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[[File:2005-YU55-Trajectory-8th-Nov-2011.png|thumb|left|alt=Skymap showing apparent trajectory of 2005 YU55.|Apparent trajectory on 8–9 November 2011.]]
[[File:2005-YU55-Trajectory-8th-Nov-2011.png|thumb|left|alt=Skymap showing apparent trajectory of 2005 YU55.|Apparent trajectory on 8–9 November 2011.]]


In February 2010, {{mp|2005 YU|55}} was rated 1 on the [[Torino Scale]], indicating that a pass near the Earth poses no unusual level of danger. On 19 April 2010, highly accurate [[radar astronomy|radar]] targeting by the [[Arecibo Observatory|Arecibo radio telescope]] reduced uncertainties about the orbit by 50%.<ref name="Cornell2010"/> This improvement eliminated any possibility of an impact with the Earth within the next 100 years.<ref name="Cornell2010"/> It was removed from the [[Sentry (monitoring system)|Sentry Risk Table]] on 22 April 2010 and as such it now has a rating of 0 on the Torino Scale.<ref name="removed"/>
In February 2010, {{mp|2005 YU|55}} was rated 1 on the [[Torino Scale]], indicating that a pass near the Earth poses no unusual level of danger. On 19 April 2010, [[radar astronomy|radar]] ranging by the [[Arecibo Observatory|Arecibo radio telescope]] reduced uncertainties about the orbit by 50%.<ref name="Cornell2010"/> This improvement eliminated any possibility of an impact with the Earth within the next 100 years.<ref name="Cornell2010"/> It was removed from the [[Sentry (monitoring system)|Sentry Risk Table]] on 22 April 2010 and as such it now has a rating of 0 on the Torino Scale.<ref name="removed"/>


On 8 November 2011 at 23:28 [[Universal Time|UT]] the asteroid safely passed {{convert|0.8453|LD|km mi|abbr=on|lk=on}} from the Earth.<ref name="NASA2011-332"/> On 9 November 2011 at 07:13 UT the asteroid passed {{convert|0.6231|LD|km mi|abbr=on}} from the Moon.<ref name=jpl-close/> During the close approach the asteroid reached about [[apparent magnitude]] 11,<ref name="news171"/><ref name="NEODyS2011"/> and would have been visible to experienced observers using high-end [[Binoculars#Astronomical|binoculars]] with an [[objective lens]] of 80+&nbsp;[[Millimetre|mm]] if it were not for bright moonlight preventing a true [[Bortle Dark-Sky Scale|dark sky]]. Since the [[Lunar phase|gibbous moon]] did interfere with the viewing,<ref name="Goldstone-planning"/> observers trying to visually locate the asteroid required a telescope with an aperture of 6&nbsp;inches (15 centimeters) or larger.<ref name="Goldstone-planning"/><ref name="NASA2011-332"/>
On 8 November 2011 at 23:28 [[Universal Time|UT]] the asteroid passed {{convert|0.8453|LD|km mi|abbr=on|lk=on}} from the Earth.<ref name="NASA2011-332"/> On 9 November 2011 at 07:13 UT the asteroid passed {{convert|0.6231|LD|km mi|abbr=on}} from the Moon.<ref name=jpl-close/> During the close approach the asteroid reached about [[apparent magnitude]] 11,<ref name="news171"/><ref name="NEODyS2011"/> and would have been visible to experienced observers using high-end [[Binoculars#Astronomical|binoculars]] with an [[objective lens]] of 80+&nbsp;[[Millimetre|mm]] if it were not for bright moonlight preventing a true [[Bortle Dark-Sky Scale|dark sky]]. Since the [[Lunar phase|gibbous moon]] did interfere with the viewing,<ref name="Goldstone-planning"/> observers trying to visually locate the asteroid required a telescope with an aperture of 6&nbsp;inches (15 centimeters) or larger.<ref name="Goldstone-planning"/><ref name="NASA2011-332"/>


The next time a known asteroid this large will come this close to Earth will be in 2028<ref name="Goldstone-planning"/> when {{mpl|(153814) 2001 WN|5}} passes {{convert|0.00166|AU|km mi|abbr=on}} from the Earth.<ref name=jpl-close-WN5/>
The next time a known asteroid this large will come this close to Earth will be in 2028<ref name="Goldstone-planning"/> when {{mpl|(153814) 2001 WN|5}} passes {{convert|0.00166|AU|km mi|abbr=on}} from the Earth.<ref name=jpl-close-WN5/>

