(47171) 1999 TC36
Encyclopedia
is a system comprising three trans-Neptunian objects (TNOs). It was discovered in 1999 by Eric P. Rubenstein and Louis-Gregory Strolger during an observing run at Kitt Peak National Observatory
(KPNO). Dr. Rubenstein was searching images taken by Dr. Strolger as part of the Low-Z Supernova Search program. It is classified as a plutino
with a 2:3 mean motion resonance
with Neptune
, and, currently only being 30.7 AU
from the Sun, is among the brighter TNOs.
and the Hubble Telescope allow an estimation of the diameters of the components and consequently provide the range of possible values for the objects’ bulk density
. The very low estimate of 0.3–0.8 g/cm3 obtained in 2006 when the system was thought to be a binary would require an unusually high porosity
of 50–75%, assuming an equal mixture of rock and ice. The direct measurement of sizes of all three components of the system in 2009 has resulted in an improved average density of 0.532 g/cm3 confirming the earlier conclusion that the object is probably a rubble pile
.
(47171) 1999 TC36 has a very red spectral slope
in visible light
and a flat spectrum in near infrared. There is also a weak absorption feature near the wavelength of 2 μm
, probably caused by water ice
. The best model reproducing the near infrared spectrum includes tholin
s, crystalline water ice, and serpentine as surface materials. These results are for the integrated spectrum of all three components of the system.
using the Hubble Space Telescope
and announced on 10 January 2002, has an estimated diameter of 139 km and a semi-major axis of , orbiting its primary in . The moon is estimated to only have a mass of about 0.75 kg.
In 2009, analysis of Hubble
images revealed that the primary is itself composed of two similar-sized components. This central pair has a semi-major axis of around 867 km and a period of about 1.9 days. Assuming equal albedos of about 0.07, the primary components are approximately A1=286 km and A2=265 km in diameter. The component B orbits the barycenter
of the A1+A2 system. The system mass estimated from the motion of the component B is . The orbital motion of the A1 and A2 components gives somewhat a higher mass estimate of . The discrepancy is probably related to unaccounted gravitational interactions of the components in a complex triple system.
. The second one is gravitational capture of third object by a preexisting binary. The similar sizes of A1 and A2 components favor the latter hypothesis.
Kitt Peak National Observatory
The Kitt Peak National Observatory is a United States astronomical observatory located on 2,096 m Kitt Peak of the Quinlan Mountains in the Arizona-Sonoran Desert on the Tohono O'odham Nation, southwest of Tucson...
(KPNO). Dr. Rubenstein was searching images taken by Dr. Strolger as part of the Low-Z Supernova Search program. It is classified as a plutino
Plutino
In astronomy, a plutino is a trans-Neptunian object in 2:3 mean motion resonance with Neptune. For every 2 orbits that a plutino makes, Neptune orbits 3 times. Plutinos are named after Pluto, which follows an orbit trapped in the same resonance, with the Italian diminutive suffix -ino...
with a 2:3 mean motion resonance
Orbital resonance
In celestial mechanics, an orbital resonance occurs when two orbiting bodies exert a regular, periodic gravitational influence on each other, usually due to their orbital periods being related by a ratio of two small integers. Orbital resonances greatly enhance the mutual gravitational influence of...
with Neptune
Neptune
Neptune is the eighth and farthest planet from the Sun in the Solar System. Named for the Roman god of the sea, it is the fourth-largest planet by diameter and the third largest by mass. Neptune is 17 times the mass of Earth and is slightly more massive than its near-twin Uranus, which is 15 times...
, and, currently only being 30.7 AU
Astronomical unit
An astronomical unit is a unit of length equal to about or approximately the mean Earth–Sun distance....
from the Sun, is among the brighter TNOs.
Physical characteristics
The combined observations by the infrared Spitzer Space TelescopeSpitzer Space Telescope
The Spitzer Space Telescope , formerly the Space Infrared Telescope Facility is an infrared space observatory launched in 2003...
and the Hubble Telescope allow an estimation of the diameters of the components and consequently provide the range of possible values for the objects’ bulk density
Density
The mass density or density of a material is defined as its mass per unit volume. The symbol most often used for density is ρ . In some cases , density is also defined as its weight per unit volume; although, this quantity is more properly called specific weight...
