 The outline of Leona's shape revealed in astellar occultation from 13 September 2023 | |
| Discovery[1] | |
|---|---|
| Discovered by | A. Charlois |
| Discovery site | Nice Obs. |
| Discovery date | 8 October 1891 |
| Designations | |
| (319) Leona | |
| Pronunciation | /liːˈoʊnə/[2] |
Named after | unknownLeona[3] |
| A920 HE | |
| main-belt · (outer)[1][4] | |
| Orbital characteristics[1] | |
| Epoch 4 September 2017 (JD 2458000.5) | |
| Uncertainty parameter 0 | |
| Observation arc | 125.32 yr (45,774 days) |
| Aphelion | 4.1451AU |
| Perihelion | 2.6655 AU |
| 3.4053 AU | |
| Eccentricity | 0.2172 |
| 6.28yr (2,295 days) | |
| 21.414° | |
| 0° 9m 24.48s / day | |
| Inclination | 10.564° |
| 184.95° | |
| 228.27° | |
| Physical characteristics | |
| Dimensions | 79.6 km × 54.8 km (± 2.2 km × 1.3 km)[5] |
| 66±2 km[5] | |
| 430±2 h[6] | |
| 0.085±0.005[1][7] | |
| P[8] · X[9] · C[4] | |
| 10.21[1][10] 10.46±0.06[6] | |
319 Leona (provisional designationA920 HE) is a dark,carbonaceous asteroid in the outer regions of theasteroid belt. It was discovered on 8 October 1891, by French astronomerAuguste Charlois atNice Observatory inFrance.[10] On 12 December 2023, Leona passed in front of the bright starBetelgeuse andocculted it, which caused the star to briefly dim as seen from Central America, Europe, and east Asia.[11] This occultation was expected to reveal the shape of Leona and the surface of Betelgeuse in high detail.
Leona orbits the Sun in theouter main-belt at a distance of 2.7–4.1 AU once every 6 years and 3 months (2,295 days). Its orbit has aneccentricity of 0.22 and aninclination of 11° with respect to theecliptic.[1]
Leona has been characterized as a dark and reddishP-type asteroid by theWide-field Infrared Survey Explorer (WISE), and as anX-type asteroid byPan-STARRS photometric survey.[8] TheCollaborative Asteroid Lightcurve Link groups it to the carbonaceousC-type asteroids.[4]
In October 2016, a rotationallightcurve of Leona was obtained from photometric observations by astronomers Frederick Pilcher(see naming cite for1990 Pilcher) at Organ Mesa Observatory (G50), United States, Lorenzo Franco at Balzaretto Observatory (A81), Italy, andPetr Pravec at theOndřejov Observatory, Czech Republic. Lightcurve analysis gave a well-definedrotation period of430±2 hours with a brightness variation of 0.5magnitude (U=3).[6]
This makes Leona one of theTop 100 slowest rotators known to exist. The astronomers also detected a non-principal axis rotation seen in distinct rotational cycles in successive order. Thistumbling also gives an alternative candidate period solution of1084±10 hours, one of thelongest periods ever measured.[6] It is the third-largest tumbler known to exist(also seeList of tumblers).
Previous observations of Leona gave a much shorter period between 6 and 15 hours,[12][13] which demonstrates the intricacy when observing slow rotators, especially those with a tumbling motion. A detailed description of the procedure of the photometric measurement is given by Pilcher.[6]
According to the surveys carried out by the JapaneseAkari satellite and theNEOWISE mission of NASA's WISE space-telescope, Leona measures between 49.943 and 89.00 kilometers in diameter and its surface has analbedo between 0.02 and 0.085.[7][8][14][15] CALL derived an albedo of 0.0318 and a diameter of 67.97 kilometers based on anabsolute magnitude of 10.2.[4]
The origin of thisminor planet's name is unknown.[3]
Among the many thousands ofnamed minor planets, Leona is one of 120 asteroids for which no official naming citation has been published. All of these low-numbered asteroids have numbers between164 Eva and1514 Ricouxa and were discovered between 1876 and the 1930s, predominantly by astronomersAuguste Charlois,Johann Palisa,Max Wolf andKarl Reinmuth.[16]
 | This section needs to beupdated. Please help update this article to reflect recent events or newly available information.(December 2023) |
On 12 December 2023 at about 01:09–01:27 UT, LeonaoccultedBetelgeuse as seen from southern Europe, Turkey, Greece and Sicily.[11] The 14th magnitude asteroid was predicted to occult Betelgeuse approximately 12 seconds; Betelgeuse was expected to dim by about 3 magnitudes.[17] The prediction was at first uncertain, visible on a very narrow path on Earth's surface, its width and location being uncertain due to lack of precise knowledge of the size and path of the asteroid).[18] Projections were later refined as more data were analyzed for[19] atotality of approximately five seconds on a 60 km wide path stretching from China, Tajikistan, Armenia, Turkey, Greece, Italy, Spain, the Atlantic Ocean, Miami, Florida and theFlorida Keys to parts of Mexico.[20] Among other programmes, 80amateur astronomers in Europe were coordinated by astrophysicistMiguel Montargès, et al. of theParis Observatory for the event.[21]Light curve studies of the event was expected to help understand the distribution of brightness down to the granular level of Beltegeuse'sconvection cells,[22] thus providing detailed data on the giant star heretofor inaccessible.
Observations of the earlier September 2023 occultation showed that the asteroid was slightly elliptical; a preliminary 3D model of Leona was able to be constructived. Leona is approximately 80 by 55 kilometres, hence is projected to have asilhouette of roughly 46 by 41 milliarcseconds (mas).[5][23] Betelgeuse has an apparent size in the sky of about 45 mas, but its diffuse atmosphere may make it appear 55 mas in size. A preliminary analysis of results showed only a slight dimming, consistent with a partial or annular eclipse.[24]
