Hungaria asteroid

Last updated April 08, 2019

The Hungaria group is a dynamical group of asteroids in the asteroid belt.^[1] The Hungaria asteroids orbit the Sun with a semi-major axis (longest radius of an ellipse) between 1.78 and 2.00 astronomical units (AU).^[2] They are the innermost dense concentration of asteroids in the Solar System—the near-Earth asteroids are much more sparse—and derive their name from their largest member 434 Hungaria. The Hungaria group includes the Hungaria family ( FIN: 003 ), a collisional asteroid family which dominates its population.^[3]^[4]

Asteroids are minor planets, especially of the inner Solar System. Larger asteroids have also been called planetoids. These terms have historically been applied to any astronomical object orbiting the Sun that did not resemble a planet-like disc and was not observed to have characteristics of an active comet such as a tail. As minor planets in the outer Solar System were discovered they were typically found to have volatile-rich surfaces similar to comets. As a result, they were often distinguished from objects found in the main asteroid belt. In this article, the term "asteroid" refers to the minor planets of the inner Solar System including those co-orbital with Jupiter.

Asteroid belt the circumstellar disk (accumulation of matter) in an orbit between those of Mars and Jupiter

The asteroid belt is the circumstellar disc in the Solar System located roughly between the orbits of the planets Mars and Jupiter. It is occupied by numerous irregularly shaped bodies called asteroids or minor planets. The asteroid belt is also termed the main asteroid belt or main belt to distinguish it from other asteroid populations in the Solar System such as near-Earth asteroids and trojan asteroids. About half the mass of the belt is contained in the four largest asteroids: Ceres, Vesta, Pallas, and Hygiea. The total mass of the asteroid belt is approximately 4% that of the Moon, or 22% that of Pluto, and roughly twice that of Pluto's moon Charon.

In physics, an orbit is the gravitationally curved trajectory of an object, such as the trajectory of a planet around a star or a natural satellite around a planet. Normally, orbit refers to a regularly repeating trajectory, although it may also refer to a non-repeating trajectory. To a close approximation, planets and satellites follow elliptic orbits, with the central mass being orbited at a focal point of the ellipse, as described by Kepler's laws of planetary motion.

Description

The Hungaria asteroids typically share the following orbital parameters:^[1]^[2]

Semi-major axis between 1.78 and 2.00 AU
Orbital period of approximately 2.5 years
Low eccentricity of below 0.18
An inclination of 16° to 34°
Approximate mean-motion resonance with Jupiter of 9:2, and with Mars of 3:2

The astronomical unit is a unit of length, roughly the distance from Earth to the Sun. However, that distance varies as Earth orbits the Sun, from a maximum (aphelion) to a minimum (perihelion) and back again once a year. Originally conceived as the average of Earth's aphelion and perihelion, since 2012 it has been defined as exactly 149597870700 metres or about 150 million kilometres. The astronomical unit is used primarily for measuring distances within the Solar System or around other stars. It is also a fundamental component in the definition of another unit of astronomical length, the parsec.

The orbital eccentricity of an astronomical object is a parameter that determines the amount by which its orbit around another body deviates from a perfect circle. A value of 0 is a circular orbit, values between 0 and 1 form an elliptic orbit, 1 is a parabolic escape orbit, and greater than 1 is a hyperbola. The term derives its name from the parameters of conic sections, as every Kepler orbit is a conic section. It is normally used for the isolated two-body problem, but extensions exist for objects following a Klemperer rosette orbit through the galaxy.

The 4:1 resonance Kirkwood gap (at 2.06 AU) marks the outer boundary of the Hungaria family, while interactions with Mars determine the inner boundary. For comparison the majority of asteroids are in core region of the asteroid belt, which lies between the 4:1 gap (at 2.06 AU) and the 2:1 gap (at 3.27 AU).

A Kirkwood gap is a gap or dip in the distribution of the semi-major axes of the orbits of main-belt asteroids. They correspond to the locations of orbital resonances with Jupiter.

