(29075) 1950 DA

{{Short description|Most hazardous risk–listed near-Earth asteroid}} {{Use dmy dates|date=March 2020}} {{Infobox planet | minorplanet = yes | name = (29075) 1950 DA | background = #FFC2E0 | image = 1950 DA.png | image_scale = | caption = Radar image of {{mp|1950 DA}} taken at Arecibo in March 2001, from a distance of 22 LD or 0.052 AU | discovery_ref = <ref name="MPC-object" /> | discoverer = Carl A. Wirtanen | discovery_site = Lick Obs. | discovered = 23 February 1950 | mpc_name = (29075) 1950 DA | alt_names = {{mp|2000 YK|66}}{{·}}Object Wirtanen<ref name="IAUCs_1950" /> | pronounced = | named_after =  | mp_category = NEO{{·}}Apollo{{·}}PHA<ref name="MPC-object" /><ref name="jpldata" />{{·}}risk listed | orbit_ref = <ref name="jpldata" /> | epoch = 17 October 2024 (JD 2460600.5) | uncertainty = 0 | observation_arc = 74.87 yr (27,345 d) | aphelion = 2.5614 AU | perihelion = 0.8364 AU | semimajor = 1.6989 AU | eccentricity = 0.5077 | period = 2.214 yr (809 d) | mean_anomaly = 223.31° | mean_motion = {{Deg2DMS|0.4451|sup=ms}} / day | inclination = 12.16° | asc_node = 356.59° | arg_peri = 224.76° | moid = 0.03853 AU (14.9948 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|1.3|ul=km}}<ref name="Busch-2007b" /> | {{val|1.1|ul=km}}<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 | S<ref name="Dandy-2003" /><ref name="lcdb" /> | 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 | 16.83<ref name="Busch-2007b" /> | 17.00<ref name="Mainzer-2016" /> | 17.28<ref name="MPC-object" /><ref name="jpldata" /> | 17.2<ref name=Neodys/> | 17.1<ref name="lcdb" /> }} }} '''{{mp|(29075) 1950 DA}}''' is a risk-listed asteroid, classified as a near-Earth object and potentially hazardous asteroid of the Apollo group, approximately {{convert|1.3|km|abbr=off|sp=us}} in diameter.<ref name="Busch-2007b" /> It once had the highest known probability of impacting Earth.<ref name="impact-risk-summary"/> In 2002, it had the highest Palermo scale rating with a value of 0.17 and a probability of 1 in 306 (0.33%) for a possible collision in 2880.<ref name="NEO-1950DA"/><ref name="Giorgini-2002"/> 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 scale rating of −1.42.<ref name="impact-risk-summary"/> {{As of|2025|10}}, it is listed on the Sentry Risk Table with the highest cumulative Palermo scale rating of −0.93.<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 Torino scale rating, because the 2880 date is over 100 years in the future. As of 25 October 2025, the odds of an Earth impact are 1 in 2,600 (0.038%).<ref name="risk-table" /><ref name="impact-risk-summary"/>

== Discovery and nomenclature == {{mp|1950 DA}} was first discovered on 23 February 1950 by Carl A. Wirtanen at 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}}, 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 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 km, assuming that {{mp|1950 DA}} is a retrograde rotator.<ref name="Farnocchia-2014" /> Optical lightcurve analysis by Lenka Šarounová and Petr Pravec shows that its rotation period is {{val|2.1216|0.0001}} hours. Due to its short rotation period and high radar albedo, {{mp|1950 DA}} is thought to be fairly dense (more than 3.5 g/cm3, assuming that it has no internal strength) and likely composed of nickel–iron.<ref name="Busch-2007b" /> In August 2014, scientists from the University of Tennessee determined that {{mp|1950 DA}} is a rubble pile rotating faster than the breakup limit for its density, implying the asteroid is held together by van der Waals forces rather than gravity.<ref name="Rozitis-2014" /><ref name="tntoday" />

