Moons of Pluto: Difference between revisions

Source: Wikipedia, the free encyclopedia.
Browse history interactively
← Previous editNext edit →
Content deleted Content added
VisualWikitext
Rescuing 1 sources and tagging 0 as dead. #IABot (v1.6.2) (Balon Greyjoy)
Line 133: Line 133:
| publisher = | location = | date = 8 January 2005 | language =
| publisher = | location = | date = 8 January 2005 | language =
| url = http://www.sciencemag.org/content/307/5709/546.abstract
| url = http://www.sciencemag.org/content/307/5709/546.abstract
⚫
| doi = 10.1126/science.1106818 | id = | accessdate = 2011-07-20|bibcode = 2005Sci...307..546C | pmid=15681378}}</ref><ref name="Stern">{{cite journal |last=Stern |first=S. A. |authorlink=Alan Stern |author2=Weaver, H. A. |author3=Steff, A. J. |author4=Mutchler, M. J. |author5=Merline, W. J. |author6=Buie, M. W. |author7=Young, E. F. |author8=Young, L. A. |author9=Spencer, J. R. |title=A giant impact origin for Pluto’s small moons and satellite multiplicity in the Kuiper belt |journal=[[Nature (journal)|Nature]] |volume=439 |issue=7079 |pages=946–948 |publisher= |location= |date=23 February 2006 |language= |url=http://ns1.plutoportal.net/~layoung/eprint/Stern2006plutosat.pdf |doi=10.1038/nature04548 |id= |accessdate=2011-07-20 |bibcode=2006Natur.439..946S |pmid=16495992 |deadurl=yes |archiveurl=https://web.archive.org/web/20120119001455/http://ns1.plutoportal.net/~layoung/eprint/Stern2006plutosat.pdf |archivedate=19 January 2012 |df=dmy-all }}</ref> In both cases, the high [[Angular momentum|angular momenta]] of the moons can only be explained by such a scenario. The nearly circular orbits of the smaller moons suggests that they were also formed in this collision, rather than being captured Kuiper Belt objects. This and their near [[orbital resonance]]s with Charon (see below) suggest that they formed closer to Pluto than they are at present and migrated outward as Charon reached its current orbit. Their grey color is different from that of Pluto, one of the reddest bodies in the Solar System. This is thought to be due to a loss of volatiles during the impact or subsequent coalescence, leaving the surfaces of the moons dominated by water ice. However, such an impact should have created additional debris (more moons), yet no moons or rings were discovered by ''New Horizons'', ruling out any more moons of significant size orbiting Pluto.
| doi = 10.1126/science.1106818 | id = | accessdate = 2011-07-20|bibcode = 2005Sci...307..546C | pmid=15681378}}</ref><ref name="Stern">{{cite journal
| last = Stern | first = S. A. | authorlink = Alan Stern
|author2=Weaver, H. A. |author3=Steff, A. J. |author4=Mutchler, M. J. |author5=Merline, W. J. |author6=Buie, M. W. |author7=Young, E. F. |author8=Young, L. A. |author9= Spencer, J. R.
| title = A giant impact origin for Pluto’s small moons and satellite multiplicity in the Kuiper belt
| journal = [[Nature (journal)|Nature]]
| volume = 439 | issue = 7079| pages = 946–948 | publisher =
| location = | date = 23 February 2006 | language =
| url = http://ns1.plutoportal.net/~layoung/eprint/Stern2006plutosat.pdf
⚫
| doi = 10.1038/nature04548 | id = | accessdate = 2011-07-20|bibcode = 2006Natur.439..946S | pmid=16495992}}</ref> In both cases, the high [[Angular momentum|angular momenta]] of the moons can only be explained by such a scenario. The nearly circular orbits of the smaller moons suggests that they were also formed in this collision, rather than being captured Kuiper Belt objects. This and their near [[orbital resonance]]s with Charon (see below) suggest that they formed closer to Pluto than they are at present and migrated outward as Charon reached its current orbit. Their grey color is different from that of Pluto, one of the reddest bodies in the Solar System. This is thought to be due to a loss of volatiles during the impact or subsequent coalescence, leaving the surfaces of the moons dominated by water ice. However, such an impact should have created additional debris (more moons), yet no moons or rings were discovered by ''New Horizons'', ruling out any more moons of significant size orbiting Pluto.


== List ==
== List ==

Revision as of 16:32, 24 January 2018

(Images not to scale)

The

tidally locked with Pluto, and is massive enough that Pluto–Charon is sometimes considered a double dwarf planet
.

History

The innermost and largest moon,

James Christy
on 22 June 1978, nearly half a century after Pluto was discovered. This led to a substantial revision in estimates of Pluto's size, which had previously assumed that the observed mass and reflected light of the system were all attributable to Pluto alone.

