13th Largest Moon of Saturn - Pandora (5th Moon outwards from Saturn)

Pandora is an inner satellite of Saturn.

Pandora is the 13th largest moon of Saturn, and the 52th largest moon in the Solar System currently known.

Discovery

Pandora was discovered in October 1980 from photos taken by the Voyager 1 probe.


Naming

Pandora was provisionally designated S/1980 S26. In late 1985, the moon was officially named after Pandora, from Greek mythology.

In Greek mythology, Pandora was allegedly the first woman, who was made out of clay. As Hesiod related it, each god helped create her by giving her unique gifts. Zeus ordered Hephaestus to mold her out of earth as part of the punishment of mankind for Prometheus' theft of the secret of fire, and all the gods joined in offering her "seductive gifts".

Pandora's Box is an artifact in Greek mythology, taken from the myth of Pandora's creation in Hesiod's Works and Days. The "box" was actually a large jar given to Pandora, which contained all the evils of the world, although the particular evils, aside from plagues and diseases, are not specified in detail by Hesiod. When Pandora opened the jar, all its contents except for one item were released into the world. The one remaining item was Hope. Today, to open Pandora's box means to create evil that cannot be undone.

Stats

Diameter (mean): 81.4 ± 3.0 km

Semi-major axis: 141,720 km

Orbital Period: 0.629 days

Orbit

Pandora rotates synchronously with its orbital period, keeping one face pointed toward Saturn.

Pandora is the outer shepherd satellite of the F Ring.

The orbit of Pandora appears to be chaotic, as a consequence of a series of four 118:121 mean motion resonances with Prometheus. The most appreciable changes in their orbits occur approximately every 6.2 years, when the periapsis of Pandora lines up with the apoapsis of Prometheus and the moons approach to within about 1,400 kilometres.

Pandora also has a 3:2 mean-motion resonance with Mimas.

Physical Characteristics

Pandora is more heavily cratered than nearby Prometheus, and has at least two large craters 30 kilometres in diameter.

From Pandora's very low density and relatively high albedo, it seems likely that it is a very porous icy body. There is a lot of uncertainty in these values, however, so this remains to be confirmed.

13th Largest Moon of Jupiter - Lysithea (12th Moon outwards from Jupiter)

Lysithea is a prograde irregular satellite of Jupiter.

Lysithea is the 13th largest moon of Jupiter and 75th largest moon in the Solar System currently known.

Discovery

Lysithea was discovered by Seth Barnes Nicholson on July 6, 1938 with the 100-inch (2.5 m) Hooker telescope at the Mount Wilson Observatory.

Naming

Lysithea the moon is named after the mythological Lysithea, daughter of Oceanus and one of Zeus' lovers.

In Greek mythology, Lysithea was a daughter of Oceanus and one of Zeus' lovers.

Lysithea didn't receive its present name until 1975; before then, it was simply known as Jupiter X. Or it was sometimes called "Demeter" from 1955 to 1975.

In Greek mythology, Demeter is the goddess of the harvest, who presided over grains and the fertility of the earth.

A name ending in "a" was chosen for this moon in keeping with the International Astronomical Union's policy for designating Jupiter's outer moons which have prograde orbits (orbiting in the same direction as Jupiter's rotation).

Stats

Diameter (mean): 36 km

Semi-major axis: 11,740,560 km

Orbital Period: 259.2 day

Orbit

Lysithea belongs to the Himalia group, a family of Jovian satellites which have similar orbits and appearance, and are therefore thought to have a common origin. Its orbital elements are as of January 2000. They are continuously changing due to solar and planetary perturbations.

Physical characteristics

Lysithea has an estimated diameter of 36 km (assuming an albedo of 0.04).

Lysithea may be a chunk of an asteroid (a C- or D-class asteroid, judging by the fact that it reflects only about 4% of the light it receives), which was broken apart in a collision either before or after being captured by Jupiter's gravity.

In this scenario, the other pieces became the other moons in the Himalia group: Leda, Himalia (the largest) and Elara. A fifth moon, called S/2000 J11, only about 2 km in radius, was considered a candidate for this group. However, it was lost before its orbit could be definitively determined.