Revision as of 21:10, 9 April 2012

2005 YU55
Goldstone radar image of asteroid 2005 YU55
taken November 7, 2011.
Discovery[1]
Discovered byR. S. McMillan
Steward Observatory,
Kitt Peak (691)
Discovery dateDecember 28, 2005
Designations
Designation
2005 YU55
PHA[2]
Apollo[2]
Orbital characteristics[2]
Epoch 2010-Jul-23 (JD 2455400.5)
(Uncertainty=1)[2]
Aphelion1.6329 AU (Q)
Perihelion0.65241 AU (q)
1.1427 AU (a)
Eccentricity0.42905
1.22 yr
26.094° (M)
Inclination0.51351°
39.304°
268.79°
Physical characteristics
Dimensions310[3]-400 meters[4][5]
18 hr[2][6]
Spectral type
C-type[4]
21.1[2]

2005 YU55, also written as 2005 YU55, is a potentially hazardous asteroid[2] 310 meters[3] or about 400 m (1,300 feet) in diameter.[4][5] It was discovered on 28 December 2005 by Robert S. McMillan at Steward Observatory, Kitt Peak.[1] On 8 November 2011 it passed 0.85 lunar distances (324,900 kilometers; 201,900 miles)[7] from the Earth. This is the closest known approach by an asteroid with an absolute magnitude this bright since 2010 XC15 (H = 21.4) approached within 0.5 lunar distances in 1976.[6]

Impact risk assessment

Animation of the trajectory of asteroid 2005 YU55 compared with the orbits of the Earth and the Moon on 8–9 November 2011.
Trajectory of asteroid 2005 YU55 compared with the orbits of the Earth and the Moon on 8–9 November 2011.
Skymap showing apparent trajectory of 2005 YU55.
Apparent trajectory on 8–9 November 2011.

In February 2010, 2005 YU55 was rated 1 on the Torino Scale, indicating that a pass near the Earth poses no unusual level of danger. On 19 April 2010, radar ranging by the Arecibo radio telescope reduced uncertainties about the orbit by 50%.[5] This improvement eliminated any possibility of an impact with the Earth within the next 100 years.[5] 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.[8]

On 8 November 2011 at 23:28 UT the asteroid passed 0.8453 LD (324,900 km; 201,900 mi) from the Earth.[7] On 9 November 2011 at 07:13 UT the asteroid passed 0.6231 LD (239,500 km; 148,800 mi) from the Moon.[9] During the close approach the asteroid reached about apparent magnitude 11,[4][10] 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,[6] observers trying to visually locate the asteroid required a telescope with an aperture of 6 inches (15 centimeters) or larger.[6][7]

The next time a known asteroid this large will come this close to Earth will be in 2028[6] when (153814) 2001 WN5 passes 0.00166 AU (248,000 km; 154,000 mi) from the Earth.[11]

According to Jay Melosh, if an asteroid the size of 2005 YU55 (~400 m across) were to hit land, it would create a crater 6.3 km (3.9 mi) across, 518 m (1,699 ft) deep and generate a seven-magnitude-equivalent-earthquake.[12]. The chances of an actual collision with an asteroid like 2005 YU55 is about 1 percent in the next thousand years.[12]

Study

Swift captures flyby of asteroid 2005 YU55.

During the 2011 passage 2005 YU55 was studied with radar using Goldstone, Arecibo, the Very Long Baseline Array, and the Green Bank Telescope.[6] The Herschel Space Observatory has made far-infrared measurements of 2005 YU55 on November 10, helping determine its temperature and composition.[13]

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.

