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| {{Infobox planet | {{Infobox planet | ||
| | image = ] | | image = ] | ||
| | caption = Asteroid 2010 |
| caption = Asteroid 2010 TK<sub>7</sub> (circled in green, lower right) in image from the Wide-field Infrared Survey Explorer spacecraft | ||
| | discovery = no | | discovery = no | ||
| | physical_characteristics = yes | | physical_characteristics = yes | ||
| | bgcolour=#FFFFC0 | | bgcolour=#FFFFC0 | ||
| | name = 2010 |
| name = 2010 TK<sub>7</sub> | ||
| | mp_category = ]<ref name=jpldata/> | | mp_category = ]<ref name=jpldata/> | ||
| | orbit_ref = <ref name=jpldata>{{cite web | | orbit_ref = <ref name=jpldata>{{cite web | ||
| Line 27: | Line 27: | ||
| | abs_magnitude = 20.586 <ref name=jpldata/> | | abs_magnitude = 20.586 <ref name=jpldata/> | ||
| }} | }} | ||
| '''2010 |
'''2010 TK<sub>7</sub>''' is the first ] to be discovered; it comes close to sharing the ] around the ].<ref name=Connors>{{cite journal |last1=Connors |first1=Martin |last2=Wieger |first2=Paul |last3=Veillet |first3=Christian |title=Earth’s Trojan asteroid |date=27 July 2011 |journal=] | ||
| |volume=475 |issue=7357 |pages=481–483 |doi=10.1038/nature10233 |accessdate=2011-07-27 }}</ref><ref name = "WISE">. Nasa.gov. Retrieved on 2011-07-29.</ref><ref name=badastronomy>. Blogs.discovermagazine.com. Retrieved on 2011-07-29.</ref> Trojan objects ideally orbit at a ] 60 degrees ahead of or behind a planet or moon in a type of 1:1 ]; in reality, they oscillate around such a point. Such objects had previously been observed only in the orbits of ], ], ] and several ]. | |volume=475 |issue=7357 |pages=481–483 |doi=10.1038/nature10233 |accessdate=2011-07-27 }}</ref><ref name = "WISE">. Nasa.gov. Retrieved on 2011-07-29.</ref><ref name=badastronomy>. Blogs.discovermagazine.com. Retrieved on 2011-07-29.</ref> Trojan objects ideally orbit at a ] 60 degrees ahead of or behind a planet or moon in a type of 1:1 ]; in reality, they oscillate around such a point. Such objects had previously been observed only in the orbits of ], ], ] and several ]. | ||
| 2010 |
2010 TK<sub>7</sub> has a diameter of about {{convert|300|m|-2|sp=us}}.<ref name=Choi/> Its path oscillates about the Sun-Earth ] ] (60 degrees ahead of Earth), shuttling between its closest approach to Earth and its closest approach to the ] point (180 degrees from Earth), with a period of about 395 years.<ref name=Connors/> | ||
| The asteroid was discovered in October 2010 by astronomers from ], ], and ] using ]'s ]. | The asteroid was discovered in October 2010 by astronomers from ], ], and ] using ]'s ]. | ||
| ==Discovery== | ==Discovery== | ||
| The Wide-field Infrared Survey Explorer (WISE), a ] launched into Earth orbit in December 2009, imaged 2010 |
The Wide-field Infrared Survey Explorer (WISE), a ] launched into Earth orbit in December 2009, imaged 2010 TK<sub>7</sub> in October 2010 while carrying out a program to scan the entire sky from January 2010 to February 2011. Spotting an asteroid sharing Earth's orbit is normally difficult from the ground, because their potential locations are generally in the daytime sky.<ref name=Wiegert >. Astro.uwo.ca. Retrieved on 2011-07-29.</ref> After follow-up work at the ] and the ], its orbit was evaluated on 21 May 2011 and the Trojan character of its motion was published in July 2011.<ref name=Connors/><ref name=Wiegert/> | ||
| ==Physical and orbital characteristics== | ==Physical and orbital characteristics== | ||
| ] | ] | ||
| 2010 |
2010 TK<sub>7</sub> has an absolute magnitude of about 20.6.<ref>http://newton.dm.unipi.it/neodys/index.php?pc=1.1.0&n=2010TK7</ref> It has an estimated diameter of about 300 meters, based on an assumed ] of 0.1.<ref name=Connors/> No spectral data are yet available to shed light on its possible composition. | ||
| The asteroid has an orbital period of 365.389 days, comparable to Earth's 365.256 days. On its eccentric (e = 0.191) orbit, 2010 |
The asteroid has an orbital period of 365.389 days, comparable to Earth's 365.256 days. On its eccentric (e = 0.191) orbit, 2010 TK<sub>7</sub>'s distance from the Sun varies annually from 0.81 AU to 1.19 AU.<ref name=Connors/> | ||
| Trojan asteroids in actuality do not orbit right at Lagrangian points but oscillate in ]-shaped loops around them (as viewed in a co] in which the planet and Lagrangian points are stationary). However, 2010 |
