Thalassa (moon)
Template:Short description Template:Use dmy dates {{#invoke:infobox|infoboxTemplate | class = vcard | titleclass = fn org | title = Thalassa | image = {{#invoke:InfoboxImage|InfoboxImage|image=Neptune Trio.jpg|upright={{#if:||1.1}}|alt=}} | caption = Thalassa (1989 N5) seen by Voyager 2 on 23 August 1989 | headerstyle = {{#if:|background-color:|background-color:#E0CCFF}}; color:inherit; | labelstyle = max-width:{{#if:||11em}}; | autoheaders = y
| header1 = Discovery
| label2 = Discovered by | data2 = Richard J. Terrile<ref name="Willman-Neptune" /> and Voyager Imaging Team | label3 = Discovery site | data3 = | label4 = Discovery date | data4 = September 1989 | label5 = Template:Longitem | data5 =
| header10 = {{#if:|Designations|Designations}}
| label11 = Template:Longitem | data11 = Neptune IV | label12 = Pronunciation | data12 = Template:IPAc-en<ref>Template:OED</ref> | label13 = Template:Longitem | data13 = Θάλασσα Thalassa | label14 = Template:Longitem | data14 = | label15 = Template:Longitem | data15 = | label16 = Adjectives | data16 = Thalassian Template:IPAc-en<ref>The complete poetical works of Robert Browning (1912)</ref> | label17 = Symbol | data17 =
| header20 = Orbital characteristics{{#ifeq:|yes| (barycentric)}}<ref name="Jacobson2004" /><ref name="Showalter2019" />
| data21 = | data22 = {{#if:18 August 1989 |Epoch 18 August 1989}} | data23 = {{#if: | Uncertainty parameter {{{uncertainty}}}}} | label24 = Observation arc | data24 = | label25 = Earliest precovery date | data25 = | label26 = {{#switch:{{{apsis}}} |apsis|gee|barion|center|centre|(apsis)=Apo{{{apsis}}} |Ap{{#if:|{{{apsis}}}|helion}}}} | data26 = | label27 = Peri{{#if:|{{{apsis}}}|helion}} | data27 = | label28 = Peri{{#if:|{{{apsis}}}|apsis}} | data28 = | label29 = {{#switch:{{{apsis}}} |helion|astron=Ap{{{apsis}}} |Apo{{#if:|{{{apsis}}}|apsis}}}} | data29 = | label30 = Periastron | data30 = | label31 = Apoastron | data31 = | label32 = Template:Longitem | data32 = Template:Val | label33 = Template:Longitem | data33 = | label34 = Eccentricity | data34 = Template:Val | label35 = Template:Longitem | data35 = Template:Val d | label36 = Template:Longitem | data36 = | label37 = Template:Longitem | data37 = | label38 = Template:Longitem | data38 = | label39 = Template:Longitem | data39 = | label40 = Inclination | data40 = Template:Ubl | label41 = Template:Longitem | data41 = | label42 = Template:Longitem | data42 = | label43 = Template:Longitem | data43 = | label44 = Template:Longitem | data44 = | label45 = Template:Longitem | data45 = | label46 = Template:Nowrap | data46 = | label47 = Satellite of | data47 = Neptune | label48 = Group | data48 = | label49 = {{#switch: |yes|true=Satellites |Known satellites}} | data49 = | label50 = Star | data50 = | label51 = Earth MOID | data51 = | label52 = Mercury MOID | data52 = | label53 = Venus MOID | data53 = | label54 = Mars MOID | data54 = | label55 = Jupiter MOID | data55 = | label56 = Saturn MOID | data56 = | label57 = Uranus MOID | data57 = | label58 = Neptune MOID | data58 = | label59 = TJupiter | data59 =
| header60 = Proper orbital elements
| label61 = Template:Longitem
| data61 = {{#if: |{{{p_semimajor}}} AU}}
| label62 = Template:Longitem
| data62 =
| label63 = Template:Longitem
| data63 =
| label64 = Template:Longitem
| data64 = {{#if: |{{{p_mean_motion}}} degTemplate:\yr}}
| label65 = Template:Longitem
| data65 = {{#if:|{{#expr:360/1 round 5}} yr
({{#expr:365.25*360/1 round 3}} d) }}
| label66 = Template:Longitem
| data66 = {{#if:|{{{perihelion_rate}}} arcsecTemplate:\yr }}
| label67 = Template:Longitem
| data67 = {{#if:|{{{node_rate}}} arcsecTemplate:\yr}}
| header70 = Template:Anchor{{#if:| Physical characteristics|Physical characteristics}}
| label71 = Dimensions | data71 = (Template:Val) × (Template:Val) × (Template:Val) km<ref name="Karkoschka2003" /> | label72 = Template:Longitem | data72 = | label73 = Template:Longitem | data73 = Template:Val<ref name="Karkoschka2003" /> | label74 = Template:Longitem | data74 = | label75 = Template:Longitem | data75 = | label76 = Flattening | data76 = | label77 = Circumference | data77 = | label78 = Template:Longitem | data78 = | label79 = Volume | data79 = | label80 = Mass | data80 = ~Template:Val (calculated) | label81 = Template:Longitem | data81 = Template:Val<ref name="Brozovic2019" /> | label82 = Template:Longitem | data82 = | label83 = Template:Longitem | data83 = | label84 = Template:Longitem | data84 = | label85 = Template:Longitem | data85 = synchronous | label86 = Template:Longitem | data86 = | label87 = Template:Longitem | data87 = | label88 = Template:Longitem | data88 = zero | label89 = Template:Longitem | data89 = | label90 = Template:Longitem | data90 = | label91 = Template:Longitem | data91 = | label92 = Template:Longitem | data92 = | label93 = {{#if: |Template:Longitem |Albedo}} | data93 = 0.091<ref name="Karkoschka2003" /><ref name="jplssd" /> | label94 = Temperature | data94 = ~51 K mean (estimate)
| data100 = {{#if:|