S/2000 J11 may have crashed into Himalia, reuniting two pieces of the former asteroid, and perhaps creating a faint temporary ring of Jupiter near the orbit of Himalia.

Centaurs (minor planets)

Centaurs are an unstable orbital class of minor planets that behave with characteristics of both asteroids and comets.

The generic definition of a centaur is a small body that orbits the Sun between Jupiter and Neptune and crosses the orbits of one or more of the giant planets.

It has been estimated that there are around 44,000 centaurs in the Solar System with diameters larger than 1 km.

Naming

They are named after the mythological race of beings, centaurs, which were a mixture of horse and human.

In Greek mythology, a centaur or hippocentaur is a member of a composite race of creatures, part human and part horse. In early Attic and Boeotian vase-paintings, they are depicted with the hindquarters of a horse attached to human; in later renderings centaurs are given the torso of a human joined at the waist to the horse's withers, where the horse's neck would be.

The centaurs were usually said to have been born of Ixion and Nephele (the cloud made in the image of Hera).

Orbits

Centaurs' orbits are characterised by a wide range of eccentricity, from highly eccentric (Pholus, Asbolus, Amicus, Nessus) to more circular (Chariklo and the Saturn-crossers: Thereus, Okyrhoe).

Since the centaurs cross the orbits of the giant planets and are not protected by orbital resonances, their orbits are unstable within a timescale of 10⁶ – 10⁷ years.

Dynamical studies of their orbits indicate that centaurs are probably an intermediate orbital state of objects transitioning from the Kuiper belt to the Jupiter family of short-period comets. Objects may be perturbed from the Kuiper belt, whereupon they become Neptune-crossing and interact gravitationally with that planet. They then become classed as centaurs, but their orbits are chaotic, evolving relatively rapidly as the centaur makes repeated close approaches to one or more of the outer planets.

Some centaurs will evolve into Jupiter-crossing orbits whereupon their perihelia may become reduced into the inner Solar System and they may be reclassified as active comets in the Jupiter family if they display cometary activity. Any centaur that is perturbed close enough to the Sun is expected to become a comet.

Centaurs will thus ultimately collide with the Sun or a planet or else they may be ejected into interstellar space after a close approach to one of the planets, particularly Jupiter.

Physical characteristics

The relatively small size of centaurs precludes surface observations, but colour indices and spectra can indicate possible surface composition and can provide insight into the origin of the bodies.

Color

Centaurs display a puzzling diversity of colour that challenges any simple model of surface composition.

Centaurs appear to be grouped into two classes:
1. Very red, for example 5145 Pholus
2. Blue (or blue-grey), for example 2060 Chiron

There are numerous theories to explain this colour difference, but they can be divided broadly into two categories:
1. The colour difference results from a difference in the origin and/or composition of the centaur.
2. The colour difference reflects a different level of space-weathering from radiation and/or cometary activity.

Spectra

The interpretation of spectra is often ambiguous, related to particle sizes and other factors. For example, if there is cometary activity, the spectra observed vary depending on the period of the observation. Water ice signature was detected during a period of low activity and disappeared during high activity.

Origin

The study of centaur development is rich in recent developments but still hampered by limited physical data. Different models have been put forward for possible origin of centaurs.

Simulations indicate that the orbit of some Kuiper-belt objects can be perturbed, resulting in the object's expulsion so that it becomes a centaur. Scattered disk objects would be dynamically the best candidates for such expulsions, but their colours do not fit the bicoloured nature of the centaurs. Plutinos are a class of Kuiper-belt object that display a similar bicoloured nature, and there are suggestions that not all plutinos' orbits are as stable as initially thought, due to perturbation by Pluto.

Further developments are expected with more physical data on KBOs.

34th Largest Asteroid, 6 Hebe

6 Hebe is a large main-belt asteroid and the 34th largest asteroid currently known.




Discovery

Hebe was the sixth asteroid to be discovered, on July 1, 1847 by Karl Ludwig Hencke at Driesen. It was the second and final asteroid discovery by Hencke, who had previously found 5 Astraea.

