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{{Short description|Near-Earth asteroid and Earth trojan}}
⚫ {{DISPLAYTITLE:{{mp|2010 TK|7}}}}
{{Use dmy dates|date=January 2022}}
⚫ {{DISPLAYTITLE:{{mp|(706765) 2010 TK|7}}}}
{{Infobox planet {{Infobox planet
| minorplanet = yes
⚫ | image = ]
| name = {{mp|(706765) 2010 TK|7}}
| background = #FFC2E0
⚫ | image = PIA14405-full crop.jpg
| image_scale =
| caption = {{longitem|Asteroid {{mp|2010 TK|7}} (circled in green) in image from the ] spacecraft|style=padding: 4px; line-height: 1.4em;}} | caption = {{longitem|Asteroid {{mp|2010 TK|7}} (circled in green) in image from the ] spacecraft|style=padding: 4px; line-height: 1.4em;}}
| discovery = yes | discovery_ref = <ref name="mpc" />
| discovered = 1 October 2010 | discovered = 1 October 2010
| discoverer = ] spacecraft | discoverer = ] spacecraft
| discovery_ref = &thinsp;<ref name="mpc" />
| discovery_site = ], ] | discovery_site = ], ]
| background = #FFFFC0 | mpc_name = {{mp|2010 TK|7}}
| name = {{mp|2010 TK|7}} | alt_names =
| pronounced =
⚫ | mp_category = ]<br>] (2014)<ref name=jpldata/><br>] (2013)<ref></ref>
| named_after =
| mp_category = {{Ubl
| ]
| ] (2014)<ref name=jpldata/>
⚫ | ] (2013)<ref></ref>
}}
| orbit_ref = <ref name="jpldata" /> | orbit_ref = <ref name="jpldata" />
| epoch = 9 December 2014 (] 2457000.5) | epoch = 13 January 2016 (]&nbsp;2457400.5)
| uncertainty = 0 | uncertainty = 0
| observation_arc = 2.10 yr | observation_arc = 768 days (2.10&nbsp;yr)
| semimajor = 0.99987 AU | semimajor = {{Convert|0.99972|AU|Gm|abbr=on}}
| perihelion = 0.80923 AU | perihelion = {{Convert|0.80918|AU|Gm|abbr=on}}
| aphelion = 1.1905 ] | aphelion = {{Convert|1.1903|AU|Gm|abbr=on|lk=on}}
| eccentricity = 0.19066 | eccentricity = 0.19059
| period = 1.00 ] (365.18 ]) | period = 1.00&nbsp;] (365.10&nbsp;])
| inclination = 20.888° | inclination = 20.890°
| asc_node = 96.506° | asc_node = 96.498°
| arg_peri = 45.902° | arg_peri = 45.927°
| mean_anomaly = 319.80° | mean_anomaly = 354.14]
| avg_speed = 9.1 m/s<ref name="mpc" /> | avg_speed = 29.8&nbsp;km/s{{efn|name=speed|1={{nowrap|1=''v'' = 42.1219 {{radic|1/''0.9989'' − 0.5/''0.9989''}}}}.}}
| mean_diameter = {{val|379|123|u=m}}<ref name="jpldata" />
| physical_characteristics = yes
| dimensions = ~&thinsp;300 m<ref name="Choi" /> | albedo = {{val|0.059|0.049}}<ref name="jpldata" />
| density = | density =
| surface_grav = | surface_grav =
| magnitude = 20.8 (when near Earth) to 23.6 | magnitude = 20.8 (when near Earth) to 23.6
| abs_magnitude = 20.8<ref name=jpldata /> | abs_magnitude = 20.8<ref name=jpldata />
| mean_motion = {{Deg2DMS|0.98602|sup=ms}} / day
| moid = {{Convert|0.0837911|AU|Gm|abbr=on}}
}} }}
⚫ '''{{mp|(706765) 2010 TK|7}}''' (] '''{{mp|2010 TK|7}}''') is a sub-kilometer ] and the first ] discovered; it precedes ] in its ] around the ].<ref name="Connors" /><ref name="WISE" /> ] are most easily conceived as orbiting at a ], a dynamically stable location (where the combined ] force acts through the Sun's and Earth's ]) 60 degrees ahead of or behind a massive orbiting body, in a type of 1:1 ]. In reality, they oscillate around such a point. Such objects had previously been observed in the orbits of ], ], ], and the ] ] and ].


⚫ {{mp|2010 TK|7}} has a diameter of about {{convert|300|m|-2|sp=us}}.<ref name=Choi /> Its path oscillates about the Sun–Earth {{L4}} ] (60 degrees ahead of Earth), shuttling between its closest approach to ] and its closest approach to the {{L3}} point (180 degrees from Earth).
⚫ '''{{mp|2010 TK|7}}''' is a ] ] and the first ] ever discovered; it precedes ] in its ] around the ].<ref name="Connors" /><ref name="WISE" /> ] are most easily conceived as orbiting at a ], a dynamically stable location (where ]al and ]s balance) 60 degrees ahead of or behind a massive orbiting body, in a type of 1:1 ]. In reality, they oscillate (]) around such a point. Such objects had previously been observed in the orbits of ], ], ], and the ] ] and ].

⚫ {{mp|2010 TK|7}} has a diameter of about {{convert|300|m|-2|sp=us}}.<ref name=Choi /> Its path oscillates about the Sun–Earth {{L4}} ] (60 degrees ahead of Earth), shuttling between its closest approach to ] and its closest approach to the {{L3}} point (180 degrees from Earth) about every 400 years.


The asteroid was discovered in October 2010 by the NEOWISE team of astronomers using ]'s ] (WISE).<ref name="MPEC-2010-T45" /> The asteroid was discovered in October 2010 by the NEOWISE team of astronomers using ]'s ] (WISE).<ref name="MPEC-2010-T45" />


== Discovery == == Discovery ==
⚫ ], a ] launched into ] in December 2009, imaged {{mp|2010 TK|7}} in October 2010 while carrying out a program to scan the entire sky from January 2010 to February 2011. Spotting an asteroid sharing ]'s orbit is normally difficult from the ground, because their potential locations are generally in the daytime sky.<ref name="Wiegert" /> 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. The orbital information was published in the journal '']'' by Paul Wiegert of the ], Martin Connors of ] and Christian Veillet, the executive director of the Canada–France–Hawaii Telescope.<ref name=Connors /><ref name=Wiegert />

⚫ ], a ] launched into ] in December 2009, imaged {{mp|2010 TK|7}} in October 2010 while carrying out a program to scan the entire sky from January 2010 to February 2011. Spotting an asteroid sharing ]'s orbit is normally difficult from the ground, because their potential locations are generally in the daytime sky.<ref name="Wiegert" /> 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. The orbital information was published in the journal '']'' by Paul Wiegert of the ], Martin Connors of ] and Christian Veillet, the executive director of the Canada–France–Hawaii Telescope.<ref name=Connors /><ref name=Wiegert />


== Physical and orbital characteristics == == Physical and orbital characteristics ==
⚫ ]
⚫ ] plot showing Earth's ]s (not to scale); contours around {{L4|nolink=yes}} and {{L5|nolink=yes}} represent ] paths]]
⚫ ]


{{mp|2010 TK|7}} has an ] of luminosity (determinable because of its known location) of about 20.8.<ref name=jpldata /> Based on an assumed ] of 0.1, its estimated diameter is about 300 meters.<ref name=Connors /> No spectral data are yet available to shed light on its composition. {{mp|2010 TK|7}} would exert a surface gravitational force of less than 1/20,000 times that of Earth. {{mp|2010 TK|7}} has an ] of luminosity (determinable because of its known location) of about 20.8.<ref name=jpldata/> Based on an assumed ] of 0.1, its estimated diameter is about 300&nbsp;meters.<ref name=Connors/> No spectral data are yet available to shed light on its composition. {{mp|2010 TK|7}} would exert a surface gravitational force of less than {{frac|1|20,000}} that of Earth.


