Earth Trojan asteroid
Encyclopedia
Earth trojans are asteroid
s that orbit in the vicinity of the Earth
-Sun
Lagrangian point
s and . They are named after the Trojan asteroid
s that are associated with the analogous Lagrangian points of Jupiter
.
Their location in the sky as observed from Earth's surface would average about 60 degrees east or west of the Sun, and as people tend to search for asteroids at much greater elongations few searches have been done in these locations.
The 300 m diameter asteroid has been determined to orbit in association with the Earth Lagrange point, leading the orbit of the Earth, by Martin Connors and colleagues of Athabasca University
using the Wide-field Infrared Survey Explorer (WISE)
satellite. It is the first confirmed Earth trojan.
such as iridium
are difficult to find, having largely sunk to the core of the planet
shortly after its formation. A small asteroid could be a rich source of such elements even if its overall composition is similar to Earth's; because of their small size, such bodies would lose heat much more rapidly than a planet once they had formed, and so would not have melted, a prerequisite for differentiation. Their weak gravitational fields also would have inhibited significant separation of denser and lighter material; a mass the size of 2010 TK7 would exert a surface gravitational force of less than 0.00005 times that of Earth.
, about 5 km across, in a peculiar type of orbital resonance called an overlapping horseshoe
. It is probably only a temporary liaison. Several other small objects have been found in similar orbits. While these objects are in 1:1 orbital resonance, they are not Earth trojans because they do not librate around the or Lagrangian point
s.
Asteroid
Asteroids are a class of small Solar System bodies in orbit around the Sun. They have also been called planetoids, especially the larger ones...
s that orbit in the vicinity of the Earth
Earth
Earth is the third planet from the Sun, and the densest and fifth-largest of the eight planets in the Solar System. It is also the largest of the Solar System's four terrestrial planets...
-Sun
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...
Lagrangian point
Lagrangian point
The Lagrangian points are the five positions in an orbital configuration where a small object affected only by gravity can theoretically be stationary relative to two larger objects...
s and . They are named after the Trojan asteroid
Trojan asteroid
The Jupiter Trojans, commonly called Trojans or Trojan asteroids, are a large group of objects that share the orbit of the planet Jupiter around the Sun. Relative to Jupiter, each Trojan librates around one of the planet's two Lagrangian points of stability, and , that respectively lie 60° ahead...
s that are associated with the analogous Lagrangian points of 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,...
.
Their location in the sky as observed from Earth's surface would average about 60 degrees east or west of the Sun, and as people tend to search for asteroids at much greater elongations few searches have been done in these locations.
The 300 m diameter asteroid has been determined to orbit in association with the Earth Lagrange point, leading the orbit of the Earth, by Martin Connors and colleagues of Athabasca University
Athabasca University
Athabasca University is a Canadian university in Athabasca, Alberta. It is an accredited research institution which also offers distance education courses and programs. Courses are offered primarily in English with some French offerings. Each year, 32,000 students attend the university. It offers...
using the Wide-field Infrared Survey Explorer (WISE)
Wide-field Infrared Survey Explorer
Wide-field Infrared Survey Explorer is a NASA infrared-wavelength astronomical space telescope launched on December 14, 2009, and decommissioned/hibernated on February 17, 2011 when its transmitter was turned off...
satellite. It is the first confirmed Earth trojan.
List
- None so far
Significance
The orbits of Earth trojans could make it less energetically costly to reach them than the Moon, even though they are dozens of times more distant. Such asteroids could one day be useful as sources of elements that are rare near the Earth's surface. On Earth, siderophilesGoldschmidt classification
The Goldschmidt classification, developed by Victor Goldschmidt, is a geochemical classification which groups the chemical elements according to their preferred host phases into lithophile , siderophile , chalcophile , and atmophile .Some elements have affinities to more than one phase...
such as iridium
Iridium
Iridium is the chemical element with atomic number 77, and is represented by the symbol Ir. A very hard, brittle, silvery-white transition metal of the platinum family, iridium is the second-densest element and is the most corrosion-resistant metal, even at temperatures as high as 2000 °C...
are difficult to find, having largely sunk to the core of the planet
Planetary differentiation
In planetary science, planetary differentiation is the process of separating out different constituents of a planetary body as a consequence of their physical or chemical behaviour, where the body develops into compositionally distinct layers; the denser materials of a planet sink to the center,...
shortly after its formation. A small asteroid could be a rich source of such elements even if its overall composition is similar to Earth's; because of their small size, such bodies would lose heat much more rapidly than a planet once they had formed, and so would not have melted, a prerequisite for differentiation. Their weak gravitational fields also would have inhibited significant separation of denser and lighter material; a mass the size of 2010 TK7 would exert a surface gravitational force of less than 0.00005 times that of Earth.
Other companions of Earth
Earth has a second companion, asteroid 3753 Cruithne3753 Cruithne
3753 Cruithne is an asteroid in orbit around the Sun in approximate 1:1 orbital resonance with the Earth. It is a periodic inclusion planetoid orbiting the Sun in an apparent horseshoe orbit. It has been incorrectly called "Earth's second moon", but it is only a quasi-satellite. Cruithne never...
, about 5 km across, in a peculiar type of orbital resonance called an overlapping horseshoe
Horseshoe orbit
A horseshoe orbit is a type of co-orbital motion of a small orbiting body relative to a larger orbiting body . The orbital period of the smaller body is very nearly the same as for the larger body, and its path appears to have a horseshoe shape in a rotating reference frame as viewed from the...
. It is probably only a temporary liaison. Several other small objects have been found in similar orbits. While these objects are in 1:1 orbital resonance, they are not Earth trojans because they do not librate around the or Lagrangian point
Lagrangian point
The Lagrangian points are the five positions in an orbital configuration where a small object affected only by gravity can theoretically be stationary relative to two larger objects...
s.
See also
- 3753 Cruithne3753 Cruithne3753 Cruithne is an asteroid in orbit around the Sun in approximate 1:1 orbital resonance with the Earth. It is a periodic inclusion planetoid orbiting the Sun in an apparent horseshoe orbit. It has been incorrectly called "Earth's second moon", but it is only a quasi-satellite. Cruithne never...
- Earth's second moonEarth's second moonClaims have existed for many centuries that the Earth might possess other natural satellites besides the Moon. Several candidates have been proposed, but all such claims have proven false...
- Natural satelliteNatural satelliteA natural satellite or moon is a celestial body that orbits a planet or smaller body, which is called its primary. The two terms are used synonymously for non-artificial satellites of planets, of dwarf planets, and of minor planets....
- Quasi-satelliteQuasi-satelliteA quasi-satellite is an object in a 1:1 orbital resonance with its planet that stays close to the planet over many orbital periods.A quasi-satellite's orbit around the Sun takes exactly the same time as the planet's, but has a different eccentricity , as shown in the diagram on the right...
- 6Q0B44E6Q0B44E6Q0B44E, sometimes abbreviated to B44E, is a small object, probably an item of space debris, currently orbiting the Earth outside the orbit of the Moon....
- 2006 RH1202006 RH1202006 RH120 is a tiny near-Earth asteroid with a diameter of about five metres, which ordinarily orbits the Sun but makes close approaches to the Earth–Moon system every twenty years or so. Occasionally the object temporarily enters Earth orbit through temporary satellite capture...
- 2003 YN1072003 YN107' is a very small Near-Earth object. It was discovered by the Lincoln Near Earth Asteroid Research system in orbit around the Sun on December 20, 2003. Its diameter is approximately 10 to 30 metres, which is near the most commonly used 10-metre demarcation line between meteoroids and asteroids...