{{Short description|Potentially hazardous near-Earth asteroid}} {{DISPLAYTITLE:{{mp|(308635) 2005 YU|55}}}} {{Infobox planet | minorplanet = yes | background = #FFC2E0 | name = {{mp|(308635) 2005 YU|55}} | image = 2005 YU55 Radar.gif | caption = Goldstone radar image of asteroid {{mp|2005 YU|55}}<br/>taken 9 November 2011. | discovery_ref = <ref name="MPEC2005-Y47"/> | discoverer = R. S. McMillan<br/>{{nowrap|Steward Observatory}}<br/>Kitt Peak (691) | discovered = 28 December 2005 | mpc_name = {{mp|(308635) 2005 YU|55}} | alt_names = | mp_category = {{ubl | {{mpcat|Apollo}} | NEO | PHA<ref name="jpldata"/> }} | orbit_ref = <ref name="jpldata"/> | epoch = 13 January 2016 (JD 2457400.5) | aphelion = {{convert|1.65562913|AU|Gm|abbr=on|lk=on}} ({{mvar|Q}}) | perihelion = {{convert|0.659003712|AU|Gm|abbr=on}} ({{mvar|q}}) | semimajor = {{convert|1.15731642|AU|Gm|abbr=on}} ({{mvar|a}}) | eccentricity = 0.430576028 ({{mvar|e}}) | period = 1.25 Jyr (454.75 d) | inclination = 0.340553512° ({{mvar|i}}) | asc_node = 35.9073158° ({{mvar|Ω}}) | mean_anomaly = 175.227687° ({{mvar|M}}) | arg_peri = 273.628156° ({{mvar|ω}}) | moid = {{Convert|0.000433476|AU|km|abbr=on}}<br/>(0.17 LD)<ref name="jpldata"/> | venus_moid = 0.0017 AU<br />(0.66 LD)<ref name="mpc"/> | mars_moid = 0.03884 AU<br />(15.11 LD)<ref name="mpc"/> | satellites = none<ref name="Goldstone-planning"/> | dimensions = {{val|360|40|ul=m}}<ref name=mpi/><ref name="news171"/><ref name="Cornell2010"/><ref name="Busch"/> | mass = | density = | surface_grav = | escape_velocity = | sidereal_day = {{Val|19.31|0.02|u=h}}<ref name="jpldata"/><ref name="Warner"/> | axial_tilt = | pole_ecliptic_lat = | pole_ecliptic_lon = | albedo = {{Val|0.042|0.008}} | spectral_type = C-type<ref name="news171"/><ref name="Warner"/><ref name="Moskovitz"/> | magnitude = | abs_magnitude = 21.9<ref name="jpldata"/><ref name="Warner"/> | mean_motion = {{Deg2DMS|0.791636668|sup=ms}} / day ({{mvar|n}}) | rotation = {{Convert|18|h|d|abbr=on|lk=on}} | mean_radius = 0.2 km | observation_arc = 2,183 days (5.98 yr) | uncertainty = 0 | jupiter_moid = {{convert|3.60813|AU|Gm|abbr=on}} | tisserand = 5.347 }}
'''{{mp|(308635) 2005 YU|55}}''' is a potentially hazardous asteroid<ref name=jpldata/> {{val|360|40}} meters in diameter, as measured after its Earth flyby.<ref name="Busch"/> Previously it was estimated to be 310 meters<ref name=mpi>[https://www.mpg.de/4652308/2005_YU55_rocks_in_space?filter_order=L The Herschel Space Observatory catches a glimpse of the minor planet during its rendezvous with Earth (17 November 2011)]</ref> or about 400 m (1,300 feet) in diameter.<ref name="news171"/><ref name="Cornell2010"/> It was discovered on 28 December 2005 by Robert S. McMillan at Steward Observatory, Kitt Peak.<ref name="MPEC2005-Y47"/> On 8 November 2011 it passed 0.85 lunar distances (324,900 kilometers; 201,900 miles)<ref name="NASA2011-332"/> from Earth.
