2101 Adonis (

provisional designation Provisional designation in astronomy is the naming convention applied to astronomical objects immediately following their discovery. The provisional designation is usually superseded by a permanent designation once a reliable orbit has been calcu ...

: ) is an

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 ...

on an extremely eccentric orbit, classified as

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 ...

. ''Adonis'' measures approximately 0.6 km in diameter. Discovered by

Eugène Delporte Eugene is a common male given name that comes from the Greek εὐγενής (''eugenēs''), "noble", literally "well-born", from εὖ (''eu''), "well" and γένος (''genos''), "race, stock, kin".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 ...

until 1977. It may also be an

extinct comet An extinct comet is a comet that has expelled most of its volatile ice and has little left to form a tail and coma. In a dormant comet, rather than being depleted, any remaining volatile components have been sealed beneath an inactive surface la ...

and a source of

meteor shower A meteor shower is a celestial event in which a number of meteors are observed to radiate, or originate, from one point in the night sky. These meteors are caused by streams of cosmic debris called meteoroids entering Earth's atmosphere at ext ...

s. It was named after

Adonis In Greek mythology, Adonis (; ) was the mortal lover of the goddesses Aphrodite and Persephone. He was considered to be the ideal of male beauty in classical antiquity. The myth goes that Adonis was gored by a wild boar during a hunting trip ...

from

Greek mythology Greek mythology is the body of myths originally told by the Ancient Greece, ancient Greeks, and a genre of ancient Greek folklore, today absorbed alongside Roman mythology into the broader designation of classical mythology. These stories conc ...

Discovery

Adonis was discovered on 12 February 1936, by Belgian astronomer

Eugène Delporte Eugene is a common male given name that comes from the Greek εὐγενής (''eugenēs''), "noble", literally "well-born", from εὖ (''eu''), "well" and γένος (''genos''), "race, stock, kin".Royal Observatory of Belgium The Royal Observatory of Belgium (; ; ) has been situated in the Uccle municipality of Brussels since 1890. It is part of the institutions of the Belgian Federal Science Policy Office (BELSPO). The Royal Observatory was first established in S ...

in Uccle. After its initial discovery, which happened during a close approach with Earth, the asteroid was observed for two months, before it 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 ...

, as not enough observations could be made to calculate a sufficiently accurate orbit. It took 41 years until it was finally rediscovered by the American astronomer Charles Kowal in 1977, based on mathematical predictions made by Dr. Brian Marsden.

Orbit and classification

The near-Earth object orbits the Sun at a distance of 0.4–3.3 AU once every 2 years and 7 months (937 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 1.87 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 0.76 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 1 ° 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 ...

. Adonis was one of the first

s ever to be discovered. It was also the second known

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 ...

after 1862 Apollo, the group's namesake discovered four years earlier in 1932.

MOID

It is a

because its Earth

minimum orbit 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 o ...

of , or 4.5 lunar distances, is less than 0.05 AU and its diameter is greater than 150 meters. It also makes close approaches to

Venus Venus is the second planet from the Sun. It is often called Earth's "twin" or "sister" planet for having almost the same size and mass, and the closest orbit to Earth's. While both are rocky planets, Venus has an atmosphere much thicker ...

and

Mars Mars is the fourth planet from the Sun. It is also known as the "Red Planet", because of its orange-red appearance. Mars is a desert-like rocky planet with a tenuous carbon dioxide () atmosphere. At the average surface level the atmosph ...

and will come within 30 Gm of the Earth six times during the 21st century, the nearest projected distance being , on 7 February 2036.

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 ...

is named from

after the handsome, ever-youthful vegetation god

, with whom the goddess

Aphrodite Aphrodite (, ) is an Greek mythology, ancient Greek goddess associated with love, lust, beauty, pleasure, passion, procreation, and as her syncretism, syncretised Roman counterpart , desire, Sexual intercourse, sex, fertility, prosperity, and ...

fell in love. Persephone was also taken by Adonis' beauty and refused to give him back to Aphrodite. The dispute between the two goddesses was settled by Zeus: Adonis was to spend one-third of every year with each goddess and the last third wherever he chose. He was killed by a boar sent by Artemis. The minor planets

105 Artemis 105 Artemis is a main-belt asteroid that was discovered by J. C. Watson on September 16, 1868, at Ann Arbor, Michigan. It was named after Artemis, the goddess of the hunt, Moon, and crossways in Greek Mythology. It is a C-type asteroid, meanin ...

399 Persephone 399 Persephone is a main belt asteroid. It was discovered by German astronomer Max Wolf on 23 February 1895 in Heidelberg. References External links * * Background asteroids Persephone Persephone In ancient Greek mythology a ...

, 1388 Aphrodite and

5731 Zeus 5731 Zeus is an Apollo asteroid and near-Earth object discovered on 4 November 1988, by Carolyn Shoemaker at Palomar Observatory. Based on its observed brightness and assumed albedo Albedo ( ; ) is the fraction of sunlight that is Diffuse ...

were named for these Greek gods. 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. Funct ...

on 1 November 1978 ().

Physical characteristics

Adonis has an absolute magnitude of 18.8, and an estimated

mean diameter In applied sciences, the equivalent radius (or mean radius) is the radius of a circle or sphere with the same perimeter, area, or volume of a non-circular or non-spherical object. The equivalent diameter (or mean diameter) (D) is twice the equiva ...

between 520 and 600 meters. As of 2017, the body's

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 ...

, composition,

spectral type In astronomy, stellar classification is the classification of stars based on their spectral characteristics. Electromagnetic radiation from the star is analyzed by splitting it with a prism or diffraction grating into a spectrum exhibiting the ...

and shape remain unknown.

Exploration

A famous ''Tintin'' book shows this asteroid too near from the Earth but Adonis was considered as a possible target for a 6 million km distant flyby by the

Vega 2 Vega 2 (along with Vega 1) was a Soviet space probe part of the Vega program to explore Halley's comet and Venus. The spacecraft was a development of the earlier '' Venera'' craft. The name VeGa (ВеГа) combines the first two letters of the R ...

spacecraft after its 1986 flyby of

Halley's Comet Halley's Comet is the only known List of periodic comets, short-period comet that is consistently visible to the naked eye from Earth, appearing every 72–80 years, though with the majority of recorded apparitions (25 of 30) occurring after ...

. In the event Vega 2 didn't have enough fuel post Halley encounter to make the necessary orbital changes for the flyby.

References

External links

Long-lost planet 1936 CA ("Adonis") recovered

Benner, et al. - Radar Detection of Near-Earth Asteroids 2062 Aten, 2101 Adonis, 3103 Eger, 4544 Xanthus, and 1992 QN (1997)
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