Dysnomia (moon)

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Dysnomia
Eris and dysnomia2.jpg
Dysnomia, to the left, and Eris, center
(Hubble Space Telescope)
Discovery
Discovered by Brown et al. [1] [2]
Discovery dateSeptember 10, 2005 [2]
Designations
Designation
Eris I
Pronunciation /dɪsˈnmiə/ [lower-alpha 1]
Named after
Δυσνομία Dysnomia
S/2005 (2003 UB313) 1
Dy /ˈd/ (nickname)
Gabrielle (nickname)
Adjectives Dysnomian
Orbital characteristics [3]
Epoch 31 August 2006 (JD 2453979.0)
37273±64 km
Eccentricity 0.0062±0.0010
15.785899±0.000050  d
Average orbital speed
0.172 km/s [lower-alpha 2]
Inclination 45.49° ±0.15° (to geocentric equator)
78.29°±0.65°(to Eris's orbit)
126.17°±0.26°
Satellite of Eris
Physical characteristics
Mean diameter
700±115 km [4]
Mean radius
350±57.5 km [4]
Mass estimated 1115 system mass, or 143×1018 kg, at density 0.8 g/cm3, to 137 system mass, or 445×1018 kg, if same density as Eris [4]
Albedo 0.04+0.02
−0.01
[4]
~25.4 [lower-alpha 3]
~5.6 [lower-alpha 3] [5] [4]

Dysnomia (formally (136199) Eris I Dysnomia) is the only known moon of the dwarf planet Eris and likely the second-largest known moon of a dwarf planet, after Pluto I Charon. It was discovered in 2005 by Mike Brown and the laser guide star adaptive optics team at the W. M. Keck Observatory, and carried the provisional designation of S/2005 (2003 UB313) 1 until officially named Dysnomia [6] (from the Ancient Greek word Δυσνομία meaning anarchy/lawlessness) after the daughter of the Greek goddess Eris.

Contents

Dysnomia has an estimated diameter of 700±115 km (25% to 35% of Eris's diameter), and is among the dozen or so largest objects in the trans-Neptunian region. [4]

Discovery

Artist's conception of dwarf planet Eris seen from above the surface of Dysnomia Eris Seen From Above Dysnomia.jpg
Artist's conception of dwarf planet Eris seen from above the surface of Dysnomia

During 2005, the adaptive optics team at the Keck telescopes in Hawaii carried out observations of the four brightest Kuiper belt objects (Pluto, Makemake, Haumea, and Eris), using the newly commissioned laser guide star adaptive optics system. Observations taken on September 10, 2005, revealed a moon in orbit around Eris, provisionally designated S/2005 (2003 UB313) 1. In keeping with the Xena nickname that was already in use for Eris, the moon was nicknamed "Gabrielle" by its discoverers, after Xena's sidekick. [7] [8]

Physical characteristics

Dysnomia has an estimated diameter of 700 ± 115 km with an albedo of 0.04+0.02
−0.01
. The estimate was obtained using radiometric observation by ALMA observatory in submillimeter spectral region. A wide range of potential masses for the satellite is possible, depending on its density, with a system mass ratio of anywhere from 37:1 to 115:1. Thus Dysnomia's mass could be anywhere from 0.143×1021 kg with a minimal 0.8 g/cm3 density, to 0.445×1021 kg if his has the same density as Eris. However, given the extreme difference in albedo, it is unlikely that Dysnomia is a solid body like Eris, and something toward the low end of that range is more likely. [4]

Although the shape of Dysnomia is not known, it is presumed to have a spherical shape due to its large dimensions; it is larger than the three smallest ellipsoidal moons of Saturn and Uranus (Enceladus, Mimas, and Miranda). [9]

In its discovery images Dysnomia was ~60 times fainter (or 4.43 magnitudes) than Eris in the K band, [10] [11] and later observations with the Hubble Space Telescope found it to be 500 times fainter in the visible band. [5] This indicates a very different, and quite redder, spectrum, indicating a significantly darker surface. [12] Of the known moons of dwarf planets, only Charon is larger than Dysnomia.

