View source for Astronomy:(29075) 1950 DA

{{Short description|Most hazardous risk–listed near-Earth asteroid}}
 <!-- MOS:RETAIN -->
{{Infobox planet
 | minorplanet     = yes
 | name            = (29075) 1950 DA
 | background      = #FFC2E0
 | image           = 1950 DA.png
 | image_scale      =
 | caption         = [[Astronomy:Radar astronomy|Radar image]] of {{mp|1950 DA}} taken at [[Astronomy:Arecibo Observatory|Arecibo]] in March 2001, from a distance of 22&nbsp;[[Astronomy:Lunar distance|LD]] or 0.052&nbsp;[[Astronomy:Astronomical unit|AU]]
 | discovery_ref   = <ref name="MPC-object" />
 | discoverer      = [[Biography:Carl A. Wirtanen|Carl A. Wirtanen]]
 | discovery_site  = [[Organization:Lick Observatory|Lick Obs.]]
 | discovered      = 23 February 1950
 | mpc_name        = (29075) 1950 DA
 | alt_names       = 1950 DA{{·}}{{mp|2000 YK|66}}
 | pronounced      = 
 | named_after     = <!--xafter<br />{{small|()}}<ref name="MPC-object" />-->
 | mp_category     = [[Astronomy:Near-Earth object|NEO]]{{·}}[[Astronomy:Apollo asteroid|Apollo]]{{·}}[[Astronomy:Potentially hazardous object|PHA]]<ref name="MPC-object" /><ref name="jpldata" />{{·}}[[Astronomy:Sentry (monitoring system)|risk listed]]
 | orbit_ref       = <ref name="jpldata" />
 | epoch           = 31 January 2012 ([[Astronomy:Julian day|JD]]&nbsp;2455957.5)
 | uncertainty     = 0
 | observation_arc = 67.96&nbsp;[[Astronomy:Julian year|yr]] (24,823&nbsp;d)
 | aphelion        = 2.5619&nbsp;[[Astronomy:Astronomical unit|AU]]
 | perihelion      = 0.8350&nbsp;AU
 | semimajor       = 1.6985&nbsp;AU
 | eccentricity    = 0.5083
 | period          = 2.21&nbsp;yr (809&nbsp;d)
 | mean_anomaly    = 315.94[[Degree (angle)|°]]
 | mean_motion     = {{Deg2DMS|0.4453|sup=ms}} / day
 | inclination     = 12.175°
 | asc_node        = 356.74°
 | arg_peri        = 224.61°
 | moid            = 0.0406&nbsp;AU (15.8169&nbsp;[[Astronomy:Lunar distance|LD]])
 | p_orbit_ref     = <ref name="Proper" />
 | node_rate       = −35.824
 | perihelion_rate = 13.655
 | dimensions      = {{val|1.39|x|1.46|x|1.07|ul=km}}<ref name="Busch-2007b" />
 | mean_diameter   = {{Ubl
   | {{val|1.1|ul=km}}<ref name="Busch-2007b" /><ref name="Giorgini-2002" />
   | {{val|1.25|0.12|u=km}}<ref name="Busch-2007b" />
   | {{val|2.00|0.20|u=km}}<ref name="Mainzer-2016" />
  }}
 | mass            = >{{val|4|e=12|ul=kg}}{{efn|name=estimate}}
 | density         = >{{val|3.5|ul=g/cm3}}<ref name="Busch-2007b" />
 | rotation        = {{val|2.12160|0.00004|ul=h}}<ref name="Busch-2007b" />
 | albedo          = {{Ubl
   | {{val|0.070}}<ref name="Mainzer-2016" />
   | {{val|0.25}}<ref name="Rivkin-2005a" />
  }}
 | spectral_type   = {{Ubl
   | [[Astronomy:S-type asteroid|S]]<ref name="Dandy-2003" /><ref name="lcdb" />
   | EM<ref name=Neodys/>
   | B–V {{=}} {{val|0.862|0.077}}<ref name="Dandy-2003" />
   | V–R {{=}} {{val|0.494|0.069}}<ref name="Dandy-2003" />
   | V–I {{=}} {{val|0.816|0.067}}<ref name="Dandy-2003" />
  }}
 | abs_magnitude   = {{Ubl
   | 17.00<ref name="Mainzer-2016" />
   | 17.1<ref name="MPC-object" /><ref name="jpldata" />
   | {{val|17.55|0.3}} {{small|(R)}}<ref name=Neodys/><ref name="lcdb" />
   | 18.0<ref name="lcdb" /><ref name="Busch-2007b" />
  }}
}}
'''{{mp|(29075) 1950 DA}}''' (provisional designation '''{{mp|1950 DA}}''') is a risk-listed [[Astronomy:Asteroid|asteroid]], classified as a [[Astronomy:Near-Earth object|near-Earth object]] and [[Astronomy:Potentially hazardous asteroid|potentially hazardous asteroid]] of the [[Astronomy:Apollo asteroid|Apollo group]], approximately {{convert|1.1|km|abbr=off|sp=us}} in diameter.<ref name="Busch-2007b" /> It once had the highest known [[Probability|probability]] of [[Astronomy:Impact event|impacting Earth]].<ref name="impact-risk-summary"/> In 2002, it had the highest [[Palermo Technical Impact Hazard Scale|Palermo rating]] with a value of 0.17 for a possible collision in 2880.<ref name="NEO-1950DA"/> Since that time, the estimated risk has been updated several times. In December 2015, the odds of an Earth impact were revised to 1 in 8,300 (0.012%) with a Palermo rating of −1.42.<ref name="impact-risk-summary"/> As of 2022, It is listed on the [[Astronomy:Sentry (monitoring system)|Sentry Risk Table]] with the second highest cumulative Palermo rating of −2.05 (impact risk of 1-in-34,000).<ref name="risk-table" /><ref name="ESASSP_2022">{{Cite web|url=https://neo.ssa.esa.int/-/impact-threat-analysis-update-completed-for-1950-da|title=Impact threat analysis update completed for 1950 DA|date=29 March 2022|publisher=European Space Agency}}</ref> {{mp|1950 DA}} is not assigned a [[Astronomy:Torino scale|Torino scale]] rating, because the 2880 date is over 100 years in the future.