Trojan asteroids in actuality do not orbit right at Lagrangian points but oscillate in ]-shaped loops around them (as viewed in a co] in which the planet and Lagrangian points are stationary). However, 2010 TK<sub>7</sub>'s loop is so unusually elongated that it sometimes travels nearly to the opposite side of the Sun from the Earth. Its orbit does not bring it any closer to the Earth than 20 million kilometers (12.4 million miles), which is more than 50 times the distance to the moon. 2010 TK<sub>7</sub> is presently at the near-Earth end of its tadpole.<ref name=Connors/> | ||
| 2010 |
2010 TK<sub>7</sub>'s orbit has a ] character, making long-range predictions difficult. Prior to A.D. 500, it may have been oscillating about the L<sub>5</sub> Lagrangian point (60 degrees behind Earth), before jumping to L<sub>4</sub> via L<sub>3</sub>. Short-term unstable ] about L<sub>3</sub>, and transitions to ]s are also possible.<ref name=Connors/> | ||
| ==Significance== | ==Significance== | ||
| 2010 |
2010 TK<sub>7</sub> is the first asteroid discovered to be a member of a category known as Earth Trojans. The orbits of such objects 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. 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, so heavier substances would not have had time to sink to their cores as ]. In fact their gravitational fields also would be far too small to cause significant separation of denser and lighter material; a mass the size of 2010 TK<sub>7</sub> would exert a gravitational effect of less than 0.001 times that of Earth. | ||
| Simultaneously, in contrast to the core of a planet or large moon, the entire mass of such a small body would be accessible to mining; equipment could dig straight through its center without significant pressure problems or risk of rockfall. Those elements that would become available would include precisely those precious ] such as ] that are largely inaccessible on Earth because they sank to the core of the planet during its formation. | Simultaneously, in contrast to the core of a planet or large moon, the entire mass of such a small body would be accessible to mining; equipment could dig straight through its center without significant pressure problems or risk of rockfall. Those elements that would become available would include precisely those precious ] such as ] that are largely inaccessible on Earth because they sank to the core of the planet during its formation. | ||
| ==Potential for exploration or mineral exploitation== | ==Potential for exploration or mineral exploitation== | ||
| Although an Earth Trojan, 2010 |
Although an Earth Trojan, 2010 TK<sub>7</sub> is not an energetically attractive target for a space mission, because it orbits the Sun in a plane inclined about 21 degrees to the ].<ref>{{cite news |url= http://www.msnbc.msn.com/id/43914196/ns/technology_and_science-space/ |title=Found at last: First Earth companion asteroid |publisher=MSNBC |date=July 27, 2011}}</ref> This takes it so far above and below the Earth's orbit that the required ] for a spacecraft to match its trajectory coming from Earth's would be 9.4 km/s, while some other near-Earth asteroids require less than 4 km/ s.<ref name=Connors/> | ||
| {{clear}} | {{clear}} | ||
| {{clear}} | {{clear}} | ||
Revision as of 22:15, 29 July 2011
 Asteroid 2010 TK7 (circled in green, lower right) in image from the Wide-field Infrared Survey Explorer spacecraft | |
| Designations | |
|---|---|
| Minor planet category | Apollo |
| Orbital characteristics | |
| Epoch August 17, 2010 (JD 2455800.5) | |
| Aphelion | 1.19095 AU |
| Perihelion | 0.80955 AU |
| Semi-major axis | 1.00025 AU |
| Eccentricity | 0.19066 |
| Orbital period (sidereal) | 365.394 d (1.0 a) |
| Mean anomaly | 217.348° |
| Inclination | 20.8656° |
| Longitude of ascending node | 96.5426° |
| Argument of perihelion | 45.7551° |
| Physical characteristics | |
| Dimensions | ~300 m |
| Mean density | ? g/cm³ |
| Surface gravity | ? |
| Absolute magnitude (H) | 20.586 |
2010 TK7 is the first Earth Trojan asteroid to be discovered; it comes close to sharing the Earth's orbit around the Sun. Trojan objects ideally orbit at a Lagrangian point 60 degrees ahead of or behind a planet or moon in a type of 1:1 orbital resonance; in reality, they oscillate around such a point. Such objects had previously been observed only in the orbits of Mars, Jupiter, Neptune and several moons of Saturn.