Orbit

Combining Keck and Hubble observations, the orbit of Dysnomia was used to determine the mass of Eris through Kepler's third law of planetary motion. Dysnomia's average orbital distance from Eris is approximately 37,300 km (23,200 mi), with a calculated orbital period of 15.786 days, or approximately half a month. [3] This shows that the mass of Eris is 1.27 times that of Pluto. [13] [14] Extensive observations by Hubble indicate that Dysnomia has a nearly circular orbit around Eris, with a low orbital eccentricity of 0.0062±0.0010. Over the course of Dysnomia's orbit, its distance from Eris varies by 462 ± 105 km (287 ± 65 mi) due to its slightly eccentric orbit. [3]

Dynamical simulations of Dysnomia suggest that its orbit should have completely circularized through mutual tidal interactions with Eris within timescales of 5–17 million years, regardless of the moon's density. A non-zero eccentricity would thus mean that Dysnomia's orbit is being perturbed, possibly due to the presence of an additional inner satellite of Eris. However, it is possible that the measured eccentricity is not real, but due to interference of the measurements by albedo features, or to systematic errors. [3]

From Hubble observations from 2005 to 2018, the inclination of Dysnomia's orbit with respect to Eris's heliocentric orbit is calculated to be approximately 78°. Since the inclination is less than 90°, Dysnomia's orbit is therefore prograde relative to Eris's orbit. In 2239, Eris and Dysnomia will enter a period of mutual events in which Dysnomia's orbital plane is aligned edge-on to the Sun, allowing for Eris and Dysnomia to take turns eclipsing each other. [3]

Formation

Astronomers now know that the six brightest Kuiper belt objects (KBOs) have satellites. Among the fainter members of the belt only about 10% are known to have satellites. This is thought to imply that collisions between large KBOs have been frequent in the past. Impacts between bodies of the order of 1000 km across would throw off large amounts of material that would coalesce into a moon. A similar mechanism is thought to have led to the formation of the Moon when Earth was struck by a giant impactor early in the history of the Solar System.

Name

Artistic comparison of Pluto, Eris, Haumea, Makemake, Gonggong, Quaoar, Sedna, Orcus, Salacia, 2002 MS4, and Earth along with the Moon
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e EightTNOs.pngCharonCharonNixNixKerberosStyxHydraHydraDysnomiaDysnomiaErisErisNamakaNamakaHi'iakaHi'iakaMK2MK2XiangliuXiangliuGonggongGonggongWeywotWeywotQuaoarQuaoarSednaSednaVanthVanthOrcusOrcusActaeaActaeaSalaciaSalacia2002 MS42002 MS4
Artistic comparison of Pluto, Eris, Haumea, Makemake, Gonggong, Quaoar, Sedna, Orcus, Salacia, 2002 MS4 , and Earth along with the Moon

Mike Brown, the moon's discoverer, chose the name Dysnomia for the moon. As the daughter of Eris, the mythological Dysnomia fit the established pattern of naming moons after gods associated with the primary body (hence, Jupiter's largest moons are named after lovers of Jupiter, while Saturn's are named after his fellow Titans). Also, the English translation of "Dysnomia", "lawlessness", echoes Lucy Lawless, the actress who played Xena in Xena: Warrior Princess on television. Before receiving their official names, Eris and Dysnomia had been nicknamed "Xena" and "Gabrielle", though Brown states that the connection was accidental. [15]

A primary reason for the name was its similarity to the name of Brown's wife, Diane, following a pattern established with Pluto. Pluto owes its name in part to its first two letters, which form the initials of Percival Lowell, the founder of the observatory where its discoverer, Clyde Tombaugh, was working, and the person who inspired the search for "Planet X". James Christy, who discovered Charon, did something similar by adding the Greek ending -on to Char, the nickname of his wife Charlene. (Christy wasn't aware that the resulting 'Charon' was a figure in Greek mythology.) "Dysnomia", similarly, has the same first letter as Brown's wife, Diane, [16] and Brown uses the nickname "Dy" /ˈdaɪ/ for the moon, which he pronounces the same as his wife's nickname, Di. Because of this, Brown pronounces the full name /dsˈnmiə/ , with a long "y" sound. [17]

Notes

  1. Brown uses the pronunciation /dsˈnmiə/ .
  2. The orbital period (P) is 15.774 d. The orbital circumference (C) is 2π*semi-major axis. Dividing these (P/C) using the correct units gives 0.172 km/s.
  3. 1 2 Dysnomia's brightness is 1/500 of Eris in the visible band. With H = −1.19 for Eris, this gives H ≈ 5.6 for Dysnomia.