== Discovery and nomenclature ==
{{mp|1950 DA}} was first discovered on 23 February 1950 by [[Biography:Carl A. Wirtanen|Carl A. Wirtanen]] at [[Organization:Lick Observatory|Lick Observatory]].<ref name=jpldata/> It was observed for seventeen days<ref name="Giorgini-2002" /> and then lost because this short observation arc resulted in large uncertainties in Wirtanen's orbital solution. On 31 December 2000, it was recovered at Lowell Observatory and was announced as {{mp|2000 YK|66}} on 4 January 2001.<ref>{{cite web|url=https://minorplanetcenter.net/mpec/K01/K01A22.html|title=MPEC 2001-A22 : 2000 YK66|publisher=Minor Planet Center|date=4 January 2001|access-date=23 February 2018}}</ref> Just two hours later it was recognized as {{mp|1950 DA}}.<ref name="Giorgini-2002" /><ref>{{cite web|url=https://minorplanetcenter.net/mpec/K01/K01A26.html|title=MPEC 2001-A26 : 1950 DA = 2000 YK66|publisher=Minor Planet Center|date=4 January 2001|access-date=23 February 2018}}</ref>

== Observations ==
{{multiple image
 |direction = vertical
 |align     = left
 |width     = 215
 |image1    = 1950 DA (color).png
 |image2    = 1950 DA radar movie.gif
 |caption1  = Asteroid ''{{mp|1950 DA}}'', [[Astronomy:Arecibo Observatory|Arecibo Observatory]] radar image (coloured version)
 |caption2  = Arecibo radar movie of {{mp|1950 DA}} obtained during 48 minutes (37% of a rotation) on 4 March 2001
}}

On 5 March 2001, {{mp|1950 DA}} made a close approach to Earth at a distance of {{convert|0.05207|AU|e6km e6mi LD|abbr=unit|lk=on}}.<ref name=jpl-close/> It was studied by radar at the Goldstone and [[Astronomy:Arecibo Observatory|Arecibo]] observatories from March 3 to 7, 2001.<ref name="Giorgini-2002" />

