19 Fortuna

19 Fortuna is one of the largest main-belt asteroids. It has a composition similar to 1 Ceres: a darkly colored surface that is heavily space-weathered with the composition of primitive organic compounds, including tholins.

19 Fortuna

Discovery
Discovered by	John Russell Hind
Discovery date	22 August 1852
Designations
MPC designation	(19) Fortuna
Pronunciation	/fɔːrˈtjuːnə/[1]
Named after	Fortūna
Alternative designations	A902 UG
Minor planet category	Main belt
Adjectives	Fortunian /fɔːrˈtjuːniən/
Symbol	(historical)
Orbital characteristics[2]
Epoch 17.0 October 2024 (JD 2460600.5)
Aphelion	2.831 AU (423.443 Gm)
Perihelion	2.052 AU (307.028 Gm)
Semi-major axis	2.441 AU (365.235 Gm)
Eccentricity	0.159
Orbital period (sidereal)	3.81 a (1393.378 d)
Average orbital speed	18.94 km/s
Mean anomaly	268.398°
Inclination	1.573°
Longitude of ascending node	211.379°
Argument of perihelion	182.091°
Earth MOID	1.06316 AU
Jupiter MOID	2.60305 AU
TJupiter	3.483
Physical characteristics
Dimensions	(225 × 205 × 195) ± 12 km[3] (242 × 203 × 192) ± 10 km[4]
Mean diameter	211±2 km[4] 225 km[5][6]
Flattening	0.21[a]
Mass	(8.8±1.4)×1018 kg[4] 12.7×1018 kg[3]
Mean density	1.80±0.29 g/cm3[4] 2.70±0.48 g/cm3[3]
Equatorial surface gravity	~0.0629 m/s²
Equatorial escape velocity	~0.1190 km/s
Synodic rotation period	7.4432 h (0.3101 d)[2] 7.443224±0.000001 h[4]
Axial tilt	29°[4]
Pole ecliptic longitude	103°±3°[4]
Pole ecliptic latitude	60°±3°[4]
Geometric albedo	0.056[4] 0.037[2]
Temperature	~180 K
Spectral type	G[2]
Apparent magnitude	8.88[7] to 12.95
Absolute magnitude (H)	7.49[2] 7.13[4]
Angular diameter	0.25" to 0.072"

Fortuna is 225 km in diameter and has one of the darkest known geometric albedos for an asteroid over 150 km in diameter. Its albedo has been measured at 0.028 and 0.037.^[8] The spectra of the asteroid displays evidence of aqueous alteration.^[9]

The Hubble Space Telescope observed Fortuna in 1993. It was resolved with an apparent diameter of 0.20 arcseconds (4.5 pixels in the Planetary Camera) and its shape was found to be nearly spherical. Satellites were searched for but none were detected.

Stellar occultations by Fortuna have been observed several times. Fortuna has been studied by radar.^[10]

It was discovered by J. R. Hind on 22 August 1852, and named after Fortuna, the Roman goddess of luck. Its historical symbol was a star over Fortune's wheel; it is in the pipeline for Unicode 17.0 as U+1CECC 𜻌 ().^[11][12]

Fortuna has been perturbed by the 80 km 135 Hertha and was initially estimated by Baer to have a mass of 1.08×10¹⁹ kg.^[6] A more recent estimate by Baer suggests it has a mass of 1.27×10¹⁹ kg.^[3]

On 21 December 2012, Fortuna (~200 km) harmlessly passed within 6.5 Gm of asteroid 687 Tinette.^[13]

Notes

1. Flattening derived from the maximum aspect ratio (c/a): ${\displaystyle f=1-{\frac {c}{a}}}$, where (c/a) = 0.79±0.05.^[4]