A new asteroid tops astronomers list of those to watch, with the odds of an impact put at about 1-in-1,000 for May 4, 2102.

The odds will likely go down or evaporate in the future when further observations allow astronomers to refine their projections of the object's path.

For now, however, the asteroid known as 2004 VD17 is the only one rated as a 2 on the Torino Scale, a zero-to-10 ranking of space-rock risk on which zero is little or no risk.

A Torino Scale 2 ranking means the object merits attention from astronomers. It does not mean they are concerned. Even if the asteroid were ultimately determined to be heading our way, there would be plenty of time to deflect it with future technologies, experts say.

The rock is about three-tenths of a mile (500 meters) in diameter. Though not big enough to cause global devastation, it could cause significant regional devastation were it to hit the planet.

"Fortunately, it is nearly a century before the close pass from VD17," wrote David Morrison, senior scientist for the NASA Astrobiology Institute, in his Near-Earth Object (NEO) newsletter today. "This should provide ample time to refine the orbit and, most probably, determine that the asteroid will miss the Earth."

Two other space rocks are of significant interest to astronomers for similar reasons.

Asteroid Apophis, formerly called 2004 MN4, is ranked Torino Scale 1, with impact odds of about 1-in-5,000 on April 13, 2036.

Asteroid 1950 DA has an even greater chance of hitting Earth, but not until the year 2880. That keeps it, by definition, off the Torino Scale for now.