At the time of discovery, the asteroid orbited the ] with a ] of 365.389 days, close to Earth's 365.256 days. As long as it remains in 1:1 resonance with Earth, its average period over long time intervals will exactly equal that of Earth. On its ] (e = 0.191) orbit, {{mp|2010 TK|7}}'s distance from the Sun varies annually from 0.81 ] to 1.19 AU.<ref name=Connors /> It orbits in a plane ] about 21 degrees to the ]. At the time of discovery, the asteroid orbited the ] with a ] of 365.389&nbsp;days, close to Earth's 365.256&nbsp;days. As long as it remains in 1:1 resonance with Earth, its average period over long time intervals will exactly equal that of Earth. On its ] (''e''&nbsp;=&nbsp;0.191) orbit, {{mp|2010 TK|7}}'s distance from the Sun varies annually from 0.81&nbsp;] to 1.19&nbsp;AU.<ref name=Connors/> It orbits in a plane ] about 21&nbsp;degrees to the ].


Trojans do not orbit right at Lagrangian points but oscillate in ] around them (as viewed in a ] in which the planet and Lagrangian points are stationary); {{mp|2010 TK|7}} traverses its loop over a period of 395&nbsp;years.{{#tag:ref|Because of its orbital inclination and eccentricity, {{mp|2010 TK|7}}'s position relative to Earth is actually a complicated, tightly coiled spiral; however, if its average position relative to Earth over a year is represented by a single point, that point will follow the tadpole loop.|group="note"}}<ref name=Connors /> {{mp|2010 TK|7}}'s loop is so elongated that it sometimes travels nearly to the opposite side of the Sun with respect to Earth. Its movements do not bring it any closer to Earth than 20 million kilometers (12.4 million miles), which is more than 50 times the distance to the ]. In 2010/2011, {{mp|2010 TK|7}} was at the near-Earth end of its tadpole,<ref name=Connors /> which facilitated its discovery. Trojans do not orbit right at Lagrangian points but oscillate in ] around them (as viewed in a ] in which the planet and Lagrangian points are stationary); {{mp|2010 TK|7}} traverses its loop over a period of 395&nbsp;years.{{refn|group=lower-alpha|Because of its orbital inclination and eccentricity, {{mp|2010 TK|7}}'s position relative to Earth is actually a complicated, tightly coiled spiral; however, if its average position relative to Earth over a year is represented by a single point, that point will follow the tadpole loop.}}<ref name=Connors/> {{mp|2010 TK|7}}'s loop is so elongated that it sometimes travels nearly to the opposite side of the Sun with respect to Earth. Its movements do not bring it any closer to Earth than 20&nbsp;million kilometers (12.4&nbsp;million miles), which is more than 50&nbsp;times the distance to the ]. {{mp|2010 TK|7}} was at the near-Earth end of its tadpole in 2010–2011,<ref name=Connors/> which facilitated its discovery.


{{mp|2010 TK|7}}'s orbit has a ] character, making long-range predictions difficult. Prior to 500 AD, it may have been oscillating about the {{L5|nolink=yes}} Lagrangian point (60 degrees behind Earth), before jumping to {{L4|nolink=yes}} via {{L3|nolink=yes}}. Short-term unstable ] about {{L3|nolink=yes}}, and transitions to ]s are also possible.<ref name=Connors /> {{mp|2010 TK|7}}'s orbit has a ] character, making long-range predictions difficult. Prior to 500&nbsp;AD, it may have been oscillating about the {{L5|nolink=yes}} Lagrangian point (60&nbsp;degrees behind Earth), before jumping to {{L4|nolink=yes}} via {{L3|nolink=yes}}. Short-term unstable ] about {{L3|nolink=yes}}, and transitions to ]s are also possible.<ref name=Connors/> Newer calculations based on an improved orbit determination confirm these results.<ref name="de la Fuente Marcos-2021"/>
{{multiple image | align = center| direction = horizontal | width = 300
| header = Animation of {{mp|2010 TK|7}} orbit from 1600 to 2500
| image1 = Animation of 2010 TK7.gif
| caption1 = ] Sun and Earth
| image2 = Animation of 2010 TK7 around Earth.gif
| caption2 = Around Earth
| image3 = Animation of 2010 TK7 around Sun.gif
| caption3 = Around Sun
| footer ={{legend2| Yellow|Sun}}{{·}}{{legend2| RoyalBlue|Earth}}{{·}}{{legend2|Magenta|{{mp|2010 TK|7}} }}
}}
{{clear}}


== Accessibility from Earth == == Accessibility from Earth ==
] ]
⚫ ] plot showing Earth's ]s (not to scale); contours around {{L4|nolink=yes}} and {{L5|nolink=yes}} represent ] paths]]