Related Research Articles

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Kuiper belt Area of the Solar System beyond the planets, comprising small bodies

The Kuiper belt is a circumstellar disc in the outer Solar System, extending from the orbit of Neptune at 30 astronomical units (AU) to approximately 50 AU from the Sun. It is similar to the asteroid belt, but is far larger – 20 times as wide and 20–200 times as massive. Like the asteroid belt, it consists mainly of small bodies or remnants from when the Solar System formed. While many asteroids are composed primarily of rock and metal, most Kuiper belt objects are composed largely of frozen volatiles, such as methane, ammonia and water. The Kuiper belt is home to three objects identified as dwarf planets by the IAU: Pluto, Haumea and Makemake. Some of the Solar System's moons, such as Neptune's Triton and Saturn's Phoebe, may have originated in the region.

Pluto Dwarf planet in the Kuiper belt of the Solar System

Pluto is a dwarf planet in the Kuiper belt, a ring of bodies beyond the orbit of Neptune. It was the first and the largest Kuiper belt object to be discovered. After Pluto was discovered in 1930, it was declared to be the ninth planet from the Sun. Beginning in the 1990s, its status as a planet was questioned following the discovery of several objects of similar size in the Kuiper belt and the scattered disc, including the dwarf planet Eris. This led the International Astronomical Union (IAU) in 2006 to formally define the term "planet"—excluding Pluto and reclassifying it as a dwarf planet.

Charon (moon) Largest natural satellite of Pluto

Charon, known as (134340) Pluto I, is the largest of the five known natural satellites of the dwarf planet Pluto. It has a mean radius of 606 km (377 mi). Charon is the sixth-largest known trans-Neptunian object after Pluto, Eris, Haumea, Makemake and Gonggong. It was discovered in 1978 at the United States Naval Observatory in Washington, D.C., using photographic plates taken at the United States Naval Observatory Flagstaff Station (NOFS).

Natural satellite Astronomical body that orbits a planet

A natural satellite is in the most common usage, an astronomical body that orbits a planet, dwarf planet, or small solar system body. While natural satellites are often colloquially referred to as moons, there is only the Moon of Earth.

Minor-planet moon Natural satellite of a minor planet

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90482 Orcus Trans-Neptunian object and dwarf planet

90482 Orcus, provisional designation 2004 DW, is a trans-Neptunian dwarf planet with a large moon, Vanth. It has a diameter of 910 km (570 mi). The surface of Orcus is relatively bright with albedo reaching 23 percent, neutral in color and rich in water ice. The ice is predominantly in crystalline form, which may be related to past cryovolcanic activity. Other compounds like methane or ammonia may also be present on its surface. Orcus was discovered by American astronomers Michael Brown, Chad Trujillo, and David Rabinowitz on 17 February 2004.

Chad Trujillo American astronomer

Chadwick A. Trujillo is an American astronomer, discoverer of minor planets and the co-discoverer of Eris, the most massive dwarf planet known in the Solar System.

Haumea Dwarf planet in the Solar System

Haumea is a dwarf planet located beyond Neptune's orbit. It was discovered in 2004 by a team headed by Mike Brown of Caltech at the Palomar Observatory in the United States and disputably also in 2005 by a team headed by José Luis Ortiz Moreno at the Sierra Nevada Observatory in Spain, though the latter claim has been contested. On September 17, 2008, it was named after Haumea, the Hawaiian goddess of childbirth, under the expectation by the International Astronomical Union (IAU) that it would prove to be a dwarf planet. Nominal estimates make it the third-largest known trans-Neptunian object, after Eris and Pluto, though the uncertainty in best-fit modeling slightly overlaps with the larger size estimates for Makemake.

Makemake Dwarf planet in the Outer Solar System

Makemake is a dwarf planet and perhaps the second-largest Kuiper belt object in the classical population, with a diameter approximately two-thirds that of Pluto. It has one known satellite. Its extremely low average temperature, about 40 K (−230 °C), means its surface is covered with methane, ethane, and possibly nitrogen ices.

