Asteroid

Composite greyscale image of Vesta

Terminology: The Greek term ἀστεροειδής, or asteroeidēs, means star-like, star-shaped, and is derived from the Ancient Greek ἀστήρ astēr (star, planet) An asteroid can be defined as "an irregularly shaped rocky body orbiting the Sun that does not qualify as a planet or a dwarf planet under the IAU definitions of those terms". Traditionally, small bodies orbiting the Sun were classified as comets, asteroids, or meteoroids, with anything smaller than one meter across being called a meteoroid.
The term "asteroid" never had a formal definition. Synonyms: planetoid (literally: planet-like); Minor Planet.

One of the smaller celestial bodies - largely made up of rocky material - that orbit the Sun in a similar way as the more well-known planets.

Astronomy

Number, History & Size

Asteroids vary greatly in size, from a few metres diameter up to nearly 950 Km. The first asteroids, which remain the most widely known, were discovered at the beginning of the 19th century (Napoleonic era): Ceres, Pallas, Juno and Vesta; although the International Astronomical Union (IAU) reclassified Ceres as a Dwarf Planet in 2006. Asteroids are distinguished from actual planets by having insufficient gravity to become round in shape and to "clear their orbit" of smaller bodies in the vicinity by attracting them to the surface or in orbit around them as satellites. The three largest asteroids are very much like miniature planets: they are roughly spherical, have at least partly differentiated interiors, and are thought to be surviving protoplanets. The vast majority, however, are much smaller and are irregularly shaped; they are thought to be either battered planetesimals or fragments of larger bodies.

As of April 2022, the Minor Planet Center had data on 1,199,224 minor planets in the inner and outer Solar System, of which about 614,690 had enough information to be given numbered designations. The total mass of all the asteroids combined is only 3% that of Earth's Moon. The dwarf planet Ceres is by far the largest asteroid, with a diameter of 940 km (580 mi). The next largest are Vesta and Pallas, both with diameters of just over 500 km (300 mi). Vesta is the brightest of the first four main-belt asteroids. The four largest objects, Ceres, Vesta, Pallas, and Hygiea, account for maybe 62% of the belt's total mass, with 39% accounted for by Ceres alone.

Contrary to popular imagery, the asteroid belt is mostly empty. The asteroids are spread over such a large volume that reaching an asteroid without aiming carefully would be improbable. Nonetheless, hundreds of thousands of asteroids are currently known, and the total number ranges in the millions or more, depending on the lower size cutoff. Over 200 asteroids are known to be larger than 100 km, and a survey in the infrared wavelengths has shown that the asteroid belt has between 700,000 and 1.7 million asteroids with a diameter of 1 km or more.

Threats to Earth?

Near-Earth asteroids can threaten all life on the planet. There is increasing interest in identifying asteroids whose orbits cross Earth's, and that could collide with Earth. The three most important groups of near-Earth asteroids are the Apollos, Amors, and Atens.

Observability

Only one asteroid, Vesta, which has a relatively reflective surface, is normally visible to the naked eye. When favorably positioned, Vesta can be seen in dark skies.

Orbits

The majority of main belt asteroids follow slightly elliptical, stable orbits, revolving in the same direction as the Earth and taking from three to six years to complete a full circuit of the Sun. Most asteroids within the asteroid belt have orbital eccentricities less than 0.4, and an inclination of less than 30°. Thus, a typical asteroid has a relatively circular orbit and lies near the plane of the ecliptic. Yet, some asteroid orbits can be highly eccentric or travel well outside the ecliptic plane. Recent observations are increasingly blurring the distinction between Comets and asteroids, suggesting "a continuum between asteroids and comets" rather than a sharp dividing line.

Numerous asteroids have orbits that lie between Mars and Jupiter, in the so-called Asteroid Belt. Ceres, Pallas and Vesta are the three largest bodies in the asteroid belt. Also, Juno is in the asteroid belt. There is another belt of asteroids in the solar system, the so-called Kuiper Belt which lies beyond the orbits of Neptune and Pluto. The Kuiper Belt is thought to contain a much greater number of asteroids than the asteroid belt. The present consensus is that the Kuiper Belt is made up of matter which was prevented from condensing into one planet - in this case by the pull of Neptune's gravitational field. Pluto has recently been classified as the largest celestial body belonging to the Kuiper Belt and reclassified as a Dwarf Planet.

The so-called Centaurs have also been classified as asteroids. Their orbits around the Sun lie between Jupiter and Neptune, and they would appear to function as a "bridge between asteroids and comets, or/ and the ancestors of comets." The most known centaur is Chiron.

