_1990_MU.svg) Orbit of asteroid (4953) 1990 MU viewed from the northecliptic pole at the epoch of 1 January 2010 | |
| Discovery[1] | |
|---|---|
| Discovered by | Robert H. McNaught |
| Discovery site | Siding Spring Obs |
| Discovery date | 23 June 1990 |
| Designations | |
| (4953) 1990 MU | |
| NEO · Apollo · PHA[1] | |
| Orbital characteristics[1] | |
| Epoch 13 January 2016 (JD 2457400.5) | |
| Uncertainty parameter 0 | |
| Observation arc | 41.16 yr (15032 days) |
| Earliestprecovery date | 21 July 1974 (Siding Spring Observatory) |
| Aphelion | 2.6874 AU (402.03 Gm) |
| Perihelion | 0.55508 AU (83.039 Gm) |
| 1.6212 AU (242.53 Gm) | |
| Eccentricity | 0.65762 |
| 2.06yr (754.00d) | |
Averageorbital speed | .4774 deg/day |
| 197.22° | |
| 0.47746°/day | |
| Inclination | 24.388° |
| 77.737° | |
| 77.748° | |
| Earth MOID | 0.0256049 AU (3,830,440 km)[1] |
| Physical characteristics | |
| 2.8 km[2] | |
| 14.218 h | |
| 14.1[1] | |
(4953) 1990 MU (prov. designation:1990 MU) is a largeEarth-crossing asteroid (ECA) belonging to theApollo group ofnear-Earth objects which also cross the orbits ofMars andVenus. At approximately 3 km in diameter,[3] it is one of the largest known ECAs.[4] It has been assigned a permanent number from theMinor Planet Center (4953) indicating that its orbit has been very well determined. With anobservation arc of 45 years, the asteroid's trajectory and uncertainty regions are well known through to the year 2186.[1]
1990 MU was first observed over three nights in 1990. By itself, this was not enough for the asteroid to be given a permanent number since the orbit could not be calculated accurately enough for the object to be subsequently recovered. However, the object wasprecovered by theAnglo-Australian Near-Earth Asteroid Survey on six photographic plates from theUK Schmidt Telescope dating back to 1974. This technique has more success with theAmor group of asteroids which do not cross the orbit of the Earth and consequently have long periods ofopposition when they can be observed. In this respect the Apollo asteroid1990 MU is somewhat unusual.[5]
_1990_MU_inc.svg)
1990 MU has an Earthminimum orbit intersection distance (MOID) of 0.0263 AU (3,930,000 km), which is close enough to classify it as apotentially hazardous asteroid (PHA). It will make a close approach to Earth on 6 June 2027 at 0.0308 AU (4,610,000 km),[1] becoming as bright as apparent magnitude 9.7 on 8 June 2027,[6] and even closer on 5 June 2058 at 0.0231 AU (3,460,000 km). It also made a close approach to Venus on 5 October 2012 at 0.0567 AU (8,480,000 km) and will again on 3 September 2041 at 0.0581 AU (8,690,000 km).[1]1990 MU has made close approaches to Earth in the past; in June 1996 it approached within 0.25 AU and in May 1990 it approached to 0.1418 AU.[7] The Earth MOID of1990 MU has been decreasing (becoming more hazardous) during the 20th century, while the Venus MOID (0.0455) has been increasing.[8]
Besides its original discovery atSiding Spring Observatory in Australia,1990 MU has also been studied by radar atGoldstone Observatory in California, andArecibo Observatory inPuerto Rico.[9][10]Lightcurves have been obtained atLa Silla Observatory in Chile.[11]
Thealbedo of1990 MU was measured by the ExploreNEOs project of theSpitzer Space Telescope in August 2009. The result obtained was 0.79 and was the second highest albedo measured by the project. However, ExploreNEO do not believe this is a plausible figure, they state that the albedo of an NEO is not likely to be much over 0.5 and their measurement uncertainty is "around a factor of 2".[12]
TheGaia mission of theEuropean Space Agency, launched in December 2013,[13] has been tasked with measuring theYarkovsky effect onnear-Earth asteroids (NEAs). The Yarkovsky effect is a small non-gravitational force on rotating bodies that can affect their trajectories. Its effect on small bodies like asteroids can be significant and needs to be taken into account in predicting an asteroid's position.1990 MU has been selected as one of the most promising NEAs for this measurement byGaia.[14]
| Asteroid | Date | Nominal approach distance (LD) | Min. distance (LD) | Max. distance (LD) | Absolute magnitude (H) | Size (meters) |
|---|---|---|---|---|---|---|
| 3200 Phaethon[19] | 2093-12-14 | 7.714 | 7.709 | 7.719 | 14.6 | 5100 |
| (4953) 1990 MU[20] | 2058-06-05 | 8.986 | 8.984 | 8.988 | 14.1 | 3000 |
