2005 YU55
Encyclopedia
, also written as 2005 YU55, is a potentially hazardous asteroid 310 meters or about 400 m (1,300 feet) in diameter. It was discovered on 28 December 2005 by Robert S. McMillan
at Steward Observatory
, Kitt Peak. On 8 November 2011 it passed 0.85 lunar distance
s (324,900 kilometers; 201,900 miles
) from the Earth. This is the closest known approach by an asteroid with an absolute magnitude this bright since (H = 21.4) approached within 0.5 lunar distances in 1976.
, indicating that a pass near the Earth is predicted that poses no unusual level of danger. On 19 April 2010, highly accurate radar
targeting by the Arecibo radio telescope
reduced uncertainties about the orbit by 50%. This improvement eliminated any possibility of an impact with the Earth within the next 100 years. It was removed from the Sentry Risk Table
on 22 April 2010 and as such it now has a rating of 0 on the Torino Scale.
On 8 November 2011 at 23:28 UT
the asteroid safely passed 0.8453 LD from the Earth. On 9 November 2011 at 07:13 UT the asteroid passed 0.6231 LD from the Moon. During the close approach the asteroid reached about apparent magnitude
11, and would have been visible to experienced observers using high-end binoculars with an objective lens of 80+ mm
if it were not for bright moonlight preventing a true dark sky
. Since the gibbous moon
did interfere with the viewing, observers trying to visually locate the asteroid required a telescope with an aperture of 6 inches (15 centimeters) or larger.
The next time a known asteroid this large will come this close to Earth will be in 2028 when passes 0.00166 AU from the Earth.
According to Jay Melosh, if an asteroid the size of (~400 m across) were to hit land, it would create a crater
6.3 km (3.9 mi) across, 518 m (1,699.5 ft) deep and generate a seven-magnitude
-equivalent-earthquake. If an asteroid such as (~580 m across) were to impact land, it would produce a crater about 10 km (6.2 mi) wide and an earthquake of magnitude 7.4. The chances of an actual collision with an asteroid like is about 1 percent in the next thousand years.
, Arecibo
, the Very Long Baseline Array
, and the Green Bank Telescope
. The Herschel Space Observatory
has made far-infrared
measurements of on November 10, helping determine its temperature and composition.
Radar analysis has also helped to pin down the asteroid's albedo
, or diffuse reflectivity
. Although radar measurements do not detect visible light they can determine the distance and size of an object with a high degree of accuracy. This information, coupled with visible light measurements, provides a more accurate measure of an object's absolute magnitude
, and therefore its albedo.
. The close approach to Venus in 2029 will determine how close the asteroid will pass the Earth in 2041. The uncertainties in the post-2029 trajectory will cause the asteroid to pass somewhere between 0.002 AU and 0.3 AU from the Earth in 2041. Radar astrometry in November 2011 should clarify the Earth encounter situation in 2041 and beyond. , the nominal solution shows passing 0.1 AU from the Earth on 12 November 2041.
Robert S. McMillan
Robert S. McMillan is an astronomer at the University of Arizona, and heads the Spacewatch project, which studies minor planets. He has made various discoveries, including notably 20000 Varuna....
at Steward Observatory
Steward Observatory
The University of Arizona's Steward Observatorys main office is located on the University's campus and is closely tied to the Department of Astronomy. Established in 1916 by its first director, Andrew Ellicott Douglass, and a $60,000 bequest made by Lavinia Steward in memory of her late husband...
, Kitt Peak. On 8 November 2011 it passed 0.85 lunar distance
Lunar distance (astronomy)
In astronomy, a lunar distance is a measurement of the distance from the Earth to the Moon. The average distance from Earth to the Moon is 384,400 kilometers...
s (324,900 kilometers; 201,900 miles
Miles
Miles is the plural of mile.Miles may also refer to:- People :*Miles Brothers, American cinema pioneers* Miles ** Miles Browning, World War II admiral** Miles Davis, jazz trumpet player** Miles Austin, Dallas Cowboys wide receiver...