Most Hungarias are E-type asteroids, which means they have extremely bright enstatite surfaces and albedos typically above 0.30. Despite their high albedos, none can be seen with binoculars because they are far too small: the largest (434 Hungaria) is only about 11 km in size. They are, however, the smallest asteroids that can regularly be glimpsed with amateur telescopes.^[5]

E-type asteroids are asteroids thought to have enstatite (MgSiO₃) achondrite surfaces. They form a large proportion of asteroids inward of the asteroid belt known as Hungaria asteroids, but rapidly become very rare as the asteroid belt proper is entered. There are, however, some that are quite far from the inner edge of the asteroid belt, such as 64 Angelina. They are thought to have originated from the highly reduced mantle of a differentiated asteroid.

Enstatite is a mineral; the magnesium endmember of the pyroxene silicate mineral series enstatite (MgSiO₃) - ferrosilite (FeSiO₃). The magnesium rich members of the solid solution series are common rock-forming minerals found in igneous and metamorphic rocks. The intermediate composition, (Mg,Fe)SiO₃, has historically been known as hypersthene, although this name has been formally abandoned and replaced by orthopyroxene. When determined petrographically or chemically the composition is given as relative proportions of enstatite (En) and ferrosilite (Fs) (e.g., En₈₀Fs₂₀).

Albedo is the measure of the diffuse reflection of solar radiation out of the total solar radiation received by an astronomical body. It is dimensionless and measured on a scale from 0 to 1.

The origin of the Hungaria group of asteroids is well known. At the 4:1 orbital resonance with Jupiter that lies at semi-major axes of 2.06 AU, any orbiting body is sufficiently strongly perturbed to be forced into an extremely eccentric and unstable orbit, creating the innermost Kirkwood gap. Interior to this 4:1 resonance, asteroids in low inclination orbits are, unlike those outside the 4:1 Kirkwood gap, strongly influenced by the gravitational field of Mars. Here, instead of Jupiter's influence, perturbations by Mars have, over the lifetime of the Solar System, thrown out all asteroids interior to the 4:1 Kirkwood gap except for those far enough from Mars's orbital plane where that planet exerts much smaller forces.^[1]

Jupiter is the fifth planet from the Sun and the largest in the Solar System. It is a giant planet with a mass one-thousandth that of the Sun, but two-and-a-half times that of all the other planets in the Solar System combined. Jupiter and Saturn are gas giants; the other two giant planets, Uranus and Neptune, are ice giants. Jupiter has been known to astronomers since antiquity. It is named after the Roman god Jupiter. When viewed from Earth, Jupiter can reach an apparent magnitude of −2.94, bright enough for its reflected light to cast shadows, and making it on average the third-brightest natural object in the night sky after the Moon and Venus.

Orbital inclination angle between a reference plane and the plane of an orbit

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.

Mars is the fourth planet from the Sun and the second-smallest planet in the Solar System after Mercury. In English, Mars carries a name of the Roman god of war, and is often referred to as the "Red Planet" because the reddish iron oxide prevalent on its surface gives it a reddish appearance that is distinctive among the astronomical bodies visible to the naked eye. Mars is a terrestrial planet with a thin atmosphere, having surface features reminiscent both of the impact craters of the Moon and the valleys, deserts, and polar ice caps of Earth.

This has left a situation where the only remaining concentration of asteroids inward of the 4:1 resonance lies at high inclination orbits, although they have fairly low eccentricities. However, even at the present time in Solar System history some Hungaria asteroids cross the orbit of Mars and are still in the process of being ejected from the Solar System due to Mars's influence (unlike asteroids in the "core" of the asteroid belt, where Jupiter's influence predominates).^[6]

Long-term changes in the orbit of Mars are believed to be a critical factor in the current removal of Hungaria asteroids. At the highest eccentricities, similar to the extreme values observed today or even slightly greater, Mars will perturb Hungaria asteroids and force them into ever more eccentric and unstable orbits when their ascending node is close in longitude to Mars's aphelion.^[7] This ultimately leads over millions of years to the formation of the short-lived Amor asteroids and Earth-crossers.

E-belt

The Hungaria asteroids are thought to be the remains of the hypothetical E-belt asteroid population.^[8] The dispersal of most of that hypothetical E-belt might have been caused by the outwards migration of the giant planets of the Solar System according to simulations done under the Nice model—and these dispersed E-belt asteroids might in turn have been the impactors of the Late Heavy Bombardment.

