385446 Manwë , or (385446) Manwë–Thorondor , is a binary

resonant Resonance describes the phenomenon of increased amplitude that occurs when the frequency of an applied periodic force (or a Fourier component of it) is equal or close to a natural frequency of the system on which it acts. When an oscilla ...

Kuiper belt object in a 4:7 mean-motion resonance with Neptune. It was discovered on 25 August 2003, by American astronomer

Marc Buie Marc William Buie (; born 1958) is an American astronomer and prolific discoverer of minor planets who works at the Southwest Research Institute in Boulder, Colorado in the Space Science Department. Formerly he worked at the Lowell Observatory ...

at Cerro Tololo Observatory in northern Chile. A study of Manwë's

light curve In astronomy, a light curve is a graph of light intensity of a celestial object or region as a function of time, typically with the magnitude of light received on the y axis and with time on the x axis. The light is usually in a particular frequ ...

in 2019 suggests that it may be a

contact binary In astronomy, a contact binary is a binary star system whose component stars are so close that they touch each other or have merged to share their gaseous envelopes. A binary system whose stars share an envelope may also be called an overconta ...

object.

Discovery and naming

Manwë was discovered on 25 August 2003 by M. W. Buie at Cerro Tololo as a part of the

Deep Ecliptic Survey The Deep Ecliptic Survey (DES) is a project to find Kuiper belt objects (KBOs), using the facilities of the National Optical Astronomy Observatory (NOAO). The principal investigator is Robert L. Millis. Since 1998 through the end of 2003, the ...

. The object was named after Manwë, the fictional king of the Valar in

J. R. R. Tolkien John Ronald Reuel Tolkien (, ; 3 January 1892 – 2 September 1973) was an English writer and philologist. He was the author of the high fantasy works ''The Hobbit'' and ''The Lord of the Rings''. From 1925 to 1945, Tolkien was the Rawlins ...

Middle-earth Middle-earth is the fictional setting of much of the English writer J. R. R. Tolkien's fantasy. The term is equivalent to the '' Miðgarðr'' of Norse mythology and ''Middangeard'' in Old English works, including ''Beowulf''. Middle-earth is ...

legendarium Tolkien's legendarium is the body of J. R. R. Tolkien's mythopoeic writing, unpublished in his lifetime, that forms the background to his ''The Lord of the Rings'', and which his son Christopher summarized in his compilation of ''The Silmaril ...

. Manwë is foremost among the great spirits who rule the world, and takes special responsibility for the air and winds. Thorondor is the Lord of Eagles in the First Age in Tolkien's writing.

Physical properties

Manwë has significant and irregular photometric variability, demonstrating that its components are not tidally locked. The surfaces of Manwë and Thorondor appear to be very red. The composition of Manwë is unknown but likely to be mostly ice, because the nominal density (with large uncertainty) is less than that of water. At least one other Kuiper belt object, , has been found with a density of less than 1 g/cm³, which implies an object made mostly of ice with a low rock fraction and high porosity.

Orbit

Manwë orbits the

Sun The Sun is the star at the center of the Solar System. It is a nearly perfect ball of hot plasma, heated to incandescence by nuclear fusion reactions in its core. The Sun radiates this energy mainly as light, ultraviolet, and infrared radi ...

at an average distance of about , taking 289 years to complete a full orbit. Manwë has a low

orbital inclination Orbital inclination measures the tilt of an object's orbit around a celestial body. It is expressed as the angle between a reference plane and the orbital plane or axis of direction of the orbiting object. For a satellite orbiting the Earth ...

of 2.6 degrees. Its orbit is elongated, with an orbital eccentricity of 0.11. Due to its eccentric orbit, Manwë's distance from the Sun varies over the course of its orbit, approaching 38.9 AU at

perihelion An apsis (; ) is the farthest or nearest point in the orbit of a planetary body about its primary body. For example, the apsides of the Earth are called the aphelion and perihelion. General description There are two apsides in any elli ...

and 48.6 AU at

aphelion An apsis (; ) is the farthest or nearest point in the orbit of a planetary body about its primary body. For example, the apsides of the Earth are called the aphelion and perihelion. General description There are two apsides in any ell ...

Satellite

Physical characteristics

Being part of a binary system, Manwë has one known companion named Thorondor, formally designated (385446) Manwë I Thorondor. It is estimated to be about two-thirds the size of the primary, approximately for a volume equivalent diameter. The rotation period of Thorondor is uncertain, though a best-fit model suggests a very slow rotation period of 309.3 days. Thorondor's rotation is expected to be

chaotic Chaotic was originally a Danish trading card game. It expanded to an online game in America which then became a television program based on the game. The program was able to be seen on 4Kids TV (Fox affiliates, nationwide), Jetix, The CW4Kid ...

like Pluto's smaller moons, as a result of gravitational torquing by Manwë over the course of their eccentric mutual orbit. Thorondor's

has considerable photometric variability, with the relative magnitude of the two objects measured variously from 0.6–2.1 over the course of a few years. This implies that Thorondor could have a very flattened shape, akin to the larger lobe of the

Kuiper belt object

486958 Arrokoth Arrokoth (minor-planet designation 486958 Arrokoth; provisional designation ), formerly nicknamed Ultima Thule, is a trans-Neptunian object located in the Kuiper belt. Arrokoth became the farthest and most primitive object in the Solar System ...

. Assuming a ellipsoid shape for Thorondor, a best-fit model for its shape suggests the aspect ratios of ''a''/''c'' = 7.33 and ''b''/''c'' = 6.67.

Orbit

The satellite's orbit has the following parameters: semi-major-axis, ; period, ; eccentricity, ; and inclination, The total system mass is about 1.94 kg.

Mutual events

Manwë and Thorondor were expected to go through a period of mutual occultations and transits from 2014–2018, where one object crosses in front of the other as seen from Earth.

Pluto Pluto (minor-planet designation: 134340 Pluto) is a dwarf planet in the Kuiper belt, a ring of bodies beyond the orbit of Neptune. It is the ninth-largest and tenth-most-massive known object to directly orbit the Sun. It is the largest ...

and Charon went through a similar series of mutual events from 1985–1990. Observations of these events could allow for better estimates of the radii of the two objects and their densities, as well as possibly determining their shapes and mapping surface color and albedo features. The first event, an inferior occultation, is predicted for 2014 July 16, and they continue until 2018 October 25. The actual observations revealed none of the four predicted occultations, likely due error measuring orbital period of Thorondor, although photometry data gathered during observation campaign have allowed to determine Manwë is highly bilobate contact binary, likely surrounded by rapidly orbiting

moonlet A moonlet, minor moon, minor natural satellite, or minor satellite is a particularly small natural satellite orbiting a planet, dwarf planet, or other minor planet. Up until 1995, moonlets were only hypothetical components of Saturn's F-ring ...

s besides Thorondor.

References

External links

* * {{DEFAULTSORT:Manwe 385446 Discoveries by Marc Buie Named minor planets Binary trans-Neptunian objects 20030825 385446 Things named after Tolkien works