Larissa (moon)

{{Infobox planet

| name = Larissa

| image = Larissa 1.jpg

| discoverer = Harold J. Reitsema, William B. Hubbard, Larry A. Lebofsky, and David J. Tholen{{cite web|url=https://solarsystem.nasa.gov/moons/neptune-moons/larissa/in-depth/ |title=Larissa In Depth|website=solarsystem.nasa.gov/|access-date=September 3, 2020}}

| discovered = May 24, 1981

| caption = Larissa from Voyager 2

| mpc_name = Neptune VII

| alt_names = S/1989 N 2
S/1981 N 1

| pronounced = {{IPAc-en|l|ə|ˈ|r|ɪ|s|ə}}{{MW|Larissa}}

| adjective = Larissean,{{cite book|last=Boccaccio|year=1974|title=The book of Theseus}} Larissan,Livy (1850 trans.) The history of Rome, v. 3 Larissian{{cite book|last=Bell|year=1790|title=Bell's New pantheon}} {{IPAc-en|l|ə|ˈ|r|ɪ|s|(|i|)|ə|n}}

| named_after = Λάρισσα Lārissa

| orbit_ref =

| epoch = 18 August 1989

| semimajor = 73 548.26 km

| eccentricity = 0.001393 ± 0.00008

| period = 0.55465332 ± 0.00000001 d

| avg_speed =

| inclination = {{ubl|0.251 ± 0.009° (to Neptune equator)|0.205° (to local Laplace plane)}}

| satellite_of = Neptune

| dimensions = {{val|216|x|204|x|168|u=km}} (± {{val|6|x|16|x|4|u=km}}) km

| mean_radius = {{val|97|3|u=km}}

| volume = ~{{val|3.64|e=6|u=km3}}{{efn|A volume of {{val|3.5|1.0|e=6|u=km3}} was obtained from a detailed shape model, assuming dimensions of {{val|208|x|192|x|178|u=km}}. The long and short dimensions were estimated based on a single image, with the medium dimension simply assumed as halfway between those values. The volume has been scaled to reflect more recently obtained dimensions of {{val|216|x|204|x|168|u=km}} based on two images.}}

| mass = ~{{val|0.19|-|5.7|e=18|u=kg}}{{efn|A density of {{val|0.05|-|1.5|u=g/cm3}} was calculated when assuming the volume as a sphere with a radius of {{val|97|3|u=km}}, and assuming Larissa and Proteus share similar densities. The mass was calculated with the provided density and volume.}}

| density = ~{{val|0.052|-|1.57|u=g/cm3}}{{efn|Density obtained from the calculated mass and the scaled volume.}}

| surface_grav = ~{{Gr|1.9e-4|108}}–{{Gr|0.0057|84}} m/s²

| escape_velocity = ~{{V2|1.9e-4|108}}–{{V2|0.0057|84}} km/s

| rotation = synchronous

| axial_tilt = zero

| albedo = 0.09

| magnitude = 21.5

| single_temperature = ~51 K mean (estimate)

| note = no

}}

Larissa, also known as Neptune VII, is the fifth-closest inner satellite of Neptune. It is named after Larissa, a lover of Poseidon (the Greek equivalent of the Roman god Neptune).

Larissa is also the eponymous nymph of the city in Thessaly, Greece.

Discovery

File:Voyager.jpg

Larissa was first discovered by Harold J. Reitsema, William B. Hubbard, Larry A. Lebofsky and David J. Tholen, based on fortuitous ground-based stellar occultation observations on May 24, 1981. It was given the temporary provisional designation S/1981 N 1 and its supposed existence was announced on May 29, 1981. The moon was later recovered and confirmed to be the only object in its orbit during the Voyager 2 flyby in 1989 after which it received the additional designation S/1989 N 2 on August 2, 1989. The announcement by Stephen P. Synnott spoke of "10 frames taken over 5 days", which gives a recovery date sometime before July 28. The name was given and then confirmed by the International Astronomical Union on September 16, 1991.

Characteristics

File:Larissa_Moon_Earth.png (upper left) and Earth]]

File:Larissa map.gif

Larissa is the fourth-largest satellite of Neptune. It is irregular (non-spherical) in shape and appears to be heavily cratered, with no sign of any geological modification. It is likely that Larissa, like the other satellites inward of Triton, is a rubble pile re-accreted from fragments of Neptune's original satellites, which were disrupted by perturbations from Triton soon after that moon's capture into a very eccentric initial orbit.

Larissa's orbit is nearly circular and lies below Neptune's synchronous orbit radius, which means 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, similarly to how Triton will eventually collide with Neptune or break into a planetary ring.

