532 Herculina
Encyclopedia
532 Herculina is a very large asteroid
, with a diameter of around 225 km.
in Heidelberg
, and initially catalogued as 1904 NY. The origin of its name is not known; it may be named after the mythical Hercules
, or after an unknown woman of that name. The bulk of the asteroids discovered by Wolf around this date were named for characters in operas, but if this name was also drawn from such a source, no explanation has been recorded.
.
It has often been noted for its complex lightcurves, which made determination of its shape and rotation somewhat difficult. A set of 1982 speckle interferometry observations led to a simple preliminary model of Herculina as a three-axis object, perhaps 260 by 220 by 215 km. 1985 analysis of this data concluded there was a nonspherical shape with one bright spot, whilst a 1987 photometric astrometry study concluded the object was spherical with two dark spots (and rotated around a completely different pole), which was in turn negated by a 1988 thermal study which showed the object could not be spherical. By the late 1980s, the generally accepted model was a three-axis object with major albedo or topographical features.
Recent (2002) modelling of photometric
data indicates that Herculina is not spherical, but a blocky shape not unlike a battered cuboid - or, as the analysis described it, it "resembles a toaster". This analysis indicates the presence of multiple largish craters, similar to 253 Mathilde
, but no major variation in albedo. The approximate ratios of the axes were suggested as 1:1.1:1.3, broadly consistent with earlier models if slightly more elongated.
of the star SAO 120774 in 1978, Herculina became the first asteroid to be "confirmed" to have an asteroid moon
, with the parent asteroid estimated at a 216 km diameter and a satellite of about 45 km orbiting at a distance of around 1,000 km. However, careful examination in 1993, using the Hubble Space Telescope
, failed to locate a secondary.
Asteroid
Asteroids are a class of small Solar System bodies in orbit around the Sun. They have also been called planetoids, especially the larger ones...
, with a diameter of around 225 km.
Discovery
It was discovered on April 20, 1904, by Max WolfMax Wolf
Maximilian Franz Joseph Cornelius Wolf was a German astronomer and a pioneer in the field of astrophotography...
in Heidelberg
Heidelberg
-Early history:Between 600,000 and 200,000 years ago, "Heidelberg Man" died at nearby Mauer. His jaw bone was discovered in 1907; with scientific dating, his remains were determined to be the earliest evidence of human life in Europe. In the 5th century BC, a Celtic fortress of refuge and place of...
, and initially catalogued as 1904 NY. The origin of its name is not known; it may be named after the mythical Hercules
Hercules
Hercules is the Roman name for Greek demigod Heracles, son of Zeus , and the mortal Alcmene...
, or after an unknown woman of that name. The bulk of the asteroids discovered by Wolf around this date were named for characters in operas, but if this name was also drawn from such a source, no explanation has been recorded.
Physical characteristics
Herculina is one of the twenty or so largest members of the main asteroid beltAsteroid belt
The asteroid belt is the region of the Solar System located roughly between the orbits of the planets Mars and Jupiter. It is occupied by numerous irregularly shaped bodies called asteroids or minor planets...
.
It has often been noted for its complex lightcurves, which made determination of its shape and rotation somewhat difficult. A set of 1982 speckle interferometry observations led to a simple preliminary model of Herculina as a three-axis object, perhaps 260 by 220 by 215 km. 1985 analysis of this data concluded there was a nonspherical shape with one bright spot, whilst a 1987 photometric astrometry study concluded the object was spherical with two dark spots (and rotated around a completely different pole), which was in turn negated by a 1988 thermal study which showed the object could not be spherical. By the late 1980s, the generally accepted model was a three-axis object with major albedo or topographical features.
Recent (2002) modelling of photometric
Photometry (astronomy)
Photometry is a technique of astronomy concerned with measuring the flux, or intensity of an astronomical object's electromagnetic radiation...
data indicates that Herculina is not spherical, but a blocky shape not unlike a battered cuboid - or, as the analysis described it, it "resembles a toaster". This analysis indicates the presence of multiple largish craters, similar to 253 Mathilde
253 Mathilde
253 Mathilde is a main-belt asteroid about 50 km in diameter that was discovered by Johann Palisa in 1885. It has a relatively elliptical orbit that requires more than four years to circle the Sun. This asteroid has an unusually slow rate of rotation, requiring 17.4 days to complete a...
, but no major variation in albedo. The approximate ratios of the axes were suggested as 1:1.1:1.3, broadly consistent with earlier models if slightly more elongated.
Satellites
Following anomalous observations during an occultationOccultation
An occultation is an event that occurs when one object is hidden by another object that passes between it and the observer. The word is used in astronomy . It can also refer to any situation wherein an object in the foreground blocks from view an object in the background...
of the star SAO 120774 in 1978, Herculina became the first asteroid to be "confirmed" to have an asteroid moon
Asteroid moon
A minor planet moon is an astronomical body that orbits a minor planet as its natural satellite. It is thought that many asteroids and Kuiper belt objects may possess moons, in some cases quite substantial in size...
, with the parent asteroid estimated at a 216 km diameter and a satellite of about 45 km orbiting at a distance of around 1,000 km. However, careful examination in 1993, using the Hubble Space Telescope
Hubble Space Telescope
The Hubble Space Telescope is a space telescope that was carried into orbit by a Space Shuttle in 1990 and remains in operation. A 2.4 meter aperture telescope in low Earth orbit, Hubble's four main instruments observe in the near ultraviolet, visible, and near infrared...
, failed to locate a secondary.
External links
- Orbital simulation from JPL (Java) / Ephemeris