Hubbry Logo
OTS 44OTS 44Main
Open search
OTS 44
Community hub
OTS 44
logo
8 pages, 0 posts
0 subscribers
Be the first to start a discussion here.
Be the first to start a discussion here.
OTS 44
OTS 44
OTS 44
View on Wikipedia
from Wikipedia

OTS 44

OTS 44 (orange crosshair) and surrounding nebulae
Observation data
Epoch J2000.0      Equinox J2000.0
Constellation Chamaeleon
Right ascension 11h 10m 11.5s
Declination −76° 32′ 13″
Characteristics
Spectral type M9.5±1.0[1][2]
Astrometry
Distance522–544 or 626 ly
(160–170 or 192 pc)[3][4]
Details
Mass6–17 MJ, average 11.5[3] MJup
Radius3.2 or 3.6[2] RJup
Luminosity0.00126±0.00023[a] – 0.0024[3] L☉
Temperature1700±100[2][3] K
Age1–6[2] Myr
Other designations
2MASS J11100934–7632178, CHSM 16658,[5] SSTgbs J1110093–763218,[5] TIC 454329342, [GMM2009] Cha I 27[5]
Database references
SIMBADdata

OTS 44 is a young, free-floating planetary-mass brown dwarf or rogue planet, located 520 to 630 light-years (160 to 192 parsecs) away in the star-forming molecular cloud Chamaeleon I in the constellation Chamaeleon. It is surrounded by a circumstellar disk of gas and dust, from which it is actively accreting mass at an approximate rate of 500 billion kilograms per second (or equivalently, 7.6×10−12 solar masses per year).[3] With an estimated age between 1 and 6 million years, OTS 44 has not existed long enough to cool down, so it glows red with a temperature of around 1,700 K (1,430 °C; 2,600 °F) and a stellar spectral type of M9.5.[2] It likely formed from the gravitational collapse of gas and dust, a similar process to how stars typically form.[6]

The disk of OTS 44 is estimated to span at least several astronomical units in radius with a flared shape—decreasing in density but increasing in vertical thickness at farther distances from the object.[3]: 2–3  OTS 44's disk contains a total estimated mass of approximately 0.1 Jupiter masses or 30 Earth masses,[3] with a small fraction of this mass constituting dust in the disk.[7][8] OTS 44's disk will eventually coalesce to form a planetary system.[9][10]

Discovery

[edit]

OTS 44 was discovered in images taken on 1–3 March 1996 by Japanese astronomers Yumiko Oasa, Motohide Tamura, and Koji Sugitani, during a search for young stellar objects and brown dwarfs in the core of the Chamaeleon I molecular cloud.[11]: 338  The discovery images were taken with the Cerro Tololo Inter-American Observatory's 1.5-metre (4.9 ft) telescope in Chile, which was equipped with the J, H, and K filters to measure the near-infrared colors of these objects.[12]: 1095 [11]: 338–339  The discoverers found 61 near-infrared-emitting objects and included them in their own catalogue,[11]: 339  which became known as the Oasa–Tamura–Sugitani (OTS) catalogue.[13][1]: 565 

OTS 44 was the 44th object and one of the dimmest objects listed in the OTS catalogue.[11]: 337 [1]: 565  The discoverers identified OTS 44 as a brown dwarf candidate because it appeared much dimmer and redder than other young stars in Chameleon I, which meant that it should have a very low mass if it shared the same age as these stars.[12]: 1046 [11]: 341  The discoverers published their analysis and identification of OTS 44 as a brown dwarf candidate in the journal Science in November 1998.[12]

In November 2004, Kevin L. Luhman, Dawn E. Peterson, and S. Thomas Megeath announced the confirmation of OTS 44 as a low-mass brown dwarf.[14] Using spectroscopic observations by the Gemini South telescope from March 2004, the researchers determined that OTS 44's mass lay close to the ~0.012 solar mass (13 Jupiter mass) boundary between giant planets and brown dwarfs, which made OTS 44 one of the least massive free-floating brown dwarfs confirmed at the time.[1][15]: L53 

Location and age

[edit]
The Chamaeleon complex photographed in far infrared by the IRAS satellite. OTS 44 is located in the Chamaeleon I region.