== 8 November 2011 flyby == [[File:2005 YU55 approach 8-9 November 2011.gif|thumb|left|alt=Animation of the trajectory of asteroid 2005 YU55 compared with the orbits of Earth and the Moon on 8–9 November 2011.|Trajectory of asteroid {{mp|2005 YU|55}} compared with the orbits of Earth and the Moon on 8–9 November 2011.]] 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 for a potential pass near Earth on 10 November 2103,<ref name=Wayback2010-03/> that posed no unusual level of danger. On 19 April 2010, radar ranging by the Arecibo radio telescope reduced uncertainties about the orbit by 50%.<ref name="Cornell2010"/> This improvement eliminated any possibility of an impact with Earth within the next 100 years.<ref name="Cornell2010"/> 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.<ref name="removed"/> It is now known that on 10 November 2103 {{mp|2005 YU|55}} will be roughly 2 AU from Earth.<ref name="NEODyS2103"/>
On 8 November 2011 at 23:28 UT the asteroid passed {{convert|0.85|LD|km mi|abbr=on|lk=on}} from 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 with an objective lens of 80{{sup|+}} mm if it were not for bright moonlight preventing a true dark sky. Since the 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 inches (15 centimeters) or larger.<ref name="Goldstone-planning"/><ref name="NASA2011-332"/>
The next few times 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 0.65 LD from Earth,<ref name=jpl-close-WN5/> and in 2029 when the 325-meter 99942 Apophis comes even closer at just 0.10 LD.<ref>{{cite web |title=NEO Earth Close-Approaches (Between 1900 A.D. and 2200 A.D., NEOs with H <=22, nominal distance within 5 LD) |work=Near-Earth Object Program Office |publisher=NASA/JPL |url=http://neo.jpl.nasa.gov/cgi-bin/neo_ca?type=NEO&hmax=22&sort=dist&sdir=ASC&tlim=all&dmax=5LD&max_rows=20&action=Display+Table&show=1 |archive-url=https://archive.today/20121213115119/http://neo.jpl.nasa.gov/cgi-bin/neo_ca?type=NEO&hmax=22&sort=dist&sdir=ASC&tlim=all&dmax=5LD&max_rows=20&action=Display+Table&show=1 |url-status=dead |archive-date=13 December 2012 |accessdate=17 May 2015}}</ref>
According to Jay Melosh, if an asteroid the size of {{mp|2005 YU|55}} (~400 m across) were to hit land, it would create a crater {{convert|6.3|km|mi|abbr=on}} across, {{convert|518|m|ft|abbr=on}} deep and generate a seven-magnitude-equivalent-earthquake.<ref name="Melosh"/> The chances of an actual collision with an asteroid like {{mp|2005 YU|55}} is about 1 percent in the next thousand years.<ref name="Melosh"/>
{{clear|left}} {{Large near earth asteroid flybys 1LD}}
== Study == [[File:Swift Captures Flyby of Asteroid 2005 YU55.ogv|thumb|right|300px|Swift captures flyby of asteroid {{mp|2005 YU|55}}.]] During the 2011 passage {{mp|2005 YU|55}} was studied with radar using Goldstone, Arecibo, the Very Long Baseline Array, and the Green Bank Telescope.<ref name="Goldstone-planning"/> The Herschel Space Observatory has made far-infrared measurements of {{mp|2005 YU|55}} on 10 November, helping determine its temperature and composition.<ref name="Herschel"/>