Related Research Articles

In celestial mechanics, an orbital resonance occurs when orbiting bodies exert a regular, periodic gravitational influence on each other, usually because their orbital periods are related by a ratio of small integers. Most commonly this relationship is found for a pair of objects. The physical principle behind orbital resonance is similar in concept to pushing a child on a swing, where the orbit and the swing both have a natural frequency, and the other body doing the "pushing" will act in periodic repetition to have a cumulative effect on the motion. Orbital resonances greatly enhance the mutual gravitational influence of the bodies, i.e., their ability to alter or constrain each other's orbits. In most cases, this results in an unstable interaction, in which the bodies exchange momentum and shift orbits until the resonance no longer exists. Under some circumstances, a resonant system can be stable and self-correcting, so that the bodies remain in resonance. Examples are the 1:2:4 resonance of Jupiter's moons Ganymede, Europa and Io, and the 2:3 resonance between Pluto and Neptune. Unstable resonances with Saturn's inner moons give rise to gaps in the rings of Saturn. The special case of 1:1 resonance between bodies with similar orbital radii causes large Solar System bodies to eject most other bodies sharing their orbits; this is part of the much more extensive process of clearing the neighbourhood, an effect that is used in the current definition of a planet.

Asteroid family population of asteroids that share similar proper orbital elements

An asteroid family is a population of asteroids that share similar proper orbital elements, such as semimajor axis, eccentricity, and orbital inclination. The members of the families are thought to be fragments of past asteroid collisions. An asteroid family is a more specific term than asteroid group whose members, while sharing some broad orbital characteristics, may be otherwise unrelated to each other.

The Eos family is a very large asteroid family located in the outer region of the asteroid belt. The family of K-type asteroids is believed to have formed as a result of an ancient catastrophic collision. The family's parent body is the asteroid 221 Eos.

Hungaria is a relatively small asteroid orbiting in the inner asteroid belt. It is an E-type (high-albedo) asteroid. It is the namesake of the Hungaria asteroids, which orbit the Sun on the inside of the 1:4 Kirkwood gap, standing out of the core of the asteroid belt.

677 Aaltje is a main-belt minor planet orbiting the Sun, discovered by August Kopff at Heidelberg on January 18, 1909. It was named after the Dutch singer Aaltje Noordewier-Reddingius.

The Massalia family is a family of asteroids in the inner asteroid belt, named after its parent body, 20 Massalia. It consists of S-type asteroids with very low inclinations, straddling the 1:2 resonances with Mars. There are more than 6,000 known Massalian asteroids.

A Hecuba-gap asteroid is a member of a dynamical group of resonant asteroids located in the Hecuba gap at 3.27 AU – one of the largest Kirkwood gaps in the asteroid belt, which is considered the borderline separating the outer main belt asteroids from the Cybeles. A Hecuba-gap asteroid stays in a 2:1 mean motion resonance with the gas giant Jupiter, which may gradually perturbe its orbits over a long period until it either intersect with the orbit of Mars or Jupiter itself. Depending on the dynamical stability of an asteroid's orbit in the Hecuba gap, three subgroups have been proposed. These are the marginally unstable Griqua asteroids, with an estimated lifetime of more than 100 million years, the stable Zhongguo asteroids, and an unnamed, strongly unstable population of asteroids with a dynamical lifetime of less than 70 million years.

7604 Kridsadaporn, provisional designation 1995 QY₂, is an unusual, carbonaceous asteroid and Mars-crosser on a highly eccentric orbit from the outer regions of the asteroid belt, approximately 12 kilometers (7.5 miles) in diameter. It was discovered on 31 August 1995, by Australian astronomer Robert McNaught at Siding Spring Observatory near Coonabarabran, Australia. Due to its particular orbit, the C-type asteroid belongs to MPC's list of "other" unusual objects, and has been classified as an "asteroid in cometary orbit", or ACO. The asteroid was named in memory of Thai astronomer Kridsadaporn Ritsmitchai.

2169 Taiwan, provisional designation 1964 VP₁, is a carbonaceous Astridian asteroid from the central regions of the asteroid belt, approximately 17 kilometers in diameter. It was discovered on 9 November 1964, by astronomers at the Purple Mountain Observatory near Nanking, China. It was named for Taiwan.

