| • Science | • People | • Locations | • Timeline |
| Discovery | |
|---|---|
| Discoverer | Karl Ludwig Harding |
| Discovery Date | September 1, 1804 |
| Alternate Designations | |
| Category | Main belt ( Juno family ) |
| Orbital Elements Epoch July 14, 2004 ( JD 2453200.5) | |
| Eccentricity (e) | 0.258 |
| Semi-Major Axis (a) | 399.102 G m (2.668 AU) |
| Perihelion (q) | 295.949 Gm (1.978 AU) |
| Aphelion (Q) | 502.255 Gm (3.357 AU) |
| Orbital Period (P) | 1591.609 d (4.36 a) |
| Mean Orbital Speed | 18.24 km/ s |
| Inclination (i) | 12.972 ° |
| Longitude of the Ascending Node (Ω) | 170.127° |
| Argument of Perihelion (ω) | 247.890° |
| Mean Anomaly (M) | 254.993° |
| Physical Characteristics | |
| Dimensions | 233.9 km |
| Mass | 2.824×1019 kgThe kilogram (symbol: kg is the SI base unit of mass. A gram is defined as one thousandth of a kilogram. Conversion of units describes equivalent units of mass in other systems. Multiples SI prefixes are used to name multiples and subdivisions of the kilo |
| Density | 4.2 g/ cm³A cubic centimetre cm is an SI derived unit of volume, equal to the volume of a cube with side length of 1 centi metre. It was the basic unit of volume of the CGS system of units. In SI units: 1 cm³ 10−6 cubic metres 1 milli litre (mL) The abbreviat |
| Surface Gravity | 0.13 m/s² |
| Escape Velocity | 0.18 km/s |
| Rotation Period | 0.3004 d |
| Spectral Class | S-type asteroidApproximately 17% of all known asteroids are of an S-type (for stony composition. S-types are moderately bright (with an albedo of 0. 22) and consist of metallic nickel- iron mixed with iron- and magnesium- silicates. They dominate the inner to central ma |
| Absolute Magnitude | 5.33 |
| Albedo | 0.238 |
| Mean Surface Temperature | ~225 KThe kelvin (symbol: K is the SI unit of temperature, and is one of the seven SI base units. It is defined by two facts: zero kelvin is absolute zero (when molecular motion stops), and one kelvin is the fraction 1/273. 16 of the thermodynamic temperature o |
Juno, head of the Juno family of asteroids, is one of the largest main belt asteroids, measuring about 234 km in diameter. It is an S-type asteroid, meaning that it is highly reflective and composed of nickel- iron mixed with iron and magnesium silicates.
According to James L. Hilton (1999), Juno's orbit was observed to change (slightly) in 1839, "very likely" due to an "unmodeled encounter" — that is to say, some other object passed very close to it or actually hit it.
Juno was the first asteroid for which an occultation was observed. It passed in front of a dim star (SAO 112328) on February 19, 1958. Since then, several occultations by Juno have been observed.
In 2003 Juno was imaged by the Hooker Telescope at Mount Wilson Observatory, using adaptive optics. Its diameter was determined to be 267 km, as was its irregular shape, which resembles a potato. Infrared photographs revealed that Juno possesses an approx. 100-kilometre crater, the result of an impact that occurred in the relatively recent past, geologically speaking. Spectroscopic studies permit the conclusion that Juno could be the body of origin of ordinary chondrites, a common group of stony meteors composed of iron-containing silicates such as olivine and pyroxene.