. The very low estimate of 0.3–0.8 g/cm3 obtained in 2006 when the system was thought to be a binary would require an unusually high porosity
Porosity
Porosity or void fraction is a measure of the void spaces in a material, and is a fraction of the volume of voids over the total volume, between 0–1, or as a percentage between 0–100%...
of 50–75%, assuming an equal mixture of rock and ice. The direct measurement of sizes of all three components of the system in 2009 has resulted in an improved average density of 0.532 g/cm3 confirming the earlier conclusion that the object is probably a rubble pile
Rubble pile
In astronomy, rubble pile is the informal name for an object that is not a monolith, consisting instead of numerous pieces of rock that have coalesced under the influence of gravity...
.
(47171) 1999 TC36 has a very red spectral slope
Spectral slope
In astrophysics and planetary science, spectral slope, also called spectral gradient , is a measure of dependence of the reflectance on the wavelength....
in visible light
Light
Light or visible light is electromagnetic radiation that is visible to the human eye, and is responsible for the sense of sight. Visible light has wavelength in a range from about 380 nanometres to about 740 nm, with a frequency range of about 405 THz to 790 THz...
and a flat spectrum in near infrared. There is also a weak absorption feature near the wavelength of 2 μm
Micrometre
A micrometer , is by definition 1×10-6 of a meter .In plain English, it means one-millionth of a meter . Its unit symbol in the International System of Units is μm...
, probably caused by water ice
Water ice
Water ice could refer to:# Ice formed by water # Italian ice, fruit flavoured deserts, sorbet# Ice made from flowing water in Ice climbing...
. The best model reproducing the near infrared spectrum includes tholin
Tholin
Tholin [after the ancient Greek word meaning "not clear"] is a heteropolymer molecule formed by solar ultraviolet irradiation of simple organic compounds such as methane or ethane. Tholins do not form naturally on modern-day Earth, but are found in great abundance on the surface of icy bodies in...
s, crystalline water ice, and serpentine as surface materials. These results are for the integrated spectrum of all three components of the system.
Components
(47171) 1999 TC36 is a triple system consisting of a central primary, which is a binary itself, and a small moon (component B). The moon, discovered from 8 December 2001 observations by C. A. Trujillo and M. E. BrownMichael E. Brown
Michael E. Brown has been a professor of planetary astronomy at the California Institute of Technology since 2003....
using the Hubble Space Telescope
Hubble Space Telescope
The Hubble Space Telescope is a space telescope that was carried into orbit by a Space Shuttle in 1990 and remains in operation. A 2.4 meter aperture telescope in low Earth orbit, Hubble's four main instruments observe in the near ultraviolet, visible, and near infrared...
and announced on 10 January 2002, has an estimated diameter of 139 km and a semi-major axis of , orbiting its primary in . The moon is estimated to only have a mass of about 0.75 kg.
In 2009, analysis of Hubble
Hubble Space Telescope
The Hubble Space Telescope is a space telescope that was carried into orbit by a Space Shuttle in 1990 and remains in operation. A 2.4 meter aperture telescope in low Earth orbit, Hubble's four main instruments observe in the near ultraviolet, visible, and near infrared...
images revealed that the primary is itself composed of two similar-sized components. This central pair has a semi-major axis of around 867 km and a period of about 1.9 days. Assuming equal albedos of about 0.07, the primary components are approximately A1=286 km and A2=265 km in diameter. The component B orbits the barycenter
Center of mass
In physics, the center of mass or barycenter of a system is the average location of all of its mass. In the case of a rigid body, the position of the center of mass is fixed in relation to the body...
of the A1+A2 system. The system mass estimated from the motion of the component B is . The orbital motion of the A1 and A2 components gives somewhat a higher mass estimate of . The discrepancy is probably related to unaccounted gravitational interactions of the components in a complex triple system.
Origin
There exist two main hypotheses on how the triple system of 1999 TC36 appeared. The first one is a giant collision and subsequent reaccretion in the discAccretion disc
An accretion disc is a structure formed by diffuse material in orbital motion around a central body. The central body is typically a star. Gravity causes material in the disc to spiral inward towards the central body. Gravitational forces compress the material causing the emission of...
. The second one is gravitational capture of third object by a preexisting binary. The similar sizes of A1 and A2 components favor the latter hypothesis.