Hungaria family
Encyclopedia
The Hungaria asteroids are a group of asteroids in the asteroid belt that orbit the Sun
between 1.78 and 2.00 AU
. The asteroids typically have a low eccentricity
(below 0.18) and an inclination
of 16 to 34 degrees.
They have an orbital period of approximately 2.5 years. They have a resonance with Jupiter of 9:2 and with Mars of 3:2. They are named after the largest member, 434 Hungaria
, and are the innermost dense concentration of asteroids, lying somewhat inwards of the "core" of the asteroid belt that lies beyond the 4:1 Kirkwood gap
.
Most Hungarias are E-type asteroid
s, which means they have extremely bright enstatite
surfaces and albedo
s 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 20 km in size. They are, however, the smallest asteroids that can regularly be glimpsed with amateur telescopes.
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' orbital plane where that planet exerts much smaller forces.
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 in the process of still being ejected from the solar system due to Mars' influence (unlike asteroids in the "core" of the asteroid belt, where Jupiter's influence predominates).
Long-term changes in the orbit of Mars are believed to be a critical factor in the 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' aphelion. This ultimately leads over millions of years to the formation of the short-lived Amor asteroid
s and Earth-crossers
.
Sun
The Sun is the star at the center of the Solar System. It is almost perfectly spherical and consists of hot plasma interwoven with magnetic fields...
between 1.78 and 2.00 AU
Astronomical unit
An astronomical unit is a unit of length equal to about or approximately the mean Earth–Sun distance....
. The asteroids typically have a low eccentricity
Orbital eccentricity
The orbital eccentricity of an astronomical body is the amount by which its orbit deviates from a perfect circle, where 0 is perfectly circular, and 1.0 is a parabola, and no longer a closed orbit...
(below 0.18) and an inclination
Inclination
Inclination in general is the angle between a reference plane and another plane or axis of direction.-Orbits:The inclination is one of the six orbital parameters describing the shape and orientation of a celestial orbit...
of 16 to 34 degrees.
They have an orbital period of approximately 2.5 years. They have a resonance with Jupiter of 9:2 and with Mars of 3:2. They are named after the largest member, 434 Hungaria
434 Hungaria
434 Hungaria is a relatively small inner Main belt asteroid. It is classified as an E-type asteroid. It is the namesake for Hungaria asteroids which orbit the sun on the inside of the 1:4 Kirkwood gap, standing out of the core of the main belt....
, and are the innermost dense concentration of asteroids, lying somewhat inwards of the "core" of the asteroid belt that lies beyond the 4:1 Kirkwood gap
Kirkwood gap
A Kirkwood gap is a gap or dip in the distribution of main-belt asteroids with semi-major axis , as seen in the histogram below...
.
E-type asteroid
E-type asteroids are asteroids thought to have enstatite achondrite surfaces. They form a large proportion of asteroids inward of the main belt known as Hungaria asteroids, but rapidly become very rare as the main belt proper is entered. There are, however, some that are quite far from the inner...
s, which means they have extremely bright enstatite
Enstatite
Enstatite is the magnesium endmember of the pyroxene silicate mineral series enstatite - ferrosilite . The magnesium rich members of the solid solution series are common rock-forming minerals found in igneous and metamorphic rocks...
surfaces and albedo
Albedo
Albedo , or reflection coefficient, is the diffuse reflectivity or reflecting power of a surface. It is defined as the ratio of reflected radiation from the surface to incident radiation upon it...
s typically above 0.30. Despite their high albedos, none can be seen with binoculars
Binoculars
Binoculars, field glasses or binocular telescopes are a pair of identical or mirror-symmetrical telescopes mounted side-by-side and aligned to point accurately in the same direction, allowing the viewer to use both eyes when viewing distant objects...
because they are far too small: the largest (434 Hungaria
434 Hungaria
434 Hungaria is a relatively small inner Main belt asteroid. It is classified as an E-type asteroid. It is the namesake for Hungaria asteroids which orbit the sun on the inside of the 1:4 Kirkwood gap, standing out of the core of the main belt....
) is only about 20 km in size. They are, however, the smallest asteroids that can regularly be glimpsed with amateur telescopes.