Two additional moons were imaged by astronomers of the Pluto Companion Search Team preparing for the New Horizons mission and working with the Hubble Space Telescope on 15 May 2005, which received the provisional designations S/2005 P 1 and S/2005 P 2. The International Astronomical Union officially named these moons Nix (or Pluto II, the inner of the two moons, formerly P 2) and Hydra (Pluto III, the outer moon, formerly P 1), on 21 June 2006.[2] Kerberos, announced on 20 July 2011, was discovered while searching for Plutonian rings. Styx, announced on 7 July 2012, was discovered while looking for potential hazards for New Horizons.[3]

Small moons of Pluto - studies suggest the moons were the result of merged bodies.

Charon

Pluto and Charon, to scale. Photo taken by New Horizons on approach.
Main article: Charon (moon)

Charon is about half the diameter of Pluto and is so massive (nearly one eighth of the mass of Pluto) that the system's barycenter lies between them, approximately 960 km above Pluto's surface.[4][a] Charon and Pluto are also tidally locked, so that they always present the same face toward each other. The IAU General Assembly in August 2006 considered a proposal that Pluto and Charon be reclassified as a double planet, but the proposal was abandoned.[5]

Small moons

Main articles: Styx (moon), Nix (moon), Kerberos (moon), and Hydra (moon)
The Hubble discovery image of Nix and Hydra
Discovery image of Styx, overlaid with orbits of the satellite system

Pluto's four small moons orbit Pluto at two to four times the distance of Charon, ranging from Styx at 42,700 kilometres to Hydra at 64,800 kilometres from the barycenter of the system. They have nearly circular

prograde
orbits in the same orbital plane as Charon.

All are much smaller than Charon. Nix and Hydra, the two larger, are roughly 42 and 55 kilometers on their longest axis respectively,[6] and Styx and Kerberos are 7 and 12 kilometers respectively.[7][8] All four are irregularly shaped.

Characteristics

The relative masses of Pluto's moons. Charon dominates the system. Nix and Hydra are barely visible and Styx and Kerberos are invisible at this scale.
An oblique schematic view of the Pluto–Charon system showing that Pluto orbits a point outside itself. Also visible is the mutual tidal locking between the two bodies.

The Pluto system is highly compact and largely empty.

prograde orbits would be stable is occupied by satellites,[9] and the region from Styx to Hydra is packed so tightly that there is little room for further moons with stable orbits.[11]
An intense search conducted by New Horizons confirmed that no moons larger than 4.5 km in diameter exist at the distances up to 180,000 km from Pluto (for smaller distances, this threshold is still smaller).[12]

The orbits of the moons are confirmed to be circular and coplanar, with inclinations differing less than 0.4° and eccentricities less than 0.005. As seen from Earth, these circular orbits appear foreshortened into ellipses depending on Pluto's position.[13]

The discovery of Nix and Hydra suggested that Pluto could have a

ring system. However, data from a deep-optical survey by the Advanced Camera for Surveys on the Hubble Space Telescope, by occultation studies,[14]
and later by New Horizons suggest that no ring system is present.

Resonances

Styx, Nix, and Hydra are thought to be in a 3-body

synodic periods are then such that there are 5 Styx–Hydra conjunctions and 3 Nix–Hydra conjunctions for every 2 conjunctions of Styx and Nix.[15] As with the Laplace resonance of the Galilean satellites
of Jupiter, triple conjunctions never occur.

All of the outer circumbinary moons are also close to mean motion resonance with the Charon–Pluto orbital period. Styx, Nix, Kerberos, and Hydra are in a 1:3:4:5:6 sequence of near resonances, with Styx approximately 5.4% from its resonance, Nix approximately 2.7%, Kerberos approximately 0.6%, and Hydra approximately 0.3%.[17] It may be that these orbits originated as forced resonances when Charon was tidally boosted into its current synchronous orbit, and then released from resonance as Charon's orbital eccentricity was tidally damped. The Pluto–Charon pair creates strong tidal forces, with the gravitational field at the outer moons varying by 15% peak to peak.[citation needed]

However, it was calculated that a resonance with Charon could boost either Nix or Hydra into its current orbit, but not both: boosting Hydra would have required a near-zero Charonian eccentricity of 0.024, whereas boosting Nix would have required a larger eccentricity of at least 0.05. This suggests that Nix and Hydra were instead captured material, formed around Pluto–Charon, and migrated inward until they were trapped in resonance with Charon.[18] The existence of Kerberos and Styx may support this idea.

Configurations of Hydra (blue), Nix (red) and Styx (black) over one quarter of the cycle of their mutual orbital resonance. Movements are counterclockwise and orbits completed are tallied at upper right of diagrams (click on image to see the complete cycle).

