69230 Hermes
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69230 Hermes is a sub-kilometer sized
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 ...
and
binary system A binary system is a system of two astronomical bodies of the same kind that are comparable in size. Definitions vary, but typically require the center of mass to be located outside of either object. (See animated examples.) The most common ki ...
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 which is large enough to cause significant regional damage in the event of impact. Th ...
and
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 ...
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. It is privately-owned by a consortium of investors including The Vistria Grou ...
, that passed Earth at approximately twice the distance of the Moon on 30 October 1937. The asteroid was named after
Hermes Hermes (; ) is an Olympian deity in ancient Greek religion and mythology considered the herald of the gods. He is also widely considered the protector of human heralds, travelers, thieves, merchants, and orators. He is able to move quic ...
from Greek mythology. It is noted for having been the last remaining named
lost asteroid Lost or LOST may refer to getting lost, or to: Arts, entertainment, and media Television * ''Lost'' (TV series), a 2004 American drama series about people who become stranded on a mysterious island * ''Lost'' (2001 TV series), a short-lived Ameri ...
, rediscovered in 2003. The
S-type asteroid S-type (stony-type or silicaceous-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 ...
has 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 13.9 hours. Its synchronous
companion Companion may refer to: Relationships Currently * Any of several interpersonal relationships such as friend or acquaintance * A domestic partner, akin to a spouse * Sober companion, an addiction treatment coach * Companion (caregiving), a caregive ...
was discovered in 2003. The primary and secondary are separated by and are similar in size; they measure approximately and in diameter, respectively, with a combined effective diameter of .


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 He ...
in images taken at
Heidelberg Observatory Heidelberg (; ; ) is the List of cities in Baden-Württemberg by population, fifth-largest city in the States of Germany, German state of Baden-Württemberg, and with a population of about 163,000, of which roughly a quarter consists of studen ...
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 Lost or LOST may refer to getting lost, or to: Arts, entertainment, and media Television * ''Lost'' (TV series), a 2004 American drama series about people who become stranded on a mysterious island * ''Lost'' (2001 TV series), a short-lived Ameri ...
. It thus did not receive a number, but Reinmuth nevertheless named it after the Greek god
Hermes Hermes (; ) is an Olympian deity in ancient Greek religion and mythology considered the herald of the gods. He is also widely considered the protector of human heralds, travelers, thieves, merchants, and orators. He is able to move quic ...
. 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, discovered in 1936 and numbered in 1977. On 15 October 2003, Brian A. 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, Ariz ...
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 In astronomy, precovery (short for pre-discovery recovery) is the process of finding the image of a celestial object in images or photographic plates predating its discovery, typically for the purpose of calculating a more accurate orbit. This ha ...
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. Funct ...
, 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 In ancient Greece, deities were regarded as immortal, anthropomorphic, and powerful. They were conceived of as individual persons, rather than abstract concepts or notions, and were described as being similar to humans in appearance, albeit larg ...
Hermes Hermes (; ) is an Olympian deity in ancient Greek religion and mythology considered the herald of the gods. He is also widely considered the protector of human heralds, travelers, thieves, merchants, and orators. He is able to move quic ...
, who is the messenger of the gods and son of
Zeus Zeus (, ) is the chief deity of the List of Greek deities, Greek pantheon. He is a sky father, sky and thunder god in ancient Greek religion and Greek mythology, mythology, who rules as king of the gods on Mount Olympus. Zeus is the child ...
and
Maia Maia (; Ancient Greek: Μαῖα; also spelled Maie, ; ), in ancient Greek religion and mythology, is one of the Pleiades and the mother of Hermes, one of the major Greek gods, by Zeus, the king of Olympus. Family Maia is the daughter of A ...
''(see also 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. Funct ...
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 Ear ...
, 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 longe ...
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-Centre (geometry), center, in geometry * Eccentricity (g ...
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 reference plane and the orbital plane or axis of direction of the orbiting object. For a satellite orbiting the Eart ...
of 6 ° 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 ...
. 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

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 (1 September 1939 – 2 September 1945) was a World war, global conflict between two coalitions: the Allies of World War II, Allies and the Axis powers. World War II by country, Nearly all of the wo ...
. 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 Amer ...
) 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 (stony-type or silicaceous-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 ...
, 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 meth ...
. 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 program, Voyager missions and is now the US n ...
. 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 0.7& ...
.


Lightcurves

Three 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 ...
s of Hermes were obtained from photometric observations in October 2003. Lightcurve analysis gave a well-defined
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 ...
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

Radar observations led by
Jean-Luc Margot Jean-Luc Margot (born 1969) is a Belgian-born astronomer and a UCLA professor with expertise in planetary sciences and SETI. Career Margot has discovered and studied several binary asteroids with radar and optical telescopes. His discoveries ...
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 a ...
. 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 A hill is a landform that extends above the surrounding terrain. It often has a distinct summit, and is usually applied to peaks which are above elevation compared to the relative landmass, though not as prominent as mountains. Hills fall unde ...
of 35 km. 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 an orbital semi-major axis of 30.1 astronomical units (AU). T ...
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 Su ...
and
Charon In Greek mythology, Charon or Kharon ( ; ) is a psychopomp, the ferryman of the Greek underworld. He carries the souls of those who have been given funeral rites across the rivers Acheron and Styx, which separate the worlds of the living and ...
). 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 * * * {{DEFAULTSORT:Hermes 069230 Discoveries by Karl Wilhelm Reinmuth Named minor planets 069230 069230 069230 19371028
69230 69 may refer to: * 69 (number) * A year, primarily 69 BC, AD 69, 1969, or 2069 *69 (sex position) *69 Hesperia, a main-belt asteroid Arts and media Music * ''69'', a 1988 album by A.R. Kane * 69", a song by Deep Purple from ''Abandon'' * Majo ...