(532037) 2013 FY27

S/2018 (532037) 1
	Animation of 2013 FY27 and its satellite, imaged by the Hubble Space Telescope from January to July 2018
Discovery
Discovered by	Scott Sheppard; Yanga R. Fernández; Arielle Moullet;
Discovery date	15 January 2018
Orbital characteristics
Semi-major axis	>9800±40 km
Orbital period (sidereal)	≈19 d (for assumed density 1.6 g/cm3)
Satellite of	2013 FY27
Physical characteristics
Mean diameter	≈186 km (assuming equal albedos)
Albedo	0.170+0.045; −0.030 (assumed)
Apparent magnitude	25.5
Absolute magnitude (H)	6.15

(532037) 2013 FY₂₇
	2013 FY27 and its satellite, imaged by the Hubble Space Telescope on 15 January 2018
Discovery
Discovered by	Scott Sheppard; Chad Trujillo (obs. 807);
Discovery date	17 March 2013; (announced on 31 March 2014)
Designations
MPC designation	2013 FY27
Minor planet category	TNO; SDO;
Orbital characteristics
	Epoch 2023 Feb 25 (JD 2460000.5)
	Uncertainty parameter 4
Observation arc	3953 days (10.82 yr)
Earliest precovery date	15 March 2011 (Pan-STARRS)
Aphelion	81.912 AU (12.2539 Tm)
Perihelion	35.199 AU (5.2657 Tm)
Semi-major axis	58.555 AU (8.7597 Tm)
Eccentricity	0.3989
Orbital period (sidereal)	448.08 yr (163,660 d)
Mean anomaly	215.947°
Mean motion	0° 0m 7.92s /day
Inclination	33.290°
Longitude of ascending node	186.922°
Time of perihelion	≈ 2202 June 15 ± 17 days
Argument of perihelion	139.752°
Known satellites	1
Physical characteristics
Mean diameter	765+80; −85 km (effective diameter); 742+78; −83 km (primary)
Geometric albedo	0.170+0.045; −0.030
Temperature	22 K (perihelion) to ; 16 K (aphelion)
Spectral type	moderately red; V–R = 0.56±0.03; R–I = 0.52±0.03;
Apparent magnitude	22.5
Absolute magnitude (H)	3.15±0.03

(532037) 2013 FY₂₇ (provisional designation 2013 FY₂₇) is a trans-Neptunian object and binary system that belongs to the scattered disc (like Eris).^[8] Its discovery was announced on 31 March 2014.^[1] It has an absolute magnitude (H) of 3.2.^[3] 2013 FY₂₇ is a binary object, with two components approximately 740 kilometres (460 mi) and 190 kilometres (120 mi) in diameter. It is the ninth-intrinsically-brightest known trans-Neptunian object,^[9]^{[failed verification]} and is approximately tied with 2002 AW197 and 2002 MS4 (to within measurement uncertainties) as the largest unnamed object in the Solar System.

Orbit

2013 FY₂₇ orbits the Sun once every 449 years. It will come to perihelion around November 2202,^[3]^[b] at a distance of about 35.6 AU. It is currently near aphelion, 80 AU from the Sun, and, as a result, it has an apparent magnitude of 22.^[1] Its orbit has a significant inclination of 33°.^[3] The sednoid 2012 VP113 and the scattered-disc object 2013 FZ27 were discovered by the same survey as 2013 FY₂₇ and were announced within about a week of one another.

Physical properties

2013 FY₂₇ has a diameter of about 740 kilometres (460 mi), placing it at a transition zone between medium-sized and large TNOs. Using the Atacama Large Millimeter Array and Magellan Telescopes, its albedo was found to be 0.17, and its colour to be moderately red. 2013 FY₂₇ is one of the largest moderately red TNOs. The physical processes that lead to a lack of such moderately red TNOs larger than 800 kilometres (500 mi) are not yet well understood.

The brightness of 2013 FY₂₇ varies by less than 0.06 mag over hours and days, suggesting that it either has a very long rotation period, an approximately spheroidal shape, or a rotation axis pointing towards Earth.^[4]

Brown estimated, prior to the discovery of its satellite, that 2013 FY₂₇ was very likely to be a dwarf planet, due to its large size.^[10] However, Grundy et al. calculate that bodies such as 2013 FY₂₇, less than about 1000 km in diameter, with albedos less than ≈0.2 and densities of ≈1.2 g/cm³ or less, may retain a degree of porosity in their physical structure, having never collapsed into fully solid bodies.^[11]

The surface area of asteroid 532037 (2013 FY27) is similar to the area of the state of Texas. ^[12]

Satellite

Using Hubble Space Telescope observations taken in January 2018, Scott Sheppard found a satellite around 2013 FY₂₇, that was 0.17 arcseconds away and 3.0±0.2 mag fainter than its primary. The discovery was announced on 10 August 2018.^[14] The satellite does not have a provisional designation nor a proper name.^[3] Assuming the two components have equal albedos, they are about 742+78
−83 km and 186±20 km in diameter, respectively.^[4] Follow-up observations were taken between May and July 2018 in order to determine the orbit of the satellite,^[5] but the results of these observations remain yet to be published as of 2022^[update].^[7] Once the orbit is known, the mass of the system can be determined.

Notes

^ Assuming the two components have equal albedos
^ The uncertainty in the time of perihelion passage is ≈1 month (1-sigma) or 3.6 months (3-sigma).^[3]
^ Given the primary's absolute magnitude of H = 3.15 and a magnitude difference of Δm = 3.00 between the primary and satellite, the sum of those magnitudes is the satellite's absolute magnitude, 6.15.^[4]^[7]