TRANS-NEPTUNIAN OBJECTS (TNO’s)

INTRODUCTION

Planetary astronomers have been intensively looking for other small bodies in the depths of the outer solar system since about 1992. After this, the numbers of them seeminly continue to increase almost exponentially. Like 134340 Eris, the regional location of these bodies in the Solar System occupies the recently termed scattered disc. Also as they lie beyond the orbit of the most distant planet, Neptune, they are collectively known as trans-Neptunian objects — abbreviated to just TNO#8217;s. Another recent more specialised term for some of these objects are Plutinos. These are often referred as a trans-Neptunian objects whose mean orbit lies in the 2:3 resonance with dwarf planet 134340 Pluto. Other examples include the largest, 90482 Orchus, followed by 28978 Ixion, 38083 Rhadamanthus, 38628 Huya, and the first discovered Plutino on 14th September 1993 — the small estimated 92km across 1993 RO. This same region is believed to be inside the Kuiper Belt where the nuclei of billions of comets are thought to reside. As of September 2006, eight large asteroid bodies exist beyond the orbit of Pluto. Largest so far discovered is the now dwarf planet, Eris.

NOTE : An continuously up-to-date link of all the current known
Trans-Neptunian Objects can be obtained at; [1.]

Before Eris’ discovery in October 2003, several team of observers from 2001 under Michael Brown found several of the largest of these newer trans-Neptunian bodies, including Quaoar, Sedna, Orcus, and the enigmatic, Haumea.

SELECTED TRANS-NEPTUNIAN OBJECTS

(134340) P L U T O

PLUTO (See the PLUTO Page)

(134340) E R I S

ERIS (See the ERIS Page)

(136472) M A K E M A K E

MAKEMAKE (See the Makemake Page)

MAKEMAKE or 2005 FY9 (136472) is now classed as a dwarf planet, being the fourth discovered.

(136108) H A U M E A

HAUMEA (See the Haumea Page)

HAUMEA (136108) 2003 EL61 is one of the most unusual trans-Neptunian objects, which is now classed as the fifth dwarf planet.

V A R U N A

VARUNA (20000) or 2000 WR106 is approximately about the size of the dwarf planet Ceres, and remains the smallest of the known TNOs, though the true diameter and size remains slightly uncertain. Although thought to be about 936 km. across, recent estimates is suggest it is likely not round but tri-axial ellipsoidal in shape. In the Vedic / Hindi religion of the Indian antiquity, Varuna is one of their principle creation gods. He importantly rules the underworld, but also is associated with control of the celestial ocean, including the rain and the sky. Varuna was discovered as another Kupier Belt object by R. McMillian on 20th November 2000.

This very deep and dark yellow body has only a very slightly elliptical orbit whose average solar distance is 43.12 AU. This varies between its perihelion and aphelion as 40.9 and 45.3 AU, respectively. Orbital inclination is 17.2°, being about the same as Pluto, though its nodes are aligned quite differently — to the extent that perturbations are unaffected by Neptune. Veruna orbital period is 284.2 years — only some 36 years longer than Pluto.

An unusual rapid sidereal rotation was discovered during 2002 from the rapid oscillating brightness in the light-curve. This is presently estimated as 6.3436 hours,and for some time the period was considered as half of this at 3.2 hours. Spectral observations have also detected water.

Invisible in all amateur telescopes, Varuna presently lies in the zodiac constellation of Gemini, and will stay there until 2015 when it crosses into Cancer. Magnitude presently is hovering between 19.9 and 20.1 magnitude, which will slowly diminish in brightness to 20.2 to 20.4 magnitude over the next few decades. Periastron last occurred on 4th November 1934, and will not again happen until early 2273 AD. Next apastron is June 2075.

Q U A O A R

QUAOAR (50000) or 2002 AW197 was discovered by Michael Brown and Chad Trujillo using the 1.2-metre Oschin Telescope at Mt. Palomar Observatory on 04th June 2002. This was almost 3½ years prior to the their most significant find, the dwarf planet Eris. Quaoar is the genderless god of the North American of the Tongva Native tribe, who during the first creation brought into existence all their worship deities used his great singing voice and complex dances.

This large 1260±190 kilometre sized Kuiper Belt asteroid has a near circular orbit, which encircles the Sun once every 282.89 years. Quaoar may still qualify as another dwarf planet, joining Pluto, Ceres and Eris, but more information about the true diameter will be required before it is categorised as such. As of October 2006, it is the fifth largest of the trans-Neptunian bodies. Like Varuna and Ixion, Quaoar is another dark reddish coloured body that poorly reflects light, implying that the surface is not entirely covered with ices. A later spectral analysis made in 2004 contradicts this, finds that Quaoar does have some quantities of frozen hard crystalline water ice its surface. This may suggests that Quaoar may have possible ice volcanos caused by internal heat from the inner core or some recent collision.