The origin of the Hungaria group of asteroids is well known. At the 4:1 orbital resonance with Jupiter
Jupiter
Jupiter is the fifth planet from the Sun and the largest planet within the Solar System. It is a gas giant with mass one-thousandth that of the Sun but is two and a half times the mass of all the other planets in our Solar System combined. Jupiter is classified as a gas giant along with Saturn,...
that lies at semi-major axes
Semi-major axis
The major axis of an ellipse is its longest diameter, a line that runs through the centre and both foci, its ends being at the widest points of the shape...
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
Kirkwood gap
A Kirkwood gap is a gap or dip in the distribution of main-belt asteroids with semi-major axis , as seen in the histogram below...
. 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
Mars
Mars is the fourth planet from the Sun in the Solar System. The planet is named after the Roman god of war, Mars. It is often described as the "Red Planet", as the iron oxide prevalent on its surface gives it a reddish appearance...
. 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' orbital plane where that planet exerts much smaller forces.
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
Mars-crosser asteroid
A Mars-crosser is an asteroid whose orbit crosses that of Mars. The known numbered Mars-crossers are listed here. They include the two numbered Mars trojans 5261 Eureka and ....
and in the process of still being ejected from the solar system due to Mars' influence (unlike asteroids in the "core" of the asteroid belt, where Jupiter's influence predominates).
Long-term changes in the orbit of Mars are believed to be a critical factor in the 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
Node (physics)
A node is a point along a standing wave where the wave has minimal amplitude. For instance, in a vibrating guitar string, the ends of the string are nodes. By changing the position of the end node through frets, the guitarist changes the effective length of the vibrating string and thereby the...
is close in longitude to Mars' aphelion. This ultimately leads over millions of years to the formation of the short-lived Amor asteroid
Amor asteroid
The Amor asteroids are a group of near-Earth asteroids named after the asteroid 1221 Amor. They approach the orbit of the Earth from beyond, but do not cross it. Most Amors do cross the orbit of Mars...
s and Earth-crossers
Earth-crosser asteroid
An Earth-crosser is a near-Earth asteroid whose orbit crosses that of Earth as observed from the ecliptic pole of Earth's orbit. The known numbered Earth-crossers are listed here. Those Earth-crossers whose semi-major axes are smaller than Earth's are Aten asteroids; the remaining ones are Apollo...
.
See also
- E-type asteroidE-type asteroidE-type asteroids are asteroids thought to have enstatite achondrite surfaces. They form a large proportion of asteroids inward of the main belt known as Hungaria asteroids, but rapidly become very rare as the main belt proper is entered. There are, however, some that are quite far from the inner...
- AubriteAubriteAubrites are meteorites named for Aubres, a small achondrite meteorite that fell near Nyons, France, in 1836. They are primarily composed of the orthopyroxene enstatite, and are often called enstatite achondrites...
- (144898) 2004 VD17(144898) 2004 VD17-External links:* *...
- 64 Angelina64 Angelina64 Angelina is a medium-sized main belt E-type asteroid discovered in 1861. It is an unusually bright form of E-type asteroid.-Discovery and naming:...
- 434 Hungaria434 Hungaria434 Hungaria is a relatively small inner Main belt asteroid. It is classified as an E-type asteroid. It is the namesake for Hungaria asteroids which orbit the sun on the inside of the 1:4 Kirkwood gap, standing out of the core of the main belt....
- 3103 Eger3103 Eger3103 Eger is an Apollo and Mars-crosser asteroid that was discovered in 1982, by Miklós Lovas. It was named after the city of Eger, Hungary.It makes eight approaches to Earth less than in the 20th and 21st centuries. The last close approach was in August 2006 at...
- 44 Nysa44 Nysa44 Nysa is a large and very bright main-belt asteroid, and the brightest member of the Nysian asteroid family. It is classified as a rare class E asteroid and is probably the largest of this type .-Discovery:...
- 55 Pandora55 Pandora55 Pandora is a fairly large and very bright main belt asteroid. Pandora was discovered by George Mary Searle on September 10, 1858 from the Dudley Observatory near Albany, NY. It was his first and only asteroid discovery....
- 2867 Šteins2867 Šteins2867 Šteins is a small main-belt asteroid that was discovered in 1969 by N. S. Chernykh. It is named after Kārlis Šteins, a Latvian and Soviet astronomer...