283 Emma is a large

asteroid An asteroid is a minor planet of the inner Solar System. Sizes and shapes of asteroids vary significantly, ranging from 1-meter rocks to a dwarf planet almost 1000 km in diameter; they are rocky, metallic or icy bodies with no atmosphere. ...

of the asteroid belt and the namesake of the Emma family. It was discovered by Auguste Charlois on 8 February 1889, in

Nice Nice ( , ; Niçard: , classical norm, or , nonstandard, ; it, Nizza ; lij, Nissa; grc, Νίκαια; la, Nicaea) is the prefecture of the Alpes-Maritimes department in France. The Nice agglomeration extends far beyond the administrative c ...

, France. The reason for its name is unknown. Measurements made with the

IRAS The Infrared Astronomical Satellite (Dutch: ''Infrarood Astronomische Satelliet'') (IRAS) was the first space telescope to perform a survey of the entire night sky at infrared wavelengths. Launched on 25 January 1983, its mission lasted ten mo ...

observatory give a diameter of 145.70 ± 5.89 km and a geometric albedo of 0.03 ± 0.01. By comparison, the MIPS

photometer A photometer is an instrument that measures the strength of electromagnetic radiation in the range from ultraviolet to infrared and including the visible spectrum. Most photometers convert light into an electric current using a photoresistor, ph ...

on the

Spitzer Space Telescope The Spitzer Space Telescope, formerly the Space Infrared Telescope Facility (SIRTF), was an infrared space telescope launched in 2003. Operations ended on 30 January 2020. Spitzer was the third space telescope dedicated to infrared astronomy, f ...

gives a diameter of 145.44 ± 7.72 km and a geometric albedo of 0.03 ± 0.01. When the asteroid was observed

occulting An occultation is an event that occurs when one object is hidden from the observer by another object that passes between them. The term is often used in astronomy, but can also refer to any situation in which an object in the foreground blocks ...

a star, the results showed a diameter of 148.00 ± 16.26 km.

Satellite

A companion for 283 Emma was detected on 14 July 2003 by W. J. Merline et al. using the Keck II telescope and is designated S/2003 (283) 1. The announcement is contained in the

International Astronomical Union The International Astronomical Union (IAU; french: link=yes, Union astronomique internationale, UAI) is a nongovernmental organisation with the objective of advancing astronomy in all aspects, including promoting astronomical research, outreac ...

Circular (IAUC) 8165.S/2003 (283) 1 (Circular No. 8165)
/ref> The satellite orbits at a

semi-major axis In geometry, the major axis of an ellipse is its longest diameter: a line segment that runs through the center and both foci, with ends at the two most widely separated points of the perimeter. The semi-major axis (major semiaxis) is the long ...

of about 581 km with an eccentricity of 0.12. Emma has a hill sphere with a radius of about 28,000 km.

References

External links

Asteroids with Satellites
Robert Johnston, johnstonsarchive.net
Orbits of Binary Asteroids with Adaptive Optics
( VLT images) * * {{DEFAULTSORT:Emma 000283 Discoveries by Auguste Charlois Named minor planets 000283 000283 18890208