) from the Earth. This is the closest known approach by an asteroid with an absolute magnitude this bright since (H = 21.4) approached within 0.5 lunar distances in 1976.
Impact risk assessment
In February 2010, was rated 1 on the Torino ScaleTorino Scale
The Torino Scale is a method for categorizing the impact hazard associated with near-Earth objects such as asteroids and comets.It is intended as a communication tool for astronomers and the public to assess the seriousness of collision predictions, by combining probability statistics and known...
, indicating that a pass near the Earth is predicted that poses no unusual level of danger. On 19 April 2010, highly accurate radar
Radar astronomy
Radar astronomy is a technique of observing nearby astronomical objects by reflecting microwaves off target objects and analyzing the echoes. This research has been conducted for six decades. Radar astronomy differs from radio astronomy in that the latter is a passive observation and the former an...
targeting by the Arecibo radio telescope
Arecibo Observatory
The Arecibo Observatory is a radio telescope near the city of Arecibo in Puerto Rico. It is operated by SRI International under cooperative agreement with the National Science Foundation...
reduced uncertainties about the orbit by 50%. This improvement eliminated any possibility of an impact with the Earth within the next 100 years. It was removed from the Sentry Risk Table
Sentry (monitoring system)
Sentry is a highly automated collision monitoring system that continually scans the most current asteroid catalog for possibilities of future impact with Earth over the next 100 years...
on 22 April 2010 and as such it now has a rating of 0 on the Torino Scale.
On 8 November 2011 at 23:28 UT
Universal Time
Universal Time is a time scale based on the rotation of the Earth. It is a modern continuation of Greenwich Mean Time , i.e., the mean solar time on the Prime Meridian at Greenwich, and GMT is sometimes used loosely as a synonym for UTC...
the asteroid safely passed 0.8453 LD from the Earth. On 9 November 2011 at 07:13 UT the asteroid passed 0.6231 LD from the Moon. During the close approach the asteroid reached about apparent magnitude
Apparent magnitude
The apparent magnitude of a celestial body is a measure of its brightness as seen by an observer on Earth, adjusted to the value it would have in the absence of the atmosphere...
11, and would have been visible to experienced observers using high-end binoculars with an objective lens of 80+ mm
Millimetre
The millimetre is a unit of length in the metric system, equal to one thousandth of a metre, which is the SI base unit of length....
if it were not for bright moonlight preventing a true dark sky
Bortle Dark-Sky Scale
The Bortle Dark-Sky Scale is a nine-level numeric scale that measures the night sky's and stars' brightness of a particular location. It quantifies the astronomical observability of celestial objects and the interference caused by light pollution and skyglow. John E...
. Since the gibbous moon
Lunar phase
A lunar phase or phase of the moon is the appearance of the illuminated portion of the Moon as seen by an observer, usually on Earth. The lunar phases change cyclically as the Moon orbits the Earth, according to the changing relative positions of the Earth, Moon, and Sun...
did interfere with the viewing, observers trying to visually locate the asteroid required a telescope with an aperture of 6 inches (15 centimeters) or larger.
The next time a known asteroid this large will come this close to Earth will be in 2028 when passes 0.00166 AU from the Earth.
According to Jay Melosh, if an asteroid the size of (~400 m across) were to hit land, it would create a crater
Impact crater
In the broadest sense, the term impact crater can be applied to any depression, natural or manmade, resulting from the high velocity impact of a projectile with a larger body...
6.3 km (3.9 mi) across, 518 m (1,699.5 ft) deep and generate a seven-magnitude
Richter magnitude scale
The expression Richter magnitude scale refers to a number of ways to assign a single number to quantify the energy contained in an earthquake....
-equivalent-earthquake. If an asteroid such as (~580 m across) were to impact land, it would produce a crater about 10 km (6.2 mi) wide and an earthquake of magnitude 7.4. The chances of an actual collision with an asteroid like is about 1 percent in the next thousand years.
Study
During the 2011 passage has been studied by radar using GoldstoneGoldstone Deep Space Communications Complex
The Goldstone Deep Space Communications Complex — commonly called the Goldstone Observatory — is located in California's Mojave Desert. Operated by ITT Corporation for the Jet Propulsion Laboratory, its main purpose is to track and communicate with space missions. It includes the Pioneer...