Naming

The name Hebe, goddess of youth, was proposed by Carl Friedrich Gauss, who was a German mathematician and physical scientist who contributed significantly to many fields, including number theory, statistics, analysis, differential geometry, geodesy, geophysics, electrostatics, astronomy and optics.

In Greek mythology, Hēbē is the goddess of youth (Roman equivalent: Juventas). She is the daughter of Zeus and Hera. Hebe was the cupbearer for the gods and goddesses of Mount Olympus, serving their nectar and ambrosia, until she was married to Heracles.

The name Hebe comes from Greek word meaning "youth" or "prime of life". Juventas likewise means "youth", as can be seen in such derivatives as juvenile. In art, Hebe is usually depicted wearing a sleeveless dress. Hebe was also worshipped as a goddess of pardons or forgiveness; freed prisoners would hang their chains in the sacred grove of her sanctuary at Phlius.

Stats

Diameter (mean): 185 km
Aphelion: 2.914 AU
Perihelion: 1.935 AU
Semi-major axis: 2.425 AU
Orbital Period: 3.78 years
Rotation period: 7.27 hrs
Date discovered: 1847.7.1
Class: S
Type: Main-belt Asteroid
Satellite: 1 ?
(data from JPL Small-Body Database)

Orbit and Brightness

In brightness, Hebe is the fifth brightest object in the asteroid belt after Vesta, Ceres, Iris and Pallas. It has a mean opposition magnitude of +8.3, about equal to the mean brightness of Titan and can reach +7.5 at an opposition near perihelion.

Physical characteristics

Hebe containing around half a percent of the mass of the asteroid belt. Hebe's size/volume does not rank among the top twenty asteroids. But its apparently high bulk density is even greater than that of the Earth's Moon or even Mars. This high bulk density suggests an extremely solid body that has not been impacted by collisions, which is not typical of asteroids of its size, as they tend to be loosely bound rubble piles.

Lightcurve analysis suggests that Hebe has a rather angular shape, which may be due to several large impact craters. Hebe rotates in a prograde direction.

Major meteorite source

6 Hebe is the probable parent body of the H chondrite meteorites and the IIE iron meteorites. Remarkably, this would imply that it is the source of about 40% of all meteorites striking Earth. Evidence for this connection includes:

- The spectrum of Hebe matches a mix of 60% H chondrite and 40% IIE iron meteorite material.

- The IIE type are unusual among the iron meteorites, and probably formed from impact melt, rather than being fragments of the core of a differentiated asteroid.

- The IIE irons and H chondrites likely come from the same parent body, due to similar trace mineral and oxygen isotope ratios.

- Asteroids with spectra similar to the ordinary chondrite meteorites (accounting for 85% of all falls, including the H chondrites) are extremely rare.

- 6 Hebe is extremely well placed to send impact debris to Earth-crossing orbits. Ejecta with even relatively small velocities (~280 m/s) can enter the chaotic regions of the 3:1 Kirkwood gap at 2.50 AU and the nearby secular resonance which determines the high-inclination edge of the asteroid belt at about 16° inclinations hereabouts.

- Of the asteroids in this "well-placed" orbit, Hebe is the largest.

- An analysis of likely contributors to the Earth's meteorite flux places 6 Hebe at the top of the list, due to its position and relatively large size. If Hebe is not the H-chondrite parent body, then where are the meteorites from Hebe?

Satellite

On March 5, 1977 Hebe occulted Kaffaljidhma (γ Ceti), a moderately bright 3rd magnitude star. No other observed occultations by Hebe have been reported.

As a result of that occultation, a small Hebean moon was reported by Paul D. Maley. It was nicknamed "Jebe". However, the discovery has not been confirmed.

33th Largest Asteroid, 16 Psyche

16 Psyche is a large main-belt asteroids and the largest member of the Themistian asteroid family. Psyche is the 33th largest asteroid and is the most massive metallic M-type asteroid currently known.