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 8 November 2011, NASA released a statement mentioning a number of structures on the surface of the asteroid, which were detected as it passed near Earth.<ref>{{cite web |url=http://www.nasa.gov/mission_pages/asteroids/news/yu55-20111108.html |title=NASA releases radar movie of Asteroid 2005 YU{{sub|55}} |publisher=NASA |date=November 8, 2011 |access-date=6 December 2011 <!--DASHBot-->|df=dmy-all}}</ref> On 11 November 2011, higher-resolution images showed concavities, a ridge near the asteroid's equator, and numerous features interpreted as decameter-scale boulders.<ref name="Busch"/><ref name="boulders"/> Shape modeling based on the radar images shows that YU55's shape is close to spheroidal, with maximum dimensions of 360±40 m, and an equator-aligned ridge. A 150–200 meter-long, ~20 meter-high rise forms a portion of the ridge-line, and the number of boulders on the surface is comparable to that seen on the asteroid 25143 Itokawa by the Hayabusa spacecraft.<ref name="Busch"/>
Optical lightcurve measurements during the flyby provided a more accurate estimate of the asteroid's spin period{{Snd}} about 19.3 hours.<ref name="Warner"/> Because {{mp|2005 YU|55}} is so nearly spheroidal, it was not significantly torqued by Earth's tides during the flyby, and there is no evidence of non-principal-axis rotation. Optical, near-infrared,<ref name=Moskovitz/> and ultraviolet<ref>{{cite web |url=http://www.cbat.eps.harvard.edu/cbet/002900/CBET002937.txt |series=Electronic Telegram |number=2937 |title=2005 YU_55 |last1=Bodewits |first1=Dennis |display-authors=etal |date=5 December 2011 |website=Central Bureau for Astronomical Telegrams |access-date=14 November 2018}}</ref> spectroscopy confirmed that {{mp|2005 YU|55}} is a C-type asteroid.
== Future trajectory == On 19 January 2029, {{mp|2005 YU|55}} will pass {{convert|0.0023|AU|km mi|abbr=on}} from Venus.<ref name=jpl-close/> The close approach distance to Venus in 2029 will determine how close the asteroid will pass to Earth in 2041.<ref name="Goldstone-planning"/> Before the November 2011 observations, the uncertainties in the post-2029 trajectory showed that the asteroid would pass somewhere between {{convert|0.002|AU|km mi|abbr=on|lk=off}} and {{convert|0.3|AU|km mi|abbr=on|lk=off}} of Earth in 2041.<ref name="Goldstone-planning"/> Radar astrometry in November 2011 clarified the Earth passage in 2041 and beyond.<ref name="Goldstone-planning"/> As a result of the November 2011 radar observations, it is now known that {{mp|2005 YU|55}} will pass between {{convert|0.1017|AU|km mi|abbr=on|lk=off}} and 0.1020 AU of Earth on 12 November 2041.<ref name=jpl-close/> Using the current uncertainty region integrated until the future, the 2075 approach will be between {{convert|0.0013|AU|km mi|abbr=on|lk=off}} and {{convert|0.0021|AU|km mi|abbr=on|lk=off}}.<ref name=jpl-close/>
== References == {{reflist|25em|refs =
<ref name="MPEC2005-Y47"> {{cite web | title = MPEC 2005 Y47 : 2005 YU55 | publisher = IAU Minor Planet Center | date = 2005-12-29 | url = https://minorplanetcenter.net/mpec/K05/K05Y47.html | access-date = 2011-05-05 |df=dmy-all }} </ref>
<ref name="mpc"> {{cite web | title = Minor Planet Center – 2005 YU55 | publisher= Minor Planet Center | url = https://www.minorplanetcenter.net/db_search/show_object?object_id=2005+YU55 | access-date = 2014-11-19 |df=dmy-all }} </ref>
