69230 Hermes is a sub-kilometer sized
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
binary system
A binary system is a system of two astronomical bodies which are close enough that their gravitational attraction causes them to orbit each other around a barycenter ''(also see animated examples)''. More restrictive definitions require that thi ...
on an eccentric orbit,
classified as a
potentially hazardous asteroid
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 are ...
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
Apollo group
Apollo Education Group, Inc. is an American corporation based in the South Phoenix area of Phoenix, Arizona, with an additional corporate office in Chicago, Illinois.
The company owns and operates several higher-learning institutions, including ...
, that passed Earth at approximately twice the distance of the Moon on 30 October 1937. The asteroid was named after
Hermes
Hermes (; grc-gre, Ἑρμῆς) is an Olympian deity in ancient Greek religion and mythology. Hermes is considered the herald of the gods. He is also considered the protector of human heralds, travellers, thieves, merchants, and orato ...
from Greek mythology.
It is noted for having been the last remaining named
lost asteroid
A minor planet is "lost" when today's observers cannot find it, because its location is too uncertain to target observations. This happens if the orbital elements of a minor planet are not known accurately enough, typically because the observat ...
, rediscovered in 2003. The
S-type asteroid
S-type asteroids are asteroids with a spectral type that is indicative of a siliceous (i.e. stony) mineralogical composition, hence the name. They have relatively high density. Approximately 17% of asteroids are of this type, making it the second ...
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 13.9 hours.
Its synchronous
companion was discovered in 2003. The primary and secondary are similar in size; they measure approximately and in diameter, respectively.
Discovery
''Hermes'' was discovered by German astronomer
Karl Reinmuth
Karl Wilhelm Reinmuth (4 April 1892 in Heidelberg – 6 May 1979 in Heidelberg) was a German astronomer and a prolific discoverer of 395 minor planets.
Scientific career
From 1912 to 1957, Reinmuth was working as an astronomer at the Lande ...
in images taken at
Heidelberg Observatory
Heidelberg (; Palatine German: ') is a city in the German state of Baden-Württemberg, situated on the river Neckar in south-west Germany. As of the 2016 census, its population was 159,914, of which roughly a quarter consisted of students.
...
on 28 October 1937.
Only four days of observations could be made before it became too faint to be seen in the telescopes of the day.
This was not enough to calculate an orbit, and ''Hermes'' became a
lost asteroid
A minor planet is "lost" when today's observers cannot find it, because its location is too uncertain to target observations. This happens if the orbital elements of a minor planet are not known accurately enough, typically because the observat ...
.
It thus did not receive a number, but Reinmuth nevertheless named it after the Greek god
Hermes
Hermes (; grc-gre, Ἑρμῆς) is an Olympian deity in ancient Greek religion and mythology. Hermes is considered the herald of the gods. He is also considered the protector of human heralds, travellers, thieves, merchants, and orato ...
. It was the third unnumbered but named asteroid, having only the provisional designation . The two others long lost were
(1862) Apollo, discovered in 1932 and numbered in 1973, and
(2101) Adonis
2101 Adonis, ''provisional designation'': , is an asteroid on an extremely eccentric orbit, classified as potentially hazardous asteroid and near-Earth object of the Apollo group. ''Adonis'' measures approximately in diameter. Discovered by Eug ...
, discovered in 1936 and numbered in 1977.
On 15 October 2003,
Brian A. Skiff
Brian A. Skiff is an American astronomer noted for discovering numerous asteroids and a number of comets including the periodic comets 114P/Wiseman–Skiff (with Jennifer Wiseman) and 140P/Bowell–Skiff (with Edward Bowell).
Biography
Skiff ...
of the
LONEOS
Lowell Observatory Near-Earth-Object Search (LONEOS) was a project designed to discover asteroids and comets that orbit near the Earth. The project, funded by NASA, was directed by astronomer Ted Bowell of Lowell Observatory in Flagstaff, Arizo ...
project made an asteroid observation that, when the orbit was calculated backwards in time (by
Timothy B. Spahr, Steven Chesley and Paul Chodas), turned out to be a rediscovery of Hermes. It has been assigned sequential number 69230. Additional precovery observations were 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
...
