![]() The outline of Leona's shape revealed in a stellar 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 | unknown Leona [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 | 4.1451 AU |
Perihelion | 2.6655 AU |
3.4053 AU | |
Eccentricity | 0.2172 |
6.28 yr (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 designation A920 HE) is a dark, carbonaceous asteroid in the outer regions of the asteroid belt. It was discovered on 8 October 1891, by French astronomer Auguste Charlois at Nice Observatory in France. [10] On 12 December 2023, Leona passed in front of the bright star Betelgeuse and occulted 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 the outer main-belt at a distance of 2.7–4.1 AU once every 6 years and 3 months (2,295 days). Its orbit has an eccentricity of 0.22 and an inclination of 11° with respect to the ecliptic. [1]
Leona has been characterized as a dark and reddish P-type asteroid by the Wide-field Infrared Survey Explorer (WISE), and as an X-type asteroid by Pan-STARRS photometric survey. [8] The Collaborative Asteroid Lightcurve Link groups it to the carbonaceous C-type asteroids. [4]
In October 2016, a rotational lightcurve of Leona was obtained from photometric observations by astronomers Frederick Pilcher (see naming cite for 1990 Pilcher) at Organ Mesa Observatory ( G50 ), United States, Lorenzo Franco at Balzaretto Observatory ( A81 ), Italy, and Petr Pravec at the Ondřejov Observatory, Czech Republic. Lightcurve analysis gave a well-defined rotation period of 430±2 hours with a brightness variation of 0.5 magnitude ( U=3 ). [6]
This makes Leona one of the Top 100 slowest rotators known to exist. The astronomers also detected a non-principal axis rotation seen in distinct rotational cycles in successive order. This tumbling also gives an alternative candidate period solution of 1084±10 hours, one of the longest periods ever measured. [6] It is the third-largest tumbler known to exist (also see List 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 Japanese Akari satellite and the NEOWISE mission of NASA's WISE space-telescope, Leona measures between 49.943 and 89.00 kilometers in diameter and its surface has an albedo 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 an absolute magnitude of 10.2. [4]
The origin of this minor planet's name is unknown. [3]
Among the many thousands of named 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 between 164 Eva and 1514 Ricouxa and were discovered between 1876 and the 1930s, predominantly by astronomers Auguste Charlois, Johann Palisa, Max Wolf and Karl Reinmuth. [16]
![]() | This section needs to be updated.(December 2023) |
On 12 December 2023 at about 01:09–01:27 UT, Leona occulted Betelgeuse 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] a totality 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 the Florida Keys to parts of Mexico. [20] Among other programmes, 80 amateur astronomers in Europe were coordinated by astrophysicist Miguel Montargès, et al. of the Paris 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's convection 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 a silhouette 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]