2100 Ra-Shalom ( ''prov. designation'': ) is an

asteroid An asteroid is a minor planet of the 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 or icy bodies with no atmosphere. ...

and

near-Earth object A near-Earth object (NEO) is any small Solar System body whose orbit brings it into proximity with Earth. By convention, a Solar System body is a NEO if its closest approach to the Sun (perihelion) is less than 1.3 astronomical units (AU). ...

of the Aten group on an eccentric orbit in the

inner Solar System The Solar SystemCapitalization of the name varies. The International Astronomical Union, the authoritative body regarding astronomical nomenclature, specifies capitalizing the names of all individual astronomical objects but uses mixed "Solar S ...

. It was discovered on 10 September 1978, by American astronomer

Eleanor Helin Eleanor Francis "Glo" Helin (née Francis, 19 November 1932 – 25 January 2009) was an American astronomer. She was principal investigator of the Near-Earth Asteroid Tracking (NEAT) program of NASA's Jet Propulsion Laboratory. (Some sources gi ...

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 ...

, California, who named it in commemoration of the

Camp David Peace Accords The Camp David Accords were a pair of political agreements signed by Egyptian President Anwar Sadat and Israeli Prime Minister Menachem Begin on 17 September 1978, following twelve days of secret negotiations at Camp David, the country retreat ...

. The C-type asteroid (Xc, K) 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 19.8 hours and measures approximately in diameter.

Orbit and classification

''Ra-Shalom'' orbits the Sun at a distance of 0.5–1.2 AU once every 9 months (277 days). Its orbit has an eccentricity of 0.44 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 Plane of reference, reference plane and the orbital plane or Axis of rotation, axis of direction of the orbiting object ...

of 16 ° with respect to the ecliptic. It was the second Aten asteroid to be discovered after

2062 Aten 2062 Aten , provisional designation , is a stony sub-kilometer asteroid and namesake of the Aten asteroids, a subgroup of near-Earth objects. The asteroid was named after Aten from Egyptian mythology. It was discovered on 7 January 1976, at the ...

, the family's namesake, also discovered by Helin in 1976. The group of Aten asteroids feature a

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 less than 1 AU. Of this group, ''Ra-Shalom'' has one of the smallest semi-major axes, just 0.832 AU. The asteroid has an ''Earth minimum orbital intersection distance'' of which corresponds to 58.3 lunar distances, far too large to make it a

potentially hazardous object A potentially hazardous object (PHO) is a near-Earth object – either an asteroid or a comet – with an orbit that can make close approaches to the Earth and is large enough to cause significant regional damage in the event of impact. They ar ...

. It also comes within 30 gigameter (Gm) of Mars, Venus and Mercury. The closest approaches are to Mercury, to about 0.0784 AU (11.7 Gm).

Naming

The

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 ...

's composed named was chosen by the discoverer to commemorate the

between Egypt and Israel in September 1978, and as a symbol for the universal hope for peace. Ra is the Egyptian Sun-god, who symbolizes enlightenment and life, while

Shalom ''Shalom'' ( he, שָׁלוֹם ''šālōm''; also spelled as ''sholom'', ''sholem'', ''sholoim'', ''shulem'') is a Hebrew word meaning ''peace'', ''harmony'', ''wholeness'', ''completeness'', ''prosperity'', ''welfare'' and ''tranquility'' and ...

is the traditional Hebrew greeting meaning peace. The official 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 1 November 1978 ().

Physical characteristics

''Ra-Shalom'' has been characterized as a C-type and

X-type asteroid The X-group of asteroids collects together several types with similar spectra, but probably quite different compositions. Tholen classification In the Tholen classification the X-group consists of the following types: * E-type – with high al ...

on the

Tholen Tholen () is a 25,000 people municipality in the southwest of the Netherlands. The municipality of Tholen takes its name from the town of Tholen, which is the largest population center in the municipality. The municipality consists of two peninsu ...

and SMASS taxonomic scheme, respectively. It has also been characterized as a

K-type asteroid K-type asteroids are relatively uncommon asteroids with a moderately reddish spectrum shortwards of 0.75 μm, and a slight bluish trend longwards of this. They have a low albedo. Their spectrum resembles that of CV and CO meteorites. A larger K t ...

. In 1981, the asteroid was detected using radar, revealing a relatively smooth surface at decimeter scales.

Rotation period

In August 2016, a rotational lightcurve of ''Ra-Shalom'' was obtained from photometric observations by American astronomer Brian Warner. Lightcurve analysis gave a well-defined

of 19.89 hours with a brightness amplitude of 0.55 magnitude (). A large number of previous photometric observations gave a period between 19.79 and 19.8201 hours with a brightness amplitude between 0.3 and 0.41 magnitude.

Diameter and albedo

According to

Spitzer Space Telescope The Spitzer Space Telescope, formerly the Space Infrared Telescope Facility (SIRTF), was an infrared space telescope launched in 2003. Operations ended on 30 January 2020. Spitzer was the third space telescope dedicated to infrared astronomy, f ...

's ExploreNEOs survey, the Japanese Akari satellite, and NASA's

Keck Observatory The W. M. Keck Observatory is an astronomical observatory with two telescopes at an elevation of 4,145 meters (13,600 ft) near the summit of Mauna Kea in the U.S. state of Hawaii. Both telescopes have aperture primary mirrors, and when comp ...

, ''Ra-Shalom'' measures between 1.98 and 2.79 kilometers in diameter and its surface has an

albedo Albedo (; ) is the measure of the diffuse reflection of sunlight, solar radiation out of the total solar radiation and measured on a scale from 0, corresponding to a black body that absorbs all incident radiation, to 1, corresponding to a body ...

between 0.080 and 0.177. The ''Collaborative Asteroid Lightcurve Link'' adopts an albedo of 0.082 and a diameter of 2.78 kilometers with an

absolute magnitude Absolute magnitude () is a measure of the luminosity of a celestial object on an inverse Logarithmic scale, logarithmic Magnitude (astronomy), astronomical magnitude scale. An object's absolute magnitude is defined to be equal to the apparent mag ...

of 16.054.

Notes

References

External links

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

– ''Geneva Observatory'',

Raoul Behrend 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 numb ...

* * * {{DEFAULTSORT:Ra-Shalom 002100 Discoveries by Eleanor F. Helin Named minor planets 002100 002100 002100 19780910