Rotation

Rotations of the small moons of Pluto
(animation; 01:00; released 10 November 2015)

tumble. The torques are increased because the moons are elongated and not spherical.[15][20][21][22] Only one other moon, Saturn's moon Hyperion, is known to tumble,[22] though it is likely that Haumea's moons do so as well.[23]

Origin

dust ring forms around Pluto; 4: the debris aggregates to form Charon; 5: Pluto and Charon
relax into spherical bodies.

It is suspected that Pluto's satellite system was

"big whack" thought to have created the Moon.[24][25] In both cases, the high angular momenta of the moons can only be explained by such a scenario. The nearly circular orbits of the smaller moons suggests that they were also formed in this collision, rather than being captured Kuiper Belt objects. This and their near orbital resonances
with Charon (see below) suggest that they formed closer to Pluto than they are at present and migrated outward as Charon reached its current orbit. Their grey color is different from that of Pluto, one of the reddest bodies in the Solar System. This is thought to be due to a loss of volatiles during the impact or subsequent coalescence, leaving the surfaces of the moons dominated by water ice. However, such an impact should have created additional debris (more moons), yet no moons or rings were discovered by New Horizons, ruling out any more moons of significant size orbiting Pluto.

List

Pluto's moons are listed here by orbital period, from shortest to longest. Charon, which is massive enough to have collapsed into a spheroid at some point in its history, is highlighted in light purple. Pluto has been added for comparison.[15][26]

Name
(
pronunciation
) 		Image Diameter
(km) 		Mass (×1019 kg) Semi-major
axis (km) 		Orbital period
(days) 		Orbital period
(relative to Charon) 		Eccentricity Inclination (°)
(to Pluto's equator) 		Magnitude (mean) Discovery
date
Pluto[27] /ˈpluːtoʊ/
2372±4 1305±7 2035 6.387230 1 : 1 0.0022[b] 0.001 15.1 1930/02/18
Pluto I Charon /ˈʃærən/,[c]
/ˈkɛərən/
1208±3 158.7±1.5 17536±3* 6.387230 1 : 1 0.0022[b] 0.001 16.8 1978/06/22
Pluto V Styx /stɪks/ 16 × 9 × 8 ±?[28] ? 42656±78 20.16155±0.00027 1 : 3.16 0.0058 ± 0.0011 0.81 ± 0.16 27 2012/06/26
Pluto II Nix /nɪks/ 50 × 35 × 33 ±?[28] 0.005 ± 0.004 48694±3 24.85463±0.00003 1 : 3.89 0.002036 ± 0.000050 0.133 ± 0.008 23.7 2005/06/15
Pluto IV Kerberos /ˈkɜːrbərəs/ 19 × 10 × 9[28] ? 57783±19 32.16756±0.00014 1 : 5.04 0.00328 ± 0.00020 0.389 ± 0.037 26 2011/06/28
Pluto III Hydra /ˈhaɪdrə/
65 × 45 × 25 ±?[28] 0.005 ± 0.004 64738±3 38.20177±0.00003 1 : 5.98 0.005862 ± 0.000025 0.242 ± 0.005 23.3 2005/06/15

The maximum distance between the centers of Pluto and Charon is 19,571 ± 4 km.

Scale model of the Pluto system

The small moons to approximate scale, compared to Charon

Mutual events

Simulated view of Charon transiting Pluto on 25 February 1989.

Occultations
occur when Pluto passes in front of and blocks one of Pluto's satellites.

Charon has an angular diameter of 4

arcseconds
. Charon's proximity further ensures that a large proportion of Pluto's surface can experience an eclipse. Because Pluto always presents the same face towards Charon due to tidal locking, only the Charon-facing hemisphere experiences solar eclipses by Charon.

The smaller moons can cast shadows elsewhere. The angular diameters of the four smaller moons (as seen from Pluto) are uncertain. Nix's is 3–9 minutes of arc and Hydra's is 2–7 minutes. These are much larger than the Sun's angular diameter, so total solar eclipses are caused by these moons.

Eclipses by Styx and Kerberos are more difficult to estimate, as both moons are very irregular, with angular dimensions of 76.9 x 38.5 to 77.8 x 38.9 arcseconds for Styx, and 67.6 x 32.0 to 68.0 x 32.2 for Kerberos. As such, Styx has no annular eclipses, its widest axis being more than 10 arcseconds larger than the Sun at its largest. However, Kerberos, although slightly larger, cannot make total eclipses as its largest minor axis is a mere 32 arcseconds. Eclipses by Kerberos and Styx will entirely consist of partial and hybrid eclipses, with total eclipses being extremely rare.

