List of objects at Lagrangian points

This is a list of known objects which occupy, have occupied, or are planned to occupy any of the five Lagrangian points of two-body systems in space.

A diagram showing the five Lagrangian points in a two-body system

Sun–Earth Lagrangian points

L₁

L₁ is the Lagrangian point located approximately 1,500,000 km towards the Sun away from the Earth.

Past probes

• International Cometary Explorer, formerly the International Sun–Earth Explorer 3 (ISEE-3), diverted out of L₁ in 1983 for a comet rendezvous mission. Currently in solar orbit, it may be captured in 2014 when it next approaches Earth.
• NASA's Genesis probe collected solar wind samples at L₁ from December 3, 2001 to April 1, 2004, when it returned the sample capsule to Earth. It returned briefly in late 2004 before being pushed into heliocentric orbit in early 2005.

Present probes

• WIND (spacecraft) (At L1 since 2004)
• The Solar and Heliospheric Observatory (SOHO)
• The Advanced Composition Explorer (ACE)

Planned probes

• LISA Pathfinder
• Kuafu
• The Deep Space Climate Observatory, designed to monitor global warming.

L₂

L₂ is the Lagrangian point located approximately 1,500,000 km away from the Earth in the direction opposite the Sun.

Past probes

• WIND (spacecraft) (October 2003 to February 2004)
• Chang'e 2 (August 2011 to April 2012)

Present probes

• Wilkinson Microwave Anisotropy Probe (WMAP)
• The ESA Planck Surveyor
• The ESA Herschel Space Observatory

Planned probes

• The joint NASA, ESA and CSA James Webb Space Telescope (JWST), formerly known as the Next Generation Space Telescope (NGST)
• The ESA Gaia probe
• The NASA Terrestrial Planet Finder mission (may be placed in an Earth-trailing orbit instead)
• The ESA Darwin mission
• The NASA Advanced Technology Large-Aperture Space Telescope, which would replace the Hubble Space Telescope and possibly the JWST.

Cancelled probes

• The ESA Eddington mission

L₃

L₃ is the Sun–Earth Lagrangian point located on the side of the Sun opposite the Earth, slightly outside the Earth's orbit.

• There are no known objects in this orbital location.

L₄

L₄ is the Sun–Earth Lagrangian point located close to the Earth's orbit 60° ahead of the Earth.

• Asteroid 2010 TK7 is the first discovered "tadpole" orbit companion to Earth, orbiting L₄ with a mean distance of about one astronomical unit.
• STEREO A (Solar TErrestrial RElations Observatory – Ahead) makes its closest pass to L₄ in September 2009, on its orbit around the Sun, slightly faster than the Earth.
• Dust clouds^{[<span title="need specific claim of observations of dust at Sun–Earth L₄ (not Earth–Moon L4), with page numbers; none found in 1998 T. Kelsall paper (November 2009)">citation needed]}

L₅

L₅ is the Sun–Earth Lagrangian point located close to the Earth's orbit 60° behind the Earth.

• Asteroid 2010 SO16, in a horseshoe companion orbit with Earth, is currently proximal to L₅ but at a high inclination.
• STEREO B (Solar TErrestrial RElations Observatory – Behind) makes its closest pass to L₅ in October 2009, on its orbit around the Sun, slightly slower than the Earth.
• Spitzer is in an Earth-trailing heliocentric orbit drifting away c. 0.1 AU per year. In c. 2013–15 it will pass L₅ in its orbit.
• Dust clouds^{[<span title="need specific claim of observations of dust at Sun–Earth L₄ (not Earth–Moon L4), with page numbers; none found in 1998 T. Kelsall paper (November 2009)">citation needed]}

Earth–Moon Lagrangian points

L₂

• ARTEMIS

L₄ and L₅

• possible Kordylewski clouds
• future location of TDRS-style communication satellites to support L₂ satellite

Past probes

• Hiten was the first spacecraft to demonstrate a low energy trajectory, passing by L4 and L5 to achieve lunar orbit at a very low fuel expense, compared to usual orbital techniques. Hiten did not find any conclusive increase in dust density at Lagrange points.

Proposed objects

• Exploration Gateway Platform
• In his book "The High Frontier" Dr. Gerard O'Neill proposed the establishment of gigantic Space Islands in L₅. The inhabitants of the L5 Society should convert Lunar material to huge solar power satellites. Many works of fiction, most notably the Gundam series, involve colonies at these locations.

Sun–Mars Lagrangian points

Asteroids in the L₄ and L₅ Sun–Mars Lagrangian points are sometimes called Mars trojans, with a lower-case t, as "Trojan asteroid" was originally defined as a term for Lagrangian asteroids of Jupiter. They may also be called Mars Lagrangian asteroids.

L₄

• 1999 UJ₇

L₅

• 5261 Eureka
• 1998 VF₃₁
• 2007 NS₂, 2001 DH₄₇, 2001 FG₂₄, 2001 FR₁₂₇ (not confirmed as true Lagrangian asteroids)

Source: Minor Planet Center [1]

Sun–Jupiter Lagrangian points

Asteroids in the L₄ and L₅ Sun–Jupiter Lagrangian points are known as Jupiter Trojan asteroids or simply Trojan asteroids.

L₄

• Trojan asteroids, Greek camp

L₅

• Trojan asteroids, Trojan camp

Saturn–Tethys Lagrangian points

L₄

• Telesto

L₅

• Calypso

Saturn–Dione Lagrangian points

L₄

• Helene

L₅

• Polydeuces, follows a "tadpole" orbit around L₅

Sun–Uranus Lagrangian points

L₄

• 2011 QF₉₉

Sun–Neptune Lagrangian points

Minor planets in the L₄ and L₅ Sun–Neptune Lagrangian points are called Neptune trojans, with a lower-case t, as "Trojan asteroid" was originally defined as a term for Lagrangian asteroids of Jupiter.

L₄

• 2001 QR₃₂₂
• 2004 UP₁₀
• 2005 TN₅₃
• 2005 TO₇₄
• 2006 RJ₁₀₃
• 2007 VL₃₀₅

L₅

• 2008 LC₁₈
• 2004 KV₁₈
• 2011 HM₁₀₂

Source: Minor Planet Center [2]

See also

• Lagrangian point
• Trojan points
• Trojan asteroid
• Trojan moon
• Trojan planet

Footnotes