Because Earth trojans share Earth's orbit and have little gravity of their own, it can sometimes be less energetically costly to reach them than the Moon, even though they are dozens of times more distant. However, {{mp|2010 TK|7}} is not an energetically attractive target for a space mission because of its orbital inclination:<ref name="msnbc" /> It moves so far above and below Earth's orbit that the required ] for a spacecraft to match its trajectory coming from Earth's would be 9.4&nbsp;km/s, whereas some other near-Earth asteroids require less than 4&nbsp;km/s.<ref name=Connors /> Because Earth trojans share Earth's orbit and have little gravity of their own, less energy might be needed to reach them than the Moon, even though they are much more distant. However, {{mp|2010 TK|7}} is not an energetically attractive target for a space mission because of its orbital inclination:<ref name="msnbc" /> It moves so far above and below Earth's orbit that the required ] for a spacecraft to match its trajectory coming from Earth's would be 9.4&nbsp;km/s, whereas some other near-Earth asteroids require less than 4&nbsp;km/s.<ref name=Connors />


During the 5 December 2012 Earth close approach of {{convert|0.197|AU|km mi|abbr=on|lk=on}},<ref name="jpl-close" /> the asteroid only had an ] of about 21.<ref name="AstDyS" /> During the 5 December 2012 Earth close approach of {{convert|0.197|AU|km mi|abbr=on|lk=on}},<ref name="jpl-close" /> the asteroid had an ] of about 21.<ref name="AstDyS" />


{{clear}} {{clear}}


== See also == == See also ==
* {{mpl|614689|2020 XL|5}}, the second Earth trojan discovered
* ] * ]
* ], the naming convention used for astronomical objects immediately following their discovery * ], the naming convention used for astronomical objects immediately following their discovery


== Notes == == Notes ==
{{reflist|group=note}} {{notelist|1}}


== References == == References ==
{{reflist {{reflist|2
|30em
|refs= |refs=


Line 80: Line 102:
|title=JPL Small-Body Database Browser: 2010 TK7 |title=JPL Small-Body Database Browser: 2010 TK7
|url=http://ssd.jpl.nasa.gov/sbdb.cgi?sstr=3548081 |url=http://ssd.jpl.nasa.gov/sbdb.cgi?sstr=3548081
|accessdate=September 2015}}</ref> |access-date=31 March 2016}}</ref>


<ref name="mpc">{{cite web <ref name="mpc">{{cite web
Line 86: Line 108:
|publisher=] |publisher=]
|url=http://www.minorplanetcenter.net/db_search/show_object?object_id=2010+TK7 |url=http://www.minorplanetcenter.net/db_search/show_object?object_id=2010+TK7
|accessdate=September 2015}}</ref> |access-date=1 September 2015}}</ref>


<ref name=Choi>{{cite web <ref name=Choi>{{cite web
Line 94: Line 116:
|date=27 July 2011 |date=27 July 2011
|publisher=] |publisher=]
|accessdate=2011-07-27}}</ref> |access-date=2011-07-27}}</ref>


<ref name=Connors>{{cite journal <ref name=Connors>{{cite journal
Line 100: Line 122:
|last2=Wiegert |first2=Paul |last2=Wiegert |first2=Paul
|last3=Veillet |first3=Christian |last3=Veillet |first3=Christian
|title=Earth’s Trojan asteroid |title=Earth's Trojan asteroid
|date=27 July 2011 |date=27 July 2011
|journal=] |journal=]
|volume=475 |issue=7357 |pages=481–483 |volume=475 |issue=7357 |pages=481–483
|doi=10.1038/nature10233 |doi=10.1038/nature10233
|accessdate=2011-07-27
|url=http://www.nature.com/nature/journal/v475/n7357/full/nature10233.html
|bibcode = 2011Natur.475..481C |bibcode = 2011Natur.475..481C
|pmid=21796207}}</ref> |pmid=21796207|s2cid=205225571
}}</ref>


<ref name="WISE">{{cite web <ref name="WISE">{{cite web
Line 115: Line 136:
|date=27 July 2011 |date=27 July 2011
|work=NASA |work=NASA
|accessdate=September 2015}}</ref> |access-date=1 September 2015
|archive-date=2 May 2017
|archive-url=https://web.archive.org/web/20170502055548/https://www.nasa.gov/mission_pages/WISE/news/wise20110727.html
|url-status=dead
⚫ }}</ref>


