(3) Juno

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(3) JunoAstronomical symbol for Juno
Properties of the orbit ( animation )
Epoch:  4th September 2017 ( JD 2,458,000.5)
Orbit type Middle main belt
Asteroid family Juno family
Major semi-axis 2,669  AU
eccentricity 0.257
Perihelion - aphelion 1,983 AU - 3,354 AU
Inclination of the orbit plane 13 °
Length of the ascending node 169.9 °
Argument of the periapsis 248.2 °
Time of passage of the perihelion 23rd November 2018
Sidereal period of rotation 4 a 131 d
Mean orbital velocity 17.93 km / s
Physical Properties
Dimensions (320 × 267 × 200) ± 6 km
Dimensions 2.86 ± 0:46  ·  10 19 Template: Infobox asteroid / maintenance / mass kg
Albedo 0.214
Medium density 3.20 ± 0.56 g / cm³
Rotation period 7 h 12 min 36 s
Absolute brightness 5.3 mag
Spectral class
(according to Tholen)
Spectral class
(according to SMASSII)
Explorer KL Harding
Date of discovery September 1, 1804
Source: Unless otherwise stated, the data comes from JPL Small-Body Database Browser . The affiliation to an asteroid family is automatically determined from the AstDyS-2 database . Please also note the note on asteroid items.

(3) Juno is an asteroid in the main asteroid belt . It was discovered on September 1, 1804 by Karl Ludwig Harding as the third asteroid and named after Juno , the highest Roman goddess. After its discovery, Juno, like the previously discovered asteroids (1) Ceres and (2) Pallas, was initially classified as a fully fledged planet . Only after 1847 was a distinction made between asteroids and planets. Its path was calculated in the 1810s in Göttingen under the direction of Carl Friedrich Gauß by Friedrich Ludwig Wachter .


Juno orbits the Sun at a distance of 1.98 ( perihelion ) to 3.35 ( aphelion ) AU in 4.36 years . The orbit is inclined 13.0 ° to the ecliptic , the orbital eccentricity is 0.26.


Image of Juno with the 2.5 meter Hooker telescope at Mt. Wilson Observatory

Juno has a mean diameter of about 257 km. Their mass was determined to be 2.86 × 10 19 kilograms. It has a relatively light surface with an albedo of 0.21. During opposition , it reaches an apparent magnitude of up to 7.7, making it one of the brightest asteroids in the night sky. It rotates around its own axis in around 7.2 hours.

In 1996 (results published in 2003) Juno was examined in detail with the help of a 2.5-meter mirror telescope from the Mount Wilson Observatory and adaptive optics . It turned out that Juno is an irregularly shaped celestial body. The images in the infrared range show an impact crater about 100 km in size , which was probably formed a short time ago geologically. Spectroscopic investigations suggest that Juno could be the original body of common chondrites , a common group of stone meteorites that are composed of iron-containing silicate compounds such as olivine and pyroxenes .

Juno was the first asteroid to have star obscuration observed. On February 19, 1958, Juno passed a faint star and eclipsed it for several seconds. Since then, other star occultations have been observed by Juno. The size of Juno was determined from these observations to be 290 × 245 km.

See also

Web links

Commons : (3) Juno  - album with pictures, videos and audio files

Individual evidence

  1. a b c Jim Baer: Recent Asteroid Mass Determinations . Personal website. 2011. Archived from the original on July 8, 2013. Retrieved March 21, 2017.
  2. Harvard-Smithsonian Center for Astrophysics Press Release: Release Number 03-18, August 6, 2003: Asteroid Juno Has A Bite Out Of It Press release on the Harvard-Smithsonian Center server