9175 Graun, provisional designation , is a stony Eunomian
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 ...
from the central region 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 10 kilometers in diameter. It was discovered on 29 July 1990, by American astronomer
Henry E. Holt at
Palomar Observatory
The Palomar Observatory is an astronomical research observatory in the Palomar Mountains of San Diego County, California, United States. It is owned and operated by the California Institute of Technology (Caltech). Research time at the observat ...
in California, United States.
The asteroid was later named for American author and amateur astronomer
Ken Graun.
Orbit and classification
''Graun'' is a member of the
Eunomia family, a large group of
S-type asteroids and the most prominent family in the
intermediate main-belt. It orbits the Sun at a distance of 2.2–3.0
AU once every 4 years and 2 months (1,531 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 0.14 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 15
° 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 ...
.
In February 1975, it was first identified as at the
Karl Schwarzschild Observatory, extending the body's
observation arc by 15 years prior to its official discovery observation at Palomar.
Alternative family
Based on its concurring orbital elements, ''Graun'' has also been group into the
Maria family, which is named after its namesake, the asteroid
170 Maria.
It is an old-type asteroid family, about years old, located near the area of a 3:1
resonances
Resonance is a phenomenon that occurs when an object or system is subjected to an external force or vibration whose frequency matches a resonant frequency (or resonance frequency) of the system, defined as a frequency that generates a maximu ...
with Jupiter that supplies near-Earth asteroids to 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 "Sola ...
. It is estimated that every 100 million years, about 37 to 75 Maria asteroids larger than 1 kilometer become
near-Earth object
A near-Earth object (NEO) is any small Solar System body orbiting the Sun whose closest approach to the Sun ( perihelion) is less than 1.3 times the Earth–Sun distance (astronomical unit, AU). This definition applies to the object's orbit a ...
s.
Physical characteristics
Lightcurves
In January 2013, 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 ''Graun'' was obtained from photometric observations. Lightcurve analysis gave 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 hours with a brightness variation of 0.16
magnitude ().
The measurement supersedes a shorter period of 20 hours with an amplitude of 0.2 magnitude ().
Diameter and albedo
According to the surveys carried out by the
NEOWISE 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 ...
and the Japanese
Akari satellite, ''Graun'' measures 10.23 and 10.35 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 ...
of 0.20 and 0.183, respectively.
Preliminary NEOWISE results gave a much higher albedo and consequently shorter diameter.
The ''Collaborative Asteroid Lightcurve Link'' assumes an albedo of 0.21 – derived from
15 Eunomia, the family's largest member and namesake – and calculates a diameter of 10.53 kilometers with an
absolute magnitude of 12.2.
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 in honor of American amateur astronomer and publisher Ken Graun (born 1955), author of two books on astronomy, owner of "Ken Press" and the website ''What's Out tonight?'', bringing astronomy to the broader public including children.
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.
Funct ...
on 9 March 2001 ().
References
External links
Asteroid Lightcurve Database (LCDB) query form
)
Dictionary of Minor Planet Names Google books
– Observatoire de Genève, Raoul Behrend
– Minor Planet Center
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009175
009175
Discoveries by Henry E. Holt
Named minor planets
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