The Palermo Technical Impact Hazard Scale is a logarithmic scale used by astronomers to rate the potential hazard of impact of a near-earth object. It combines two types of data—probability of impact, and estimated kinetic yield—into a single "hazard" value. A rating of 0 means the hazard is as likely as the background hazard (defined as the average risk posed by objects of the same size or larger over the years until the date of the potential impact). A rating of +2 would indicate the hazard is 100 times more likely than a random background event. A similar but less complex scale is the Torino scale, which is used for simpler descriptions in the non-scientific media. Value A logarithmic scale is a scale of measurement that gives the logarithm of a physical quantity instead of the quantity itself. ... An astronomer or astrophysicist is a scientist whose area of research is astronomy or astrophysics. ... Near-Earth objects (NEO) are asteroids, comets and large meteoroids whose orbit intersects Earths orbit and which may therefore pose a collision danger. ... A datum is a statement accepted at face value (a given). Data is the plural of datum. ... The word probability derives from the Latin probare (to prove, or to test). ... Kinetic energy (also called vis viva, or living force) is energy possessed by a body by virtue of its motion. ... Yield may mean: In economics, yield is a measure of the amount of income an investment generates over time (related to return on investment). ... The Torino Scale is a method for categorizing the impact hazard associated with near-Earth objects (NEOs) such as asteroids and comets. ...

The Palermo Scale value, P, is defined as the base 10 logarithm of the ratio of the impact probability p_i to the background impact probability over the time T to the event:

The annual background impact frequency is defined for this purpose as:

where the energy threshold E is measured in megatons. A megaton or megatonne is a unit of mass equal to 1,000,000 metric tons, i. ...

The near-Earth object (89959) 2002 NT₇ was the first near-Earth object detected by NASA's latest NEO programme to be given a positive rating on the scale of 0.06, indicating a higher than background threat. The value was subsequently lowered to -0.25 after more measurements were taken. (89959) 2002 NT7 (also written (89959) 2002 NT7) is a near-Earth object (NEO) that became the first object observed by NASAs NEO program to be assigned a positive rating on the Palermo Technical Impact Hazard Scale for a potential impact date of February 1, 2019. ... The National Aeronautics and Space Administration (NASA) (established 1958) is the government agency responsible for the United States of Americas space program and long-term general aerospace research. ...

Asteroid (99942) 2004 MN₄ briefly (on December 27, 2004) held the record for Palermo scale values, with a value of 1.10 for a possible collision in the year 2029. The 1.10 value indicated that a collision with this object was considered to be almost 12.6 times more likely than a random background event: 1 in 37 instead of 1 in 472. The asteroid 2004 MN₄ was subsequently demoted to have a Palermo rating of -1.59. Before 2004 MN₄, asteroid (29075) 1950 DA held the record for Palermo scale values, with a value of 0.17 for a possible collision in the year 2880. Close approach of 2004 MN4 on April 13, 2029 The white bar indicates uncertainty in the range of positions (99942) 2004 MN4 (also written (99942) 2004 MN4) is a Near-Earth asteroid discovered by David J. Tholen that caused a brief period of concern in late 2004. ... December 27 is the 361st day of the year in the Gregorian Calendar. ... 2004 is a leap year starting on Thursday of the Gregorian calendar. ... 2029 is a Common year starting on Monday. ... Asteroid 1950 DA (29075) 1950 DA is an asteroid considered to be the near Earth object with the highest known likelihood of crashing into Earth, according to the Palermo Technical Impact Hazard Scale. ... (Redirected from 2880) (28th century - 29th century - 30th century - more centuries) The 29th century (Gregorian Calendar) comprises the years 2801-2900. ...

See also

• Near-Earth object
• Torino scale

Near-Earth objects (NEO) are asteroids, comets and large meteoroids whose orbit intersects Earths orbit and which may therefore pose a collision danger. ... The Torino Scale is a method for categorizing the impact hazard associated with near-Earth objects (NEOs) such as asteroids and comets. ...

External links

• NASA NEO Programme http://neo.jpl.nasa.gov/index.html
• Description of the scale http://neo.jpl.nasa.gov/risk/doc/palermo.html
• (89959) 2002 NT₇ is the first object discovered with a positive measurement on the Palermo scale