<ref name="jpldata"> {{cite web | title=last observation: 2011-12-16; arc: 5.98 years | series = JPL Small-Body Database Browser: 308635 (2005 YU55) | url = https://ssd.jpl.nasa.gov/sbdb.cgi?sstr=2005YU55 | access-date = 7 April 2016 }} </ref>
<ref name="news171"> {{cite web |date=March 10, 2011 |title=Asteroid 2005 YU55 to approach Earth on November 8, 2011 |publisher=NASA/JPL Near-Earth Object Program Office |author=Don Yeomans |author2=Lance Benner |author3=Jon Giorgini |name-list-style=amp|url=http://neo.jpl.nasa.gov/news/news171.html |access-date=2011-05-05 |df=dmy-all |archiveurl=https://web.archive.org/web/20110424015323/http://neo.jpl.nasa.gov/news/news171.html |archivedate=24 April 2011 |url-status=dead }} </ref>
<ref name="Cornell2010"> {{cite web |date=April 30, 2010 |title=Arecibo telescope tracks 'potentially dangerous' asteroid within 1.5 million miles of Earth |publisher=Cornell Chronicle @ Cornell University |author=Blaine Friedlander, Jr. |url=https://www.news.cornell.edu/stories/April10/AreciboAsteroid.html |access-date=2011-05-05 |df=dmy-all |archiveurl=https://web.archive.org/web/20110523103203/http://www.news.cornell.edu/stories/April10/AreciboAsteroid.html |archive-date=23 May 2011 |url-status=live }} </ref>
<ref name="Goldstone-planning"> {{cite web | date = 2011-10-29 | title = 2005 YU55 Goldstone Radar Observations Planning | publisher = NASA/JPL Asteroid Radar Research | author = Dr. Lance A. M. Benner | url = http://echo.jpl.nasa.gov/asteroids/2005YU55/2005YU55_planning.html | access-date = 2011-10-30 |df=dmy-all }} </ref>
<ref name="NASA2011-332">{{cite web | date = October 26, 2011 | title = NASA in Final Preparations for Nov. 8 Asteroid Flyby | publisher = NASA/JPL | url = http://www.jpl.nasa.gov/news/news.cfm?release=2011-332 | access-date = 2011-10-26 | df = dmy-all | archive-date = 2012-01-13 | archive-url = https://web.archive.org/web/20120113035736/http://www.jpl.nasa.gov/news/news.cfm?release=2011-332 | url-status = dead }}</ref>
<ref name="removed"> {{cite web |title=Date/Time Removed |publisher=NASA/JPL Near-Earth Object Program Office |url=http://neo.jpl.nasa.gov/risk/removed.html |access-date=2011-05-06 |df=dmy-all |archiveurl=https://web.archive.org/web/20110426000059/http://neo.jpl.nasa.gov/risk/removed.html |archive-date=26 April 2011 |url-status=dead }} </ref>
<ref name="NEODyS2011"> {{cite web | title = 2005 YU55 Ephemerides for 9 Nov 2011 | website= Near Earth Objects – Dynamics (NEODyS) | url = https://newton.spacedys.com/neodys/index.php?pc=1.1.3.1&n=2005YU55&oc=500&y0=2011&m0=11&d0=8&h0=0&mi0=0&y1=2011&m1=11&d1=12&h1=0&mi1=0&ti=1.0&tiu=hours | access-date = 2011-05-05 |df=dmy-all }} </ref>
<ref name=jpl-close-WN5> {{cite web | title=Last observation: 2011-01-04; arc: 14.9 years | series = JPL close-approach data: 153814 (2001 WN5) | url = https://ssd.jpl.nasa.gov/sbdb.cgi?sstr=2001WN5;cad=1#cad | access-date = 2011-10-16 |df=dmy-all }} </ref>
<ref name=jpl-close> {{cite web | title=last observation: 2011-12-16; arc: 5.98 years | series = JPL close-approach data: (2005 YU55) | url = https://ssd.jpl.nasa.gov/sbdb.cgi?sstr=2005YU55;cad=1#cad | access-date = 2013-09-07 |df=dmy-all }} </ref>