<ref name="MPEC-2010-T45">{{cite web <ref name="MPEC-2010-T45">{{cite web
Line 121: Line 146:
|first=Sonia |first=Sonia
|title=MPEC 2010-T45 : 2010 TK7 |title=MPEC 2010-T45 : 2010 TK7
|work=
|publisher=] |publisher=]
|date=2010-10-07 |date=2010-10-07
|url=http://www.minorplanetcenter.net/mpec/K10/K10T45.html |url=http://www.minorplanetcenter.net/mpec/K10/K10T45.html
|accessdate=2011-07-31}}</ref> |access-date=2011-07-31}}</ref>


<ref name=Wiegert >{{cite web <ref name=Wiegert >{{cite web
Line 132: Line 156:
|work=Astro.uwo.ca |work=Astro.uwo.ca
|date=27 July 2011 |date=27 July 2011
|accessdate=September 2015}}</ref> |access-date=1 September 2015}}</ref>


<ref name="msnbc">{{cite news <ref name="msnbc">{{cite news
|url=http://www.msnbc.msn.com/id/43914196/ns/technology_and_science-space/ |url=http://www.nbcnews.com/id/43914196
⚫ |archive-url=https://web.archive.org/web/20200924000821/http://www.nbcnews.com/id/43914196
|url-status=dead
|archive-date=24 September 2020
|title=Found at last: First Earth companion asteroid |title=Found at last: First Earth companion asteroid
|work=]
|publisher=MSNBC
|date=July 27, 2011 |date=27 July 2011
|accessdate=28 July 2011 |access-date=28 July 2011
}}</ref>
⚫ |archiveurl=http://web.archive.org/web/20110728230620/http://www.msnbc.msn.com/id/43914196/ns/technology_and_science-space/
|archivedate=28 July 2011
⚫ |deadurl=no}}</ref>


<ref name=jpl-close>{{cite web <ref name=jpl-close>{{cite web
Line 148: Line 173:
|title=JPL Close-Approach Data: (2010 TK7) |title=JPL Close-Approach Data: (2010 TK7)
|url=http://ssd.jpl.nasa.gov/sbdb.cgi?sstr=2010TK7;cad=1#cad |url=http://ssd.jpl.nasa.gov/sbdb.cgi?sstr=2010TK7;cad=1#cad
|accessdate=2012-01-21}}</ref> |access-date=2012-01-21}}</ref>


<ref name="AstDyS">{{cite web <ref name="AstDyS">{{cite web
|title=AstDyS 2010TK7 Ephemerides for 2012 |title=AstDyS 2010TK7 Ephemerides for 2012
|publisher=Department of Mathematics, University of Pisa, Italy |publisher=Department of Mathematics, University of Pisa, Italy
|url=http://hamilton.dm.unipi.it/astdys/index.php?pc=1.1.3.1&n=2010TK7&oc=500&y0=2012&m0=11&d0=01&h0=0&mi0=0&y1=2013&m1=1&d1=1&h1=0&mi1=0&ti=1.0&tiu=days |url=https://newton.spacedys.com/astdys/index.php?pc=1.1.3.1&n=2010TK7&oc=500&y0=2012&m0=11&d0=01&h0=0&mi0=0&y1=2013&m1=1&d1=1&h1=0&mi1=0&ti=1.0&tiu=days
|accessdate=2012-01-21}}</ref> |access-date=2012-01-21}}</ref>

<ref name="de la Fuente Marcos-2021">{{Cite journal
|first1 = Carlos |last1 = de la Fuente Marcos
|first2 = Raúl |last2 = de la Fuente Marcos
|date = 18 February 2021
|title = Transient Terrestrial Trojans: Comparative Short-term Dynamical Evolution of 2010 TK<sub>7</sub> and 2020 XL<sub>5</sub>
|journal = Research Notes of the American Astronomical Society
|volume = 5
|issue = 2
|pages = 29
|bibcode = 2021RNAAS...5...29D
|doi = 10.3847/2515-5172/abe6ad
|doi-access= free
}}</ref>


