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How does an object get its Torino Scale number?

An object is assigned a 0 to 10 value on the Torino Scale based on its collision probability and its kinetic energy (proportional to its mass times the square of its encounter velocity). Categorization on the Torino Scale is based on the placement of a close approach event within a graphical representation of kinetic energy and collision probability. An object that is capable of making multiple close approaches to the Earth will have a separate Torino Scale value associated with each approach. (An object may be summarized by the single highest value that it attains on the Torino Scale.) There are no fractional values or decimal values used in the Torino Scale.

Massachusetts Institute of Technology Professor Richard P. Binzel stands next to the Torino Scale he devised. The scale ranks the potential danger of asteroids hitting the Earth. (Donna Coveney/MIT/AP Photo)

Source: http://impact.arc.nasa.gov/torino/prof.html
Permission for image use, granted by Professor Richard P. Binzel, MIT

Can the Torino Scale value for an object change?

Yes! It is important to note that the Torino Scale value for any object initially categorized as 1 or greater _will_ change with time. The change will result from improved measurements of the object's orbit showing, most likely in all cases, that the object will indeed miss the Earth. Thus, the most likely outcome for a newly discovered object is that it will ultimately be re-assigned to category 0. Any object initially placed in category 0 is unlikely to have its Torino Scale value change with time.

How did the Torino Scale get its name?

The Torino Scale was created by Professor Richard P. Binzel in the Department of Earth, Atmospheric, and Planetary Sciences, at the Massachusetts Institute of Technology (MIT). The first version, called "A Near-Earth Object Hazard Index", was presented at a United Nations conference in 1995 and was published by Binzel in the subsequent conference proceedings (Annals of the New York Academy of Sciences, volume 822, 1997.)

A revised version of the "Hazard Index" was presented at a June 1999 international conference on near-Earth objects held in Torino (Turin) Italy. The conference participants voted to adopt the revised version, where the bestowed name "Torino Scale" recognizes the spirit of international cooperation displayed at that conference toward research efforts to understand the hazards posed by near-Earth objects. ("Torino Scale" is the proper usage, not "Turin Scale.)