<ref name="Herschel"> {{cite web | date = 6 November 2011 | title = Herschel to observe near-Earth asteroid | publisher = UK outreach site for the Herschel Space Observatory | author = Chris North | url = http://herschel.cf.ac.uk/news/herschel-observe-near-earth-asteroid | access-date = 2011-11-07 |df=dmy-all }} </ref>
<ref name="Melosh"> {{cite web | date = October 31, 2011 | title = Large asteroid to pass by Earth Nov. 8, but what if it didn't? | publisher = Purdue University | author = Elizabeth K. Gardner | url = http://www.purdue.edu/newsroom/research/2011/111031T-MeloshAsteroid.html | access-date = 2011-11-07 |df=dmy-all}} </ref>
<ref name="boulders">{{cite web |date=2011-11-11 |title=NASA releases updated radar movie of asteroid 2005 YU55 (2011–351) |publisher=NASA/JPL |url=http://www.nasa.gov/mission_pages/asteroids/news/yu55-20111111_prt.htm |access-date=2011-12-06 |df=dmy-all}}</ref>
<ref name="Busch"> {{cite web | date = March 31, 2012 | title = Shape and spin of near-Earth asteroid 308635 (2005 YU55) from radar images and speckle tracking | publisher = LPI | author1= M.W. Busch | url=https://www.lpi.usra.edu/meetings/acm2012/pdf/6179.pdf | access-date= 9 April 2012 |df=dmy-all | display-authors=etal}} </ref>
<ref name="Moskovitz"> {{cite web | date = March 31, 2012 | title = The near-Earth encounter of 2005 YU55: Time-resolved visible and near-infrared spectroscopy | publisher = LPI | author = N.A. Moskovitz | url = https://www.lpi.usra.edu/meetings/acm2012/pdf/6382.pdf | access-date = 9 April 2012 |df=dmy-all}} </ref>
<ref name="Warner"> {{cite web | date = March 31, 2012 | title = CCD photometric observations of 2005 YU55 during the 2011 November flyby | publisher = LPI | author1= B.D. Warner | url=https://www.lpi.usra.edu/meetings/acm2012/pdf/6013.pdf | access-date= 9 April 2012 |df=dmy-all |display-authors=etal}} </ref>
<ref name=Wayback2010-03>{{cite web |date=2010-03-25 |title=Earth impact risk summary: 2005 YU55 |publisher=NASA/JPL Near-Earth Object program office |via=Wayback Machine |url=http://neo.jpl.nasa.gov/risk/2005yu55.html |archive-url=https://web.archive.org/web/20100325062602/http://neo.jpl.nasa.gov/risk/2005yu55.html |archive-date=2010-03-25 |access-date=2013-10-23 |df=dmy-all |url-status=dead }} <br/>{{cite web |url=http://neo.jpl.nasa.gov/cgi-bin/ip?6.1e-04 |title=6.1e-04 = 1 in 1,640 chance |website=jpl.nasa.gov |access-date=2013-10-23 |archive-date=2013-10-24 |archive-url=https://archive.today/20131024023156/http://neo.jpl.nasa.gov/cgi-bin/ip?6.1e-04 |url-status=dead }}</ref>
<ref name="NEODyS2103">{{cite web |title=(308635) 2005YU55 Ephemerides for 10 November 2103 |publisher=NEODyS (Near Earth Objects{{Snd}} Dynamic Site) |url=https://newton.spacedys.com/neodys/index.php?pc=1.1.3.1&n=308635&oc=500&y0=2103&m0=11&d0=09&h0=0&mi0=0&y1=2103&m1=11&d1=11&h1=0&mi1=0&ti=1.0&tiu=days |access-date=2013-10-23 |df=dmy-all }}</ref>
}}
