21795 Masi (

provisional designation Provisional designation in astronomy is the naming convention applied to astronomical objects immediately following their discovery. The provisional designation is usually superseded by a permanent designation once a reliable orbit has been calcu ...

) is a

Nysian asteroid The Nysa family (adj. ''Nysian''; FIN: 405) is part of the Nysa–Polana complex, the largest cluster of asteroid families in the asteroid belt. It is located in the inner region of the asteroid belt, orbiting the Sun between 2.41 and 2.5 AU. ...

from the inner regions of the asteroid belt, approximately in diameter. It was discovered on 29 September 1999, by Italian amateur astronomer

Franco Mallia This is a list of minor-planet discoverers credited by the Minor Planet Center with the discovery of one or several minor planets (such as near-Earth and main-belt asteroids, Jupiter trojans and distant objects). , the discovery of 612,011 nu ...

at the

Campo Catino Astronomical Observatory This is a list of observatory codes (IAU codes or MPC codes) published by the Minor Planet Center. For a detailed description, ''see observations of small Solar System bodies Observations of minor planets as well as comets and natural satellit ...

in Lazio, Italy. The likely S-type asteroid has a

rotation period The rotation period of a celestial object (e.g., star, gas giant, planet, moon, asteroid) may refer to its sidereal rotation period, i.e. the time that the object takes to complete a single revolution around its axis of rotation relative to the ...

of 13.86 hours. It was named for Italian astronomer

Gianluca Masi Gianluca Masi (born 22 January 1972) is an Italian astrophysicist and astronomer, as well as a discoverer of minor planets and variable stars. Scientific career He started his interest in astronomy in childhood, later becoming a professional ...

Orbit and classification

Masi is member of the

Nysa family The Nysa family (adj. ''Nysian''; FIN: 405) is part of the Nysa–Polana complex, the largest cluster of asteroid families in the asteroid belt. It is located in the inner region of the asteroid belt, orbiting the Sun between 2.41 and 2.5 A ...

(), located in the Nysa–Polana complex and one of the largest

asteroid families 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 ...

of the asteroid belt, named after

44 Nysa Nysa (minor planet designation: 44 Nysa) is a large and very bright main-belt asteroid, and the brightest member of the Nysian asteroid family. It is classified as a rare class E asteroid and is probably the largest of this type (though 55 Pan ...

. It orbits the Sun in the

inner Interior may refer to: Arts and media * ''Interior'' (Degas) (also known as ''The Rape''), painting by Edgar Degas * ''Interior'' (play), 1895 play by Belgian playwright Maurice Maeterlinck * ''The Interior'' (novel), by Lisa See * Interior de ...

main-belt at a distance of 1.9–2.8 AU once every 3 years and 8 months (1,342 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 long ...

of 2.38 AU). Its orbit has an eccentricity of 0.19 and an inclination of 2 ° with respect to the ecliptic. The body's observation arc begins with a

precovery In astronomy, precovery (short for pre-discovery recovery) is the process of finding the image of an object in images or photographic plates predating its discovery, typically for the purpose of calculating a more accurate orbit. This happens mos ...

published by the

Digitized Sky Survey The Digitized Sky Survey (DSS) is a digitized version of several photographic astronomical surveys of the night sky, produced by the Space Telescope Science Institute between 1983 and 2006. Versions and source material The term Digitized Sky S ...

and taken at the

Palomar Observatory Palomar Observatory is an astronomical research observatory in San Diego County, California, United States, in the Palomar Mountain Range. It is owned and operated by the California Institute of Technology (Caltech). Research time at the observat ...

in April 1954, more than 45 years prior to its official discovery observation at Campo Catino.

Physical characteristics

Masi is an assumed, stony S-type asteroid, which is also the overall spectral type for members of the Nysa family of asteroids.

Rotation period

In September 2010, a rotational lightcurve of Masi was obtained from photometric observations in the R-band by 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. Lightcurve analysis gave a

of 13.862 hours with a relatively high brightness amplitude of 0.68 magnitude ().

Diameter and albedo

According to the survey carried out by the NEOWISE mission of NASA's Wide-field Infrared Survey Explorer, Masi measures 3.150 kilometers in diameter and its surface has an albedo of 0.235, while the ''Collaborative Asteroid Lightcurve Link'' assumes a standard albedo for a stony asteroid of 0.20, and calculates a diameter of 2.45 kilometers based on an absolute magnitude of 15.42.

Naming

This minor planet was named after Italian astrophysicist and astronomer,

(born 1972), a researcher and discoverer of minor planets and variable stars, who became an avid amateur astronomer when he was 8 years old. The official naming citation was published by the

Minor Planet Center The Minor Planet Center (MPC) is the official body for observing and reporting on minor planets under the auspices of the International Astronomical Union (IAU). Founded in 1947, it operates at the Smithsonian Astrophysical Observatory. Function ...

on 9 May 2001 ().

References

External links

Asteroid Lightcurve Database (LCDB)
query form

)
Dictionary of Minor Planet Names
Google books

– Minor Planet Center * * {{DEFAULTSORT:Masi 021795 Discoveries by Franco Mallia Named minor planets 19990929