Department of Physics AstroLab

The Orbits of Trojan Asteroids

Apart from the major planets, the Solar System contains a large number of smaller bodies. The asteroids (i.e. the minor planets) are the small rocky objects that are found mainly between the orbits of Mars and Jupiter, e.g. the main-belt. The Trojan asteroids orbit the Sun in the vicinity of one of the Lagrangian points of Jupiter's orbit. These are considerably fainter than the main-belt asteroids and hence are more difficult to study.

The aim of the project is to independently determine the orbits of four Trojan asteroids by making a series of positional measurements. This is achieved by measuring the asteroid's position on a CCD image relative to that of the stars. Trojan asteroids typically move about 5 arcmin per 24 hours. By tracking an asteroid over the term its orbit can be well determined. The goal will be to obtain about 7 observations per asteroid.

The main-belt asteroid page gives an example of type of results that can be obtained.

By reference to the UCAC4 or URAT1 star catalog astrometry measurements can be made with uncertainties of better than 0.1 arcsec. The plot below compares the measured astrometric positions with the asteroid positions predicted from the JPL Horizons On-line Ephemeris. JPL's formal +/− 1, 2, 3 standard-deviation uncertainties are showed as error ellipses; these are described as "optimistic" (see Horizons Manual).

Trojan asteroids have been observed by AstroLab students since 1996.

1996 Hektor, Agamemnon
1997 Hektor, Agamemnon, Odysseus, Achilles, Nestor, Ajax, Diomedes, Antilochus
1998 Achilles, Agamemnon, Hektor, Odysseus
1999 Achilles, Ajax, Androgeos, Askalaphus, Diomedes, Eurybates, Krethon, Makhaon, Meriones, Nestor, Odysseus, Podalirius, Prostesiloas, Sthemelos, Telamon, Cebriones, Sarpedon, Bitias, Iphidamas, Ennomos, Menor, Aneas
2000 Achilles, Agamemnon, Diomedes, Hektor, Nestor, Odysseus, Anchises, Aneas, Priamus, Deiphobus, Laocoon, Sarpeden
2001 Hektor, Telamon, Odysseus, Nestor, Makhaon, Agamemnon, Alcathous, Aneas, Deiphobus, Mentor, Patroclus, Priamus.
2002 Patroclus, Priamus, Aneas, Mentor, Paris, Nestor, Odysseus, Telamon, Trolius
2003 Patroclus, Priamus, Anchises, Helenos, Aneas, Trolius
2004 Patroclus, Priamus, Anchises, Helenos, Aneas, Trolius
2005 Patroclus, Priamus, Menelaus, Pandarus, Trolius, Peiroos
2007 Patroclus, Peiroos, Paris, Achates, (7352) 1994 CO, (34746) 2001 QE91
2008 Hektor, Agamemnon, Ajax, Achilles, Automedon, Diomedes
2009 Hektor, Agamemnon, Antilochus, Automedon, Diomedes, Makhaon, Meriones
2012 Ajax, Agamemnon, Achilles, Diomedes, 1989BQ, 1998 VF30, 2000 AG191, Thersites, Odysseus, Telamon, Hektor, Priamus, Ennomos, Aneas, Anchises, Deiphobus, 1974 FV1 ,Sarpedon, Bitias, Helenos, 1999 UJ7
2013 Hektor, Agamemnon, Ajax, Achilles, Odysseus, Makhaon, Telamon, 1974 FV1, Achates, Alcathous, Anchises, Antenor, Deiphobus, Patroclus, Pandarus, Phereclos, Poulydamas

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