The studies showed that the asteroid has a mean diameter of 1.1&nbsp;km, assuming that {{mp|1950 DA}} is a retrograde rotator.<ref name="Farnocchia-2014" /> Optical [[Astronomy:Lightcurve|lightcurve]] analysis by Lenka Šarounová and [[Biography:Petr Pravec|Petr Pravec]] shows that its rotation period is {{val|2.1216|0.0001}} hours. Due to its short rotation period and high radar [[Earth:Albedo|albedo]], {{mp|1950 DA}} is thought to be fairly dense (more than 3.5&nbsp;g/cm<sup>3</sup>, assuming that it has no internal strength) and likely composed of [[Chemistry:Nickel|nickel]]–[[Chemistry:Iron|iron]].<ref name="Busch-2007b" /> In August 2014, scientists from the [[Organization:University of Tennessee|University of Tennessee]] determined that ''{{mp|1950 DA}}'' is a [[Astronomy:Rubble pile|rubble pile]] rotating faster than the breakup limit for its density, implying the asteroid is held together by [[Physics:Van der Waals force|van der Waals force]]s rather than gravity.<ref name="Rozitis-2014" /><ref name="tntoday" />

{{mp|1950 DA}} made a distant approach to Earth on 5 February 2021.<ref name=jpl-close/> However, at that time it was half an AU away from Earth, preventing more useful [[Astronomy:Astrometry|astrometrics]] and timing that occurs when an object is closer to Earth. The next close approach that presents a good opportunity to observe the asteroid will be on 2 March 2032, when it will be {{convert|0.075|AU|e6km|abbr=unit|lk=off}} from Earth. The following table lists next five approaches closer than 0.10&nbsp;AU.<ref name=jpl-close/> By 2136 the close approach solutions are becoming notably more divergent.

{| class="wikitable sortable" style="font-size: 0.9em;"
|+Position uncertainty and increasing divergence<ref name=jpl-close/>
! Date
! JPL SBDB<br />[[Curve fitting|nominal]] geocentric<br />distance ([[Astronomy:Astronomical unit|AU]])
! uncertainty<br />region<br/>(3-sigma)
|-
|2032 March 2 ||{{Convert|0.0757523|AU|e6km|abbr=unit}} || ±52&nbsp;km
|-
|2074 March 19 ||{{Convert|0.0954596|AU|e6km|abbr=unit}} || ±131&nbsp;km
|-
|2105 March 10 ||{{Convert|0.0363159|AU|e6km|abbr=unit}} || ±22&nbsp;km
|-
|2136 March 1 ||{{Convert|0.0425957|AU|e6km|abbr=unit}} || ±1010&nbsp;km
|-
|2187 March 8 ||{{Convert|0.0352249|AU|e6km|abbr=unit}} || ±2795&nbsp;km
|}

== Possible Earth impact ==
That {{mp|1950 DA}} has one of the best-determined asteroid orbital solutions is due to a combination of:<ref name="Giorgini-2002" />
* an orbit moderately [[Astronomy:Orbital inclination|inclined]] (12 degrees)<ref name=jpldata/> to the ecliptic plane (reducing in-plane [[Astronomy:Perturbation|perturbations]]);
* high-precision radar astrometry, which provides its distance and is complementary to the measurements of angular positions;
* a 68-year [[Astronomy:Observation arc|observation arc]];<ref name=jpldata/>
* an uncertainty region controlled by resonance.<ref name="Giorgini-2002" />

Main-belt asteroid [[Astronomy:78 Diana|78 Diana]] (~125&nbsp;km in diameter) will pass about {{convert|0.003|AU|km mi|abbr=on|lk=on}} from {{mp|1950 DA}} on 5 August 2150.<ref name="Giorgini-2002" /> At that distance and size, Diana will perturb {{mp|1950 DA}} enough so that the change in trajectory is notable by 2880 (730 years later). In addition, over the intervening time, {{mp|1950 DA}}'s rotation will cause its orbit to slightly change as a result of the [[Yarkovsky effect]]. If {{mp|1950 DA}} continues on its present orbit, it may approach Earth on 16 March 2880, though the mean trajectory passes many millions of kilometres from Earth, so {{mp|1950 DA}} does not have a significant chance of impacting Earth. As of the 7 December 2015 solution, the probability of an impact in 2880 is 1 in 8,300 (0.012%).<ref name=impact-risk-summary/>

The energy released by a collision with an object the size of {{mp|1950 DA}} would cause major effects on the [[Earth:Climate|climate]] and [[Biology:Biosphere|biosphere]], which would be devastating to [[Biology:Human|human]] [[Social:Civilization|civilization]]. The discovery of the potential impact heightened interest in asteroid deflection strategies.