Hiʻiaka (moon) Larger moon of Haumea

Hiʻiaka is the larger, outer moon of the trans-Neptunian dwarf planet Haumea. It is named after one of the daughters of Haumea, Hiʻiaka, the patron goddess of the Big Island of Hawaii. It orbits once every 49.12±0.03 d at a distance of 49880±198 km, with an eccentricity of 0.0513±0.0078 and an inclination of 126.356±0.064°. Assuming its estimated diameter of over 300 km is accurate, it may be the fourth- or fifth-largest known moon of a Trans-Neptunian object, after Pluto I Charon, Eris I Dysnomia, Orcus I Vanth, very possibly Varda I Ilmarë, and perhaps Salacia I Actaea.

Dwarf planet Planetary-mass object

A dwarf planet is a small planetary-mass object that is in direct orbit of the Sun – something smaller than any of the eight classical planets, but still a world in its own right. The prototypical dwarf planet is Pluto. The interest of dwarf planets to planetary geologists is that, being possibly differentiated and geologically active bodies, they may display planetary geology, an expectation borne out by the 2015 New Horizons mission to Pluto.

Eris (dwarf planet) Dwarf planet beyond Pluto in the Solar System

Eris is the most massive and second-largest known dwarf planet in the Solar System. Eris is a trans-Neptunian object (TNO), has a high-eccentricity orbit, and is a member of the scattered disk. Eris was discovered in January 2005 by a Palomar Observatory-based team led by Mike Brown, and its discovery was verified later that year. In September 2006 it was named after the Greco-Roman goddess of strife and discord. Eris is the ninth-most massive known object orbiting the Sun, and the sixteenth-most massive overall in the Solar System. It is also the largest object that has not been visited by a spacecraft. Eris has been measured at 2,326 ± 12 kilometers (1,445 ± 7 mi) in diameter. Its mass is 0.27 percent that of the Earth and 127 percent that of dwarf planet Pluto, though Pluto is slightly larger by volume. As Eris orbits the Sun, it completes one rotation every 25.9 hours, making its day length similar to Earth's. However, other sources disagree on the rotation period.

Moons of Haumea Natural satellites orbiting dwarf planet Haumea

The outer Solar System planetoid Haumea has two known moons, Hiʻiaka and Namaka, named after Hawaiian goddesses. These small moons were discovered in 2005, from observations of Haumea made at the large telescopes of the W. M. Keck Observatory in Hawaii.

225088 Gonggong Dwarf planet in the scattered-disc

225088 Gonggong (provisional designation: 2007 OR10) is a dwarf planet, a member of the scattered disc beyond Neptune. It has a highly eccentric and inclined orbit during which it ranges from 34–101 astronomical units (5.1–15.1 billion kilometers; 3.2–9.4 billion miles) from the Sun. As of 2019, its distance from the Sun is 88 AU (13.2×10^9 km; 8.2×10^9 mi), and it is the sixth-farthest known Solar System object. Gonggong is in a 3:10 orbital resonance with Neptune, in which it completes three orbits around the Sun for every ten orbits completed by Neptune. Gonggong was discovered in July 2007 by American astronomers Megan Schwamb, Michael Brown, and David Rabinowitz at the Palomar Observatory, and the discovery was announced in January 2009.

50000 Quaoar Cold classical Kuiper belt object

50000 Quaoar, provisional designation 2002 LM60, is a dwarf planet in the Kuiper belt, a region of icy planetesimals beyond Neptune. A non-resonant object (cubewano), it measures approximately 1,121 km (697 mi) in diameter, about half the diameter of Pluto. The object was discovered by American astronomers Chad Trujillo and Michael Brown at the Palomar Observatory on 4 June 2002. Signs of water ice on the surface of Quaoar have been found, which suggests that cryovolcanism may be occurring on Quaoar. A small amount of methane is present on its surface, which can only be retained by the largest Kuiper belt objects. In February 2007, Weywot, a synchronous moon in orbit around Quaoar, was discovered by Brown. Weywot is measured to be 170 km (110 mi) across. Both objects were named after mythological figures from the Native American Tongva people in Southern California. Quaoar is the Tongva creator deity and Weywot is his son.

Vanth (moon) Moon of 90482 Orcus

Vanth, full designation (90482) Orcus I Vanth, is the single known natural satellite of the plutino and likely dwarf planet 90482 Orcus. With a diameter of about 440 km, it is half the size of Orcus and probably the third-largest known moon of a known trans-Neptunian object, after Pluto I Charon and Eris I Dysnomia, though it is possible that the poorly resolved Varda I Ilmarë or Haumea I Hiʻiaka might be comparable in size. Vanth was discovered by Michael Brown and T.-A. Suer using discovery images taken by the Hubble Space Telescope on 13 November 2005. The discovery was announced in an IAU Circular notice published on 22 February 2007.