Discovery

16 Psyche was discovered on 17 March 1852 by Annibale de Gasparis at Naples.

Naming

Psyche the asteroid was named after the Greek mythological figure Psyche.

In Greek mythology, Psyche was the deification of the human soul. She was portrayed in ancient mosaics as a goddess with butterfly wings (because psyche is also the Greek word for 'butterfly').

Psyche was originally the youngest daughter of the king and queen of Sicily, and the most beautiful person on the island. Suitors flocked to ask for her hand.

She eventually boasted that she was more beautiful than Aphrodite (Venus) herself, and Aphrodite sent Eros to transfix her with an arrow of desire, to make her fall in love with the nearest person or thing available. But even Eros (Cupid) fell in love with her, and took her to a secret place, eventually marrying her and having her made a goddess by Zeus (Jupiter).

Stats

Diameter (mean): 186 km
Aphelion: 3.328 AU
Perihelion: 2.521 AU
Semi-major axis: 2.922 AU
Orbital Period: 4.99 years
Rotation period: 4.20 hrs
Date discovered: 1852.3.17
Class: M
Type: Main-belt Asteroid

Physical Characteristics

Radar observations indicate Pysche has a fairly pure iron–nickel composition. Psyche appears to be a genuine case of an exposed metallic core from a larger differentiated parent body. Psyche is the most massive metallic M-type asteroid currently known.

Unlike some other M-type asteroids, Psyche shows no sign of the presence of water or water-bearing minerals on its surface, consistent with its interpretation as a metallic body. Small amounts of pyroxene appear to be present.

It is possible that at least some examples of enstatite chondrite meteorites originated from this asteroid, based on similar spectral analysis results.

Asteroid family ?

If Psyche is the core remnant of a larger parent body, we might expect other asteroids on similar orbits. However, we do not find any asteroid family belonging to Psyche.

One hypothesis is that the collision occurred very early in the Solar System's history, and all the other remnants have since been ground into fragments by subsequent collisions or had their orbits perturbed beyond recognition.

Star occultation

16 Psyche on August 21, 2010 occulted the star HIP 22112 in Taurus over a long path that passed from the central Baja peninsula to the central Atlantic coast. Maximum duration was predicted to be 10.3 seconds. For this event, 12 observers at 17 sites recorded 14 chords across the profile of the asteroid. Fifteen sites used video to record the event while one station used visual techniques and one station used drift scan.

The resulting chords and least squares ellipse produce a smooth ellipse with dimensions of 235.4 ± 3.9 x 230.4 ± 2.4 km. The maximum occultation duration of 10.12 seconds occurred at station nine and is just 2% shorter than predicted. The observed path was just 32 km north of the prediction.

Only two other occultations by Psyche have been observed: a single-chord event on 2002 March 22 and a five-chord occultation on 2004 May 16 (TYC 5783-01228-1). The four useable chords for the 2004 event were spaced well across the asteroid, being fit by an ellipse with axes of 214 ± 6 km by 181 ± 7 km.

32th Largest Asteroid, 128 Nemesis

128 Nemesis is a large asteroid in the main asteroid belt. It is the 32th largest asteroid currently known.

Discovery

Nemesis was discovered by James Craig Watson on November 25, 1872 from Ann Arbor, Michigan, USA.

Naming

Nemesis the asteroid was named after Nemesis, the goddess of retribution in Greek mythology.

In Greek mythology, Nemesis, also called Rhamnousia/Rhamnusia ("the goddess of Rhamnous") at her sanctuary at Rhamnous, north of Marathon, was the spirit of divine retribution against those who succumb to hubris (arrogance before the gods). The Greeks personified vengeful fate as a remorseless goddess: the goddess of revenge.

Stats

Diameter (mean): 188 km
Aphelion: 3.099 AU
Perihelion: 2.408 AU
Semi-major axis: 2.751 AU
Orbital Period: 4.56 years
Rotation period: 39 hrs
Date discovered: 1872.11.25
Class: C
Group: Nemesis group
Type: Main-belt Asteroid
Satellite: 0
(data from JPL Small-Body Database)

Orbit

Nemesis is the largest member of the Nemesian asteroid family bearing its name.