== See also ==
*{{Section link|List of exceptional asteroids|Landmark asteroids}}
*[[Astronomy:Asteroid impact prediction|Asteroid impact prediction]]
*[[Astronomy:Earth-grazing fireball|Earth-grazing fireball]]
*[[Astronomy:List of asteroid close approaches to Earth|List of asteroid close approaches to Earth]]

== Notes ==
{{notelist|refs=
{{efn|name=estimate|1=A reported volume of 1.14&nbsp;km<sup>3</sup> × density of 3.5&nbsp;g/cm<sup>3</sup> yields a mass (m = d × v) of {{Val|3.99e12|u=kg}}}}

}} <!-- end of notelist -->

== References ==
{{reflist|refs=

<ref name="jpldata">{{cite web
  |type       = 2018-02-09 last obs.
  |title      = JPL Small-Body Database Browser: 29075 (1950 DA)
  |url        = https://ssd.jpl.nasa.gov/sbdb.cgi?sstr=2029075
  |publisher  = [[Organization:Jet Propulsion Laboratory|Jet Propulsion Laboratory]]
  |access-date = 5 July 2018}}</ref>

<ref name="MPC-object">{{cite web
  |title      = 29075 (1950 DA)
  |work       = Minor Planet Center
  |url        = https://www.minorplanetcenter.net/db_search/show_object?object_id=29075
  |access-date = 5 July 2018}}</ref>

<ref name=jpl-close>{{cite web
  |type=last observation: 2018-02-09; [[Astronomy:Observation arc|arc]]: 67.96 years
  |title=JPL Close-Approach Data: 29075 (1950 DA)
  |url=https://ssd.jpl.nasa.gov/sbdb.cgi?sstr=1950DA;cad=1#cad
  |access-date=11 March 2018}}</ref>

<ref name="NEO-1950DA">{{cite web
 |title=Asteroid 1950 DA
 |publisher=NASA/JPL Near-Earth Object Program Office
 |url=http://neo.jpl.nasa.gov/1950da/
 |access-date=2011-10-14
 |archive-url=https://web.archive.org/web/20110721050545/http://neo.jpl.nasa.gov/1950da/
 |archive-date=July 21, 2011
 |url-status=dead }}</ref>

<ref name="Proper">{{cite web
  |title=(29075) 1950DA NeoDys{{Snd}} Proper Elements
  |url=https://newton.spacedys.com/neodys/index.php?pc=1.1.6&n=29075
  |access-date=11 March 2018}}</ref>

<ref name=Neodys>{{cite web
  |type=Physical Info
  |title=NeoDys Near Earth Objects Dynamic Site
  |url=https://newton.spacedys.com/neodys/index.php?pc=1.1.9&n=29075
  |access-date=11 March 2018}}</ref>

<ref name="impact-risk-summary">{{cite web
  |title=29075 (1950 DA) Earth Impact Risk Summary
  |publisher=NASA/JPL Near-Earth Object Program Office
  |url=https://cneos.jpl.nasa.gov/sentry/details.html#?des=29075
  |date=7 December 2015
  |access-date=11 March 2018}}</ref>

<ref name="risk-table">{{cite web
 |title=Sentry Risk Table
 |publisher=NASA/JPL Near-Earth Object Program Office
 |url=https://cneos.jpl.nasa.gov/sentry/
 |access-date=2018-03-20}} (Use Unconstrained Settings)</ref>

<ref name="tntoday">{{cite web
  |title=UT Research uncovers forces that hold asteroid together
  |publisher=University of Tennessee
  |date=13 August 2014
  |url=http://tntoday.utk.edu/2014/08/13/ut-research-uncovers-forces-hold-gravitydefying-nearearth-asteroid/
  |access-date=17 August 2015}}</ref>

