 | |
| Discovery[1] | |
|---|---|
| Discovered by | Carl A. Wirtanen |
| Discovery site | Lick Obs. |
| Discovery date | 23 February 1950 |
| Designations | |
| (29075) 1950 DA | |
| 1950 DA · 2000 YK66 · Object Wirtanen[2] | |
| NEO · Apollo · PHA[1][3] · risk listed | |
| Orbital characteristics[3] | |
| Epoch 17 October 2024 (JD 2460600.5) | |
| Uncertainty parameter 0 | |
| Observation arc | 74.87 yr (27,345 d) |
| Aphelion | 2.5614 AU |
| Perihelion | 0.8364 AU |
| 1.6989 AU | |
| Eccentricity | 0.5077 |
| 2.214 yr (809 d) | |
| 223.31° | |
| 0° 26m 42.36s / day | |
| Inclination | 12.16° |
| 356.59° | |
| 224.76° | |
| Earth MOID | 0.03853 AU (14.9948 LD) |
| Proper orbital elements[4] | |
Precession ofperihelion | 13.655 arcsec / yr |
Precession of theascending node | −35.824 arcsec / yr |
| Physical characteristics | |
| Dimensions | 1.39 km × 1.46 km × 1.07 km[5] |
| Mass | >4×1012 kg[a] |
Meandensity | >3.5 g/cm3[5] |
| 2.12160±0.00004 h[5] | |
(29075) 1950 DA (provisional designation1950 DA) is a risk-listedasteroid, classified as anear-Earth object andpotentially hazardous asteroid of theApollo group, approximately 1.3 kilometers (0.81 miles) in diameter.[5] It once had the highest knownprobability ofimpacting Earth.[12] In 2002, it had the highestPalermo scale rating with a value of 0.17 and a probability of 1 in 306 (0.33%) for a possible collision in 2880.[13][6] 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.[12] As of February 2025[update], it is listed on theSentry Risk Table with the highest cumulative Palermo scale rating of −0.92.[14][15]1950 DA is not assigned aTorino scale rating, because the 2880 date is over 100 years in the future. As of 2 February 2025, the odds of an Earth impact are 1 in 2,600 (0.039%).[14][12]
1950 DA was first discovered on 23 February 1950 byCarl A. Wirtanen atLick Observatory.[3] It was observed for seventeen days[6] and thenlost because this short observation arc resulted in large uncertainties in Wirtanen's orbital solution. On 31 December 2000, it was recovered atLowell Observatory and was announced as2000 YK66 on 4 January 2001.[16] Just two hours later it was recognized as1950 DA.[6][17]
.png)
On 5 March 2001,1950 DA made a close approach to Earth at a distance of 0.05207 AU (7.790 million km; 4.840 million mi; 20.26 LD).[18] It was studied by radar at theGoldstone andArecibo observatories from March 3 to 7, 2001.[6]
The studies showed that the asteroid has amean diameter of 1.1 km, assuming that1950 DA is a retrograde rotator.[19] Opticallightcurve analysis byLenka Šarounová andPetr Pravec shows that its rotation period is2.1216±0.0001 hours. Due to its short rotation period and high radaralbedo,1950 DA is thought to be fairly dense (more than 3.5 g/cm3, assuming that it has no internal strength) and likely composed ofnickel–iron.[5] In August 2014, scientists from theUniversity of Tennessee determined that1950 DA is arubble pile rotating faster than the breakup limit for its density, implying the asteroid is held together byvan der Waals forces rather than gravity.[20][21]
1950 DA made distant approaches to Earth on 20 May 2012, 5 February 2021 and 5 February 2023.[18] However, at these times it was a quarter to half an AU away from Earth, preventing more usefulastrometrics 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 0.076 AU (11.4 million km) from Earth. The following table lists the approaches closer than 0.1 AU until the year 2500.[22] By 2136 the close approach solutions are becoming notably more divergent.[citation needed]
| Date | JPL SBDB nominal geocentric distance (AU) | uncertainty region (1-sigma) |
|---|---|---|
| 2 March 2032 | 0.075752 AU (11,332,300 km) | ±10 km |
| 19 March 2074 | 0.095459 AU (14,280,500 km) | ±30 km |
| 10 March 2105 | 0.036316 AU (5,432,800 km) | ±43 km |
| 11 March 2136 | 0.042596 AU (6,372,300 km) | ±387 km |
| 8 March 2187 | 0.035224 AU (5,269,400 km) | ±1717 km |
| 20 March 2218 | 0.084849 AU (12,693,200 km) | ±8712 km |
| 18 March 2373 | 0.058991 AU (8,824,900 km) | ±2508 km |
| 6 March 2455 | 0.087706 AU (13,120,600 km) | ±1650 km |
| Date | JPL Solution | Impact probability |
|---|---|---|
| 5 April 2002 | [6] | 1/306 |
| 7 December 2015 | [23] | 1/8300 |
| 29 March 2022 | [24] | 1/34000 |
| 18 June 2024 | [25] | 1/2600 |
| 23 January 2025 | JPL276 | 1/2600 |
1950 DA has one of the best-determined asteroid orbital solutions. This is due to a combination of:[6]
Main-belt asteroid78 Diana (~125 km in diameter) will pass about 0.003 AU (450,000 km; 280,000 mi) from1950 DA on 5 August 2150.[6] At that distance and size, Diana will perturb1950 DA enough so that the change in trajectory is notable by 2880 (730 years later). In addition, over the intervening time,1950 DA's rotation will cause its orbit to slightly change as a result of theYarkovsky effect. If1950 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, so1950 DA does not have a significant chance of impacting Earth. As of February 2025[update], according to the latest solution dated 2 February 2025, the probability of an impact in 2880 is 1 in 2,600 (0.039%).[12]
The energy released by a collision with an object the size of1950 DA would cause major effects on theclimate andbiosphere, which would be devastating tohumancivilization. The discovery of the potential impact heightened interest inasteroid deflection strategies.
