Halimede (moon)

{{Infobox planet

| name = Halimede

| image = N2002n1b.jpg

| image_scale =

| caption = Halimede imaged by the Very Large Telescope during follow-up observations on 3 September 2002

| discovery_ref =

| discoverer = {{unbulleted list | M. Holman | J. J. Kavelaars | T. Grav, W. Fraser | D. Milisavljevic }}

| discovered = August 14, 2002

| mpc_name = Neptune IX

| alt_names = S/2002 N 1

| pronounced = {{IPAc-en|h|æ|l|ə|ˈ|m|iː|d|iː}}Noah Webster (1884) A Practical Dictionary of the English Language

| adjective = Halimedean {{IPAc-en|ˌ|h|æ|l|ə|m|ə|ˈ|d|iː|ə|n}}

| named_after = Ἁλιμήδη Halimēdē

| orbit_ref =

| epoch = June 10, 2003

| semimajor = 16,611,000 km

| eccentricity = 0.2646

| inclination = 134.1°

| period = 1879.08 d
(5.14 a)

| mean_diameter = 62 km {{small|(for albedo 0.04)}}

| albedo = 0.04 {{small|(assumed)}}

| spectral_type = neutral (grey)
{{small|1=B-V=0.73 R-V=0.35}}

}}

Halimede {{IPAc-en|h|æ|l|ə|ˈ|m|iː|d|iː}}, or Neptune IX, is a retrograde irregular satellite of Neptune. It was discovered by Matthew J. Holman, John J. Kavelaars, Tommy Grav, Wesley C. Fraser and Dan Milisavljevic on August 14, 2002.

Name

Halimede, like many of the outer satellites of Neptune, is named after one of the Nereids, the fifty daughters of Nereus and Doris. Before the announcement of its name on February 3, 2007 (IAUC 8802), Halimede was known by the provisional designation S/2002 N 1.

Orbit

File:TheIrregulars NEPTUNE GROUPS.svg

Halimede has the second most eccentric and third most inclined orbit around Neptune. This is illustrated on the diagram in relation to other irregular satellites of Neptune. The satellites above the horizontal axis are prograde, the satellites beneath it are retrograde. The yellow segments extend from the pericentre to the apocentre, showing the eccentricity. It is also worth mentioning that Sao and Laomedeia are similar to Halimede but they both have prograde orbits unlike Halimede which has a retrograde orbit.{{Cite web|title=In Depth {{!}} Halimede|url=https://solarsystem.nasa.gov/moons/neptune-moons/halimede/in-depth|access-date=2020-11-10|website=NASA Solar System Exploration}}

Physical characteristics

Halimede is about 62 kilometers in diameter (assuming an albedo of 0.04) and appears neutral (grey) in the visible light. Given the very similar colour of the satellite to that of Nereid together with the high probability (41%) of collision in the past lifespan of the Solar System, it has been suggested that the satellite could be a fragment of Nereid.

References

{{reflist

| refs =

{{cite web

| author = JPL

| date = 2011-07-21

| title = Planetary Satellite Discovery Circumstances

| publisher = Jet Propulsion Laboratory

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

| access-date = 2011-10-24

}}

{{cite journal

| last = Green

| first = Daniel W. E.

| title = Satellites of Neptune

| date = January 13, 2003

| journal = IAU Circular

| volume = 8047

| url = http://www.cbat.eps.harvard.edu/iauc/08000/08047.html

| access-date = 2011-10-24

}}

{{cite web

| last = Jacobson

| first = R. A.

| year = 2008

| title = NEP078 – JPL satellite ephemeris

| work = Planetary Satellite Mean Orbital Parameters

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

| access-date = 2009-09-23

}}

{{cite journal| doi = 10.1086/504799| last1 = Sheppard| first1 = Scott S.| author-link1 = Scott S. Sheppard| last2 = Jewitt| first2 = David C.| author-link2 = David C. Jewitt| last3 = Kleyna| first3 = Jan| author-link3 = Jan Kleyna| year = 2006| title = A Survey for "Normal" Irregular Satellites around Neptune: Limits to Completeness| journal = The Astronomical Journal| volume = 132| issue = 1| pages = 171–176| bibcode = 2006AJ....132..171S| arxiv = astro-ph/0604552| s2cid = 154011}}

{{cite journal| doi = 10.1086/424997| last1 = Grav| first1 = Tommy| last2 = Holman| first2 = Matthew J.| author-link2 = Matthew J. Holman| last3 = Fraser| first3 = Wesley C.| date = 2004-09-20| title = Photometry of Irregular Satellites of Uranus and Neptune| journal = The Astrophysical Journal| volume = 613| issue = 1| pages = L77–L80| arxiv = astro-ph/0405605| bibcode = 2004ApJ...613L..77G| s2cid = 15706906}}

{{cite journal| doi = 10.1038/nature02832| last1 = Holman| first1 = M. J.| author-link = Matthew J. Holman| last2 = Kavelaars| first2 = J. J.| author-link2 = John J. Kavelaars| last3 = Grav| first3 = T.| display-authors = 3| year = 2004| last4 = Gladman| first4 = B. J.| author-link4 = Brett J. Gladman| last5 = Fraser| first5 = W. C.| last6 = Milisavljevic| first6 = D.| last7 = Nicholson| first7 = P. D.| last8 = Burns| first8 = J. A.| last9 = Carruba| first9 = V.| title = Discovery of five irregular moons of Neptune| journal = Nature| volume = 430| issue = 7002| pages = 865–867| pmid = 15318214| bibcode = 2004Natur.430..865H| s2cid = 4412380| url = https://www.cfa.harvard.edu/~mholman/nature_final.pdf| access-date = 24 October 2011}}

{{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

| access-date = 2011-11-03

}}

External links

[http://cfa-www.harvard.edu/~mholman/neptunians-press-release.html Matthew Holman's Neptune's page]
[http://www.ifa.hawaii.edu/~jewitt/irregulars.html David Jewitt's pages]
[http://www.dtm.ciw.edu/users/sheppard/satellites/nepsatdata.html Neptune's Known Satellites] (by Scott S. Sheppard)
[http://www.minorplanetcenter.org/iau/NatSats/NaturalSatellites.html MPC: Natural Satellites Ephemeris Service]
Mean orbital parameters [http://ssd.jpl.nasa.gov/?sat_elem from JPL]

Category:Moons of Neptune

Category:Irregular satellites

Category:Discoveries by Tommy Grav

20020814

Category:Moons with a retrograde orbit