 UScoCTIO 108A is the yellow object in the middle and the B component is the orange object below Credit: legacy surveys | |
| Observation data Epoch J2000.0 Equinox J2000.0 (ICRS) | |
|---|---|
| Constellation | Scorpius |
| Right ascension | 16h 05m 53.94s [1] |
| Declination | −18° 18′ 42.7″ [1] |
| Characteristics | |
| Spectral type | M7 [2] +M9.5 |
| Astrometry | |
| Proper motion (μ) | RA: -7.4 ± 4.6 [3] mas/yr Dec.: -20.4 ± 4.6 [3] mas/yr |
| Distance | 473 ± 6 ly (145 ± 2 [2] pc) |
| Details | |
| A | |
| Mass | 0.057 ± 0.019 [2] M☉ |
| Radius | 0.46 R☉ |
| Luminosity | 0.011+0.06 −0.03 [2] L☉ |
| Temperature | 2700 ± 100 [2] K |
| Age | 11 Myr |
| B | |
| Mass | 14 MJup |
| Temperature | 2300 K |
| Database references | |
| SIMBAD | data |
 UScoCTIO 108 B's orbit | |
| Position (relative to A) | |
|---|---|
| Epoch of observation | J2007.5 |
| Angular distance | 4.6 ± 0.1″ [2] |
| Position angle | 177 ± 1° [2] |
| Projected separation | ~670 AU [2] |
| Characteristics | |
| Spectral type | M9.5 ± 0.5 [4] |
| Details | |
| Mass | 0.015+0.009 −0.004 [4] M☉ |
| Mass | 15.79 MJup |
| Radius | 0.16 ± 0.01 [4] R☉ |
| Radius | 1.557 RJup |
| Luminosity | 0.00065 ± 0.00007 [4] L☉ |
| Surface gravity (log g) | 4.0 ± 0.5 [4] cgs |
| Temperature | 2300 ± 100 [4] K |
| Orbit | |
| Primary | UScoCTIO 108 A |
| Semi-major axis (a) | 670 AU |
| Other designations | |
| UscoCTIO 108b [5] | |
| Database references | |
| SIMBAD | data |
UScoCTIO 108 is a binary system, approximately 470 light-years away in the Upper Scorpius (USco) OB association. The primary, UScoCTIO 108A, with mass around 0.06 solar masses, is a brown dwarf or low-mass red dwarf. The secondary, UScoCTIO 108B, with a mass around the deuterium burning limit of 13 Jupiter masses, would be classified as either a brown dwarf or an extrasolar planet. [2]
Contents
The primary component of the system was discovered in 2000 as a possible member of the Upper Scorpius association, based on its position in a HR diagram, in a search for new member of the association by the Cerro Tololo Inter-American Observatory (CTIO), where it received the designation UScoCTIO 108. [6] Later, spectroscopic and photometric observations confirmed that the object is a real member of the association, showing signs of low gravity and youth, and estimated a mass of 60 times the mass of Jupiter (MJ), an effective temperature of 2,800 K and a spectral type of M7. The low mass indicates that the object is not able to sustain hydrogen fusion, making it a brown dwarf. [2]
The secondary member of the system was found in 2008 as an object located at a separation of 4.6 arcseconds, which corresponds to a physical separation of more than 670 AU, and is also a confirmed member of the Upper Scorpius association. [2] Its spectrum shows it is also a cold substellar object, with an effective temperature of 2,300 K and a spectral type of M9.5. [4] Its mass was originally estimated at 14 MJ, [2] very close to the nominal boundary between planets and brown dwarf, but a recent revision of the age of the Upper Scorpius association to 11 million years increased this value to 16 MJ, indicating that the object is likely a low mass brown dwarf. [7] The physical association between the two brown dwarfs has not been confirmed by observation of common proper motion, but is considered very likely given the proximity between them. [2] [3]
The minimum separation between the two brown dwarfs, 670 AU, is much larger than the mean of other similar mass systems, and indicates that the pair (if they really form a binary system) is very weakly bound, with an escape velocity for the secondary component of only 0.4 km/s. Considering the average stellar density in an association like Upper Scorpius, it is estimated that perturbations by passing stars will cause the rupture of the system in a few million years. [2]
Observations by the infrared telescope WISE revealed excess emission at 12 and 22 μm, indicating the presence of a debris disk around the brown dwarf. [8]
