42355 Typhon

{{Infobox planet

| minorplanet=yes

| background=#C2E0FF

| name=42355 Typhon

| symbol=24px (rare)

| image=typhon-echidna hst.jpg

| image_scale=

| caption=Hubble Space Telescope image of Typhon and its moon Echidna, taken in 2006

| discoverer=NEAT

| discovered=5 February 2002

| mpc_name=(42355) Typhon

| alt_names={{mp|2002 CR|46}}

| pronounced={{IPAc-en|ˈ|t|aɪ|f|ɒ|n}}{{OED|Typhon}}

| adjectives=Typhonian {{IPAc-en|t|aɪ|ˈ|f|oʊ|n|i|@|n}}{{OED|Typhonian}}

| named_after=Τυφών Typhōn

| mp_category=SDO
Centaur

| epoch=13 January 2016 (JD 2457400.5)

| semimajor={{Convert|38.263987|AU|Tm|abbr=on}}

| perihelion={{Convert|17.545721|AU|Tm|abbr=on}}

| aphelion={{Convert|58.982252|AU|Tm|abbr=on|lk=on}}

| eccentricity=0.5414560

| period=236.70 yr (86453.7 d)

| inclination=2.4252078°

| asc_node=351.9098598°

| arg_peri=159.3215723°

| mean_anomaly=14.61898075°

| avg_speed=

| mean_diameter={{val|138|9|u=km}}
{{val|162|7|u=km}}

| mass={{val|9.082e17|u=kg|p=≈}}

| density={{val|0.66|0.09|0.08|u=g/cm3}}

| surface_grav=

| escape_velocity=

| rotation={{Convert|9.67|h|d|abbr=on|lk=on}}

| spectral_type=B−V={{val|0.74|0.02}} V−R={{val|0.52|0.01}}

| abs_magnitude=7.5

| albedo={{val|0.044|0.003}}
{{Val|0.10|0.02}}

| single_temperature=

| mean_motion={{Deg2DMS|0.0041640770|sup=ms}} / day

| orbit_ref=

| observation_arc=9563 days (26.18 yr)

| uncertainty=2

| tisserand=4.692

| satellites=1 (Echidna)

}}

42355 Typhon ({{IPAc-en|ˈ|t|aɪ|f|ɒ|n}}; provisional designation {{mp|2002 CR|46}}) is a scattered disc object that was discovered on February 5, 2002, by the NEAT program. It measures {{val|162|7|u=km}} in diameter, and is named after Typhon, a monster in Greek mythology.

Typhon is the first known binary centaur, using an extended definition of a centaur as an object on a non-resonant (unstable) orbit with the perihelion inside the orbit of Neptune.

Planetary symbols are no longer much used in astronomy, so Typhon never received a symbol in the astronomical literature. There is no standard symbol for Typhon used by astrologers either. A hurricane symbol (16px), which might be identified with {{unichar|1F300}}, has been used.{{cite web |url=https://www.unicode.org/L2/L2023/23207-historical-asteroids.pdf |title=Unicode request for historical asteroid symbols |last1=Bala |first1=Gavin Jared |last2=Miller |first2=Kirk |date=18 September 2023 |website=unicode.org |publisher=Unicode |access-date=19 March 2025 |quote=}}

Physical properties

Typhon has a BR taxonomic class, with a blue surface. It has a resulting B–R magnitude of 1.274.

Based on a conventional magnitude-to-diameter conversion, the body measures 162 km in diameter, with an albedo of 0.044 and a magnitude of 7.5. Mike Brown gives it a diameter of 192 km with a magnitude of 7.5. Due to its small size, it is unlikely to be classified as a dwarf planet. As of 2021, no rotational lightcurve has been analyzed. The body's rotational period, pole, and actual shape remain unknown.

Moon

{{Infobox planet

| minorplanet=yes

| background=

| name=Echidna

| image=

| image_size=

| caption=

| discoverer=

| discovered= 2006

| mpc_name= (42355) Typhon I Echidna

| alt_names=

| pronounced={{IPAc-en|ᵻ|ˈ|k|ɪ|d|n|ə}}{{OED|Echidna}}

| adjectives=Echidnian
Echidnean (rarely)
(both {{IPAc-en|ᵻ|ˈ|k|ɪ|d|n|i|ə|n}})

| named_after=Έχιδνα

| semimajor= ~1300 km

| eccentricity=

| period= 11 d

| inclination=

| dimensions={{val|89|6|u=km}}

| mass=

| density=

| rotation=

| spectral_type=

| abs_magnitude=

| albedo=

| single_temperature=

| mean_motion=

| orbit_ref=

| observation_arc=

| uncertainty=

| satellite_of = Typhon

}}

A large moon was identified in 2006. It is named Echidna (formal designation (42355) Typhon I Echidna), after the monstrous mate of Typhon. It orbits Typhon at ~1300 km, completing one orbit in about 11 days. Its diameter is estimated to be {{val|89|6|u=km}}.