Nice model astrophysical model of planetary migration in the Solar System

The Nicemodel is a scenario for the dynamical evolution of the Solar System. It is named for the location of the Observatoire de la Côte d'Azur, where it was initially developed, in 2005 in Nice, France. It proposes the migration of the giant planets from an initial compact configuration into their present positions, long after the dissipation of the initial protoplanetary disk. In this way, it differs from earlier models of the Solar System's formation. This planetary migration is used in dynamical simulations of the Solar System to explain historical events including the Late Heavy Bombardment of the inner Solar System, the formation of the Oort cloud, and the existence of populations of small Solar System bodies including the Kuiper belt, the Neptune and Jupiter trojans, and the numerous resonant trans-Neptunian objects dominated by Neptune. Its success at reproducing many of the observed features of the Solar System means that it is widely accepted as the current most realistic model of the Solar System's early evolution, although it is not universally favoured among planetary scientists. Later research revealed a number of differences between the original Nice model's predictions and observations of the current Solar System, for example the orbits of the terrestrial planets and the asteroids, leading to its modification.

5477 Holmes, provisional designation 1989 UH₂, is a Hungaria asteroid and binary system from the innermost regions of the asteroid belt, approximately 3 kilometers (2 miles) in diameter. It was discovered on 27 October 1989, by American astronomer Eleanor Helin at the Palomar Observatory in California. The presumed E-type asteroid is likely spherical in shape and has a short rotation period of 2.99 hours. It was named for American amateur astronomer Robert Holmes. The discovery of its 1-kilometer-sized minor-planet moon was announced in November 2005.

The Late Heavy Bombardment is an event thought to have occurred approximately 4.1 to 3.8 billion years (Ga) ago, at a time corresponding to the Neohadean and Eoarchean eras on Earth. During this interval, a disproportionately large number of asteroids are theorized to have collided with the early terrestrial planets in the inner Solar System, including Mercury, Venus, Earth, and Mars.

The five-planet Nice model is a recent variation of the Nice model that begins with five giant planets, the current four plus an additional ice giant, in a chain of mean-motion resonances. After the resonance chain is broken, the five giant planets undergo a period of planetesimal-driven migration, followed by an instability with gravitational encounters between planets similar to that in the original Nice model. During the instability the additional giant planet is scattered inward onto a Jupiter-crossing orbit and is ejected from the Solar System following an encounter with Jupiter. An early Solar System with five giant planets was proposed in 2011 after numerical models indicated that this is more likely to reproduce the current Solar System.

The E-belt asteroids were the population of a hypothetical extension of the primordial asteroid belt proposed as the source of most of the basin-forming lunar impacts during the Late Heavy Bombardment.

The jumping-Jupiter scenario specifies an evolution of giant-planet migration described by the Nice model, in which an ice giant is scattered inward by Saturn and outward by Jupiter, causing their semi-major axes to jump, quickly separating their orbits. The jumping-Jupiter scenario was proposed by Ramon Brasser, Alessandro Morbidelli, Rodney Gomes, Kleomenis Tsiganis, and Harold Levison after their studies revealed that the smooth divergent migration of Jupiter and Saturn resulted in an inner Solar System significantly different from the current Solar System. The sweeping of secular resonances through the inner Solar System during the migration excited the orbits of the terrestrial planets, leaving them too eccentric, and left the asteroid belt with too many high-inclination objects. The jumps in the semi-major axes of Jupiter and Saturn described in the jumping-Jupiter scenario can allow these resonances to quickly cross the inner Solar System without altering orbits excessively, although the terrestrial planets remain sensitive to its passage. The jumping-Jupiter scenario also results in a number of other differences with the original Nice model. The fraction of lunar impactors from the core of the asteroid belt during the Late Heavy Bombardment is significantly reduced, most of the Jupiter trojans are captured during Jupiter's encounters with the ice giant, as are Jupiter's irregular satellites. In the jumping-Jupiter scenario, the likelihood of preserving four giant planets on orbits resembling their current ones appears to increase if the early Solar System originally contained an additional ice giant, which was later ejected by Jupiter into interstellar space. However, this remains an atypical result, as is the preservation of the current orbits of the terrestrial planets.

In planetary astronomy, the grand tack hypothesis proposes that after its formation at 3.5 AU, Jupiter migrated inward to 1.5 AU, before reversing course due to capturing Saturn in an orbital resonance, eventually halting near its current orbit at 5.2 AU. The reversal of Jupiter's migration is likened to the path of a sailboat changing directions (tacking) as it travels against the wind.

