| 词条 | Galatea (moon) |
| 释义 |
| name = Galatea | adjectives = | image = Galatea moon.jpg | discoverer = Stephen P. Synnott[1] and Voyager Imaging Team | discovered = July 1989 | caption = Galatea as seen by Voyager 2 (elongation is due to smearing) | orbit_ref = [2][3] | epoch = 18 August 1989 | semimajor = 61 952.57 km | eccentricity = 0.00022 ± 0.00008 | period = 0.42874431 ± 0.00000001 d | avg_speed = | inclination = {{ubl | 0.052 ± 0.011° (to Neptune equator) | 0.06° (to local Laplace plane) }} | satellite_of = Neptune | dimensions = 204×184×144 km (±~10 km)[4][5] | mean_radius = 87.4 ± 4.9 km[3] | volume = ~2.8{{e|6}}km³ | mass = 2.12 ± 0.08 {{e|18}} kg[7] | density = ~0.75 g/cm³ (estimate)[8] | surface_grav = ~{{Gr|0.0021|88|3}} m/s2 | escape_velocity = ~{{V2|0.0021|88|3}} km/s | rotation = synchronous | axial_tilt = zero | albedo = 0.08[4][8] | magnitude = 21.9[8] | single_temperature = ~51 K mean (estimate) | note = no }} Galatea ({{IPAc-en|ˈ|ɡ|æ|l|ə|ˈ|t|iː|ə}} {{Respell|GAL|ə|TEE|ə}}; Greek: Γαλάτεια), also known as Neptune VI, is the fourth-closest inner satellite of Neptune. It is named after Galatea, one of the fifty Nereids of Greek legend, with whom Cyclops Polyphemus was vainly in love. DiscoveryGalatea was discovered in late July 1989 from the images taken by the Voyager 2 probe. It was given the temporary designation S/1989 N 4.[14] The discovery was announced (IAUC 4824) on 2 August 1989, and mentions "10 frames taken over 5 days", implying a discovery date of sometime before July 28. The name was given on 16 September 1991.[15] Physical propertiesGalatea is irregularly shaped and shows no sign of any geological modification. It is likely that it is a rubble pile re-accreted from fragments of Neptune's original satellites, which were smashed up by perturbations from Triton soon after that moon's capture into a very eccentric initial orbit.[16] OrbitGalatea's orbit lies below Neptune's synchronous orbit radius, so it is slowly spiralling inward due to tidal deceleration and may eventually impact the planet or break up into a new planetary ring system upon passing its Roche limit due to tidal stretching. Galatea appears to be a shepherd moon for the Adams ring that is {{convert|1000|km}} outside its orbit. Resonances with Galatea in the ratio 42:43 are also considered the most likely mechanism for confining the unique ring arcs that exist in this ring.[17] Galatea's mass has been estimated based on the radial perturbations it induces on the ring.[7] Notes1. ^1 Planet Neptune Data http://www.princeton.edu/~willman/planetary_systems/Sol/Neptune/ }}.2. ^1 {{cite journal| doi = 10.1086/423037| last1 = Jacobson | first1 = R. A.| last2 = Owen | first2 = W. M., Jr.| year = 2004| pages = 1412–1417| title = The orbits of the inner Neptunian satellites from Voyager, Earthbased, and Hubble Space Telescope observations| journal = Astronomical Journal| volume = 128| issue = 3| bibcode = 2004AJ....128.1412J| ref = harv}} 3. ^1 2 {{cite journal| doi = 10.1016/S0019-1035(03)00002-2| last = Karkoschka| first = Erich| year = 2003| title = Sizes, shapes, and albedos of the inner satellites of Neptune| journal = Icarus| volume = 162| issue = 2| pages = 400–407| bibcode = 2003Icar..162..400K| ref = harv}} 4. ^1 2 {{cite journal|last1= Showalter|first1=M. R.|last2=de Pater|first2= I.|last3= Lissauer|first3=J. J.|last4= French|first4=R. S.|url=https://www.spacetelescope.org/static/archives/releases/science_papers/heic1904/heic1904a.pdf|title= The seventh inner moon of Neptune|journal= Nature|volume= 566|issue= 7744|year= 2019|pages= 350–353|doi= 10.1038/s41586-019-0909-9}} 5. ^1 {{cite web| last = Williams| first = Dr. David R.| date = 2008-01-22| title = Neptunian Satellite Fact Sheet| publisher = NASA (National Space Science Data Center)| url = http://nssdc.gsfc.nasa.gov/planetary/factsheet/neptuniansatfact.html| accessdate = 2008-12-13}} 6. ^1 2 3 {{cite web| title = Planetary Satellite Physical Parameters| date = 2008-10-24| publisher = JPL (Solar System Dynamics)| url = http://ssd.jpl.nasa.gov/?sat_phys_par| accessdate = 2008-12-13}} 7. ^1 2 {{cite journal| doi = 10.1126/science.253.5023.995| last = Porco| first = C.C.| year = 1991| title = An Explanation for Neptune's Ring Arcs| journal = Science| volume = 253| issue = 5023| pages = 995–1001| pmid = 17775342| bibcode = 1991Sci...253..995P}} 8. ^1 {{cite journal| last = Marsden| first = Brian G.| title = Satellites of Neptune| date = August 2, 1989| journal = IAU Circular| volume = 4824| url = http://www.cbat.eps.harvard.edu/iauc/04800/04824.html| accessdate = 2011-10-26}} 9. ^1 {{cite journal| last = Marsden| first = Brian G.| title = Satellites of Saturn and Neptune| date = September 16, 1991| journal = IAU Circular| volume = 5347| url = http://www.cbat.eps.harvard.edu/iauc/05300/05347.html| accessdate = 2011-10-26}} 10. ^1 {{cite journal| doi = 10.1016/0019-1035(92)90155-Z| last1 = Banfield| first1 = Don| last2 = Murray| first2 = Norm| date=October 1992 | title = A dynamical history of the inner Neptunian satellites| journal = Icarus| volume = 99| issue = 2| pages = 390–401| pmid = | pmc = | bibcode = 1992Icar...99..390B| ref = harv}} 11. ^1 {{cite journal| doi = 10.1038/417045a| last = Namouni| first = F.|author2=C. Porco| year = 2002| title = The confinement of Neptune's ring arcs by the moon Galatea| journal = Nature| volume = 417| issue = 6884| pages = 45–7| url = http://www.nature.com/cgi-taf/DynaPage.taf?file=/nature/journal/v417/n6884/abs/417045a_fs.html| pmid = 11986660|bibcode = 2002Natur.417...45N }} }} References{{reflist| refs =[1][2][3][4][5][6][7][8][9][10][11] }} External links{{Commons|Galatea (moon)}}
2 : Moons of Neptune|Astronomical objects discovered in 1989 |
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