OTS 44 is located in the constellation Chamaeleon at a declination of approximately 76.5° south of the celestial equator.[5] It is situated within the core of Chamaeleon I, one of the three major star-forming molecular clouds of the Chamaeleon complex.[12][11] Chamaeleon I is one of the nearest star-forming regions to the Sun,[11]: 336  at an estimated distance of either 160–170 parsecs (520–550 light-years) (according to 1999 parallax measurements by the Hipparcos satellite[16]: 580 [1]: 565 ) or 192 pc (630 ly) (according to 2018 parallax measurements by the Gaia satellite[4]: 565 ). Astronomers assume that OTS 44 lies at the same distance as Chamaeleon I.[7]: 2 [4]: 565 

As a member of Chamaeleon I, OTS 44 is inferred to share the same age as other young stellar objects in the region, which are known to be between 1 and 6 million years old.[2]: 13, 19  At this age, substellar objects like OTS 44 are hot and luminous.[2]: 1–2  Observations of active accretion around OTS 44 indicate that it formed in a similar process to how stars form—via direct gravitational collapse of concentrated gas and dust.[6]: 1019–1020  OTS 44 will gradually cool and contract over time—becoming an L-type brown dwarf at about 10 million years of age, and then a Y dwarf after 1 billion years of age.[6]: 1024 

Physical characteristics

[edit]
The near-infrared spectrum of OTS 44 (black) shows deep absorption bands due to steam (H
2O vapor) in its atmosphere. The spectrum of the M8-type brown dwarf CHSM 17173 (red) is shown for comparison.[1]

The near-infrared spectrum of OTS 44 exhibits deep absorption bands caused by steam (water vapor) in its atmosphere, indicating a relatively cool temperature corresponding to a late spectral type of M9.5±1.0.[1] Additional substances including elemental sodium (Na), potassium (K), iron hydride (FeH), and carbon monoxide (CO) have been spectroscopically detected in OTS 44's atmosphere.[2]: 4, 7, 10  OTS 44 is estimated to have an effective temperature of 1,700 ± 100 K (1,427 ± 100 °C; 2,600 ± 180 °F), based on spectral energy distribution modeling with the object's atmospheric dust taken into account.[3]: 2 [2]: 17  OTS 44 stands out from cool main-sequence stars and red giants because it is much redder and brighter in near-infrared.[11]: 339–340  Extinction by foreground dust has been observed to cause additional reddening in OTS 44's near-infrared colors (0.3±0.3-magnitude dimming in J-band),[1]: 567  but not in its optical colors.[2]: 3 

OTS 44 is a dim object with a luminosity between 0.001 and 0.002 times that of the Sun.[3]: 2 [a] As a young and hot object, OTS 44 is expected to have a radius larger than that of Jupiter.[2]: 1, 19, 23  A Stefan–Boltzmann law calculation using OTS 44's luminosity and temperature suggests a "semi-empirical" radius of 3.5+0.6
−0.5 RJ, whereas a spectral energy distribution fit with OTS 44's disk taken into account suggests a radius between 3.2 and 3.6 RJ.[2]: 15, 17, 19  OTS 44 is estimated to be 6–17 times more massive than Jupiter,[7] though it is more likely below 13 Jupiter masses—in the planetary mass range, where it cannot fuse deuterium unlike brown dwarfs.[2] Hence, astronomers have also categorized OTS 44 as a free-floating planet.[6][7]

Circumstellar disk

[edit]
Cross-section diagram of the OTS 44's flared disk model proposed by Joergens et al. (2013)[3]
An artist's concept of OTS 44's dust disk

In February 2005, a team of astronomers led by Kevin Luhman announced the discovery of a circumstellar disk around OTS 44.[10][9] Their discovery was based on the Spitzer Space Telescope's detection of excess mid-infrared thermal emission from OTS 44, which indicated the presence of warm dust surrounding the object.[15] As one of the least massive free-floating objects known at the time, OTS 44 claimed the record for the least massive object known to have a circumstellar disk and demonstrated that such disks could exist around planetary-mass objects.[15]

Estimates based on OTS 44's spectral energy distribution (SED) suggests that its disk contains a total mass of about 30 Earth masses.[3] Observations with the SINFONI spectrograph at the Very Large Telescope show that OTS 44 is accreting matter from its disk at the rate of approximately 10−11 of the mass of the Sun per year.[3] It could eventually develop into a planetary system.[17]

Observations with ALMA detected OTS 44's disk in millimeter wavelengths. The observations constrained the dust mass of the disk between 0.07 and 0.63 M🜨, but these mass estimates are limited by assumptions on poorly constrained parameters.[7] Another work estimates the dust mass to 0.064 M🜨 (5.2 M☾) for dust particles of 1 mm in size and 0.295 M🜨 (24 M☾) for dust particles of 1 μm in size.[4]

