Asteroid to Make Near Earth Pass

An aircraft carrier-sized asteroid is hurtling through our cosmic neighborhood. 2005 YU55 is going to be zipping by on November 8 in what scientists are calling a close encounter. The asteroid is not going to hit Earth but it will be about 15 percent closer to Earth than the moon, making it quite an astronomical event.

This is the first time that scientists will have a front row seat to view an asteroid that they know is on close approach.

Barbara Wilson, a scientist at NASA’s Jet Propulsion Laboratory tells the Daily Mail in the UK, “While near-Earth objects of this size have flown within a lunar distance in the past, we did not have the foreknowledge and technology to take advantage of the opportunity.”

For the occasion NASA is pulling out the big radio telescope guns to get a clear picture of what will whiz by next week. Radar, visual and infrared imaging will follow the track of the big space rock and gather as much information as possible. This will help scientists better track its course, which does pose a minor threat to Earth. The next time this asteroid will be close to Earth will be in another hundred years.

NASA says, “Although 2005 YU55 is in an orbit that regularly brings it to the vicinity of Earth (and Venus and Mars), the 2011 encounter with Earth is the closest this space rock has come for at least the last 200 years.”

The next time a rock of this size will buzz Earth will be in 2028.

Scientists have been following 2005 YU55 and for six years and have been preparing for its near-Earth arrival for months. Generally space-based telescopes and instruments study asteroids up close. But this will be a “science target of opportunity” for spacecraft Earth to scan the asteroid.

Dr. Wilson says, “When it flies past, it should be a great opportunity for science instruments on the ground to get a good look.”

Starting November 4, the Deep Space Network antennas in Goldstone, California will begin tracking the asteroid from the ground. Then on November 8 — the day the asteroid makes its closest pass of Earth — the giant radio telescope at Arecibo Planetary Radar Facility in Puerto Rico will begin bouncing radio waves off the giant rock to understand its composition, size, surface features and other physical properties.

The closest 2005 YU55 will get to Earth is about .85 lunar distances or 201,000 miles. That distance is not enough to have any affect on anything here on Earth, including tides or tectonic plates.

Radar observations made in April 2010 by the Arecibo telescope show the asteroid to be about 1,300-feet wide and sphere shaped. It slowly spins, with one rotation about every 18 hours. The asteroid’s surface is likely dark. And amateur astronomers who want to get a glimpse at 2005 YU55 will need a telescope with an aperture of 6 inches or larger.

A NASA spokesman says that there are only two places in the world where radar astronomy is effectively performed — the 1,000-foot diameter Arecibo telescope and the 70-meter Goldstone antenna in California’s Mojave Desert. He says, “Together they make a formidable asteroid reconnaissance team.”

The Arecibo radar is 30 times more sensitive than Goldstone but not fully steerable. Goldstone is fully steerable but not as sensitive. Together, the two instruments are complimentary.

JPL radar astronomer Steve Ostro says, “The closer the target, the better the echo.” Using the radio wave echos astronomers generate detailed three-dimensional models of the asteroid, define its rotation and get a good idea of its internal density distribution. Dr. Ostro says, “You can even make out surface features. A good echo can give us a spatial resolution finer than 10 meters.”

2005 YU55 will be close enough for astronomers to get high resolution, somewhere in the neighborhood of 2 meters, which means scientists will be able to see any features that are just over six feet across on the surface of the asteroid, including any moons that might be accompanying the big rock.

The last time a space rock as big came this close to Earth was in 1976, although astronomers did not know about the flyby at the time.

NASA detects, tracks and characterizes asteroids and comets passing close to Earth using both ground- and space-based telescopes. The Near-Earth Object Observations Program, commonly called “Spaceguard,” discovers these objects, characterizes a subset of them, and plots their orbits to determine if any could be potentially hazardous to our planet.