References

  1. Michael E. Brown, M. A. van Dam, A. H. Bouchez, D. Le Mignant, R. D. Campbell, J. C. Y. Chin, A. Conrad, S. K. Hartman, E. M. Johansson, R. E. Lafon, D. L. Rabinowitz, P. J. Stomski Jr., D. M. Summers, C. A. Trujillo, and P. L. Wizinowich
  2. 1 2 Brown, M. E.; et al. (2006). "Satellites of the Largest Kuiper Belt Objects" (PDF). Astrophysical Journal Letters . 639 (1): L43–L46. arXiv: astro-ph/0510029 . Bibcode:2006ApJ...639L..43B. doi:10.1086/501524. S2CID   2578831 . Retrieved 2011-10-19.
  3. 1 2 3 4 5 Holler, Bryan J.; Grundy, William M.; Buie, Marc W.; Noll, Keith S. (February 2021). "The Eris/Dysnomia system I: The orbit of Dysnomia". Icarus. 355: 114130. arXiv: 2009.13733 . Bibcode:2021Icar..35514130H. doi:10.1016/j.icarus.2020.114130. S2CID   221995416. 114130.
  4. 1 2 3 4 5 6 7 Brown, Michael E.; Butler, Bryan J. (2018). "Medium-sized satellites of large Kuiper belt objects". The Astronomical Journal. 156 (4): 164. arXiv: 1801.07221 . Bibcode:2018AJ....156..164B. doi:10.3847/1538-3881/aad9f2. S2CID   119343798.
  5. 1 2 Brown, M. E. (14 June 2007). "Dysnomia, the moon of Eris". Caltech . Retrieved 2011-07-03.
  6. Green, D. W. E. (13 September 2006). "(134340) Pluto, (136199) Eris, and (136199) Eris I (Dysnomia)". IAU Circular . 8747: 1. Bibcode:2006IAUC.8747....1G . Retrieved 12 January 2012.
  7. Zabarenko, D. (3 October 2005). "Planet Xena has moon called Gabrielle". Australian Broadcasting Corporation . Retrieved 9 March 2008.
  8. Ingham, R. (2 February 2006). "'Tenth planet' Xena bigger than Pluto". Australian Broadcasting Corporation . Retrieved 9 March 2008.
  9. Lakdawalla, Emily (25 January 2018). "Some big moons in the Kuiper belt". The Planetary Society.
  10. Johnston, W. R. (30 December 2008). "(136199) Eris and Dysnomia". Johnston's Archive. Retrieved 2012-04-12.
  11. Green, D. W. E. (4 October 2005). "S/2005 (2003 UB313) 1". IAU Circular . 8610. Retrieved 12 January 2012.
  12. Sicardy, B.; et al. (2011). "A Pluto-like radius and a high albedo for the dwarf planet Eris from an occultation" (PDF). Nature . 478 (7370): 493–496. Bibcode:2011Natur.478..493S. doi:10.1038/nature10550. PMID   22031441. S2CID   4422527.
  13. Brown, M. E.; Schaller, E. L. (2007). "The Mass of Dwarf Planet Eris". Science . 316 (5831): 1585. Bibcode:2007Sci...316.1585B. doi:10.1126/science.1139415. PMID   17569855. S2CID   21468196.
  14. Brown, M. E.; Schaller, E. L. (2007). "Supporting Online Material for The Mass of Dwarf Planet Eris" (PDF). Science. 316 (5831): 1585. doi:10.1126/science.1139415. PMID   17569855. S2CID   21468196 . Retrieved 2 February 2019.
  15. Mike Brown (2012) How I Killed Pluto and Why It Had It Coming, p. 239
  16. Tytell, D. (14 September 2006). "All Hail Eris and Dysnomia". Sky & Telescope . Retrieved 30 December 2006.
  17. "Julia Sweeney and Michael E. Brown". Hammer Conversations: KCET podcast. 2007. 42 min 12 sec. Archived from the original on 26 June 2008. Retrieved 28 June 2008.