Compositionally, Larissa appears to be similar to other small inner Neptunian satellites, with a deep 3.0 micron feature attributed to water ice or hydrated silicate minerals. It has a 0.08 albedo at 1.4 and 2.0 microns, dropping to 0.03 at 3.0 microns, and increasing to 0.09 at 4.6 microns.{{Cite journal |last1=Belyakov |first1=Matthew |last2=Davis |first2=M. Ryleigh |last3=Milby |first3=Zachariah |last4=Wong |first4=Ian |last5=Brown |first5=Michael E. |date=2024-05-01 |title=JWST Spectrophotometry of the Small Satellites of Uranus and Neptune |journal=The Planetary Science Journal |volume=5 |issue=5 |pages=119 |doi=10.3847/PSJ/ad3d55 |doi-access=free |arxiv=2404.06660 |bibcode=2024PSJ.....5..119B |issn=2632-3338}}

Exploration

File:Larissa.jpg

Larissa has only been visited once by Voyager 2 in 1989. The probe was able to get some photographs with details of Larissa, showing its cratered surface; unlike the other inner moons of Neptune that only appeared as dots or smudges.

Notes

{{reflist

| group = lower-alpha

| refs =

Surface gravity derived from the mass m, the gravitational constant G and the radius r: $\frac{Gm}{r^2}$

Escape velocity derived from the mass m, the gravitational constant G and the radius r: $\sqrt{\frac{2Gm}{r}}$

}}

References

{{reflist

| refs =

{{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| s2cid = 121398325 }}

{{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}}

{{cite web

| title = Planetary Satellite Physical Parameters

| date = 2010-10-18

| publisher = JPL (Solar System Dynamics)

| url = http://ssd.jpl.nasa.gov/?sat_phys_par

| access-date = 2011-10-11

}}

{{cite journal| doi = 10.1007/BF00572198| last = Stooke| first = Philip J.| year = 1994| title = The surfaces of Larissa and Proteus| journal = Earth, Moon, and Planets| volume = 65| issue = 1| pages = 31–54| bibcode = 1994EM&P...65...31S| s2cid = 121825800}}

{{cite journal |doi=10.1126/science.215.4530.289 |last1=Reitsema |first1=Harold J. |last2=Hubbard |first2=William B. |last3=Lebofsky |first3=Larry A. |last4=Tholen |first4=David J. |title=Occultation by a Possible Third Satellite of Neptune |journal=Science |volume=215 |issue=4530 |pages=289–291 |year=1982 |bibcode=1982Sci...215..289R |pmid=17784355 |s2cid=21385195 }}

{{cite journal

| last = Marsden

| first = Brian G.

| title = S/1981 N 1

| date = May 29, 1981

| journal = IAU Circular

| volume = 3608

| url = http://www.cbat.eps.harvard.edu/iauc/03600/03608.html

| access-date = 2011-10-26

}}

{{cite journal| doi = 10.1126/science.246.4936.1422| last1 = Smith| first1 = B. A.| last2 = Soderblom| first2 = L. A.| last3 = Banfield| first3 = D.| last4 = Barnet| first4 = C.| last5 = Basilevsky| first5 = A. T.| last6 = Beebe| first6 = R. F.| last7 = Bollinger| first7 = K.| last8 = Boyce| first8 = J. M.| last9 = Brahic| first9 = A.| year = 1989| title = Voyager 2 at Neptune: Imaging Science Results| journal = Science| volume = 246| issue = 4936| pages = 1422–1449| bibcode = 1989Sci...246.1422S| pmid = 17755997| s2cid = 45403579| ref = {{sfnRef|Smith Soderblom et al.|1989}}| url = https://zenodo.org/record/1230992}} [on page 1435]

{{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

| access-date = 2011-10-26

}}

{{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

| access-date = 2011-10-26

}}

{{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| bibcode = 1992Icar...99..390B}}

{{cite journal |last1=Showalter |first1=M. R. |last2=de Pater |first2=I. |last3=Lissauer |first3=J. J. |last4=French |first4=R. S. |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 |pmid=30787452 |pmc=6424524 |bibcode=2019Natur.566..350S }}

{{Cite journal |last1=Zhang |first1=Ke |last2=Hamilton |first2=Douglas P. |date=2007-06-01 |title=Orbital resonances in the inner neptunian system: I. The 2:1 Proteus–Larissa mean-motion resonance |url=https://www.sciencedirect.com/science/article/pii/S0019103506004428 |journal=Icarus |volume=188 |issue=2 |pages=386–399 |doi=10.1016/j.icarus.2006.12.002 |bibcode=2007Icar..188..386Z |issn=0019-1035|url-access=subscription }}

{{Cite journal |last1=Thomas |first1=P. |last2=Veverka |first2=J. |date=1991-10-30 |title=Neptune's small inner satellites |url=https://agupubs.onlinelibrary.wiley.com/doi/10.1029/91JA01461 |journal=Journal of Geophysical Research: Space Physics |language=en |volume=96 |issue=S01 |pages=19261–19268 |doi=10.1029/91JA01461 |bibcode=1991JGR....9619261T |issn=0148-0227|url-access=subscription }}

}}

External links

[https://web.archive.org/web/20070801204426/http://solarsystem.nasa.gov/planets/profile.cfm?Object=Nep_Larissa Larissa Profile] by [http://solarsystem.nasa.gov NASA's Solar System Exploration]
[https://web.archive.org/web/20090607094220/http://www.dtm.ciw.edu/users/sheppard/satellites/nepsatdata.html Neptune's Known Satellites] (by Scott S. Sheppard)

Category:Moons of Neptune

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