References

{{reflist|refs=

{{cite web

|type=2008-03-14 last obs

|title=JPL Small-Body Database Browser: (42355 Typhon)

|url=https://ssd.jpl.nasa.gov/sbdb.cgi?sstr=42355

|access-date=12 April 2016}}

{{cite web

|title=List Of Centaurs and Scattered-Disk Objects

|publisher=Minor Planet Center

|url=http://www.minorplanetcenter.org/iau/lists/Centaurs.html

|access-date=2008-09-21}}

[http://www.johnstonsarchive.net/astro/astmoons/am-42355.html (42355) Typhon and Echidna]

Santos-Sanz, P., Lellouch, E., Fornasier, S., Kiss, C., Pal, A., Müller, T. G., Vilenius, E., Stansberry, J., Mommert, M., Delsanti, A., Mueller, M., Peixinho, N., Henry, F., Ortiz, J. L., Thirouin, A., Protopapa, S., Duffard, R., Szalai, N., Lim, T., Ejeta, C., Hartogh, P., Harris, A. W., & Rengel, M. (2012). [https://arxiv.org/abs/1202.1481 “TNOs are Cool”: A Survey of the Transneptunian Region IV - Size/albedo characterization of 15 scattered disk and detached objects observed with Herschel Space Observatory-PACS]

{{cite journal

|display-authors = 6

|first1 = R. |last1 = Duffard

|first2 = N. |last2 = Pinilla-Alonso

|first3 = P. |last3 = Santos-Sanz

|first4 = E. |last4 = Vilenius

|first5 = J. L. |last5 = Ortiz

|first6 = T. |last6 = Mueller

|first7 = S. |last7 = Fornasier

|first8 = E. |last8 = Lellouch

|first9 = M. |last9 = Mommert

|first10 = A. |last10 = Pal

|first11 = C. |last11 = Kiss

|first12 = M. |last12 = Mueller

|first13 = J. |last13 = Stansberry

|first14 = A. |last14 = Delsanti

|first15 = N. |last15 = Peixinho

|first16 = D. |last16 = Trilling

|date = April 2014

|title = "TNOs are Cool": A survey of the trans-Neptunian region. XI. A Herschel-PACS view of 16 Centaurs

|journal = Astronomy and Astrophysics

|volume = 564

|page = 17

|bibcode = 2014A&A...564A..92D

|doi = 10.1051/0004-6361/201322377

|arxiv = 1309.0946

|s2cid = 119177446 }}

{{cite journal

|author=K. Noll

|author2=H. Levison

|author3=W. Grundy

|author4=D. Stephens

|title=Discovery of a binary Centaur

|journal=Icarus

|volume=184|date=October 2006

|arxiv=astro-ph/0605606

|doi=10.1016/j.icarus.2006.05.010

|bibcode=2006Icar..184..611N

|issue=2

|pages=611

|s2cid=18927838}}

{{cite journal

|display-authors=6

|author=J. L. Elliot

|author2=S. D. Kern

|author3=K. B. Clancy

|author4=A. A. S. Gulbis

|author5=R. L. Millis

|author6=M. W. Buie

|author7=L. H. Wasserman

|author8=E. I. Chiang

|author9=A. B. Jordan

|author10=D. E. Trilling

|author11=K. J. Meech

|name-list-style=amp

|title=The Deep Ecliptic Survey: A Search for Kuiper Belt Objects and Centaurs. II. Dynamical Classification, the Kuiper Belt Plane, and the Core Population

|journal=The Astronomical Journal

|volume=129

|date=February 2005

|url=http://occult.mit.edu/_assets/documents/publications/Elliot2005AJ129.1117.pdf

|page=1117

|bibcode=2005AJ....129.1117E

|doi=10.1086/427395

|issue=2

|doi-access=free}}

François Hartog (Janet Lloyd, trans., 1988) The Mirror of Herodotus, p. 25

J. A. Weinstock (2014) The Ashgate Encyclopedia of Literary and Cinematic Monsters, p. 79

George Sandys (1669) Ovid's Metamorphosis Englished, 6th ed., p. 134.