diameter and albedo

According to the surveys carried out by the Infrared Astronomical Satellite

IRAS The Infrared Astronomical Satellite (Dutch language, Dutch: ''Infrarood Astronomische Satelliet'') (IRAS) was the first space telescope to perform a astronomical survey, survey of the entire night sky at infrared wavelengths. Launched on 25 Janu ...

, the Japanese

Akari AKARI (ASTRO-F) was an infrared astronomy satellite developed by Japan Aerospace Exploration Agency, in cooperation with institutes of Europe and Korea. It was launched on 21 February 2006, at 21:28 UTC (06:28, 22 February JST) by M-V rocket ...

satellite, and NASA's

Wide-field Infrared Survey Explorer Wide-field Infrared Survey Explorer (WISE, List of observatory codes, observatory code C51, Explorer 92 and MIDEX-6) was a NASA infrared astronomy Space observatory, space telescope in the Explorers Program launched in December 2009.. . WISE L ...

with its subsequent

NEOWISE Wide-field Infrared Survey Explorer (WISE, observatory code C51, Explorer 92 and MIDEX-6) was a NASA infrared astronomy space telescope in the Explorers Program launched in December 2009.. . WISE discovered thousands of minor planets and nu ...

mission, ''Erna'' measures between 41.52 and 49.19 kilometers in diameter and its surface has an

albedo Albedo ( ; ) is the fraction of sunlight that is Diffuse reflection, diffusely reflected by a body. It is measured on a scale from 0 (corresponding to a black body that absorbs all incident radiation) to 1 (corresponding to a body that reflects ...

between 0.0524 and 0.060. The ''Collaborative Asteroid Lightcurve Link'' adopts the results obtained by IRAS, that is, an albedo of 0.0524 and a diameter of 49.19 kilometers based on an absolute magnitude of 10.36.

Naming

This

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 ...

was likely named after Erna Bidschof, the granddaughter of Austrian astronomer

, who was one of the most prolific discoverer of minor planets at the time. Erna is the daughter of the astronomer Friedrich Bidschof (1864–1915) and his wife Helene (née Palisa).

References

External links

Asteroid Lightcurve Database (LCDB)
query form

)
Dictionary of Minor Planet Names
Google books

– Observatoire de Genève, Raoul Behrend

– Minor Planet Center * * {{DEFAULTSORT:Erna 000406 Discoveries by Auguste Charlois Named minor planets 000406 18950822