1999 JM8

Discoverer

USAF Telescope 1999

Diameter (km)

3.5

Mass (kg)

?

Rotation period (hrs)

slow

Orbital period (yrs)

4.49219

Semimajor axis (AU)

2.72267

Orbital eccentricity

0.64366

Orbital Inclination (deg)

13.69243

Albedo

?

Type

?

Asteroid 1999 JM8 was observed by NASA's Goldstone Solar System Radar in California and the Arecibo Observatory in Puerto Rico. Images revealed that 1999 JM8 is a several-kilometer-wide object with a peculiar shape and an unusually slow and possibly complex spin state. With an average diameter of about 3.5 kilometers, 1999 JM8 is on of the largest near-Earth asteroid ever studied in detail.

Although this object can pass fairly close to Earth in celestial terms, astronomers concur that an actual encounter with Earth is not of concern in the next few centuries.

The asteroid was discovered on May 13, 1999, at a U.S. Air Force telescope in New Mexico. The discovery provided adequate notice for radar observations to be scheduled at Goldstone from July 18 to August 8 and at Arecibo from August 1-9 during the asteroid's close approach to 8.5 million kilometers the equivalent of 22 Earth-Moon distances.

Asteroid 1999 JM8 bears a striking resemblance to Toutatis, a similar-sized, slowly rotating object also studied in detail with radar. The fact that both these several-kilometer-wide asteroids are in extremely slow spin states suggests that slow rotators are fairly common among near-Earth asteroids. Collisions are thought to be the primary process that determines asteroid spin states.The images show impact craters with diameters as small as 100 meters - about the length of a football field - and a few as large as 1 kilometer. The density of craters suggest that the surface is geologically old, and is not simply a chip off of a parent asteroid. There is a concavity that is about half as wide as the asteroid itself, but it is not known yet whether or not it's an impact crater.

Images of 1999 JM8

Images, were taken on August 5, July 28, August 2 and August 1. Radar illumination is from the top and the asteroid's rotation is clockwise. The Goldstone images taken on July 28 have a vertical resolution of 38 meters per pixel and those taken on August 1 have a vertical resolution of 19 meters per pixel. The images taken by the Arecibo Observatory on August 2 and 5 have a vertical resolution of 15 meters per pixel.

1999 JM8

1999 JM8

1999 JM8

1999 JM8

1999 JM8

1999 JM8

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Last updated: March 15, 2002.

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