Physical Characteristics

Nemesis is a very dark main-belt asteroid, of carbonaceous composition.

Rotation

Nemesis rotates very slowly, taking about one and half Earth days (39 hours) to complete one revolution.

Extensive photoelectric lightcurves of Nemesis show that it has extremely long rotational period, the longest known currently for asteroids.

31th Largest Asteroid, 372 Palma

372 Palma is a large asteroid in the main asteroid belt. It is the 31th largest asteroid currently known.

Discovery

Palma was discovered by Auguste Honoré Charlois on August 19, 1893 from Nice.

Naming

Palma the asteroid is named for the capital city of Majorca, an island located in the Mediterranean Sea, one of the Balearic Islands (Spain), and south of France.

The capital of Majorca, Palma, was founded as a Roman camp called Palmaria upon the remains of a Talaiotic settlement. The turbulent history of the city saw it subject to several Vandal sackings during the fall of the Roman Empire. It was later reconquered by the Byzantines, colonised by the Moors (who called it Medina Mayurqa), and finally established by James I of Aragon. In 1983, Palma became the capital of the autonomous region of the Balearic Islands.

Palma the asteroid is one of seven of Charlois's discoveries that was expressly named by the Astromomisches Rechen-Institut (Astronomical Calculation Institute).

Stats

Diameter (mean): 189 km
Aphelion: 3.971 AU
Perihelion: 2.327 AU
Semi-major axis: 3.149 AU
Orbital Period: 5.59 years
Rotation period: 8.57 hrs
Date discovered: 1893.8.19
Class: B
Type: Main-belt Asteroid
(data from JPL Small-Body Database)

Star Occultation

On the morning of January 26, 2007 the occultation of the star 32 Lyncis by 372 Palma was observed.

The observations can be fit to an ellipse with dimensions 207 kilometers by 184 kilometers, to an accuracy of +/-2 km.

Moons of outer solar system - S/2007 (148780) 1 (moon of Altjira)

S/2007(148780)1, is a retrograde natural satellite of 148780 Altjira, which is a binary classical Kuiper belt object (cubewano).

S/2007(148780)1, is large compared to the primary, estimated diameter 246 km vs 340 km.

S/2007(148780)1 is the 25th largest moon in the Solar System currently known.

Discovery

S/2007(148780)1 was reported in March 2007.

Naming

Upon discovery, the moon was issued a provisional designation, S/2007 (148780)1.

Stats

Diameter (estimated): 246 km (200 - 360 km)

Semi-major axis: 9904 ± 56 km

Orbital Period: 139.56 days

Rotation Period: ?

How big is it?

Altjira and S/2007(148780)1 are so far away in the outer solar system that we don't know for sure how large they are. Because all we see is a dot of light, which is sunlight reflected off the surface of the TNO. But we don't know if the object is bright because it is large or if it is bright because it is highly reflective or both.

(28978) Ixion - 24th Largest TNO? 4th Largest Plutino ?

28978 Ixion is a trans-Neptunian object in the Kuiper belt. It is considered to be a dwarf planet by some astronomers, but the IAU has not formally designated it as such.

Ixion is possibly the 24th largest TNO and 4th largest Plutino currently known.

Discovery

Ixion was discovered on May 22, 2001 by Deep Ecliptic Survey (DES) at the Cerro Tololo Inter-American Observatory in the Atacama Desert of northern Chile.

Other than Pluto, Ixion was the first TNO discovered that was originally estimated to be larger than asteroid Ceres. Even in 2002, a year after its discovery, Ixion was still believed to be more than 1000 km in diameter. More recent estimates suggest that Ixion has a high albedo and is smaller than Ceres. Observations of Ixion by Spitzer Space Telescope in the far-infrared part of the spectrum revealed that its size is about 650 km.

Naming

Ixion the TNO is named after Ixion, a figure from Greek mythology. The name was suggested by E. K. Elliot.

In Greek mythology, Ixion was king of the Lapiths, the most ancient tribe of Thessaly. By killing his father-in-law, Ixion was reckoned the first man guilty of kin-slaying in Greek mythology. That alone would warrant him a terrible punishment.

