42355 Typhon
First known binary centaur, a scattered disc object with a large moon.
42355 Typhon, originally labeled 2002 CR46, is a scattered disc object first spotted on February 5, 2002, during the NEAT survey. With a diameter of 162±7 km, it takes its name from the monstrous figure Typhon of Greek myth. It holds the distinction of being the first binary centaur identified, using a broader definition of a centaur as an object with an unstable, non-resonant orbit whose perihelion lies within Neptune's orbit.
No astronomical symbol for Typhon has ever been established in the literature, and astrologers have not adopted a standard one either. A hurricane symbol (🌀︎) has occasionally been used.
Thermal radiation measurements have yielded two possible diameter estimates: about 138±9 km or 185±7 km, with the larger figure considered more reliable. In that case, the central body (Typhon) itself is 162±7 km across. Because of its small size, it is unlikely to qualify as a dwarf planet. As of 2021, no rotational lightcurve has been analyzed, so its actual shape remains unknown. Typhon has a blue surface, classified as BR taxonomic type, with a B–R color difference near 1.3 and a V–I difference around 1. Its spectra indicate the presence of water ice and possibly water-altered silicates.
A sizable moon was discovered in 2006, named Echidna (formally designated (42355) Typhon I) after Typhon's monstrous partner. It orbits Typhon at a distance of 1628±29 km, completing one revolution every 18.9709±0.0064 days. Echidna is estimated to be 89±6 km in diameter and shares the same color as Typhon.
Quick Facts
- Minorplanet
- yes
- Background
- #C2E0FF
- Symbol
- (rare)
- Discoverer
- NEAT
- Discovered
- 5 February 2002
- Mpc Name
- (42355) Typhon
- Pronounced
- ˈ · t · aɪ · f · ɒ · n
- Adjectives
- Typhonian t · aɪ · ˈ · f · oʊ · n · i · @ · n
- Named After
- Τυφών Typhōn
- Mp Category
- SDO / Centaur
- Epoch
- 13 January 2016 (JD 2457400.5)
- Semimajor
- 38.263987 AU
Facts from the source article.
Lore & Background
42355 Typhon was discovered on February 5, 2002, by the NEAT program. It is a scattered disc object named after Typhon, a monster in Greek mythology. Typhon is the first known binary centaur, under an extended definition of a centaur as an object on a non-resonant (unstable) orbit with the perihelion inside the orbit of Neptune. Measurements of its thermal radiation led to an equivalent diameter of about either 138±9 km or 185±7 km, with the latter value preferable; the diameter of the central body is in the latter case 162±7 km. Due to its small size, it is unlikely to be classified as a dwarf planet. As of 2021, no rotational lightcurve has been analyzed and the body's actual shape remains unknown. Typhon has a BR taxonomic class, with a blue surface, a B–R color difference of about 1.3, and a V–I color difference of about unity. Its spectra show the presence of water ice and possibly of water altered silicates. A large moon was identified in 2006, named Echidna (formal designation (42355) Typhon I), after the monstrous mate of Typhon. It orbits Typhon at a distance of 1628±29 km, completing one orbit in 18.9709±0.0064 days. Its diameter is estimated at 89±6 km, and it has the same color as Typhon.
Reader's Guide
42355 Typhon holds significance as the first known binary centaur, a classification that extends the definition of centaurs to include objects on non-resonant, unstable orbits with perihelia inside Neptune's orbit. Its discovery and subsequent identification of a large moon, Echidna, in 2006, provided early evidence that such distant, icy bodies can host satellites. The system's physical properties, including a diameter of 162±7 km for Typhon and 89±6 km for Echidna, along with their identical blue surface colors and the presence of water ice and possibly water-altered silicates, offer clues about the composition and formation processes in the outer Solar System. The uncertainty in diameter measurements (with alternative values of 138±9 km or 185±7 km) and the lack of a rotational lightcurve as of 2021 highlight the ongoing challenges in characterizing these distant objects. Typhon's status as a binary centaur underscores the dynamic and complex nature of trans-Neptunian populations, bridging the gap between centaurs and scattered disc objects.
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