Io (
minor planet designation
A formal minor-planet designation is, in its final form, a number–name combination given to a minor planet (asteroid, centaur, trans-Neptunian object and dwarf planet but not comet). Such designation always features a leading number (catalog o ...
: 85 Io is carbonaceous
asteroid
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 ...
from the central region of the
asteroid belt
The asteroid belt is a torus-shaped region in the Solar System, located roughly between the orbits of the planets Jupiter and Mars. It contains a great many solid, irregularly shaped bodies, of many sizes, but much smaller than planets, called ...
, approximately 170 kilometers in diameter. It is an identified
Eunomian interloper.
Discovery and naming
It was discovered by
C. H. F. Peters
Christian Heinrich Friedrich Peters (September 19, 1813 – July 18, 1890) was a German–American university teacher and astronomer at the Litchfield Observatory of Hamilton College, New York, and a pioneer in the study and visual discovery of ...
on 19 September 1865, and named after
Io, a lover of
Zeus
Zeus or , , ; grc, Δῐός, ''Diós'', label=genitive Boeotian Aeolic and Laconian grc-dor, Δεύς, Deús ; grc, Δέος, ''Déos'', label=genitive el, Δίας, ''Días'' () is the sky and thunder god in ancient Greek religion, ...
in
Greek mythology
A major branch of classical mythology, Greek mythology is the body of myths originally told by the ancient Greeks, and a genre of Ancient Greek folklore. These stories concern the origin and nature of the world, the lives and activities of ...
.
Io is also the name of the
volcanic
A volcano is a rupture in the crust of a planetary-mass object, such as Earth, that allows hot lava, volcanic ash, and gases to escape from a magma chamber below the surface.
On Earth, volcanoes are most often found where tectonic plates ...
satellite
A satellite or artificial satellite is an object intentionally placed into orbit in outer space. Except for passive satellites, most satellites have an electricity generation system for equipment on board, such as solar panels or radioiso ...
of
Jupiter
Jupiter is the fifth planet from the Sun and the largest in the Solar System. It is a gas giant with a mass more than two and a half times that of all the other planets in the Solar System combined, but slightly less than one-thousandt ...
. With a two-digit number and a two-letter name, 85 Io has the shortest designation of all minor planets.
Orbit and physical characteristics
Io is a
retrograde rotator, with its pole pointing towards one of
ecliptic coordinates (β, λ) = (-45°, 105°) or (-15°, 295°) with a 10° uncertainty.
[ This gives an ]axial tilt
In astronomy, axial tilt, also known as obliquity, is the angle between an object's rotational axis and its orbital axis, which is the line perpendicular to its orbital plane; equivalently, it is the angle between its equatorial plane and orb ...
of about 125° or 115°, respectively. Its shape is quite regular.
In the SMASS classification
An asteroid spectral type is assigned to asteroids based on their emission spectrum, color, and sometimes albedo. These types are thought to correspond to an asteroid's surface composition. For small bodies that are not internally differentiat ...
, ''Io'' 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 ...
, which means that it is probably a primitive body composed of carbonate
A carbonate is a salt of carbonic acid (H2CO3), characterized by the presence of the carbonate ion, a polyatomic ion with the formula . The word ''carbonate'' may also refer to a carbonate ester, an organic compound containing the carbonat ...
s. Like 141 Lumen
Lumen (minor planet designation: 141 Lumen) is a carbonaceous asteroid from the intermediate asteroid belt
The asteroid belt is a torus-shaped region in the Solar System, located roughly between the orbits of the planets Jupiter and Mars. I ...
it is an interloper
Interloper, Interlopers or The Interlopers may refer to:
Entertainment
* '' The Interloper: Lee Harvey Oswald Inside the Soviet Union'', a 2013 book by Peter Savodnik
* Interloper (comics), a fictional character in the Marvel Comics universe
* I ...
that orbits within the Eunomia asteroid family but it is not related to the shattered parent body.
An Ionian diameter of 178 kilometres was measured from an occultation
An occultation is an event that occurs when one object is hidden from the observer by another object that passes between them. The term is often used in astronomy, but can also refer to any situation in which an object in the foreground blocks ...
of a star
A star is an astronomical object comprising a luminous spheroid of plasma held together by its gravity. The nearest star to Earth is the Sun. Many other stars are visible to the naked eye at night, but their immense distances from Earth make ...
on 10 December 1995.[ Another ]asteroid occultation
An occultation is an event that occurs when one object is hidden from the observer by another object that passes between them. The term is often used in astronomy, but can also refer to any situation in which an object in the foreground blocks ...
of Io (magnitude 13.2) occurred on 12 March 2009, from the eastern United States
The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country primarily located in North America. It consists of 50 U.S. state, states, a Washington, D.C., federal district, five ma ...
, with the star 2UCAC 35694429
(magnitude 13.8).[http://www.asteroidoccultation.com/2009_03/0312_85_20455.htm ]
See also
* List of Solar System objects by size
This article includes a list of the most massive known objects of the Solar System and partial lists of smaller objects by observed mean radius. These lists can be sorted according to an object's radius and mass and, for the most massive objects, ...
References
External links
Shapes and rotational properties of thirty asteroids from photometric data, Torppa (2003)
*
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Discoveries by Christian Peters
Named minor planets
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