Potentially Hazardous Asteroids (PHA's):

are currently defined based on parameters that measure the asteroid's potential to make threatening close approaches to the Earth.

Specifically, all asteroids with an Earth Minimum Orbit Intersection Distance (M.O.I.D.) of 0.05 AU or less and an absolute V-magnitude (H) of 22.0 or less are considered PHA's. In other words, asteroids that can't get any closer to the Earth (i.e. M.O.I.D) than 0.05 AU (roughly 7,480,000 km or 4,650,000 mi) or are smaller than about 150 m (500 ft) in diameter (i.e. H = 22.0 with assumed albedo of 13%) are not considered PHA's.

There are currently 241 known PHA's.

On March 23, 2000 a newly discovered PHA (2000 EW70) passed within 0.013 AU of Earth.

Below is a list of PHA's for 2000 - 2003:

Object	Name	Date of encounter	Distance (A.U.)
4486	Mithra	2000 08 14.34	0.0465
1999	KW4	2001 05 25.98	0.0323
1998*	WT24	2001 12 16.24	*0.0125
4660	Nereus	2002 01 22.52	0.0290
1998	FH12	2003 06 27.22	0.0495
1994	PM	2003 08 16.59	0.0250
1998	FG2	2003 10 21.77	0.0360
1996	GT	2003 11 12.91	0.0479

* closest approach PHA for the next 20 years (that we know about).

updated: