Click on image for animation
Near-Earth asteroid 2005 YU55 will pass within 0.85 lunar distances from the Earth on November 8, 2011. The upcoming close approach by this relatively large 400 meter-sized, C-type asteroid presents an excellent opportunity for synergistic ground-based observations including optical, near infrared and radar data. The attached animated illustration shows the Earth and moon flyby geometry for November 8th and 9th when the object will reach a visual brightness of 11th magnitude and should be easily visible to observers in the northern and southern hemispheres. The closest approach to Earth and the Moon will be respectively 0.00217 AU and 0.00160 AU on 2011 November 8 at 23:28 and November 9 at 07:13 UT.
Discovered December 28, 2005 by Robert McMillan of the Spacewatch Program near Tucson Arizona, the object has been previously observed by Mike Nolan, Ellen Howell and colleagues with the Arecibo radar on April 19-21, 2010 and shown to be a very dark, nearly spherical object 400 meters in diameter. Because of its approximate 20-hour rotation period, ideal radar observations should include tracks that are 8 hours or longer on multiple dates at Goldstone (November 3-11) and when the object enters Arecibo's observing window on November 8th.
Using the Goldstone radar operating in a relatively new "chirp" mode, the November 2011 radar opportunity could result in a shape model reconstruction with a resolution of as fine as 4 meters. Several days of high resolution imaging (about 7.5 meters) are also planned at Arecibo. As well as aiding the interpretation of the radar observations, collaborative visual and near infrared observations could define the object's rotation characteristics and provide constraints upon the nature of the object's surface roughness and mineral composition.
Since the asteroid will approach the Earth from the sunward direction, it will be a daylight object until the time of closest approach. The best time for new ground-based optical and infrared observations will be late in the day on November 8, after 21:00 hours UT from the eastern Atlantic and western Africa zone. A few hours after its close Earth approach, it will become generally accessible for optical and near-IR observations but will provide a challenging target because of its rapid motion across the sky.
Edge-on view to the ecliptic plane
The near-Earth asteroid 2005 YU55 — on the list of potentially dangerous asteroids — was observed with the Arecibo Telescope's planetary radar on April 19, 2010, when it was about 1.5 million miles from Earth.
Mark your calendars for an impressive and upcoming flyby of an asteroid that’s one of the larger potentially perilous space rocks in the heavens – in terms of smacking the Earth in the future.
It’s the case of asteroid 2005 YU55, a round mini-world that is about 1,300 feet (400 meters) in diameter. In early November, this asteroid will approach Earth within a scant 0.85 lunar distances. [Photo of Asteroid 2005 YU55]
Due the object’s size and whisking by so close to Earth, an extensive campaign of radar, visual and infrared observations are being planned.
Asteroid 2005 YU55 was discovered by Spacewatch at the University of Arizona, Tucson’s Lunar and Planetary Laboratory on Dec. 28, 2005. En route and headed our way, the cosmic wanderer is another reminder about life here on our sitting duck of a planet
Close and big
“The close Earth approach of 2005 YU55 on Nov. 8, is unusual since it is close and big. On average, one wouldn’t expect an object this big to pass this close but every 30 years,” said Don Yeomans, manager of NASA’s Near-Earth Object Program Office and the Jet Propulsion Laboratory in Pasadena, Calif. [Photos: Asteroids in Deep Space]
Yeomans said that with new radar capabilities at Goldstone in California — part of NASA’s Deep Space Network — there is a good chance of obtaining radar imaging of 2005 YU55 down to the 5-meter resolution level. Doing so, he said, would mean obtaining higher spatial resolution of the object than that attained by recent spacecraft flyby missions.
“So we like to think of this opportunity as a close flyby mission with Earth as the spacecraft,” Yeomans told SPACE.com. “When combined with ground-based optical and near-infrared observations, the radar data should provide a fairly complete picture of one of the larger potentially hazardous asteroids,” he said.
Asteroid 2005 YU55 is a slow rotator. Because of its size and proximity to Earth, the Minor Planet Center in Cambridge, Mass., has designated the space rock as a “potentially hazardous asteroid.” [5 Reasons to Care About Asteroids]
Dishing it out
“We’re already preparing for the 2005 YU55 flyby,” said Lance Benner, a research scientist at JPL and a specialist on radar imaging of near-Earth objects. He said part of the plan is to observe the asteroid with radar using both the huge Arecibo dish in Puerto Rico and equipment at Goldstone.
“The asteroid will approach from the south, so Goldstone has the first chance to observe it due to its declination coverage,” Benner told SPACE.com.
To help coordinate the observing campaigns, “Radar Observations Planning” websites have been set up for this unusual occasion, Benner said.
“This flyby will be the closest by any near-Earth asteroid with an absolute magnitude this bright since 1976 and until 2028,” Benner added. “Having said that, nobody saw 2010 XC15 during its close flyby within 0.5 lunar distance in 1976,” he said, noting that this asteroid wasn’t discovered until late in 2010.
“Thus, the flyby by 2005 YU55 will be the closest actually observed by something this large, so it represents a unique opportunity,” Benner said. “In a real sense, this will provide imaging resolution comparable to or even better than a spacecraft mission flyby.”
Benner said that because the asteroid is zooming by Earth so very close, radar echoes will be extremely strong. One facility at Goldstone will be used to transmit and “radar paint” the object…another Goldstone dish is on tap to snag the reflected echo of radar data.
What can radar do?
Information collected by this technique, for example, can be transformed into 3-D shapes, with surface features and spin rates identified. The asteroid’s roughness and density can also be assessed. Furthermore, radar can improve the whereabouts of the object. By greatly shrinking uncertainties for newly discovered meandering NEOs, that in turn enables motion prediction for decades to centuries.
As for seeing the asteroid with small telescopes, start getting your gear ready.
Initially, the object will be too close to the sun and too faint for optical observers. But late in the day (Universal Time) on Nov. 8, the solar elongation will grow sufficiently to see it. Early on Nov. 9, the asteroid could reach about 11th magnitude for several hours before it fades as its distance rapidly increases, Benner explained.
Leonard David has been reporting on the space industry for more than five decades. He is past editor-in-chief of the National Space Society's Ad Astra and Space World magazines and has written for SPACE.com since 1999.