However, Zeus had pity on Ixion and brought him to Olympus and introduced him at the table of the gods. Instead of being grateful, Ixion grew lustful for Hera, Zeus's wife, a further violation of guest-host relations.

Zeus thwarted this by creating the cloud Nephele, which resembled Hera and by whom Ixion fathered the Centaurs. For his crimes Ixion was bound to a wheel that turns forever in the underworld.

Stats

Estimated Diameter: 650 km (430 – 910 km)
Aphelion: 49.27 AU
Perihelion: 29.73 AU
Semi-major axis: 39.42 AU
Orbital Period: 247.53 years
Rotation period: ? hrs
Date discovered: 2001.5.22
Satellite: 0
Classification: TNO, KBO - Plutino

Orbit

Ixion is a plutino, locked in a 2:3 resonance with Neptune, making two revolutions around the Sun, while Neptune makes three.

Ixion and Pluto follow similar but differently oriented orbits: Ixion’s perihelion is below the ecliptic whereas Pluto's is above it. Uncharacteristically for bodies locked in resonance with Neptune (such as Orcus), Ixion approaches Pluto with less than 20 degrees of angular separation.

Ixion is currently crossing the ecliptic heading below, and will reach its perihelion in 2070. Pluto has passed its perihelion (1989) and is descending toward the ecliptic.

Ixion does demonstrate some regular changes in brightness, which are thought to be caused by its rotation. As of 2010, however, the rotation period of Ixion remains undetermined.

Physical characteristics

Ixion is moderately red in visible light and has a surface made of a mixture of tholin and water ice.

Ixion has a higher albedo (>0.15) than the mid-sized red cubewanos. There may be an absorption feature at the wavelength of 0.8 μm in its spectrum, which is commonly attributed to the alteration of surface materials by water.

Both visible and infrared spectroscopic results indicate that Ixion's surface is a mixture of water ice, dark carbon and tholin, which is a heteropolymer formed by irradiation of clathrates of water and organic compounds.

The Very Large Telescope (VLT) has checked Ixion for cometary activity, but did not detect a coma. Ixion is currently about 41 AU from the Sun, and it is possible that Ixion could develop a coma or temporary atmosphere when it is closer to perihelion.

How big is it?

Ixion is so far away in the outer solar system that we don't know for sure how large it is. Because all we see is a dot of light, which is sunlight reflected off the surface of the TNO. But we don't know if the object is bright because it is large or if it is bright because it is highly reflective or both.

2010 KZ39 - 23th Largest TNO? 10th Largest Cubewano ?

2010 KZ39 is a large trans-Neptunian object. 2010 KZ39 is possibly the 23th largest TNO and 10th largest Cubewano currently known.

Discovery

2010 KZ39 was discovered by Andrzej Udalski, Scott S. Sheppard, M. Szymanski and Chad Trujillo on May 21, 2010 at Las Campanas Observatory, located in the southern Atacama Desert of Chile.

2010 KZ39 has been observed 19 times over two oppositions.

Stats

Estimated Diameter: 661 km (440 – 980 km)
Aphelion: 52.5 AU
Perihelion: 39.11 AU
Semi-major axis: 45.75 AU
Orbital Period: 309.44 years
Rotation period: ?
Date discovered: 2010.5.21
Satellite: ?
Classification: TNO, KBO - Cubewano

Orbit

2010 KZ39 is currently 46.3 AU from the Sun. Using the best-fit values for its orbit it is expected to come to perihelion in 2085.

Physical Characteristics

Very little is known about 2010 KZ39.

How big is it?

2010 KZ39 is so far away in the outer solar system that we don't know for sure how large it is. Because all we see is a dot of light, which is sunlight reflected off the surface of the TNO. But we don't know if the object is bright because it is large or if it is bright because it is highly reflective or both.

Dwarf planet candidate?