Attributes of largest asteroids

Name	Orbital radius (AU)	Orbital period (years)	Inclination	Eccentricity	Diameter (km)	Diameter (% of Moon)	Mass(kg)	Mass(% of Ceres)	Density(g/cm3)	Rotation period (hr)
Ceres	2.77	4.60	10.6°	0.079	964×964×892 (mean 939.4)	27%	938	100%	2.16±0.01	9.07
Vesta	2.36	3.63	7.1°	0.089	573×557×446 (mean 525.4)	15%	259	28%	3.46 ± 0.04	5.34
Pallas	2.77	4.62	34.8°	0.231	550×516×476 (mean 511±4)	15%	204±3	21%	2.92±0.08	7.81
Hygiea	3.14	5.56	3.8°	0.117	450×430×424 (mean 433±8)	12%	87±7	9%	2.06±0.20	13.8

Meteorites

Some of the debris from collisions can form Meteoroids that enter the Earth's atmosphere. Of the 50,000 meteorites found on Earth to date, 99.8 percent are believed to have originated in the asteroid belt.

Asteroid mining?

The concept of asteroid mining was proposed in 1970s. As resource depletion on Earth becomes more real, the idea of extracting valuable elements from asteroids and returning these to Earth for profit, or using space-based resources to build solar-power satellites and space habitats, becomes more attractive.

Exploration

The first spacecraft to traverse the asteroid belt was Pioneer 10, which entered the region on 16 July 1972. At the time there was some concern that the debris in the belt would pose a hazard to the spacecraft, but it has since been safely traversed by multiple spacecraft without incident. Pioneer 11, Voyagers 1 and 2 and Ulysses passed through the belt without imaging any asteroids. Cassini measured plasma and fine dust grains while traversing the belt in 2000. On its way to Jupiter, Juno traversed the asteroid belt without collecting science data. Due to the low density of materials within the belt, the odds of a probe running into an asteroid are estimated at less than 1 in 1 billion.

Most main belt asteroids imaged to date have come from brief flyby opportunities by probes headed for other targets. Only the Dawn mission has studied main belt asteroids for a protracted period in orbit. The Galileo spacecraft imaged 951 Gaspra in 1991 and 243 Ida in 1993, then NEAR imaged 253 Mathilde in 1997 and landed on near–Earth asteroid 433 Eros in February 2001. Cassini imaged 2685 Masursky in 2000, Stardust imaged 5535 Annefrank in 2002, New Horizons imaged 132524 APL in 2006, and Rosetta imaged 2867 Šteins in September 2008 and 21 Lutetia in July 2010. Dawn orbited Vesta between July 2011 and September 2012 and has orbited Ceres since March 2015.

The Lucy space probe is expected to make a flyby of 152830 Dinkinesh in 2023, on its way to the Jupiter Trojans. ESA's JUICE mission will pass through the asteroid belt twice, with a proposed flyby of the asteroid 223 Rosa in 2029. The Psyche spacecraft is a planned NASA mission to the large M-type (metallic) asteroid 16 Psyche.

Inner solar system objects (top view)

Astrology

Asteroids are relatively new to astrology, and still only a minority of astrologers use them in chart interpretation. Their use in astrology began with Eleanor Bach's publication of the first asteroid ephemeris in 1973. Their use was popularized following Demetria George's publication of Asteroid Goddesses in 1986.

The first four

Ceres, Pallas, Juno and Vesta (in order of discovery) were the only known asteroids from 1808 until 1845, when additional asteroids began to be discovered. They started being recognized by astrologers in the 1970s.

Ceres

Ceres was the first asteroid discovered and now is labeled as a dwarf planet, taking up about 1/3 of the entire mass of the asteroid belt. (According to some astrologers, to get an understanding of the nature of a planet, astrologers may study the characteristics and positions of known planets at the time of discovery, observe the trend of significant events at the time, and evaluate over time what the newly discovered celestial body tends to relate to in the charts of living people.) In mythology Ceres was the Roman equivalent of the Greek goddess Demeter. She was the goddess of agriculture and when her daughter Persephone was kidnapped by Pluto in an attempt to force her to marry him, Demeter became so distraught looking for her daughter that she neglected the Earth which became cold and most plants died. This was the first autumn and winter season, which came back every year even after Persephone had been saved by Hermes because she had eaten a pomegranate that made her Pluto's wife forever, and he demanded she return to him once a year. These myths, including the fact that Ceres is the roundest asteroid (it resembles the Moon) signify that in astrology the placement of Ceres in a birth chart is said to show what the native needs to feel loved and nurtured.