{{mp|1950 DA}} made distant approaches to Earth on 20 May 2012, 5 February 2021 and 5 February 2023.<ref name=jpl-close/> However, at these times it was a quarter to half an AU away from Earth, preventing more useful 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|0.076|AU|e6km|abbr=unit|lk=off}} from Earth. The following table lists the approaches closer than 0.1 AU until the year 2500.<ref name="jpl-close-hor"/> By 2136 the close approach solutions are becoming notably more divergent.{{citation needed|date=June 2024}}

{| class="wikitable sortable" style="font-size: 0.9em;" |+Position uncertainty and increasing divergence<ref name="jpl-close-hor">{{Cite web|url=https://ssd.jpl.nasa.gov/api/horizons.api?format=text&COMMAND=%2729075%27&EPHEM_TYPE=%27APPROACH%27&CA_TABLE_TYPE=%27EXTENDED%27&CALIM_SB=%270.10%27&START_TIME=%272020-01-01%27&STOP_TIME=%272500-01-01%27|title=Close-approach results|work=JPL Horizons|access-date=7 December 2024}} Soln.date: 2024-Dec-05 05:58:05</ref> ! Date ! JPL SBDB nominal geocentric distance (AU) ! uncertainty region (1-sigma) |- | 2 March 2032 ||{{Convert|0.075752|AU|km|abbr=unit}} || ±10 km |- |19 March 2074 ||{{Convert|0.095459|AU|km|abbr=unit}} || ±30 km |- |10 March 2105 ||{{Convert|0.036316|AU|km|abbr=unit}} || ±43 km |- |11 March 2136 ||{{Convert|0.042596|AU|km|abbr=unit}} || ±387 km |- | 8 March 2187 ||{{Convert|0.035224|AU|km|abbr=unit}} || ±1717 km |- |20 March 2218 ||{{Convert|0.084849|AU|km|abbr=unit}} || ±8712 km |- |18 March 2373 ||{{Convert|0.058991|AU|km|abbr=unit}} || ±2508 km |- | 6 March 2455 ||{{Convert|0.087706|AU|km|abbr=unit}} || ±1650 km |} {| class="wikitable sortable" style="font-size: 0.9em;" |+Impact probability at different times

! Date ! JPL Solution ! Impact probability |- | 5 April 2002 ||<ref name="Giorgini-2002"/> || 1/306 |- |7 December 2015 ||<ref>{{cite journal |last1=Farnocchia |first1=D. |last2=Chesley |first2=S.R. |last3=Chamberlin |first3=A.B. |last4=Tholen |first4=D.J. |title=Star catalog position and proper motion corrections in asteroid astrometry |journal=Icarus |date=January 2015 |volume=245 |pages=94–111 |doi=10.1016/j.icarus.2014.07.033 |arxiv=1407.8317 |bibcode=2015Icar..245...94F }}</ref> || 1/8300 |- |29 March 2022 ||<ref>{{cite web | url=https://cneos.jpl.nasa.gov/sentry/notes.html | title=Sentry: Earth Impact Monitoring }}</ref> || 1/34000 |- |18 June 2024 ||<ref>{{cite journal |last1=Fuentes-Muñoz |first1=Oscar |last2=Farnocchia |first2=Davide |last3=Naidu |first3=Shantanu P. |last4=Park |first4=Ryan S. |title=Asteroid Orbit Determination Using Gaia FPR: Statistical Analysis |journal=The Astronomical Journal |date=1 June 2024 |volume=167 |issue=6 |pages=290 |doi=10.3847/1538-3881/ad4291 |doi-access=free |bibcode=2024AJ....167..290F }}</ref> || 1/2600

|- |23 January 2025 ||JPL276|| 1/2600 |}

== Possible Earth impact == {{mp|1950 DA}} has one of the best-determined asteroid orbital solutions. This is due to a combination of:<ref name="Giorgini-2002" /> * an orbit moderately inclined (12 degrees)<ref name=jpldata/> to the ecliptic plane (reducing in-plane perturbations); * high-precision radar astrometry, which provides its distance and is complementary to the measurements of angular positions; * a 74-year observation arc;<ref name=jpldata/> * an uncertainty region controlled by resonance.<ref name="Giorgini-2002" />