== External links == {{Commons category}} * {{cite web |url=http://www.keckobservatory.org/news_preview/live_webcast_keck_telescope_to_watch_asteroid_flyby/ |url-status=dead |archive-date=2012-04-02 |df=dmy-all |archive-url=https://web.archive.org/web/20120402211723/http://www.keckobservatory.org/news_preview/live_webcast_keck_telescope_to_watch_asteroid_flyby/ |title=Live webcast: Keck telescope to watch asteroid flyby |type=Ustream video}} * {{cite web |url=http://www.minorplanet.info/ObsGuides/YU55/ |title=2005 YU55 observing campaign |access-date=2011-10-28 |archive-date=2011-11-01 |archive-url=https://web.archive.org/web/20111101002734/http://www.minorplanet.info/ObsGuides/YU55/ |url-status=dead }} * {{cite web |url=http://www.nasa.gov/images/content/541440main_2005_YU55_approach.gif |title=Orbital simulation of 2005 YU55 |medium=animated GIF image |website=nasa.gov}} * {{cite web |url=https://www.ustream.tv/recorded/18250783 |title=NASA asteroid Q&A (on YU55) |date=1 November 2011}} * {{cite web |url=https://planetary.org/blog/article/00002463/ |title=Arecibo saves us from another potentially hazardous asteroid |author=Emily Lakdawalla |date=29 April 2010 |access-date=3 November 2011 |archive-date=4 November 2011 |archive-url=https://web.archive.org/web/20111104172332/http://planetary.org/blog/article/00002463 |url-status=dead }} * {{cite web |url=http://blogs.discovermagazine.com/badastronomy/2011/05/09/no-2005-yu55-wont-destroy-the-earth/ |title=No, 2005 YU55 won't destroy the Earth |author=Phil Plait |date=9 May 2011 |access-date=3 November 2011 |archive-date=30 October 2011 |archive-url=https://web.archive.org/web/20111030230335/http://blogs.discovermagazine.com/badastronomy/2011/05/09/no-2005-yu55-wont-destroy-the-earth/ |url-status=dead }} * {{cite web |url=https://www.usatoday.com/tech/science/space/story/2011-11-01/asteroid-viewing-tuesday/51035012/1 |title=Asteroid 2005 YU55 will zip by Earth next week}} * {{cite web |url=http://astroguyz.com/2011/11/05/the-passage-of-asteroid-2005-yu55-how-to-see-it |title=The passage of asteroid 2005 YU55 & how to see it |author=David Dickinson |date=5 November 2011 |access-date=7 November 2011 |archive-date=9 November 2011 |archive-url=https://web.archive.org/web/20111109215759/http://astroguyz.com/2011/11/05/the-passage-of-asteroid-2005-yu55-how-to-see-it/ |url-status=dead }} * {{cite web |url=http://www.global-rent-a-scope.com/aartscope/2011/11/7/2005-yu55-passes-inside-1-lunar-distance-nov-8th-2011.html |archive-url=https://web.archive.org/web/20111110183855/http://www.global-rent-a-scope.com/aartscope/2011/11/7/2005-yu55-passes-inside-1-lunar-distance-nov-8th-2011.html |url-status=dead |archive-date=10 November 2011 |title=Photos of flyby and Observation guide |author=Peter Lake |date=8 November 2011}} * {{cite web |url=http://www.nasa.gov/multimedia/videogallery/index.html?collection_id=77341&media_id=120141271 |title=Rotation simulation |series=Video gallery |website=Nasa.Gov}} * {{NeoDys|308635}} * {{ESA-SSA|308635|2005YU55}} * {{JPL small body|id=308635}}
{{s-start}} {{s-bef|before={{mpl|2002 MN}}}} {{s-ttl|title=Large NEO Earth close approach<br />(inside the orbit of the Moon)|years=8 November 2011, and<br/>8 November 2075}} {{s-aft|after={{mpl|2011 XC|2}}}} {{end}}
{{Minor planets navigator| |number=308635 |PageName={{mp|(308635) 2005 YU|55}} | }} {{Small Solar System bodies}} {{2011 in space}} {{Authority control}}
{{DEFAULTSORT:2005 YU55}} 308635 308635 308635 308635 308635 308635 20111108 20051228