Back on May 29, asteroid 1998 QE2 passed some 3.75 million miles (6 million km) from Earth before receding back into deep space. Measuring 1.9 miles (3 km) across, this visitor from the main asteroid belt was never a threat to our planet. Instead it became a perfect target to ping with radio waves using the NASA’s Goldstone radar dish in California and the huge 1,000-foot (300-m) Arecibo Observatory in Puerto Rico.
Measuring the returned radar echoes, astronomers created images revealing 1998 QE2 as a dark object riddled with craters and orbited by a large moon about 2,500 feet in diameter. We saw the Goldstone pictures earlier this month, but recently I came across the higher-resolution images from Arecibo.
Why the moon appears brighter is not completely clear, but surface smoothness, composition (metal reflects radar better than stone) and even rotation rate can make an object appear brighter or fainter in radar. It’s important to remember these aren’t photos in the usual sense but maps of radio wave reflections that depend upon many factors.
Earlier this week we looked at galaxies that devour one another or whose motions through space lead to their convergence into a single larger galaxy by collision.
The Hubble Space Telescope recently photographed an amazing galactic duo - NGC 2936 and 2937 – caught in the act of a violent merger. As prelude to the “final event”, the gravitational might of the elliptical galaxy NGC 2937 has warped its companion’s stately spiral into a weird shape resembling a bird. Gas and dust pulled from the spiral and compressed by the elliptical’s gravity have ignited into brilliant new clusters of stars visible in the photo as sparkly blue patches.
The reddish-brown dust, once sedately striping the galaxy’s central plane, has been twisted into strands silhouetted against bursts of new star formation. Such fireworks!
If your tastes lean toward distorted and warped galaxies, take a few minutes to peruse astronomer Halton Arp’s Atlas of Peculiar Galaxies. 338 oddities, including many interacting pairs like the featured Arp 142, highlight the work.