<ref name="Farnocchia-2014">{{Cite journal
  |first1     = D. |last1 = Farnocchia
  |first2     = S. R. |last2 = Chesley
  |date       = February 2014
  |title      = Assessment of the 2880 impact threat from Asteroid (29075) 1950 DA
  |journal    = Icarus
  |volume     = 229
  |pages      = 321–327
  |bibcode    = 2014Icar..229..321F
  |doi        = 10.1016/j.icarus.2013.09.022
  |arxiv      = 1310.0861}}</ref>

<ref name="lcdb">{{cite web
  |title      = LCDB Data for (29075) 
  |publisher  = Asteroid Lightcurve Database (LCDB)
  |url        = http://www.minorplanet.info/PHP/generateOneAsteroidInfo.php?AstInfo=29075%7C
  |access-date = 5 July 2018}}</ref>

<ref name="Busch-2007b">{{Cite journal
  |display-authors = 6
  |first1     = Michael W. |last1 = Busch
  |first2     = Jon D. |last2 = Giorgini
  |first3     = Steven J. |last3 = Ostro
  |first4     = Lance A. M. |last4 = Benner
  |first5     = Raymond F. |last5 = Jurgens
  |first6     = Randy |last6 = Rose
  |first7     = Michael D. |last7 = Hicks
  |first8     = Petr |last8 = Pravec
  |first9     = Peter |last9 = Kusnirak
  |first10    = Michael J. |last10 = Ireland
  |first11    = Daniel J. |last11 = Scheeres
  |first12    = Stephen B. |last12 = Broschart
  |first13    = Christopher |last13 = Magri
  |first14    = Michael C. |last14 = Nolan
  |first15    = Alice A. |last15 = Hine
  |first16    = Jean-Luc |last16 = Margot
  |date       = October 2007
  |title      = Physical modeling of near-Earth Asteroid (29075) 1950 DA
  |url        = https://echo.jpl.nasa.gov/asteroids/29075_1950DA/busch.etal.2007.1950da.pdf
  |journal    = Icarus
  |volume     = 190
  |issue      = 2
  |pages      = 608–621
  |bibcode    = 2007Icar..190..608B
  |doi        = 10.1016/j.icarus.2007.03.032
  |access-date= 5 July 2018}}</ref>

<ref name="Giorgini-2002">{{Cite journal
  |display-authors = 6
  |first1     = J. D. |last1 = Giorgini
  |first2     = S. J. |last2 = Ostro
  |first3     = L. A. M. |last3 = Benner
  |first4     = P. W. |last4 = Chodas
  |first5     = S. R. |last5 = Chesley
  |first6     = R. S. |last6 = Hudson
  |first7     = M. C. |last7 = Nolan
  |first8     = A. R. |last8 = Klemola
  |first9     = E. M. |last9 = Standish
  |first10    = R. F. |last10 = Jurgens
  |first11    = R. |last11 = Rose
  |first12    = A. B. |last12 = Chamberlin
  |first13    = D. K. |last13 = Yeomans
  |first14    = J.-L. |last14 = Margot
  |date       = April 2002
  |title      = Asteroid 1950 DA's Encounter with Earth in 2880: Physical Limits of Collision Probability Prediction
  |url        = http://neo.jpl.nasa.gov/1950da/1950da.pdf
  |archive-url = https://web.archive.org/web/20080704103055/http://neo.jpl.nasa.gov/1950da/1950da.pdf
  |url-status = dead
  |archive-date = 2008-07-04
  |journal    = Science
  |volume     = 296
  |issue      = 5565
  |pages      = 132–136
  |bibcode    = 2002Sci...296..132G
  |doi        = 10.1126/science.1068191
  |pmid       = 11935024
  |access-date= 5 July 2018}}</ref>