Assuming a generic trans-Neptunian albedo of 0.09, it would be about 735 km in diameter. But since its albedo is unknown and it has a preliminary absolute magnitude of 3.9, it could easily be somewhere between 440 (albedo: 0.25) and 980 km (albedo: 0.05) in diameter.

Mike Brown's automatically updated website lists it as a highly likely dwarf planet.

(145452) 2005 RN43 - 22th Largest TNO? 9th Largest Cubewano ?

2005 RN43 is a large trans-Neptunian object. 2005 RN43 is possibly the 22th largest TNO and 9th largest Cubewano currently known.

Discovery

2005 RN43 was discovered by Andrew C. Becker, Andrew W. Puckett and Jeremy M. Kubica on September 10, 2005 at Apache Point Observatory in Sunspot, New Mexico.

2005 RN43 has been observed 119 times over 13 oppositions with precovery images back to 1954.

Stats

Estimated Diameter: 661 km
Aphelion: 42.55 AU
Perihelion: 40.55 AU
Semi-major axis: 41.61 AU
Orbital Period: 268.45 years
Rotation period: 5.62 hours
Date discovered: 2005.9.10
Satellite: 0
Classification: TNO, KBO - Cubewano

Classification

The Minor Planet Center (MPC) classifies it as a cubewano. But since 2005 RN43 has an inclination of 19.3°, and it is unknown how it acquired this moderate inclination, the Deep Ecliptic Survey (DES) classifies it as scattered-extended.

Physical Characteristics

Very little is known about 2005 RN43.

How big is it?

2005 RN43 is so far away in the outer solar system that we don't know for sure how large it is. Because all we see is a dot of light, which is sunlight reflected off the surface of the TNO. But we don't know if the object is bright because it is large or if it is bright because it is highly reflective or both.

Dwarf planet candidate?

2005 RN43 is very likely a dwarf planet. Mike Brown's automatically updated website lists it as a highly likely dwarf planet, but the diameter of the object has never been measured.

(90568) 2004 GV9 - 21th Largest TNO? 8th Largest Cubewano ?

2004 GV9 is a large trans-Neptunian object. 2004 GV9 is possibly the 21th largest TNO and 8th largest Cubewano currently known.

Discovery

2004 GV9 was discovered on April 13, 2004, by the Near-Earth Asteroid Tracking (NEAT) at Palomar.

2004 GV9 has been observed 47 times with precovery images back to 1954.

Stats

Estimated Diameter: 677 km (677 ± 70 km)
Aphelion: 45.74 AU
Perihelion: 38.7 AU
Semi-major axis: 41.81 AU
Orbital Period: 270.37 years
Rotation period: 5.86 hours
Date discovered: 2004.4.13
Satellite: 0
Classification: TNO, KBO - Cubewano

Physical Characteristics

Very little is known about 2004 GV9.

How big is it?

2004 GV9 is so far away in the outer solar system that we don't know for sure how large it is. Because all we see is a dot of light, which is sunlight reflected off the surface of the TNO. But we don't know if the object is bright because it is large or if it is bright because it is highly reflective or both.

Dwarf planet candidate?

2004 GV9 is very likely a dwarf planet. The Spitzer Space Telescope has estimated it to have a diameter of 677 ± 70 km. Light-curve-amplitude analysis shows only small deviations, suggesting that 2004 GV9 could be a spheroid with small albedo spots and hence a dwarf planet.

2010 EK139 - 20th Largest TNO?

2010 EK139 is a large, 2:7 resonant trans-Neptunian object.

Discovery

2010 EK139 was discovered on March 13, 2010 by astronomers from the OGLE team led by Andrzej Udalski from Warsaw University.

There are precovery images dating back to 2002.

Stats

Estimated Diameter: 677 km (462 – 1033 km)
Aphelion: 106.25 AU
Perihelion: 32.49 AU
Semi-major axis: 68.91 AU
Orbital Period: 572 years
Rotation period: ? hrs
Date discovered: 2010.3.13
Satellite: 0
Classification: TNO, 2:7 resonance

Orbit

2010 EK139 will come to perihelion around 2038, and is currently 39.1 AU from the Sun.

2010 EK139 has been observed 122 times over 5 oppositions and has an orbit quality of 2 [JPL ranks orbital quality from 0 to 9 (0 being best)].