, the earliest being found in images taken serendipitously by the
MPG/ESO 2.2-m La Silla telescope on 16 September 2000.
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 the
Greek god
The following is a list of gods, goddesses, and many other divine and semi-divine figures from ancient Greek mythology and ancient Greek religion.
Immortals
The Greeks created images of their deities for many purposes. A temple would house the ...
Hermes
Hermes (; grc-gre, Ἑρμῆς) is an Olympian deity in ancient Greek religion and mythology. Hermes is considered the herald of the gods. He is also considered the protector of human heralds, travellers, thieves, merchants, and orato ...
, who is the messenger of the gods and son of Zeus and Maia ''(also see and )''. Recovered and numbered in late 2003, ''Hermes'' was originally named by the
Astronomical Calculation Institute as early as 1937.
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 November 2003 ().
Orbit and classification
''Hermes'' is an
Apollo asteroid
The Apollo asteroids are a group of near-Earth asteroids named after 1862 Apollo, discovered by German astronomer Karl Reinmuth in the 1930s. They are Earth-crossing asteroids that have an orbital semi-major axis greater than that of the Earth ...
, a subgroup of near-Earth asteroids that
cross the orbit of Earth. It orbits the Sun at a distance of 0.6–2.7
AU once every 2 years and 2 months (778 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 1.66 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-center, in geometry
* Eccentricity (graph theory) of a v ...
of 0.62 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 6
° with respect to the
ecliptic
The ecliptic or ecliptic plane is the orbital plane of the Earth around the Sun. From the perspective of an observer on Earth, the Sun's movement around the celestial sphere over the course of a year traces out a path along the ecliptic again ...
.
Due to its eccentricity, ''Hermes'' is also a
Mars- and
Venus-crosser
A Venus-crosser is an asteroid whose orbit crosses that of Venus. There are 2,809 . Frequent close approaches to both Earth and Venus make it unusually challenging to forecast its orbit more than a century in advance, though there is no impact risk within that timeframe.
[https://science.nasa.gov/science-news/science-at-nasa/2003/31oct_hermes "The Curious Tale of Asteroid Hermes." Retrieved 27/12/2017.]
Close approaches
![Animation of 69230 Hermes's orbit around Sun](https://upload.wikimedia.org/wikipedia/commons/7/77/Animation_of_69230_Hermes%27s_orbit_around_Sun.gif)
The asteroid has an Earth
minimum orbital intersection distance
Minimum orbit intersection distance (MOID) is a measure used in astronomy to assess potential close approaches and collision risks between astronomical objects. It is defined as the distance between the closest points of the osculating orbits of ...
of which translates into 1.6
LD.
On 30 October 1937, ''Hermes'' passed from Earth, and on 26 April 1942, from Earth.
In retrospect it turned out that Hermes came even closer to the Earth in 1942 than in 1937, within 1.7
lunar distances; the second pass was unobserved at the height of the
Second World War
World War II or the Second World War, often abbreviated as WWII or WW2, was a world war that lasted from 1939 to 1945. It involved the vast majority of the world's countries—including all of the great powers—forming two opposin ...
.
For decades, ''Hermes'' was known to have made the closest known approach of an asteroid to the Earth. Not until 1989 was a closer approach (by
4581 Asclepius
4581 Asclepius , provisional designation , is a sub-kilometer-sized asteroid, classified as near-Earth object and potentially hazardous asteroid of the Apollo group that makes close orbital passes with Earth. Discovered on 31 March 1989 by America ...
) observed. At closest approach, ''Hermes'' was moving 5° per hour across the sky and reached 8th
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 ...
.
Physical characteristics
Spectral type
''Hermes'' is a stony
S-type asteroid
S-type asteroids are asteroids with a spectral type that is indicative of a siliceous (i.e. stony) mineralogical composition, hence the name. They have relatively high density. Approximately 17% of asteroids are of this type, making it the second ...
