(47171) Lempo
|
Asteroid (47171) Lempo |
|
|---|---|
|
|
| Lempo seen with the Hubble Space Telescope in 2001 as a two-part system | |
| Properties of the orbit ( animation ) | |
| Orbit type | Plutino |
| Major semi-axis | 39.266 AU |
| eccentricity | 0.222 |
| Perihelion - aphelion | 30.546 AU - 47.985 AU |
| Inclination of the orbit plane | 8.4 ° |
| Length of the ascending node | 97 ° |
| Argument of the periapsis | 294.5 ° |
| Time of passage of the perihelion | April 19, 2015 |
| Sidereal period | 246 a 18.5 d |
| Mean orbital velocity | 4.731 km / s |
| Physical Properties | |
| Medium diameter | 272.0 + 17.0- 19.0 km |
| Dimensions | ~ 6 - 7 · 10 19 kg |
| Albedo | 0.079 + 0.013- 0.011 |
| Medium density | 0.64 + 0.15- 0.11 g / cm³ |
| Rotation period | 6 h 12.6 min |
| Absolute brightness | 4.90 likes |
| history | |
| Explorer | Eric P. Rubenstein Louis-Gregory Strolger |
| Date of discovery | October 1, 1999 |
| Another name | 1999 TC 36 |
| Source: Unless otherwise stated, the data comes from JPL Small-Body Database Browser . The affiliation to an asteroid family is automatically determined from the AstDyS-2 database . Please also note the note on asteroid items. | |
(47171) Lempo is a large trans-Neptunian object in the Kuiper Belt that is classified as Plutino because of its 2: 3 orbital resonance to the planet Neptune . Initially, Lempo was classified as a single relatively large object. Eight years after its discovery, Lempo was found to be a triple system of two major components and a distant third component. It was the first Trans-Neptunian object to be recognized as a system of multiple objects.
Discovery and naming
(47171) Lempo was discovered on October 1, 1999 by Eric P. Rubenstein and Louis-Gregory Strolger at the Kitt Peak National Observatory in Arizona . Rubenstein searched images that were created by Strolger as part of the Low-Z Supernova search program. The asteroid was given the provisional name 1999 TC 36 . After its discovery, (47171) Lempo was also found on older recordings from June 18, 1974, May 30, 1976 and September 16, 1976. This allowed his orbit to be calculated more precisely and on September 21, 2002 he received the minor planet number 47171 from the IAU .
Since the companions' discovery, the designation "(47171) 1999 TC 36 " has officially been used for the largest component of the system, while the designation S / 2007 (47171) 1 for the smaller component and S / 2001 ( for the larger, more distant moon) 47171) 1 applied. But the name of the largest body is often used for the whole system. Unofficially, the asteroid was sometimes referred to as "(47171) 1999 TC 36 A 1 " or simply "A 1 " .
On October 5, 2017, the Minor Planet Center announced the name Lempo . Lempo is a god from Finnish mythology . His highest servants are Hiisi and Paha , after whom the other two components of the system are named.
The Lempo system has been observed through several space-based and earth-based telescopes. In December 2017, there were a total of 331 observations over a period of 43 years.
properties
Orbit
(47171) Lempo orbits the sun in a prograde , relatively elliptical orbit between 4,570,500,000 km (30.55 AU ) and 7,159,400,000 km (47.86 AU) from its center. The orbital eccentricity is 0.221, the web is of 8.4 ° relative to the ecliptic inclined . The orbital period is 245.48 years.
The planetoid is currently 30.6 AU from the sun. He passed his perihelion in July 2015.
rotation
There are different information about the rotation period of Lempo. A rotation determination based on the light curve gave 6 hours, 12.6 minutes. From this it follows that the asteroid performs 346,519.4 self- rotations in a Lempo year .
