981 Martina ('' prov. designation:'' ''or'' ) is a carbonaceous Themistian asteroid from 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 in diameter. It was discovered on 23 September 1917, by Russian astronomer Sergey Belyavsky at the

Simeiz Observatory Simeiz Observatory (also spelled Simeis or Simeïs) was an astronomy research observatory until the mid-1950s. It is located on Mount Koshka, Crimea, by the town of Simeiz. Part of the Crimean Astrophysical Observatory, it is currently used fo ...

on the Crimean peninsula. The C/

B-type asteroid B-type asteroids are a relatively uncommon type of carbonaceous asteroid, falling into the wider C-type asteroid#C-group asteroids, C-group; the 'B' indicates these objects are spectrally blue. In the asteroid population, B-class objects can be f ...

has a

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 11.3 hours. It was named after French historian and revolutionary Henri Martin (1810–1883).

Orbit and classification

''Martina'' is a core member of the

Themis family The Themis family (''adj. Themistian''; ) is a family of carbonaceous asteroids located in the outer portion of the asteroid belt, at a mean distance of 3.13 AU from the Sun. It is one of the largest families with over 4700 known members, and c ...

(), a very large

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 ...

of carbonaceous asteroids, named after 24 Themis. It orbits the Sun in the outer asteroid belt at a distance of 2.5–3.7 AU once every 5 years and 5 months (1,992 days;

semi-major axis In geometry, the major axis of an ellipse is its longest diameter: a line segment that runs through the center and both foci, with ends at the two most widely separated points of the perimeter. The semi-major axis (major semiaxis) is the longe ...

of 3.1 AU). 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 0.20 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 2 ° 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 with its first observation as () at

Lowell Observatory Lowell Observatory is an astronomical observatory in Flagstaff, Arizona, United States. Lowell Observatory was established in 1894, placing it among the oldest observatories in the United States, and was designated a National Historic Landmark ...

in August 1906, more than 11 years prior to its official discovery observation at Crimea–Simeis.

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 named after French historian and revolutionary politician, Henri Martin (1810–1883). The was mentioned in '' The Names of the Minor Planets'' by Paul Herget in 1955 ().

Physical characteristics

In the SDSS-based taxonomy, ''Martina'' is a carbonaceous

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 ...

, while in the classical Tholen classification, it has been classified as a CFU: asteroid, closest to a C-type and somewhat similar to an F-type, though with an unusual (U) and noisy spectra (:). In both the Tholen- and SMASS-like taxonomy of the Small Solar System Objects Spectroscopic Survey (S3OS2), ''Martina'' is a

, a "brighter" variant of the more common C-type. Members of the Themis family are typically classified as C-types with an albedo of 0.07, a value notably lower than for this asteroid at 0.10–0.13 ''(see below)''.

Rotation period

In August 2004, 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 ''Martina'' was obtained from photometric observations by David Higgins at the Hunters Hill Observatory in Australia. Lightcurve analysis gave a

of hours with a brightness variation of

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 ...

(). Astronomers at 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 California also determined the period in the R-band on two occasions, measuring 11.263 and 11.268 hours with an amplitude of 0.24 and 0.15 in 2010 and 2012, respectively ().

Diameter and albedo

According to the survey 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 satellite, and the

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 of 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 ...

, ''Franklina'' measures between 28.8 and 32.5 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 0.10 and 0.13. The ''Collaborative Asteroid Lightcurve Link'' adopts the results from IRAS, that is, an albedo of 0.1254 and a diameter of 28.87 kilometers, based on an absolute magnitude of 10.9.

References

External links

Lightcurve Database Query
(LCDB), at ''www.minorplanet.info''
Dictionary of Minor Planet Names
Google books

– Minor Planet Center * * {{DEFAULTSORT:Martina 000981 Discoveries by Sergei Belyavsky Named minor planets 000981 19170923