Hundreds of millions of miles beyond the orbit of Neptune lurks one of the most intriguing objects in the Solar System, 50000 Quaoar.
The Mighty 50000 Quaoar 50000 Quaoar is notable for multiple reasons, but the most apparent is its name. Quaoar is the name of the creator deity of the Tongva people in the Los Angeles Basin. The deity Quaoar was believed to have control of a group of “avengers” who spied on humanity and enforced Quaoar’s will. While 50000 Quaoar certainly has an impressive namesake, the 50000 portion is also interesting from an astronomical point of view.
Ordinarily, Solar System objects will be named along with a number denoting how many similar objects had been found before. For instance, 1154 Astronomia was the 1154th minor planet found in the solar system. This chart has all of the minor planets found in order. But for a Solar System object as interesting as Quaoar, scientists decided to break entirely with this tradition to give it a number more fitting to its power; thus we have 50,000 Quaoar.
Another interesting fact concerning Quaoar is that it is a cubewano, and despite the fact that WordPress has underlined it in red on my screen, this strange term cubewano is really an English word. It comes from the provisional name of trans-Neptunian object 15760 Albion, 1992 QB1. 1992 QB1 was left unnamed for over two decades, so whenever another trans-Neptunian object was located it was named after this provisional name (if you say QB1 fast enough it begins to sound like cubewano).
Cubewanos are often very large. The largest of them Makemake is actually a dwarf planet, although this isn’t unique to Makemake. 50000 Quaoar may also be a dwarf planet, and it even has its own 50 km moon, Weywot.
Orbit and classification Ecliptic view of Quaoar's orbit (blue) compared to Pluto (red) and Neptune (white). The approximate perihelion (q) and aphelion (Q) dates are marked for their respective orbits.
Polar view of Quaoar's orbit (yellow) along with various other large Kuiper belt objects Quaoar orbits the Sun at an average distance of 43.7 astronomical units (6.54×109 km; 4.06×109 mi), taking 288.8 years to complete one full orbit around the Sun. With an orbital eccentricity of 0.04, Quaoar follows a nearly circular orbit, only slightly varying in distance from 42 AU at perihelion to 45 AU at aphelion. At such distances, light from the Sun takes more than 5 hours to reach Quaoar. Quaoar has last passed aphelion in late 1932 and is currently approaching the Sun at a rate of 0.035 AU per year, or about 0.17 kilometres per second (380 mph). Quaoar will reach perihelion around February 2075.
Because Quaoar has a nearly circular orbit, it does not approach close to Neptune such that its orbit can become significantly perturbed under the gravitational influence of Neptune. Quaoar's minimum orbit intersection distance from Neptune is only 12.3 AU—it does not approach Neptune within this distance over the course of its orbit, as it is not in a mean-motion orbital resonance with Neptune. Simulations by the Deep Ecliptic Survey show that the perihelion and aphelion distances of Quaoar's orbit do not change significantly over the next 10 million years; Quaoar's orbit appears to be stable over the long term.
Quaoar is generally classified as a trans-Neptunian object or distant minor planet by the Minor Planet Centre since it orbits in the outer Solar System beyond Neptune. Since Quaoar is not in a mean-motion resonance with Neptune, it is also classified as a classical Kuiper belt object (cubewano) by the Minor Planet Centre and Deep Ecliptic Survey. Quaoar's orbit is moderately inclined to the ecliptic plane by 8 degrees, relatively high when compared to the inclinations of Kuiper belt objects within the dynamically cold population. Because Quaoar's orbital inclination is greater than 4 degrees, it is part of the dynamically hot population of high-inclination classical Kuiper belt objects. The high inclinations of hot classical Kuiper belt objects such as Quaoar are thought to have resulted from gravitational scattering by Neptune during its outward migration in the early Solar System.
At the time of its discovery in 2002, Quaoar was the largest object found in the Solar System since the discovery of Pluto. Quaoar's size was subsequently revised downward and was later superseded in size as larger objects (Eris, Haumea, Makemake and Gonggong) were discovered. The uncorrected 2004 Hubble estimates only marginally agree with the 2007 infrared measurements by the Spitzer Space Telescope that suggest a higher albedo (0.19) and consequently a smaller diameter (844.4+206.7 −189.6 km). Adopting a Uranian satellite limb darkening profile suggests that the 2004 Hubble size estimate for Quaoar was approximately 40 percent too large, and that a more proper estimate would be about 900 km. In 2010, Quaoar was estimated to be about 890 km in diameter, using a weighted average of Spitzer and corrected Hubble estimates. In observations of the object's shadow as it occulted an unnamed 16th-magnitude star on 4 May 2011, Quaoar was estimated to be 1,170 km (730 mi) in diameter. Measurements from the Herschel Space Observatory in 2013 suggested that Quaoar has a diameter of 1,070 km (660 mi). In that same year, Quaoar occulted a 15.8 magnitude star, yielding a chord length of 1100±5 km, consistent with the Herschel estimate. Another occultation by Quaoar in June 2019 also yielded a similar chord length of 1121±1.2 km.
In 2004, signs of crystalline ice were found on Quaoar, indicating that the temperature rose to at least 110 K (−163 °C) sometime in the last ten million years. Speculation began as to what could have caused Quaoar to heat up from its natural temperature of 55 K (−218.2 °C). Some have theorized that a barrage of mini-meteors may have raised the temperature, but the most discussed theory speculates that cryovolcanism may be occurring, spurred by the decay of radioactive elements within Quaoar's core. Since then (2006), crystalline water ice was also found on Haumea, but present in larger quantities and thought to be responsible for the very high albedo of that object (0.7). More precise observations of Quaoar's near infrared spectrum in 2007 indicated the presence of small quantities (5%) of solid methane and ethane. Given its boiling point of 112 K (−161 °C), methane is a volatile ice at average surface temperatures of Quaoar, unlike water ice or ethane. Both models and observations suggest that only a few larger bodies (Pluto, Eris, and Makemake) can retain the volatile ices whereas the dominant population of small TNOs lost them. Quaoar, with only small amounts of methane, appears to be in an intermediary category.
Rotation Quaoar's rotation period is uncertain, and two possible rotation periods of Quaoar are given (8.64 hours or 17.68 hours). Derived from the rotational light curves of Quaoar observed on March through June 2003, its rotation period is measured to be 17.6788 hours.
Satellite Main article: Weywot (moon) Quaoar has one known moon, Weywot (full designation (50000) Quaoar I Weywot), discovered in 2006. It is thought to be somewhere around 170 km (110 mi) in diameter.
Exploration Quaoar from New Horizons, viewed at a distance of 14 AU. It was calculated that a flyby mission to Quaoar could take 13.57 years using a Jupiter gravity assist, based on launch dates of 25 December 2016, 22 November 2027, 22 December 2028, 22 January 2030 or 20 December 2040. Quaoar would be 41 to 43 AU from the Sun when the spacecraft arrives. In July 2016, the Long Range Reconnaissance Imager (LORRI) aboard the New Horizons spacecraft took a sequence of four images of Quaoar from a distance of about 14 AU. Pontus Brandt at Johns Hopkins Applied Physics Laboratory and his colleagues have studied an interstellar probe that would potentially fly by Quaoar in the 2030s before continuing to the interstellar medium, and the China National Space Administration has considered it as a potential target for the first Interstellar Express probe designed to explore the heliosphere. Quaoar has been chosen as a flyby target for missions like these particularly for its escaping methane atmosphere and possible cryovolcanism, as well as its close proximity to the heliospheric nose.
