Bye, Bye #55

So, YU55 has been here and gone.  Check out a video and more:


Huge Asteroid 2005 YU55 Zips by Earth in Rare Close Flyby

by Mike Wall, Senior Writer
Date: 08 November 2011 Time: 06:28 PM ET
Asteroid 2005 YU55
This radar image of asteroid 2005 YU55 was obtained on Nov. 7, 2011, at 11:45 a.m. PST (2:45 p.m. EST/1945 UTC), when the space rock was at 3.6 lunar distances, which is about 860,000 miles, or 1.38 million kilometers, from Earth.

An asteroid the size of a city block zoomed inside the moon’s orbit today (Nov. 8) in a rare flyby that marked the closest approach to Earth by such a big space rock in 35 years.

The asteroid 2005 YU55 came within 201,700 miles (324,600 kilometers) of Earth at 6:28 p.m. EST (2328 GMT) Tuesday evening before speeding off into deep space once again at about 29,000 mph (46,700 kph).

The space rock is about 1,300 feet (400 meters) wide. An asteroid this large hasn’t come so near to Earth since 1976 and won’t again until 2028, researchers said.

The asteroid encounter brought 2005 YU55 closer than the moon, which orbits Earth at an average distance of 238,864 miles (384,499 km). But there was never any danger that 2005 YU55 would slam into Earth today.

Scientists eagerly awaited the close encounter all the same, since it’s providing an unprecedented opportunity to learn more about the asteroid and its orbit.

“We would really like to characterize it as much as possible, and learn about its past and about its future,” said Marina Brozovic, a scientist with NASA’s Near-Earth Object Office at the Jet Propulsion Laboratory (JPL) in Pasadena, Calif., before today’s flyby. “I really can’t wait to see the images.”

Photos and videos of asteroid 2005 YU55 released by NASA just before and during the flyby revealed the space rock to be a relatively round but lumpy object. [See the latest photos and videos of asteroid 2005 YU55]

Studying 2005 YU55

Astronomers are taking advantage of the close encounter with 2005 YU55, which was discovered in 2005 by Robert McMillan of the University of Arizona’s Lunar and Planetary Laboratory.

Scientists have trained a suite of instruments on the asteroid, including giant radio telescopes at the Arecibo observatory in Puerto Rico and NASA’s Deep Space Network facility in Goldstone, Calif.

The aim is to get a better idea of 2005 YU55’s size, surface features, rotational period and orbit, researchers said.

2005 YU55 makes one complete lap around the sun every 15 months. Astronomers have already determined that the asteroid poses no threat to Earth for at least the next century, but observations made during this close approach should help them predict its movements even further into the future.

“For many centuries, we’ll know exactly where this object is going to be,” Brozovic said.

NASA has already released a new image of 2005 YU55 taken by the big Goldstone antenna, with many more surely on the way. And several organizations, including the Clay Center Observatory in Massachusetts and the online telescope service Slooh, provided live webcasts of the space rock’s close flyby.

2005 YU55 sky chart
This sky chart shows the motion of asteroid 2005 YU55 as it zooms by Earth on the evening of Nov. 8, 2011.
CREDIT: Sky & Telescope magazine (

Still visible in telescopes

Skywatchers under clear, dark skies still have a chance to spot 2005 YU55 before it disappears into deep space. The best time to look up is a few hours after closest approach, according to Sky & Telescope magazine.

You’ll need a telescope to find the space rock, which is relatively small and dim. Any scope with an aperture greater than 6 inches should be able to spot 2005 YU55, experts say.

The tricky part will be knowing where to look, since 2005 YU55 will be moving across the sky at about 7 degrees per hour (your clenched fist held at arm’s length measures about 10 degrees). You can look up the asteroid’s coordinates at JPL’s Solar System Dynamics website, which is found here:

if you missed the video, you can get it here, at the article’s source:

NASA Live Track YU55 Asteroid 11/08

ASA in Final Preparations for Nov. 8 Asteroid Flyby

Radar image of asteroid 2005 YU55This radar image of asteroid 2005 YU55 was generated from data taken in April 2010 by the Arecibo Radar Telescope in Puerto Rico. Image credit: NASA/Cornell/Arecibo

Animation of the trajectory for asteroid 2005 YU55Animation of the trajectory for asteroid 2005 YU55 – November 8-9, 2011. Image credit: NASA/JPL-Caltech

NASA scientists will be tracking asteroid 2005 YU55 with antennas of the agency’s Deep Space Network at Goldstone, Calif., as the space rock safely flies past Earth slightly closer than the moon’s orbit on Nov. 8. Scientists are treating the flyby of the 1,300-foot-wide (400-meter) asteroid as a science target of opportunity – allowing instruments on “spacecraft Earth” to scan it during the close pass.

Tracking of the aircraft carrier-sized asteroid will begin at 9:30 a.m. local time (PDT) on Nov. 4, using the massive 70-meter (230-foot) Deep Space Network antenna, and last for about two hours. The asteroid will continue to be tracked by Goldstone for at least four hours each day from Nov. 6 through Nov. 10. Radar observations from the Arecibo Planetary Radar Facility in Puerto Rico will begin on Nov. 8, the same day the asteroid will make its closest approach to Earth at 3:28 p.m. PST.

The trajectory of asteroid 2005 YU55 is well understood. At the point of closest approach, it will be no closer than 201,700 miles (324,600 kilometers) or 0.85 the distance from the moon to Earth. The gravitational influence of the asteroid will have no detectable effect on anything here on Earth, including our planet’s tides or tectonic plates. 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.

During tracking, scientists will use the Goldstone and Arecibo antennas to bounce radio waves off the space rock. Radar echoes returned from 2005 YU55 will be collected and analyzed. NASA scientists hope to obtain images of the asteroid from Goldstone as fine as about 7 feet (2 meters) per pixel. This should reveal a wealth of detail about the asteroid’s surface features, shape, dimensions and other physical properties (see “Radar Love” –

Arecibo radar observations of asteroid 2005 YU55 made in 2010 show it to be approximately spherical in shape. It is slowly spinning, with a rotation period of about 18 hours. The asteroid’s surface is darker than charcoal at optical wavelengths. Amateur astronomers who want to get a glimpse at YU55 will need a telescope with an aperture of 6 inches (15 centimeters) or larger.

The last time a space rock as big came as close to Earth was in 1976, although astronomers did not know about the flyby at the time. The next known approach of an asteroid this large will be in 2028.

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.

NASA’s Jet Propulsion Laboratory manages the Near-Earth Object Program Office for NASA’s Science Mission Directorate in Washington. JPL is a division of the California Institute of Technology in Pasadena.

More information about asteroids and near-Earth objects is at:

More information about asteroid radar research is at: .

More information about the Deep Space Network is at: .