, as reported by Andy Rivkin and
Richard Binzel
Richard "Rick" P. Binzel (born 1958) is an American astronomer and professor of planetary sciences at the Massachusetts Institute of Technology (MIT). He is a discoverer of minor planets, photometrist and the inventor of the Torino Scale, a metho ...
.
It has been characterized as a Sq-subtype using the
SpeX instrument at
NASA Infrared Telescope Facility
The NASA Infrared Telescope Facility (NASA IRTF) is a telescope optimized for use in infrared astronomy and located at the Mauna Kea Observatory in Hawaii. It was first built to support the Voyager missions and is now the US national facility ...
. Sq-types transition to the
Q-type asteroid
Q-type asteroids are relatively uncommon inner-belt asteroids with a strong, broad 1 micrometre olivine and pyroxene feature, and a spectral slope that indicates the presence of metal. There are absorption features shortwards and longwards of 0. ...
.
Lightcurves
Three rotational
lightcurve
In astronomy, a light curve is a graph of light intensity of a celestial object or region as a function of time, typically with the magnitude of light received on the y axis and with time on the x axis. The light is usually in a particular frequ ...
s of ''Hermes'' were obtained from
photometric observations in October 2003. Lightcurve analysis gave a well-defined
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 ...
between 13.892 and 13.894 hours with a brightness variation between and 0.06 and 0.08
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 ...
, which indicates that the body has a nearly spherical shape ().
Binary system
![Hermes radar 2003](https://upload.wikimedia.org/wikipedia/commons/4/48/Hermes_radar_2003.jpg)
Radar observations led by
Jean-Luc Margot
Jean-Luc Margot (born 1969) is a Belgian-born astronomer and a UCLA professor who specializes in planetary sciences.
Career
Margot has discovered and studied several binary asteroids with radar and optical telescopes. His discoveries include ( ...
at
Arecibo Observatory
The Arecibo Observatory, also known as the National Astronomy and Ionosphere Center (NAIC) and formerly known as the Arecibo Ionosphere Observatory, is an observatory in Barrio Esperanza, Arecibo, Puerto Rico owned by the US National Science F ...
and
Goldstone in October and November 2003 showed Hermes to be a
binary asteroid
A binary asteroid is a system of two asteroids orbiting their common barycenter. The binary nature of 243 Ida was discovered when the Galileo spacecraft flew by the asteroid in 1993. Since then numerous binary asteroids and several triple ast ...
. The primary and secondary components have nearly identical radii of and , respectively,
and their orbital separation is only 1,200 metres,
much smaller than the
Hill radius
The Hill sphere of an astronomical body is the region in which it dominates the attraction of satellites. To be retained by a planet, a moon must have an orbit that lies within the planet's Hill sphere. That moon would, in turn, have a Hill sp ...
of 35 km, The satellite is nicknamed "Peitho" after the wife of Hermes.
The two components are in
double synchronous rotation (similar to the
trans-Neptunian
A trans-Neptunian object (TNO), also written transneptunian object, is any minor planet in the Solar System that orbits the Sun at a greater average distance than Neptune, which has a semi-major axis of 30.1 astronomical units (au).
Typically, ...
system
Pluto
Pluto (minor-planet designation: 134340 Pluto) is a dwarf planet in the Kuiper belt, a ring of trans-Neptunian object, bodies beyond the orbit of Neptune. It is the ninth-largest and tenth-most-massive known object to directly orbit the S ...
and
Charon
In Greek mythology, Charon or Kharon (; grc, Χάρων) is a psychopomp, the ferryman of Hades, the Greek underworld. He carries the souls of those who have been given funeral rites across the rivers Acheron and Styx, which separate the wo ...
).
Hermes is one of only four systems of that kind known in the near-Earth object population. The other three are , , and .
In popular culture
In the 1978 novel ''The Hermes Fall'' by
John Baxter, the asteroid endangers the Earth in 1980.
It is not explicitly made clear as to whether or not the Hermes asteroid from The Hermes Fall is 69230 Hermes.
Notes
References
External links
Arecibo 2003 press release Robert Johnston, johnstonsarchive.net
Dictionary of Minor Planet Names Google books
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Discoveries by Karl Wilhelm Reinmuth
Named minor planets
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