According to another source, one revolution takes 1 day, 21 hours and 45.8 minutes. In this case, the orbit time would be the same as the rotation time, and since the smaller component Hiisi would have to behave in the same way, it would be a doubly bound rotation . This meant that both bodies were always facing the same side. According to the Pluto / Charon system , it would be the first time that a further double-bound rotation in the Kuiper belt could be detected. In the main belt , this is about at (90) Antiope A and B the case. The prerequisite for this is a similar mass and a narrow orbit of the two bodies. In this case the asteroid would complete 47,022.4 self-rotations in one Lempo year.
size
The single body diameter (effective system diameter) is currently 393.1 + 25.2- 26.8km estimated. But the three-part system (47171) Lempo consists in orbital dynamics of a main body, which is itself a double asteroid, and a moon about half the size. Therefore, the actual mean diameter of the "A 1 " component, ie the asteroid itself, is estimated to be 272 km; it is only 7.3% larger than its "twin" "A 2 " .
Assuming a mean diameter of 272 km, the surface area is about 232,400 km², which is just about the size of Laos .
| year | Dimensions km | source |
|---|---|---|
| 2009 | 281.0 + 45.0- 38.0 | Benecchi et al. a. |
| 2010 | 286.0 + 45.0- 38.0 | Benecchi et al. a. |
| 2012 | 272.0 + 17.0- 19.0 | Mommert et al. a. |
| 2018 | 403.0 | Brown |
| The most precise determination is marked in bold . | ||
internal structure
The combined observations with the Spitzer, Herschel and Hubble telescopes made it possible to determine the density. The first (very low) density determination 0.3 to 0.8 g / cm³ in 2006, when the system was still known as a double system, would require a porosity of 50–75%. The direct light curve measurement of all three components by Hubble in 2009 showed an average density of 0.532 + 0.317- 0.211g / cm³, which confirmed the previous assumption that the asteroid could possibly be a rubble pile , a loose accumulation of dust and rocks. In 2012 the density was revised again due to new findings from the Herschel telescope; the current estimate is 0.64 g / cm³. The porosity is still estimated to be 36-68%.
(47171) Lempo has a very red spectral drop in visible light and a flat spectrum in the near infrared. There is a faint absorption feature near the 2 μm wavelength, possibly due to the existence of water ice. The best model for near infrared results includes tholine , crystalline water ice, and serpentine as surface materials. These results apply to all three components of the system.
The total mass of the system, which was determined by moving the third component, is 1.275 ± 0.006 ∙ 10 19 kg. The mass of the A 1 and A 2 components was determined to be slightly higher than 1.420 ± 0.005 ∙ 10 19 kg. This discrepancy is perhaps due to the gravitational interactions of the components in a complex triple system. The mass of the A 1 component should therefore be 6-7 · 10 19 kg.
The mean surface temperature is 44–45 K (–229 to –228 ° C).
Emergence
So far, there are two hypotheses about the origin of the triple system. Either it came about as a result of a major collision, after which the entire system was re-formed from the accretion disk that had arisen, or the third component was gravitationally captured by the already existing double asteroid. The similar sizes and masses of the A 1 and A 2 components favor the latter hypothesis.
The (47171) Lempo triple system
On December 8, 2001, astronomers Chadwick A. Trujillo and Michael E. Brown discovered a first companion at Lempo on images from the Hubble space telescope . The moon Paha , provisionally designated as S / 2001 (47171) 1 , has a diameter of 132 km and orbits the common center of gravity of the system at a distance of 7,411 km in 50.3 days.
Further examination of the images from the Hubble Space Telescope in 2007 revealed that the main body consists of two objects of similar mass and diameter. This was confirmed in 2009. The companion Hiisi , temporarily designated as S / 2007 (47171) 1 , is 251 km tall; it moves at a distance of 867 km in 45.763 hours around the common center of mass.