}} <!-- end of reflist--> }} <!-- end of reflist-->


*{{cite news|url=http://www.bbc.co.uk/news/science-environment-14307987|title=Trojan asteroid seen in Earth's orbit by Wise telescope|publisher= ]|date=2011-07-28|accessdate=2011-07-29|first=Jonathan |last= Amos}} *{{cite news|url=https://www.bbc.co.uk/news/science-environment-14307987|title=Trojan asteroid seen in Earth's orbit by Wise telescope|publisher= ]|date=2011-07-28|access-date=2011-07-29|first=Jonathan |last= Amos}}


== External links == == External links ==
* *
* {{dead link|date=August 2014}} *
* * {{Webarchive|url=https://web.archive.org/web/20130302070109/http://www.nasa.gov/mission_pages/WISE/news/wise20110727vid.html |date=2 March 2013 }}
* {{NeoDys|2010+TK7}}
* {{ESA-SSA|2010TK7}}
* {{JPL small body}}


{{Minor planets navigator | |number=706765 |PageName={{mp|(706765) 2010 TK|7}} | }}
⚫ {{DEFAULTSORT:2010 T007K}}
{{Small Solar System bodies}}
⚫ ]
{{Portal bar|Astronomy|Stars|Spaceflight|Outer space|Solar System}}
{{Authority control}}

⚫ {{DEFAULTSORT:706765}}
]
] ]
] ]
] ]
⚫ ]

Latest revision as of 13:03, 20 December 2024

Near-Earth asteroid and Earth trojan

(706765) 2010 TK7
Asteroid 2010 TK7 (circled in green) in image from the WISE spacecraft
Discovery
Discovered byWISE spacecraft
Discovery siteLEO, polar orbit
Discovery date1 October 2010
Designations
MPC designation2010 TK7
Minor planet category
Orbital characteristics
Epoch 13 January 2016 (JD 2457400.5)
Uncertainty parameter 0
Observation arc768 days (2.10 yr)
Aphelion1.1903 AU (178.07 Gm)
Perihelion0.80918 AU (121.052 Gm)
Semi-major axis0.99972 AU (149.556 Gm)
Eccentricity0.19059
Orbital period (sidereal)1.00 yr (365.10 d)
Average orbital speed29.8 km/s
Mean anomaly354.14°
Mean motion0° 59 9.672 / day
Inclination20.890°
Longitude of ascending node96.498°
Argument of perihelion45.927°
Earth MOID0.0837911 AU (12.53497 Gm)
Physical characteristics
Mean diameter379±123 m
Geometric albedo0.059±0.049
Apparent magnitude20.8 (when near Earth) to 23.6
Absolute magnitude (H)20.8

(706765) 2010 TK7 (provisional designation 2010 TK7) is a sub-kilometer Near-Earth asteroid and the first Earth trojan discovered; it precedes Earth in its orbit around the Sun. Trojan objects are most easily conceived as orbiting at a Lagrangian point, a dynamically stable location (where the combined gravitational force acts through the Sun's and Earth's barycenter) 60 degrees ahead of or behind a massive orbiting body, in a type of 1:1 orbital resonance. In reality, they oscillate around such a point. Such objects had previously been observed in the orbits of Mars, Jupiter, Neptune, and the Saturnian moons Tethys and Dione.

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).

The asteroid was discovered in October 2010 by the NEOWISE team of astronomers using NASA's Wide-field Infrared Survey Explorer (WISE).

Discovery

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. The orbital information was published in the journal Nature by Paul Wiegert of the University of Western Ontario, Martin Connors of Athabasca University and Christian Veillet, the executive director of the Canada–France–Hawaii Telescope.

Physical and orbital characteristics

2010 TK7's spiraling path (green) relative to Earth and its orbit (blue dots) over the course of half a tadpole loop; each spiral turn represents a year's motion

2010 TK7 has an absolute magnitude of luminosity (determinable because of its known location) of about 20.8. Based on an assumed albedo of 0.1, its estimated diameter is about 300 meters. No spectral data are yet available to shed light on its composition. 2010 TK7 would exert a surface gravitational force of less than 1⁄20,000 that of Earth.