The next period of mutual events due to Charon will begin in October 2103, peak in 2110, and end in January 2117. During this period, solar eclipses will occur once each Plutonian day, with a maximum duration of 90 minutes.[29][30]

Exploration

The Pluto system was visited by the New Horizons spacecraft in July 2015. Images with resolutions of up to 330 meters per pixel were returned of Nix and up to 1.1 kilometers per pixel of Hydra. Lower-resolution images were returned of Styx and Kerberos.[31]

Notes

  1. barycenter
    for animations
  2. ^ a b Orbital eccentricity and inclination of Pluto and Charon are equal because they refer to the same two-body problem (the gravitational influence of the smaller satellites is neglected here).
  3. ^ Many astronomers use this, Christy's pronunciation, rather than the classical /ˈkɛərɒn/, but both are acceptable.

References

  1. ^ "Moons dance around Pluto". Smithsonian Institution. 9 June 2015. Retrieved 9 April 2016.
  2. ^ Green, Daniel W. E. (21 June 2006). "Satellites of Pluto". IAU Circular. 8723. Retrieved 26 November 2011. "NASA's Hubble Discovers Another Moon Around Pluto". NASA. 20 July 2011. Retrieved 20 July 2011.
  3. ^ "Hubble Discovers a Fifth Moon Orbiting Pluto". hubblesite.org. 29 July 2012. Retrieved 29 July 2015.
  4. ^ Staff (30 January 2014). "Barycenter". Education.com. Retrieved 4 June 2015.
  5. ^ "The IAU draft definition of "planet" and "plutons"". International Astronomical Union. 16 August 2006. Retrieved 4 June 2015.
  6. ^ "New Horizons 'Captures' Two of Pluto's Smaller Moons". New Horizons. Retrieved 29 July 2015.
  7. ^ New Horizons Picks Up Styx
  8. ^ Last of Pluto’s Moons – Mysterious Kerberos – Revealed by New Horizons
  9. ^
    Bibcode:2005astro.ph.12599S.{{cite journal}}: CS1 maint: multiple names: authors list (link
    )
  10. doi:10.1086/505424
    .
  11. PMID 26040888
    .
  12. PMID 26472913. (Supplements
    )
  13. ^ "Orbits of 4 Bodies in Pluto System about Barycenter as Seen from Earth". Hubblesite. Retrieved 21 June 2006.
  14. ^ Pasachoff, Jay M.; Babcock, Bryce A.; Souza, Steven P.; et al. (2006). "A Search for Rings, Moons, or Debris in the Pluto System during the 2006 July 12 Occultation". Bulletin of the American Astronomical Society. 38 (3): 523.
    Bibcode:2006DPS....38.2502P
    .
  15. ^
    PMID 26040889
    .
  16. doi:10.1038/nature.2015.17681
    .
  17. ^ Matson, J. (11 July 2012). "New Moon for Pluto: Hubble Telescope Spots a 5th Plutonian Satellite". Scientific American web site. Retrieved 12 July 2012.
  18. arXiv:0802.2951 [astro-ph
    ].
  19. New York Times
    . Retrieved 4 June 2015.
  20. ^ "NASA's Hubble Finds Pluto's Moons Tumbling in Absolute Chaos". Retrieved 3 June 2015.
  21. ^ "Hubble Finds Two Chaotically Tumbling Pluto Moons". hubblesite.org. 3 June 2015. Retrieved 3 June 2015.
  22. ^ a b Drake, Nadia; 03, National Geographic Published June. "Pluto's Moons Dance to a Random Beat". National Geographic News. Retrieved 4 June 2015. {{cite web}}: |last2= has numeric name (help)
  23. ^ Ragozzine, Darin (17 October 2016). "Rapidly Rotating Regular Satellites and Tides". Planetary Society. Retrieved 12 September 2017.
  24. PMID 15681378
    . Retrieved 20 July 2011.
  25. PMID 16495992. Archived from the original (PDF) on 19 January 2012. Retrieved 20 July 2011. {{cite journal}}: Unknown parameter |deadurl= ignored (|url-status= suggested) (help
    )
  26. ^ Orbital elements of small satellites from Showalter and Hamilton, 2015; mass and magnitude from Buie & Grundy, 2006
  27. ^ Pluto data from D. R. Williams (7 September 2006). "Pluto Fact Sheet". NASA. Retrieved 24 March 2007..
  28. ^ a b c d Weaver et al. (2016)
  29. ^ "Start of Eclipse". JPL Solar System Simulator. 12 December 1987. Retrieved 29 July 2014. (Pluto as seen from the Sun during mid-eclipse)
  30. ^ "End of Eclipse". JPL Solar System Simulator. 12 December 1987. Retrieved 29 July 2014.
  31. ^ New Horizons flyby timeline

Sources

External links

Wikimedia Commons has media related to Moons of Pluto.
Retrieved from "https://en.wikipedia.org/w/index.php?title=Moons_of_Pluto&oldid=822137279"