Pallas

Sometimes known as "Pallas Athene", this is the second asteroid discovered and the third in mass. There are many Pallases in mythology. Some sources say Pallas was Triton's daughter and Athena's playmate who was killed and Athena mourned her by changing her name to Pallas and making a wooden statue of her, which Zeus dropped to the Land of Troy where a temple was built in its honor. Others say that Pallas was an old god who combined with Athena. In these respects, Pallas can be interpreted as an indicator of effort. Other astrologers interpret it as an indicator of wisdom, intelligence, healing (perhaps through effort) as the titan named Pallas was a god of these things. This asteroid, like Vesta, is also sometimes called an influencer of Virgo.

Juno

This asteroid was the 3rd to be discovered and is 9th in mass ranking (1 Ceres, 2 Pallas, 4 Vesta, 10 Hygiea, 511 Davida, 704 Interamnia, 65 Cybele, 52 Europa are considerably bigger and more massive). In mythology Juno is the Roman equivalent of the Greek Hera. Hera was a very important goddess in both Greek and Roman culture. She was a wife of Zeus and hailed as the Queen of Gods and Zeus' main concubine (at least the myths imply that this was what she thought herself). She was the goddess of marriages, unions, and was also associated with finance and found cows and peacocks to be sacred. She was also very jealous and aggressive, especially when Zeus was involved with another woman; she would often kill the children Zeus and the other women or goddesses would create together, including attempts to kill Hercules and Dionysus — or the woman herself. For these reasons, Juno is used in astrology as an indicator of what a native requires to feel satisfied in love or romance, or what is one needs in order to feel their marriage is successful and satisfying. Because of Juno's association with relationships, money, cows and jealousy, it also appears to have an influence of the sign Taurus.

Vesta

This asteroid is the second largest in mass, fourth to be discovered of which it is the fastest to travel the zodiac and the last asteroid to be counted as a planet. In mythology Vesta is the virgin goddess, the Roman version of Hestia, though she was of higher importance to the Romans. She was regarded as one of the most important goddesses of all, though ironically she never was depicted in any visual art (in Greece, some vases with her image however have been found), or at least none of it has ever been found. She was the goddess of hearth, when a baby was born she was the goddess they would ask to bless it and protect the home. In every city and home in Rome there was a sacred fire made to Vesta that was protected and not allowed to go out. Astrologers use Vesta to determine what it is that you are devoted to and how your sexuality will develop. Vesta, having been a protective virgin goddess is said by some to be an influencer of the sign Virgo, this is accepted by many in the astrological community, but many prefer to instead of calling the influence an outright rulership an "affinity" or simply do not support this claim. It also seems to bear influence over Scorpio.

Other asteroids

After the first four asteroids were discovered, there wouldn't be another discovered for 38 years (Astraea). The first four gained popularity as full-fledged planets, but the rapid development of telescopes led to new asteroids being frequently discovered in what is now known as the Asteroid Belt, and they started being called "Minor Planets".

Hygiea

The asteroid Hygiea was the 10th discovered and is fourth in mass ranking. In mythology Hygieia was the feminine part and the consort of Asclepios, the Greek god of medicine and a mythological healer strongly connected to the Solar cult of Apollo. It seems that Hygiea rules the health practices and is integrated into medical astrology, but in her negative side has something to bring in cases of depression and anxiety of a higher level than usual. The status of Hygiea is practically unknown at the moment in western astrology.

Chiron and the Centaurs

The centaurs were recognized as a distinct population with the discovery of Chiron in 1977. It was initially announced as the Tenth Planet, and received attention from astrologers. A few astrologers have investigated other centaurs, but only Chiron is commonly treated.

Situation of Discussion Today

Considerable differences of opinion mark western astrologers’ approach to asteroids. Some astrologers find them meaningless in a horoscope, arguing that there are so many thousands of asteroids in the heavens that they can only be considered as so much “space junk.” Even some committed believers in astrology have difficulty in believing that a small rock chunk named Elvis or Lancelot has much impact on an individual, especially when it makes no major contact with his natal planets or angles. If one uses asteroids with a range of aspects, midpoints, Arabian Parts, and so on, one can probably make a chart express anything one wants — or nothing.

Asteroids are little used today by practitioners of traditional western, horary, or Vedic astrology. Not only are asteroids invisible to the naked eye, but they simply do not fit easily into these astrological systems.

Some of the first twentieth century astrologers to work with asteroids felt that the confusion surrounding asteroids could be minimized if each asteroid signified one or only a limited number of attributes; in contrast with the planets that might each indicate multiple attributes. For example, asteroid 275, Sapientia, would represent the single quality of wisdom; whereas the planet Jupiter signifies wisdom, travel, theology, philosophy, good luck, expansion, and a generally beneficial influence.