On November 8, 2011, NASA released a statement mentioning a number of structures on the surface of the asteroid, which were detected as it passed near the Earth.[14] On November 11, 2011, more refined images provided evidence that these structures are concavities, a ridge near the asteroid's equator, and numerous features that may be large boulders.[15]

Future trajectory

On 19 January 2029, 2005 YU55 will pass 0.0023 AU (340,000 km; 210,000 mi) from Venus.[9] The close approach distance to Venus in 2029 determined how close the asteroid will pass the Earth in 2041.[6] Before the November 2011 observations, the uncertainties in the post-2029 trajectory showed that the asteroid would pass somewhere between 0.002 AU (300,000 km; 190,000 mi) and 0.3 AU (45,000,000 km; 28,000,000 mi) of the Earth in 2041.[6] Radar astrometry in November 2011 clarified the Earth passage in 2041 and beyond.[6] As a result of the November 2011 radar observations, it is now known that 2005 YU55 will pass between 0.1017 AU (15,210,000 km; 9,450,000 mi) and 0.1023 AU of the Earth on 12 November 2041.[9] Using the current uncertainty region integrated until the future, the 2075 approach will be between 0.0013 AU (190,000 km; 120,000 mi) and 0.0042 AU (630,000 km; 390,000 mi).[9]

References

  1. ^ a b "MPEC 2005-Y47 : 2005 YU55". IAU Minor Planet Center. 2005-12-29. Retrieved 2011-05-05.
  2. ^ a b c d e f g "JPL Small-Body Database Browser: (2005 YU55)". 2011-11-06 last obs. Retrieved 2011-05-05. {{cite web}}: Check date values in: |date= (help)
  3. ^ a b The Herschel Space Observatory catches a glimpse of the minor planet during its rendezvous with Earth (November 17, 2011)
  4. ^ a b c d Don Yeomans, Lance Benner and Jon Giorgini (March 10, 2011). "Asteroid 2005 YU55 to Approach Earth on November 8, 2011". NASA/JPL Near-Earth Object Program Office. Archived from the original on 24 April 2011. Retrieved 2011-05-05. {{cite web}}: Unknown parameter |deadurl= ignored (|url-status= suggested) (help)
  5. ^ a b c d Blaine Friedlander Jr. (April 30, 2010). "Arecibo telescope tracks 'potentially dangerous' asteroid within 1.5 million miles of Earth". Cornell Chronicle @ Cornell University. Archived from the original on 23 May 2011. Retrieved 2011-05-05. {{cite web}}: Unknown parameter |deadurl= ignored (|url-status= suggested) (help)
  6. ^ a b c d e f g h i Dr. Lance A. M. Benner (2011 Oct 29). "2005 YU55 Goldstone Radar Observations Planning". NASA/JPL Asteroid Radar Research. Retrieved 2011-10-30. {{cite web}}: Check date values in: |date= (help); External link in |author= (help)
  7. ^ a b c "NASA in Final Preparations for Nov. 8 Asteroid Flyby". NASA/JPL. October 26, 2011. Retrieved 2011-10-26.
  8. ^ "Date/Time Removed". NASA/JPL Near-Earth Object Program Office. Archived from the original on 26 April 2011. Retrieved 2011-05-06. {{cite web}}: Unknown parameter |deadurl= ignored (|url-status= suggested) (help)
  9. ^ a b c d "JPL Close-Approach Data: (2005 YU55)". 2011-11-06 last obs. Retrieved 2011-05-05. {{cite web}}: Check date values in: |date= (help)
  10. ^ "2005YU55 Ephemerides for 9 Nov 2011". NEODyS (Near Earth Objects – Dynamic Site). Retrieved 2011-05-05.
  11. ^ "JPL Close-Approach Data: 153814 (2001 WN5)". 2011-01-04 last obs (arc=14.9 years). Retrieved 2011-10-16. {{cite web}}: Check date values in: |date= (help)
  12. ^ a b Elizabeth K. Gardner (October 31, 2011). "Large asteroid to pass by Earth Nov. 8, but what if it didn't?". Purdue University. Retrieved 2011-11-07.
  13. ^ chrisnorth (06/11/2011). "Herschel to observe near-Earth asteroid". UK Outreach Site for the Herschel Space Observatory. Retrieved 2011-11-07. {{cite web}}: Check date values in: |date= (help)
  14. ^ "NASA Releases Radar Movie of Asteroid 2005 YU55". NASA. November 8, 2011. Retrieved 6 December 2011.
  15. ^ "NASA Releases Updated Radar Movie of Asteroid 2005 YU55 (2011-351)". NASA/JPL. 11.11.11. Retrieved 2011-12-06. {{cite web}}: Check date values in: |date= (help)
Wikimedia Commons has media related to (308635) 2005 YU55.
Preceded by Large NEO Earth close approach
(inside the orbit of the moon)
8 November 2011 		Succeeded by
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