Main-belt asteroid 78 Diana (~125 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|2025|9}}, according to the latest solution dated 11 September 2025, the probability of an impact in 2880 is 1 in 2,600 (0.038%).<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 climate and biosphere, which would be devastating to human civilization. The discovery of the potential impact heightened interest in asteroid deflection strategies.{{citation needed|date=April 2025}}

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

== Notes == {{notelist|refs= {{efn|name=estimate|1=A reported volume of 1.14 km3 × density of 3.5 g/cm3 yields a mass (m = d × v) of {{Val|3.99e12|u=kg}}}}

}}

== References == <references> <ref name="jpldata">{{cite web |type = 2023-10-03 last obs. |title = JPL Small-Body Database Browser: 29075 (1950 DA) |url = https://ssd.jpl.nasa.gov/tools/sbdb.cgi?sstr=2029075 |publisher = Jet Propulsion Laboratory |access-date = 18 June 2024}}</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 = 24 February 2024}}</ref>

<ref name=jpl-close>{{cite web |type=solution: 2024-04-24; last observation: 2023-10-03; arc: 73.61 years |title=JPL Close-Approach Data: 29075 (1950 DA) |url=https://ssd.jpl.nasa.gov/tools/sbdb_lookup.html#/?sstr=1950%20DA&view=OPC |access-date=18 June 2024}}</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=14 October 2011 |archive-url=https://web.archive.org/web/20110721050545/http://neo.jpl.nasa.gov/1950da/ |archive-date=21 July 2011 |url-status=dead}}</ref>

<ref name="Proper">{{cite web |title=(29075) 1950DA NeoDys{{Snd}} Proper Elements |website=NeoDys Near Earth Objects Dynamic Site |url=https://newton.spacedys.com/neodys/index.php?pc=1.1.6&n=29075 |access-date=24 February 2024}}</ref>

<ref name=Neodys>{{cite web |title=(29075) 1950DA |website=NeoDys Near Earth Objects Dynamic Site |url=https://newton.spacedys.com/neodys/index.php?pc=1.1.0&n=29075 |access-date=24 February 2024}}</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=6 February 2022 |access-date=18 June 2024}}</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=18 June 2024}} (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 LCDB|number = 29075 |access-date = 24 February 2024}}</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 = 24 February 2024}}</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 = https://cneos.jpl.nasa.gov/doc/1950da/1950da_published.pdf |journal = Science |volume = 296 |issue = 5565 |pages = 132–136 |bibcode = 2002Sci...296..132G |doi = 10.1126/science.1068191 |pmid = 11935024}}</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 |volume = 247 |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 |bibcode = 2014Natur.512..174R|url = https://oro.open.ac.uk/44912/1/BR_1950DA_accepted.pdf }}</ref> <ref name="IAUCs_1950">{{Cite web |title = IAUC 1258, 1259, 1262: Rapidly Moving Object Wirtanen [1950 DA] |url = http://www.cbat.eps.harvard.edu/indexto_iauc8000.html |year = 1950 |work = IAU Circulars |publisher = Central Bureau for Astronomical Telegrams |access-date = 10 February 2025}}</ref> </references>

== External links == {{Commons category}} * [https://www.minorplanetcenter.net/iau/mpec/K01/K01A26.html MPEC 2001-A26 : 1950 DA = 2000 YK66] (K00Y66K). ''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}}

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{{DEFAULTSORT:1950 DA}} 029075 Category:Discoveries by Carl A. Wirtanen 029075 029075 19500222 029075