The (47171) Lempo system at a glance:
| Components | Physical parameters | Path parameters | discovery | |||||
|---|---|---|---|---|---|---|---|---|
| Surname | Throughput diameter (km) |
Relative size % |
Mass (kg) |
Major semi-axis (km) |
Orbital time (d) |
eccentricity |
Inclination to Eugenia's equator |
Date of discovery Date of publication |
| (47171) Lempo | 272.0 | 100.00 | 6 - 7 · 10 19 | - | - | - | - | October 1, 1999 September 21, 2002 |
|
Hiisi (Lempo II) |
251.0 | 92.7 | 6 - 7 · 10 19 | 867 | 1.907 | ? | ? | October 2007 October 2007 |
|
Paha (Lempo I) |
132.0 | 48.6 | 7.5 · 10 17 | 7411 | 50,302 | ? | ? | December 8, 2001 January 10, 2002 |
(47171) Lempo is the first multiple asteroid system to be discovered in the Kuiper Belt and in the trans-Neptunian area at all. Apart from the dwarf planets Pluto and Haumea - which also have an asteroid number - after (87) Sylvia and (45) Eugenia it is the third proven multiple asteroid system in the solar system and the only one in the Kuiper Belt. The Lempo system is unique in the solar system in that the third companion of the two main bodies is also comparatively large. The size ratio is roughly 2: 2: 1. This is not the case with any of the multiple systems found so far.
The Lempo system was one of the candidates in the planning for a New Horizons 2 mission (2004-2005), which included a flyby of Jupiter and Uranus and up to four Kuiper belt objects.
See also
- List of trans-Neptunian objects
- List of dwarf planets of the solar system
- List of asteroids
- List of moons from asteroids
Web links
- Precovery photos by Lempo
- How many dwarf planets are there in the outer solar system? Current list of the largest TNOs from Mike Brown
- Free the dwarf planets! Mike Brown's column on the IAU and the dwarf planets regarding their classifications (23 August 2011)
Individual evidence
- ↑ Guido Meyer: Astronomers discover celestial body trio (December 19, 2007). Retrieved September 17, 2017 .
- ↑ IAU: IAU: MPEC 1999-Y19: 1999 RV214, 1999 TC36, 1999 XX143, 1999 XY143 discovery publication (December 21, 1999). Retrieved September 17, 2017 .
- ↑ MPC / MPO / MPS archives. In: Minor Planet Center. Retrieved October 9, 2017 .
- ↑ JPL: 47171 Lempo (1999 TC 36 ) at the JPL. Retrieved December 14, 2017 .
- ↑ AstDyS: (47171) Lempo. Retrieved December 27, 2018 .
- ^ Silvia Protopapa: Surface characterization of Pluto, Charon, and (47171) 1999 TC 36 (2009). Retrieved September 17, 2017 .
- ↑ a b S. D. Benecchi et al .: (47171) 1999 TC 36 , A transneptunian triple (June 2010). Retrieved September 17, 2017 .
- ↑ SD Benecchi et al .: (47171) 1999 TC36, A Transneptunian Triple (September 2009) (PDF). Retrieved September 17, 2017 .
- ↑ M. Mommert, AW Harris, C. Kiss, A. Pál, P. Santos-Sanz, J. Stansberry, A. Delsanti, E. Vilenius, TG Müller, N. Peixinho, E. Lellouch, N. Szalai, F. Henry, R. Duffard, S. Fornasier, P. Hartogh, M. Mueller, JL Ortiz, S. Protopapa, M. Rengel, A. Thirouin: “TNOs are Cool”: A survey of the trans-Neptunian region. V. Physical characterization of 18 Plutinos using Herschel-PACS observations . In: Astronomy and Astrophysics . 541, no.A93 , May 4, 2012. arxiv : 1202.3657 . bibcode : 2012A & A ... 541A..93M . doi : 10.1051 / 0004-6361 / 201118562 .
- ↑ M. Brown : How many dwarf planets are there in the outer solar system? (November 2018)
- ↑ JA Stansberry et al .: The Albedo, Size, and Density of Binary Kuiper Belt Object (47171) 1999 TC36 (February 14, 2006) (PDF). Retrieved September 17, 2017 .
- ^ Daniel WE Green: IAUC No. 7787: S / 2001 (47171) 1 Discovery Publication (Jan. 10, 2002). Retrieved September 17, 2017 .