The next expected periastron for Quaoar is 14th February 2081, whose coinciding aphelion dates are March 1821 and December 2340 AD. Presently (2006) Quaoar lies in northern Ophiuchus as a 19th magnitude star, varing in brightness between opposition and conjunction by merely 0.3 or 0.4 magnitudes. By 2009, Quaoar with move into Serpens, followed by Scutum in January 2022 and then Sagittarius in December 2028. Over the coming decades the brightness will very slowly increase, where the maximum opposition magnitude of 18.8 will occur within the constellation of Pisces. Regardless, Quaoar will remain invisible to amateur telescopes, though it might be possible to obtain using an CCD imaging.

S E D N A

S E D N A (90377) or 2003 VB12, is like Eris, as it is a known scattered disk object. Sedna was discovered on 14th November 2003 by the same team lead by Michael Brown who found Eris. Pending the decision by the IAU, in the near future, the 1490±310 km diameter may make Sedna qualify as another dwarf planet, and this will depend on more accurate size determination.

Sedna is quite remarkable because of its extreme elliptical orbit, which can vary between 76.7 AU and an estimated 970 AU or 145 billion kilometers, in an astounding period of around 12 000 years or 4.4 million days! When first found, Sedna just happened to be near perihelion, which is currently expect to occur in early April 2076. Problems now exist with how such an object could have formed in the early solar system, and it has been suggested that the orbit has been influenced by passing nearby stars or even another undiscovered large planet. Another possibility is that Sedna was captured by the gravitation of the Sun sometime in the distant past.

Little is really known about this object, but spectroscopy suggests this is a very dark reddish coloured body — in fact rating the reddest in the whole solar system — possibly even beating Mars for the crown! Obtained spectra is radially different than other bodies at these depths, suggesting materials like complex hydrocarbon-like sludge, amorphous carbon, mixed with ices of methanol and methane — the later making up one-third of the material on the surface. Unlike many similar distance objects, little evidence of water ice has been found to exist. From slight changes in brightness over time, an estimated rotational period has been determined as roughly 10 hours 15 minutes.

At present, Sedna lies in Cetus near the border of Taurus, shining as a very faint 21.1 magnitude star. Due to the enormous distance from the sun, the movement against the background sky is very sluggish. After moving into Taurus, Sedna will not reach another constellation until it moves into northern Orion in 2040, then into neighbouring Gemini in 2075. A maximum brightness 20.4 magnitude will be reached in January 2078. When placed near aphelion in 8061 AD, the estimated magnitude drop will be below 30th magnitude, and will be near impossible to see even with the largest of telescopes available today!

O R C U S

ORCUS (90482) or 2004 DW on 17th August 2004 another planetoid body that was discovered by the team under Michael Brown. He is named after one of the Etruscan or Roman god of the underworld, being also associated as the underworld itself or as the inflicter of punishments in Hades. He particularly acts on those who brake sacred oaths or promises, and later became as punisher of evils. The Greek equivalent of the god Orcus is likely Horkos, being the son of the goddess, Eris.

Mean distance from the Sun is 39.386 AU, whose perihelion distance is 30.72 AU and at aphelion increases to 48.05 AU. Its orbit is highly inclined to the ecliptic at 20.6°, having the high orbital eccentricity of 0.220. In 2006, the initial estimated diameter was around 1600 km, and this this still remained rather uncertain for some time. By 2011, the mean diameter has been downgraded to 850±90 km. or 807±100 km.

Vanth is a body is presently accepted as some 267 or 378km. across, depending on the source, is roughly one-third the size of Orcus. Vanth has a mean distance of 9030±89 km. from Orcus, whose orbital period is 9.5406 days.

I X I O N

IXION (28978) or 2001 KX76, pronounced Ik-sar-on, is a small plutino body similarly placed near to the orbit of Pluto that, was discovered on 22nd May 2001. Ixion#8217;s mean distance from the Sun is 39.6 AU, whose highly inclined orbit is 19.6° to the ecliptic. Its moderately eccentricity (e = 0.382) causes the distance to vary between 30.1 and 49.2 AU in an orbital period of 248.6 years. Ixion is currently 19.6v and 19.8v magnitude in the zodiacal constellation of Ophiuchus (2008), and is now approaching perihelion in 18th November 2070, having had its last aphelion in May 1945. Between these extremes, Ixion will vary between 18.2 and 20.5 magnitude, and therefore remains invisible to all amateur telescopes except through CCD imaging.

Little else is known about Ixion itself. It seems to be a fairly small reddish coloured body that is currently estimated to be about 800 kilometres across.

Ixion is named in legend after the ancient Greek king of Thessaly, who in an act of vengeance killed his father-in-law by fire. Due to his totally unmerciful attitude, he soon became shunned and eventually exiled from the city. For this he was pitied by Zeus, who brought him into Olympus with the other gods. In some myths, while there Ixion was in Olympus he had an affair with the manifestation of human-shaped spirit in the form of a cloud, named Nephele, whose offspring became the mythical creatures known as Centaurs — half man and half horse. However, Ixion soon acted improperly by making untoward advances to Zeus#8217;s wife, Hera. After firing his thunderbolt at him in anger, Zeus the forced Ixion into Tartarus (Hell) where he was permanently fixed to a burning spinning wheel, which keeps on spinning for eternity.

Also See : DWARF PLANET Page.

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Last Update : 1st March 2014

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