, Arecibo
Arecibo Observatory
The Arecibo Observatory is a radio telescope near the city of Arecibo in Puerto Rico. It is operated by SRI International under cooperative agreement with the National Science Foundation...
, the Very Long Baseline Array
Very Long Baseline Array
The Very Long Baseline Array is a system of ten radio telescopes controlled remotely from the Array Operations Center in Socorro, New Mexico by the National Radio Astronomy Observatory. The array works together as the world's largest dedicated, full-time astronomical instrument using the...
, and the Green Bank Telescope
Green Bank Telescope
The Robert C. Byrd Green Bank Telescope is the world's largest fully steerable radio telescope and the world's largest land-based movable structure. It is part of the National Radio Astronomy Observatory site at Green Bank, West Virginia, USA. The telescope honors the name of the late Senator...
. The Herschel Space Observatory
Herschel Space Observatory
The Herschel Space Observatory is a European Space Agency space observatory sensitive to the far infrared and submillimetre wavebands. It is the largest space telescope ever launched, carrying a single mirror of in diameter....
has made far-infrared
Infrared
Infrared light is electromagnetic radiation with a wavelength longer than that of visible light, measured from the nominal edge of visible red light at 0.74 micrometres , and extending conventionally to 300 µm...
measurements of on November 10, helping determine its temperature and composition.
Radar analysis has also helped to pin down the asteroid's albedo
Albedo
Albedo , or reflection coefficient, is the diffuse reflectivity or reflecting power of a surface. It is defined as the ratio of reflected radiation from the surface to incident radiation upon it...
, or diffuse reflectivity
Diffuse reflection
Diffuse reflection is the reflection of light from a surface such that an incident ray is reflected at many angles rather than at just one angle as in the case of specular reflection...
. Although radar measurements do not detect visible light they can determine the distance and size of an object with a high degree of accuracy. This information, coupled with visible light measurements, provides a more accurate measure of an object's absolute magnitude
Absolute magnitude
Absolute magnitude is the measure of a celestial object's intrinsic brightness. it is also the apparent magnitude a star would have if it were 32.6 light years away from Earth...
, and therefore its albedo.
Future trajectory
On 19 January 2029, will pass about 0.0023 AU from VenusVenus
Venus is the second planet from the Sun, orbiting it every 224.7 Earth days. The planet is named after Venus, the Roman goddess of love and beauty. After the Moon, it is the brightest natural object in the night sky, reaching an apparent magnitude of −4.6, bright enough to cast shadows...
. The close approach to Venus in 2029 will determine how close the asteroid will pass the Earth in 2041. The uncertainties in the post-2029 trajectory will cause the asteroid to pass somewhere between 0.002 AU and 0.3 AU from the Earth in 2041. Radar astrometry in November 2011 should clarify the Earth encounter situation in 2041 and beyond. , the nominal solution shows passing 0.1 AU from the Earth on 12 November 2041.
External links
- Orbital simulation from JPL (Java) / Horizons Ephemeris
- Live Webcast: Keck Telescope To Watch Asteroid Flyby (Ustream video)
- 2005 YU55 Observing Campaign
- Close, but no Cigar: The Flyby of Asteroid 2005 YU55 (MPC blog with flyby simulated animations)
- Orbital simulation of 2005 YU55 in an animated GIF image provided by nasa.gov
- NASA Asteroid Q&A (on YU55) (November 1, 2011)
- Arecibo saves us from another potentially hazardous asteroid (Emily Lakdawalla Apr. 29, 2010)
- No, 2005 YU55 won’t destroy the Earth (Phil Plait 9 May 2011)
- Asteroid 2005 YU55 will zip by Earth next week
- The Passage of Asteroid 2005 YU55 & How to See It. (David Dickinson November 5, 2011)
- Photos of flyby and Observation guide (Peter lake November 8, 2011)
- Rotation Simulation at Nasa.Gov
