Arecibo Observatory took radar images of asteroid 1998 QE2 and its moon as the space rock sailed safely past earth. The sequence of images show a dark, cratered asteroid 3.0 kilometers across (1.9 miles) across with a companion moon about 750 meters (2500 feet) in size. Both the asteroid and its moon passed 6 million kilometers (3.8 million miles) from earth. This object has no chance of hitting the Earth, but comes close enough to study with a variety of telescopes, large and small.
Each vertical pixel corresponds to 7.5 meters (25 feet) in range, while horizontal pixels correspond to 0.075 Hz (Doppler shift due to rotation).
|Radar images of asteroid 1998 QE2 (bottom) and its satellite (top) on June 6. Each frame in the animation is a sum of 4 images, spaced apart by about 10 minutes. Credit: Arecibo Observatory/NAIC/Sean Marshall|
|Radar images of asteroid 1998 QE2 (center) and its satellite (bottom left) on June 7. Each frame in the animation is a sum of 4 images, spaced apart by about 10 minutes. Credit: Arecibo Observatory/NAIC/Sean Marshall|
|Radar images of asteroid 1998 QE2 (bottom) and its satellite (top) on June 6. Each image is a sum of 4, spaced apart by about 10 minutes.|
|Radar image from June 7 showing the satellite moving past the primary. Orbital period is about 32 hours.|
|Radar image from June 9 showing some surface details and the satellite moving past the primary. Orbital period is about 32 hours.|
|Spectrum of 1998 QE2 taken 30 May at the NASA IRTF on Mauna Kea, Hawaii. The spectrum is red sloped and linear, which indicates a primitive composition, not matching any meteorites we have in our collection. The steep rise beyond 2.0 microns is due to the thermal emission of this dark asteroid, since it is so close to the Earth at 1 AU. We will analyze the spectra to determine the composition and thermal properties of this NEA binary system. The orbit should let us determine the mass of the primary. The radar images will give us the size, so we can determine the density of this asteroid, and get clues to its composition and structure.|
Aritst's conception of 1998 QE with 29 Queen Elizabeth II ships for size comparison.