References

1 2 3 Spratt, Christopher E. (April 1990). "The Hungaria group of minor planets". Journal of the Royal Astronomical Society of Canada. 84: 123–131. Bibcode:1990JRASC..84..123S. ISSN 0035-872X . Retrieved 25 August 2018.
1 2 Warner, Brian D.; Harris, Alan W.; Vokrouhlický, David; Nesvorný, David; Bottke, William F. (November 2009). "Analysis of the Hungaria asteroid population" (PDF). Icarus. 204 (1): 172–182. Bibcode:2009Icar..204..172W. doi:10.1016/j.icarus.2009.06.004 . Retrieved 25 August 2018.
↑ Ćuk, Matija; Gladman, Brett J.; Nesvorný, David (2014). "Hungaria asteroid family as the source of aubrite meteorites". Icarus. 239: 154–159. arXiv: 1406.0825 . Bibcode:2014Icar..239..154C. doi:10.1016/j.icarus.2014.05.048.
↑ Galiazzo, Mattia A.; Bazsó, Ákos; Dvorak, Rudolf (2013). "Fugitives from the Hungaria region: Close encounters and impacts with terrestrial planets". Planetary and Space Science. 84: 5–13. arXiv: 1210.1418 . Bibcode:2013P&SS...84....5G. doi:10.1016/j.pss.2013.03.017.
↑ Asteroid lightcurves Archived 2007-10-08 at the Wayback Machine
↑ Milani, Andrea; Knezevic, Zoran; Novakovic, Bojan; Cellino, Alberto (June 2010). "Dynamics of the Hungaria asteroids" (PDF). Icarus. 207 (2): 769–794. Bibcode:2010Icar..207..769M. CiteSeerX 10.1.1.151.6659 . doi:10.1016/j.icarus.2009.12.022 . Retrieved 25 August 2018.
↑ Distance of Mars from Earth Archived 2007-09-07 at the Wayback Machine
↑ Late, Late Heavy Bombardment - Bill Bottke (SETI Talks) – Youtube.com

External links

Hungaria group
Orbital diagram, EasySky

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[Spratt-1990-1] 1 2 3 Spratt, Christopher E. (April 1990). "The Hungaria group of minor planets". Journal of the Royal Astronomical Society of Canada. 84: 123–131. Bibcode:1990JRASC..84..123S. ISSN 0035-872X . Retrieved 25 August 2018.

[Warner-2009-2] 1 2 Warner, Brian D.; Harris, Alan W.; Vokrouhlický, David; Nesvorný, David; Bottke, William F. (November 2009). "Analysis of the Hungaria asteroid population" (PDF). Icarus. 204 (1): 172–182. Bibcode:2009Icar..204..172W. doi:10.1016/j.icarus.2009.06.004 . Retrieved 25 August 2018.

[Cuk_etal_2014-3] Ćuk, Matija; Gladman, Brett J.; Nesvorný, David (2014). "Hungaria asteroid family as the source of aubrite meteorites". Icarus. 239: 154–159. arXiv: 1406.0825 . Bibcode:2014Icar..239..154C. doi:10.1016/j.icarus.2014.05.048.

[Galiazzo_etal_2013-4] Galiazzo, Mattia A.; Bazsó, Ákos; Dvorak, Rudolf (2013). "Fugitives from the Hungaria region: Close encounters and impacts with terrestrial planets". Planetary and Space Science. 84: 5–13. arXiv: 1210.1418 . Bibcode:2013P&SS...84....5G. doi:10.1016/j.pss.2013.03.017.

[5] Asteroid lightcurves Archived 2007-10-08 at the Wayback Machine

[Milani-2010-6] Milani, Andrea; Knezevic, Zoran; Novakovic, Bojan; Cellino, Alberto (June 2010). "Dynamics of the Hungaria asteroids" (PDF). Icarus. 207 (2): 769–794. Bibcode:2010Icar..207..769M. CiteSeerX 10.1.1.151.6659 . doi:10.1016/j.icarus.2009.12.022 . Retrieved 25 August 2018.

[7] Distance of Mars from Earth Archived 2007-09-07 at the Wayback Machine

[8] Late, Late Heavy Bombardment - Bill Bottke (SETI Talks) – Youtube.com