<ref name="Mainzer-2016">{{cite journal
  |display-authors = 6
  |first1     = A. K. |last1 = Mainzer
  |first2     = J. M. |last2 = Bauer
  |first3     = R. M. |last3 = Cutri
  |first4     = T. |last4 = Grav
  |first5     = E. A. |last5 = Kramer
  |first6     = J. R. |last6 = Masiero
  |first7     = C. R. |last7 = Nugent
  |first8     = S. M. |last8 = Sonnett
  |first9     = R. A. |last9 = Stevenson
  |first10    = E. L. |last10 = Wright
  |date       = June 2016
  |title      = NEOWISE Diameters and Albedos V1.0
  |url        = https://sbnarchive.psi.edu/pds3/non_mission/EAR_A_COMPIL_5_NEOWISEDIAM_V1_0/data/neowise_mainbelt.tab
  |journal    = NASA Planetary Data System
  |pages = EAR-A-COMPIL-5-NEOWISEDIAM-V1.0 |bibcode    = 2016PDSS..247.....M
  |access-date= 5 July 2018}}</ref>

<ref name="Dandy-2003">{{Cite journal
  |first1     = C. L. |last1 = Dandy
  |first2     = A. |last2 = Fitzsimmons
  |first3     = S. J. |last3 = Collander-Brown
  |date       = June 2003
  |title      = Optical colors of 56 near-Earth objects: trends with size and orbit
  |journal    = Icarus
  |volume     = 163
  |issue      = 2
  |pages      = 363–373
  |bibcode    = 2003Icar..163..363D
  |doi        = 10.1016/S0019-1035(03)00087-3}}</ref>

<ref name="Rivkin-2005a">{{Cite journal
  |first1     = A. S. |last1 = Rivkin
  |first2     = R. P. |last2 = Binzel
  |first3     = S. J. |last3 = Bus
  |date       = May 2005
  |title      = Constraining near-Earth object albedos using near-infrared spectroscopy
  |journal    = Icarus
  |volume     = 175
  |issue      = 1
  |pages      = 175–180
  |bibcode    = 2005Icar..175..175R
  |doi        = 10.1016/j.icarus.2004.11.005}}</ref>

<ref name="Rozitis-2014">{{Cite journal
  |first1     = Ben |last1 = Rozitis
  |first2     = Eric |last2 = MacLennan
  |first3     = Joshua P. |last3 = Emery
  |date       = 13 August 2014
  |title      = Cohesive forces prevent the rotational breakup of rubble-pile asteroid (29075) 1950 DA
  |journal    = Nature
  |volume     = 512
  |issue = 7513
 |pages      = 174–176
  |doi        = 10.1038/nature13632
  |pmid = 25119234
 |url = http://oro.open.ac.uk/44912/1/BR_1950DA_accepted.pdf
 }}</ref>

}} <!-- end of reflist-->

== External links ==
* [https://www.minorplanetcenter.net/iau/mpec/K01/K01A26.html MPEC 2001-A26 : 1950 DA = 2000 YK66] (K00Y66K). ''[[Organization:Minor Planet Center|MPC]]'' 4 January 2001
* [http://space.frieger.com/asteroids/asteroids.php?id=29075 3D model] Rotating model of the asteroid (preferred rotation model is ''retrograde'', [https://newton.spacedys.com/neodys/index.php?pc=1.1.9&n=29075 NeoDys])
* [http://www.minorplanet.info/PHP/lcdbsummaryquery.php Asteroid Lightcurve Database (LCDB)], query form ([http://www.minorplanet.info/lightcurvedatabase.html info] {{Webarchive|url=https://web.archive.org/web/20171216050541/http://www.minorplanet.info/lightcurvedatabase.html |date=16 December 2017 }})
* [http://obswww.unige.ch/~behrend/page_cou.html Asteroids and comets rotation curves, CdR]{{Snd}} Observatoire de Genève, Raoul Behrend
* [https://www.minorplanetcenter.net/iau/lists/NumberedMPs025001.html Discovery Circumstances: Numbered Minor Planets (25001)-(30000)]{{Snd}} Minor Planet Center
* {{NeoDys|29075}}
* {{JPL small body|id=29075}}

{{Planetary defense}}

{{DEFAULTSORT:1950 DA}}
[[Category:Apollo asteroids|029075]]
[[Category:Potentially hazardous asteroids|029075]]

{{Sourceattribution|(29075) 1950 DA}}