2010 TK7 has a diameter of about 300 meters (1,000 ft). Its path oscillates about the Sun-Earth L4 Lagrangian point (60 degrees ahead of Earth), shuttling between its closest approach to Earth and its closest approach to the L3 point (180 degrees from Earth), with a period of about 395 years.
The asteroid was discovered in October 2010 by astronomers from Athabasca University, UCLA, and University of Western Ontario using NASA's Wide-field Infrared Survey Explorer.
Discovery
The Wide-field Infrared Survey Explorer (WISE), a space telescope launched into Earth orbit in December 2009, imaged 2010 TK7 in October 2010 while carrying out a program to scan the entire sky from January 2010 to February 2011. Spotting an asteroid sharing Earth's orbit is normally difficult from the ground, because their potential locations are generally in the daytime sky. After follow-up work at the University of Hawaii and the Canada-France-Hawaii Telescope, its orbit was evaluated on 21 May 2011 and the Trojan character of its motion was published in July 2011.
Physical and orbital characteristics
2010 TK7 has an absolute magnitude of about 20.6. It has an estimated diameter of about 300 meters, based on an assumed albedo of 0.1. No spectral data are yet available to shed light on its possible composition.
The asteroid has an orbital period of 365.389 days, comparable to Earth's 365.256 days. On its eccentric (e = 0.191) orbit, 2010 TK7's distance from the Sun varies annually from 0.81 AU to 1.19 AU.
Trojan asteroids in actuality do not orbit right at Lagrangian points but oscillate in tadpole-shaped loops around them (as viewed in a corotating reference frame in which the planet and Lagrangian points are stationary). However, 2010 TK7's loop is so unusually elongated that it sometimes travels nearly to the opposite side of the Sun from the Earth. Its orbit does not bring it any closer to the Earth than 20 million kilometers (12.4 million miles), which is more than 50 times the distance to the moon. 2010 TK7 is presently at the near-Earth end of its tadpole.
2010 TK7's orbit has a chaotic character, making long-range predictions difficult. Prior to A.D. 500, it may have been oscillating about the L5 Lagrangian point (60 degrees behind Earth), before jumping to L4 via L3. Short-term unstable libration about L3, and transitions to horseshoe orbits are also possible.
Significance
2010 TK7 is the first asteroid discovered to be a member of a category known as Earth Trojans. The orbits of such objects 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. 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, so heavier substances would not have had time to sink to their cores as they did on Earth. In fact their gravitational fields also would be far too small to cause significant separation of denser and lighter material; a mass the size of 2010 TK7 would exert a gravitational effect of less than 0.001 times that of Earth.
Simultaneously, in contrast to the core of a planet or large moon, the entire mass of such a small body would be accessible to mining; equipment could dig straight through its center without significant pressure problems or risk of rockfall. Those elements that would become available would include precisely those precious siderophiles such as iridium that are largely inaccessible on Earth because they sank to the core of the planet during its formation.
Potential for exploration or mineral exploitation
Although an Earth Trojan, 2010 TK7 is not an energetically attractive target for a space mission, because it orbits the Sun in a plane inclined about 21 degrees to the plane of the ecliptic. This takes it so far above and below the Earth's orbit that the required delta-v for a spacecraft to match its trajectory coming from Earth's would be 9.4 km/s, while some other near-Earth asteroids require less than 4 km/ s.
References
- ^ "JPL Small-Body Database Browser: 2010 TK7". 2010-10-31 last obs. Retrieved 2011-07-27.
{{cite web}}: Check date values in:|date=(help) - ^ Choi, Charles Q. (27 July 2011). "First Asteroid Companion of Earth Discovered at Last". Space.com. Retrieved 2011-07-27.
- ^ Connors, Martin; Wieger, Paul; Veillet, Christian (27 July 2011). "Earth's Trojan asteroid". Nature. 475 (7357): 481–483. doi:10.1038/nature10233.
{{cite journal}}:|access-date=requires|url=(help) - NASA's WISE Mission Finds First Trojan Asteroid Sharing Earth's Orbit. Nasa.gov. Retrieved on 2011-07-29.
- WISE finds the very first Earth Trojan asteroid. Blogs.discovermagazine.com. Retrieved on 2011-07-29.
- ^ Earth's first Trojan asteroid: 2010 TK7. Astro.uwo.ca. Retrieved on 2011-07-29.
- http://newton.dm.unipi.it/neodys/index.php?pc=1.1.0&n=2010TK7
- "Found at last: First Earth companion asteroid". MSNBC. July 27, 2011.
- "Trojan asteroid seen in Earth's orbit by Wise telescope". BBC. 28 July 2011.
{{cite web}}: Text "accessdate-2011-07-29" ignored (help)