This concept of each asteroid representing one quality as expressed by its name, however, troubles other astrologers who are puzzled as to why an arbitrary name, perhaps given by an astronomer without due consideration, should somehow influence human behavior through the operations of a rock the size of an apartment building.

Asteroids do have a following in modern astrology, however. Demetra George’s work on female-named asteroids countered a solar system heavily weighted in favour of masculine-named planets and male-oriented chart interpretations. Other astrologers find that there is a story of mythology behind many of the asteroids’ names, and that once these narratives are understood, an asteroid conjunct a natal planet or angle should give further information on how planets and angles function in the horoscope. For example, if an astrologer is undecided whether Jupiter in a horoscope indicates the traveler or the philosopher, a conjunction with asteroid Sapientia may indicate the philosopher.

Astrologers who use asteroids caution that they cannot be applied indiscriminately. It is important to focus on asteroids whose names are meaningful to the individual person or event. For example, many asteroids are named for astronomers or their family members and associates. It would make little sense to apply these to the chart of composer Wolfgang Amadeus Mozart. However, asteroid Euterpe (81), the classical muse of music, conjuncts Mozart’s Venus within five degrees. Venus is the traditional ruler of the fine arts.

One interesting application of asteroids is so-called name-sake asteroids. Not everyone has an asteroid bearing his or her name, but many people do, especially when cognate names, including in other languages, are considered. For example, Eileen (11836), Helena (101), and Eleonora (354) are variants or foreign-language versions of the English name Helen. In Synastry it is helpful to see how the namesake asteroid of one person falls into the other person’s chart. Former US President Bill Clinton, for example, has asteroid Hillary (3130) conjunct his moon (4 degree orb). Asteroid Michelle is within 3 degrees of US President Barack Obama’s midheaven. While this orb is wide, the placement is consistent with Obama’s crediting his wife with much of his success in life (an MC matter.)

Asteroids themselves cannot cast much of an Orb. Astrologers disagree on whether one should therefore use only tight orbs within a degree in any consideration, or whether one can use the wider orb of the planet they conjunct.

Some asteroids are used more generally to indicate a suite of characteristics. For example, Juno — the mythological wife of Jupiter — may be used to consider marriage prospects in a chart. Because mythological Juno was constantly jealous about her husband’s infidelity, asteroid Juno may indicate both jealousy and faithfulness within a person’s married life. Amor (1221) is considered an indicator of love and affection, ranging from platonic to intimate.

Sign Rulers?

Another area of debate amongst astrologers concerns whether any of the larger asteroids can qualify a Ruler of zodiacal signs; and if so which ones, and whether the asteroids thereby depose the traditional planetary rulers. Proponents of assigning Vesta (or Chiron or Ceres, etc.) to Virgo, for example, generally point to strong affinities in the narratives linking the asteroid and sign. Traditionalists, however, point to a standard scheme of planetary rulership (Domicile) going back two thousand years, based on a logic of the planet’s distance from the sun and moon. Moreover, astrologers who use house cusp lords (accidental house cusp rulers) need some convincing that asteroids have utility as sign rulers for astrological techniques that go beyond simple match-ups based upon similar characteristics. At present individual astrologers may use particular asteroids or Ceres as the domiciled ruler of a sign, but there is no widespread agreement as to such planet-sign pairs.

Substantial research remains to be done on the asteroids in astrology, together with the transneptunian objects and centaurs. Whether they will fit neatly into pre-existing techniques in astrology, or whether they demand new ways of thinking about our solar system remain to be seen.

Astrodienst’s chart construction page offers over 17,000 asteroids that can be added to its horoscopes.

Weblinks

The smaller bodies of the Solar System

• Wikipedia: List of Asteroids in Astrology
• Asteroids and Comets (David McCann, 1997)
• Wikipedia: Asteroid belt
• List of Known Asteroids (Astrodienst's swiss ephemeris)
• Wikipedia: List of Minor Planets Named after Places
• NASA: Near-Earth Object Program
• The Centaur Research Project (Robert von Heeren)
• Collection of Asteroid Keywords (astrologyweekly.com)
• Asteroid Astrology (linda-goodman forum)
• Demetra George: Asteroids: Windows into Fate and Destiny (lecture 2014, 1h11min)

Bibliography

• Demetra George, 1986, Asteroid Goddesses: The Mythology, Psychology and Astrology of the Reemerging Feminine, ACS Publications, Inc.
• J. Lee Lehman, 1988, The Ultimate Asteroid Book, Whitford Press