A ten million year integration of the orbit shows that 2010 EK139 may be in a 7:2 resonance with Neptune.

How big is it?

2010 EK139 is so far away in the outer solar system that we don't know for sure how large it is. Because all we see is a dot of light, which is sunlight reflected off the surface of the TNO. But we don't know if the object is bright because it is large or if it is bright because it is highly reflective or both.

Dwarf-planet candidate

Assuming a generic trans-Neptunian albedo of 0.09, but since the true albedo is unknown and it has an absolute magnitude of 3.8, 2010 EK139 could easily be from about 462 to 1033 km in diameter.

Mike Brown lists 2010 EK139 as highly likely dwarf planet.

2006 QH181 - 19th Largest TNO? 5th Largest SDO ?

2006 QH181 is a large trans-Neptunian object. 2006 QH181 is possibly the 19th largest TNO and 5th largest SDO currently known.

Discovery

2006 QH181 was discovered on August 21, 2006. The discover was not known.

Stats

Estimated Diameter: 677 km (460 - 1030 km)
Aphelion: 97.02 AU
Perihelion: 38.24 AU
Semi-major axis: 67.71 AU
Orbital Period: 557.16 years
Rotation period: ?
Date discovered: 2006.8.21
Classification: TNO, SDO, 1:5 resonance?

Orbit

2006 QH181 came to perihelion around 1859. 2006 QH181 is currently 82.7 AU from the Sun. The only dwarf-planet-type bodies currently further from the Sun are Eris (96 AU), Sedna (87 AU) and 2007 OR10 (86 AU). Being so far from the Sun, it only has an apparent magnitude of 23.

2006 QH181 has been observed 10 times over only 2 oppositions and thus currently has a poorly known orbit. JPL ranks orbital quality from 0 to 9 (0 being best), and 2006 QH181 is currently listed with a poor orbital quality of 8.

2006 QH181 could be part of the scattered disc. 2006 QH181 may be a detached object since a perihelion of 38.24 AU may place it outside of the direct influence of Neptune, or it could have a 5:1 resonance with Neptune. Further observations of the orbit will be required.

How big is it?

2006 QH181 is so far away in the outer solar system that we don't know for sure how large it is. Because all we see is a dot of light, which is sunlight reflected off the surface of the TNO. But we don't know if the object is bright because it is large or if it is bright because it is highly reflective or both.

Dwarf-planet candidate

Mike Brown lists 2006 QH181 as highly likely dwarf planet.

12th Largest Moon of Neptune - Laomedeia (11th Moon outwards from Neptune)

Laomedeia is a prograde irregular satellite of Neptune.

Laomedeia is the 12th largest satellite of Neptune and 71th largest moon in the Solar System currently known.

Discovery

Laomedeia was discovered 13 August 2002 by Matthew J. Holman, John J. Kavelaars, Tommy Grav, Wesley C. Fraser and Dan Milisavljevic using images taken by the 4.0-m Blanco telescope at the Cerro Tololo Inter-American Observatory in Chile and the 3.6-m Canada-France-Hawaii Telescope in Hawaii. Multiple images were digitally combined until stars appeared as streaks, while the moons appeared as points of light.

Laomedeia is so distant and so small it is about 100 million times fainter than can be seen with the unaided eye. Laomedeia was missed by the Voyager 2 spacecraft in 1989 because it is so faint and distant from Neptune.

Naming

The moon was given the temporary designation S/2002 N3.

Laomedeia the moon is named after one of the Nereids, the fifty daughters of Nereus and Doris. Laomedeia was The Nereid "leader of the folk".

Orbit

Laomedeia is considered an irregular satellite because of its distant, eccentric orbit around Neptune. Like most irregular satellites of the giant planets in our outer solar system, Laomedeia most likely formed after a collision between a larger moon and a comet or an asteroid.

Physical characteristics

Very little is known about Laomedeia.

Laomedeia is about 42 kilometers in diameter (assuming an albedo of 0.04).