At the time of discovery, the asteroid orbited the Sun with a period of 365.389 days, close to Earth's 365.256 days. As long as it remains in 1:1 resonance with Earth, its average period over long time intervals will exactly equal that of Earth. On its eccentric (e = 0.191) orbit, 2010 TK7's distance from the Sun varies annually from 0.81 AU to 1.19 AU. It orbits in a plane inclined about 21 degrees to the plane of the ecliptic.

Trojans 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); 2010 TK7 traverses its loop over a period of 395 years. 2010 TK7's loop is so elongated that it sometimes travels nearly to the opposite side of the Sun with respect to Earth. Its movements do not bring it any closer to Earth than 20 million kilometers (12.4 million miles), which is more than 50 times the distance to the Moon. 2010 TK7 was at the near-Earth end of its tadpole in 2010–2011, which facilitated its discovery.

2010 TK7's orbit has a chaotic character, making long-range predictions difficult. Prior to 500 AD, 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. Newer calculations based on an improved orbit determination confirm these results.

Animation of 2010 TK7 orbit from 1600 to 2500Relative to Sun and EarthAround EarthAround Sun  Sun ·   Earth ·   2010 TK7

Accessibility from Earth

Position of 2010 TK7 relative to Earth in 2011
Effective potential plot showing Earth's Lagrangian points (not to scale); contours around L4 and L5 represent tadpole loop paths

Because Earth trojans share Earth's orbit and have little gravity of their own, less energy might be needed to reach them than the Moon, even though they are much more distant. However, 2010 TK7 is not an energetically attractive target for a space mission because of its orbital inclination: It moves so far above and below Earth's orbit that the required change in velocity for a spacecraft to match its trajectory coming from Earth's would be 9.4 km/s, whereas some other near-Earth asteroids require less than 4 km/s.

During the 5 December 2012 Earth close approach of 0.197 AU (29,500,000 km; 18,300,000 mi), the asteroid had an apparent magnitude of about 21.

See also

Notes

  1. v = 42.1219 √1/0.9989 − 0.5/0.9989.
  2. Because of its orbital inclination and eccentricity, 2010 TK7's position relative to Earth is actually a complicated, tightly coiled spiral; however, if its average position relative to Earth over a year is represented by a single point, that point will follow the tadpole loop.

References

  1. "2010 TK7 Orbit". Minor Planet Center. Retrieved 1 September 2015.
  2. ^ "JPL Small-Body Database Browser: 2010 TK7" (2012-11-07 last obs). Retrieved 31 March 2016.
  3. WayBack Machine 2013 Epoch@MPC
  4. ^ Connors, Martin; Wiegert, Paul; Veillet, Christian (27 July 2011). "Earth's Trojan asteroid". Nature. 475 (7357): 481–483. Bibcode:2011Natur.475..481C. doi:10.1038/nature10233. PMID 21796207. S2CID 205225571.
  5. "NASA's WISE Mission Finds First Trojan Asteroid Sharing Earth's Orbit". NASA. 27 July 2011. Archived from the original on 2 May 2017. Retrieved 1 September 2015.
  6. Choi, Charles Q. (27 July 2011). "First Asteroid Companion of Earth Discovered at Last". Space.com. Retrieved 27 July 2011.
  7. Keys, Sonia (7 October 2010). "MPEC 2010-T45 : 2010 TK7". IAU Minor Planet Center. Retrieved 31 July 2011.
  8. ^ "Earth's first Trojan asteroid: 2010 TK7". Astro.uwo.ca. 27 July 2011. Retrieved 1 September 2015.
  9. de la Fuente Marcos, Carlos; de la Fuente Marcos, Raúl (18 February 2021). "Transient Terrestrial Trojans: Comparative Short-term Dynamical Evolution of 2010 TK7 and 2020 XL5". Research Notes of the American Astronomical Society. 5 (2): 29. Bibcode:2021RNAAS...5...29D. doi:10.3847/2515-5172/abe6ad.
  10. "Found at last: First Earth companion asteroid". NBC News. 27 July 2011. Archived from the original on 24 September 2020. Retrieved 28 July 2011.
  11. "JPL Close-Approach Data: (2010 TK7)" (2011-08-03 last obs (arc=40 days; Uncertainty=2)). Retrieved 21 January 2012.
  12. "AstDyS 2010TK7 Ephemerides for 2012". Department of Mathematics, University of Pisa, Italy. Retrieved 21 January 2012.

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