(136472) 2005 FY9

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The correct title of this article is (136472) 2005 FY₉. It features superscript or subscript characters that are substituted or omitted because of technical limitations.

**(136472) 2005 FY₉**
Discovery ^A
Image:2005FY9art.jpg
Artist's conception of 2005 FY₉
Discoverer	Michael E. Brown, Chad Trujillo, David Rabinowitz
Discovery date	March 31 2005
Alternate designations ^B	none
Category	Trans-Neptunian object
Orbital elements ^C
Epoch January 28, 1955 (JD 2435135.5)
Eccentricity (e)	0.159
Semi-major axis (a)	6850.2 G m (45.791 AU)
Perihelion (q)	5760.7 Gm (38.508 AU)
Aphelion (Q)	7939.7 Gm (53.0736 AU)
Orbital period (P)	113179 d (309.868 a)
Mean orbital speed	4.419 km/s
Inclination (i)	28.963°
Longitude of the ascending node (Ω)	79.3816°
Argument of perihelion (ω)	298.407°
Mean anomaly (M)	85.14653°
Physical characteristics ^D
Dimensions	1600 – 2000? km
Mass	?×10^? kg
Density	? g/cm³
Surface gravity	? m/s²
Escape velocity	? km/s
Rotation period	? d
Spectral class	?
Absolute magnitude	-0.4
Albedo (geometric)	0.8 ± 0.2
Mean surface temperature	~? K

(136472) 2005 FY₉ (also written (136472) 2005 FY9) is a very large Kuiper belt object discovered on March 31, 2005 by the team led by Michael Brown. Its discovery was announced on July 29, 2005 on the same day as two other very large trans-Neptunian objects, 2003 EL₆₁ and Eris.

The designation 2005 FY₉ was given to the object when the discovery was made public. Before that, the discovery team used the codename "Easterbunny" for the object because of the discovery time shortly after Easter. The designation is only provisional; according to the current naming rules of the International Astronomical Union, it will receive a permanent name after a creation or underworld deity.

1 Physical characteristics
- 1.1 Size
- 1.2 Spectra
2 Satellites
3 Discovery circumstances
4 Orbit
5 External links
6 References

[edit] Physical characteristics

Image:EightTNOs.png

[edit] Size

The albedo of 2005 FY₉ remains unknown leading to a significant uncertainty in the object’s size. The detection in infrared by the Spitzer space telescope, combined with the similarities of spectrum with Pluto yield a conservative estimate of 1500 km. This is similar to the size of 2003 EL₆₁ making 2005 FY₉ the largest known Kuiper belt object after Eris and Pluto. However, should the albedo prove to be closer to that of Quaoar for example, the size of the object diameter could reach 3000 km. 2005 FY₉ is currently visually the second brightest Kuiper belt object after Pluto having the apparent magnitude of nearly 17. Therefore it is visible to high-end amateur telescopes.

[edit] Spectra

In a recent paper, Licandro et al. showed that the surface of 2005 FY₉ resembles that of Pluto by measuring its visible and near infrared spectrum using the William Herschel Telescope and Telescopio Nazionale Galileo.

The object appears red in the visible spectrum (see colour comparison for TNOs).

The infrared spectrum is marked by the presence of methane (CH_{4_{) as observed on both Pluto and Eris. However, Eris presents neutral (and not red) spectrum. In addition Eris is a scattered disk object, implying much wider seasonal changes than for the classical objects.}}

The presence of methane, even more prominent that on Pluto, leads to a possibility that 2005 FY₉ could have a similar transient atmosphere as Pluto near perihelion.

[edit] Satellites

No satellites have been detected so far, distinguishing 2005 FY₉ from the other largest known trans-Neptunian objects: Eris (1 satellite), 2003 EL₆₁ (2) and Pluto (3). 10% to 20% of all trans-Neptunian objects are expected to have one or more satellites.

[edit] Discovery circumstances

Despite its relative brightness, 2005 FY₉ was not discovered until fairly recently, well after many much fainter Kuiper belt objects. This is probably due to its relatively high orbital inclination, and the fact that its angular distance from the ecliptic was near maximum at the time of its discovery (in the northern constellation of Coma Berenices). Most searches for minor planets are conducted relatively close to the ecliptic, due to the greater probability of finding objects there.

However, at the time of Clyde Tombaugh's discovery of Pluto, 2005 FY₉ was only a few degrees from the ecliptic, near the border of Taurus and Auriga. Unfortunately, this position was also very near the galactic equator, making it almost impossible to find such an object within the dense concentration of background stars of the Milky Way. Tombaugh continued searching for some years after the discovery of Pluto, but he failed to find 2005 FY₉ or any other trans-Neptunian objects.

[edit] Orbit

Image:TheKuiperBelt Orbits 2003EL61 2005FY9.svg

2005 FY₉ is classified a classical Kuiper belt object and follows an orbit very similar to that of 2003 EL₆₁: highly inclined (29°) and moderately eccentric (e~0.16). 2005 FY₉ is slightly farther from the Sun (both the semi major axis and perihelion). Unlike Pluto and plutinos approaching the Sun closer than Neptune thanks to the resonance, the classical objects have perihelia further from the Sun, free from Neptune’s perturbation.

The diagram shows the similar orbits of the two cubewanos contrasted with the orbit of Pluto. The perihelia (q) and the aphelia (Q) are marked with the dates of passage. The present positions (as of April 2006) are marked with the spheres illustrating relative sizes and differences in albedo and colour. Both cubewanos are currently far from (above) the ecliptic (illustrated as Neptune orbit in grey). 2005 FY₉ approaches its aphelion while 2003 EL₆₁ passed its own in 1991.

[edit] External links

MPEC listing for 2005 FY₉
AstDys orbital elements
Orbital simulation from JPL (Java)
Press release from WHT and TNG on 2005 FY₉ 's similarity to Pluto.
2005 FY9 chart and Orbit Viewer

[edit] References

Licandro, J.; Pinilla-Alonso, N.; Pedani, M.; Oliva, E.; Tozzi, G. P.; Grundy, W. M. The methane ice rich surface of large TNO 2005 FY_9: a Pluto-twin in the trans-neptunian belt? , Astronomy and Astrophysics, 445 (2006), pp.L35-L38 Abstract.
S.C. Tegler, W. Grundy, W. Romanishin, G. Consolmagno, K. Mogren, F. Vilas: Optical Spectroscopy of the Large Kuiper Belt Objects 136472 (2005 FY9) and 136108 (2003 EL61). Preprint

v • d • e</span>

Large trans-Neptunian objects

Kuiper belt: Orcus | Pluto (Charon) | Ixion | 2002 UX₂₅ | Varuna | 2002 TX₃₀₀ | 2003 EL₆₁ | Quaoar | 2005 FY₉ | 2002 AW₁₉₇

Scattered disc: 2002 TC₃₀₂ | Eris | 2004 XR₁₉₀ | Sedna

See also Triton, astronomical objects and the solar system's list of objects, sorted by radius or mass.
For pronunciation, see: Centaur and TNO pronunciation.

v • d • e</span> Small Solar System bodies
Vulcanoids \| Near-Earth asteroids \| Main belt \| Jupiter Trojans \| Centaurs \| Damocloids \| Comets \| Trans-Neptunians (Kuiper belt · Scattered disc · Oort cloud)
For other objects and regions, see: asteroid groups and families, binary asteroids, asteroid moons and the Solar system For a complete listing, see: List of asteroids. See also Pronunciation of asteroid names and Meanings of asteroid names.