{{#if:|}}{{#if:|}}{{#if:|}}{{#if:|}}| Surface temp. | min | mean | max |
|---|---|---|---|
| {{{temp_name1}}} | |||
| {{{temp_name2}}} | |||
| {{{temp_name3}}} | |||
| {{{temp_name4}}} |
}}
| label101 = Surface absorbed dose rate | data101 = | label102 = Surface equivalent dose rate | data102 = | label103 = Template:Longitem | data103 = | label104 = Template:Longitem | data104 = | label105 = Template:Longitem | data105 = 23.32<ref name="jplssd" /> | label106 = Template:Longitem | data106 = | label107 = Template:Longitem | data107 =
| header110 = Atmosphere
| label111 = Template:Longitem | data111 = | label112 = Template:Longitem | data112 = | label113 = Composition by volume | data113 =
| below = {{#if:no||Template:Reflist }}
}}{{#invoke:Check for unknown parameters|check|unknown=Template:Main other|preview=Page using Template:Infobox planet with unknown parameter "_VALUE_"|ignoreblank=y| abs_magnitude | adjective | adjectives | albedo | allsatellites | alt_names | angular_dist | angular_size | aphelion | apoapsis | apsis | apoastron | arg_peri | asc_node | atmosphere | atmosphere_composition | atmosphere_ref | avg_speed | axial_tilt | background | barycentric | bgcolour | caption | circumference | declination | density | dimensions | discovered | discoverer | discovery_method | discovery_ref | discovery_site | earliest_precovery_date | eccentricity | epoch | equatorial_radius | escape_velocity | exosolar planets | extrasolarplanet | family | flattening | group | image | image_alt | image_scale | inclination | jupiter_moid | label_width | long_periastron | magnitude | mars_moid | mass | max_temp_1 | max_temp_2 | max_temp_3 | max_temp_4 | mean_anomaly | mean_diameter | mean_motion | mean_orbit_radius | mean_radius | mean_temp_1 | mean_temp_2 | mean_temp_3 | mean_temp_4 | mercury_moid | min_temp_1 | min_temp_2 | min_temp_3 | min_temp_4 | minorplanet | moid | moment_of_inertia_factor | mp_category | mp_name | mpc_name | name | named_after | neptune_moid | node_rate | note | observation_arc | orbit_diagram | orbit_ref | p_eccentricity | p_inclination | p_mean_motion | p_orbit_ref | p_semimajor | periapsis | periastron | perihelion | perihelion_rate | period | physical_ref | polar_radius | pole_ecliptic_lat | pole_ecliptic_lon | pronounce | pronounced | right_asc_north_pole | rot_velocity | rotation | satellite_of | satellites | saturn_moid | scale_height | semi-amplitude | semimajor | sidereal_day | single_temperature | spectral_type | star | surface_area | surface_grav | surface_pressure | surface_absorbed_dose_rate | surface_equivalent_dose_rate | symbol | synodic_period | temp_name1 | temp_name2 | temp_name3 | temp_name4 | time_periastron | tisserand | uncertainty | uranus_moid | venus_moid | volume }}
Thalassa Template:IPAc-en, also known as Neptune IV, is the second-innermost satellite of Neptune. Thalassa was named after sea goddess Thalassa, a daughter of Aether and Hemera from Greek mythology. "Thalassa" is also the Greek word for "sea".
Discovery
Thalassa was discovered sometime before mid-September 1989 from the images taken by the Voyager 2 probe. It was given the temporary designation S/1989 N 5.<ref name="IAUC 4867" /> The discovery was announced (IAUC 4867) on 29 September 1989, and mentions "25 frames taken over 11 days", implying a discovery date of sometime before 18 September. The name was given on 16 September 1991.<ref name="IAUC 5347" />
Physical properties
Thalassa is irregularly shaped. 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.<ref name="BanfieldMurray1992" /> Unusually for irregular bodies, it appears to be roughly disk-shaped.
Orbit
Since the Thalassian orbit is below Neptune's synchronous orbit radius, it is slowly spiralling inward due to tidal deceleration and may eventually impact Neptune's atmosphere, or break up into a planetary ring upon passing its Roche limit due to tidal stretching. Relatively soon after, the spreading debris may impinge upon Despina's orbit.
Thalassa is currently in a 69:73 orbital resonance with the innermost moon, Naiad, in a "dance of avoidance". As it orbits Neptune, the more inclined Naiad successively passes Thalassa twice from above and then twice from below, in a cycle that repeats every ~21.5 Earth days. The two moons are about 3540 km apart when they pass each other. Although their orbital radii differ by only 1850 km, Naiad swings ~2800 km above or below Thalassa's orbital plane at closest approach. Thus this resonance, like many such orbital correlations, stabilizes the orbits by maximizing separation at conjunction. However, the role of Naiad's nearly 5° orbital inclination in this avoidance in a situation where eccentricities are minimal is unusual.<ref name="JPLnews2019" /><ref name="Brozovic2019" />
References
External links
- Thalassa Profile by NASA's Solar System Exploration
- Neptune's Known Satellites (by Scott S. Sheppard)
- Template:YouTube from NASA Jet Propulsion Laboratory
{{#invoke:Navbox|navbox}} Template:Solar System moons (compact) Template:Neptune