See also

[edit]

Other free-floating rogue planets and brown dwarfs with protoplanetary disks:

  • Cha 110913-773444, rogue planet or brown dwarf surrounded by what appears to be a dusty disk
  • Cha 1107−7626, a young rogue planet that underwent an episode of rapid accretion of material from its disk
  • 2MASS J11151597+1937266, a young rogue planet or brown dwarf actively accreting material from its disk
  • KPNO-Tau 12, another young rogue planet or brown dwarf that is actively accreting material from its disk
  • J1407b, a possible disked object thought to have transited the star V1400 Centauri

Notes

[edit]

References

[edit]
[edit]
Revisions and contributorsEdit on WikipediaRead on Wikipedia

OTS 44

View on Grokipedia
from Grokipedia
OTS 44 is a free-floating planetary-mass of spectral type M9.5, located approximately 530 light-years (163 parsecs) away in the I star-forming region within the constellation . With an estimated mass of 6–17 masses, it represents one of the least massive known substellar objects, bordering the traditional distinction between and near the deuterium-burning limit of around 13 masses. Discovered in 1998 and spectroscopically confirmed in 2004, OTS 44 is notable for hosting a substantial and exhibiting active accretion, providing key insights into the formation processes of low-mass objects. Estimated to be about 2 million years old, OTS 44 is a young member of the Chamaeleon I association, a region rich in low-mass stars and substellar objects. Its is 1700 K, giving it a reddish appearance typical of young , which cool and fade over time. Observations with NASA's in 2005 revealed a circumstellar disk surrounding OTS 44, with a mass of approximately 9 masses and an outer radius extending to 100 AU. This flared disk, inclined at about 60°, shows mid-infrared excess emission indicative of dust and gas, sufficient to potentially form a small and several Earth-sized rocky worlds—making OTS 44 the smallest known with such a planet-forming structure at the time of discovery. Further studies have confirmed ongoing accretion onto OTS 44, with a mass accretion rate of about 7.6 × 10^{-12} M_⊙ yr^{-1}, evidenced by strong hydrogen emission lines such as Hα (equivalent width -141 Å) and Paβ. This activity places OTS 44 in a T Tauri-like phase, analogous to young stars, and highlights its role in probing the deuterium-burning limit where planetary and stellar formation mechanisms overlap. As a free-floating object not bound to any star, OTS 44 exemplifies rogue planetary-mass bodies and contributes to understanding the initial mass function at the low-mass end in star-forming regions.

Discovery

Object identification

OTS 44 was discovered in 1998 by astronomers Y. Oasa, M. Tamura, and K. Sugitani as part of a deep near-infrared imaging survey targeting low-mass young stellar objects in the core of the I dark cloud. The survey utilized ground-based observations to detect faint sources across the J, H, and K bands, identifying OTS 44 (source ID 44) at coordinates R.A. (J2000) 11^h 10^m 09^s.3, Decl. (J2000) -76° 32' 18" with dereddened magnitudes indicating a very faint, embedded object. Photometric analysis positioned OTS 44 on the near-infrared color-color diagram within the Class II region, classifying it as a candidate likely surrounded by a circumstellar disk. Early estimates derived from its J-band and pre-main-sequence evolutionary models (such as those by Baraffe et al. 1998 and D'Antona & Mazzitelli 1997), assuming an age of 1 Myr consistent with the Chamaeleon I star-forming region, yielded an upper limit of less than 0.025 solar masses (approximately 26 masses). Follow-up near-infrared spectroscopy in 2004, conducted with the Gemini Near-Infrared Spectrograph (GNIRS) on the Gemini South telescope, provided the first confirmation of OTS 44's nature. The spectrum revealed strong steam absorption bands and a spectral type of M9.5 ±1, later than M8, marking it as one of the coolest known objects at the time and indicative of a very low-mass brown dwarf. Gravity-sensitive features, including triangular-shaped continua in the H and K bands, confirmed its youth and membership in Chamaeleon I, distinguishing it from field dwarfs. Refined mass estimates, based on a bolometric luminosity of 0.0013 solar luminosities at a distance of 168 pc and evolutionary tracks from Chabrier & Baraffe (2000), placed OTS 44 at approximately 0.015 solar masses (around 15 Jupiter masses), with uncertainties of at least a factor of two due to model dependencies and age assumptions of 1–10 Myr for the region.

Disk and accretion detection

In February 2005, K. L. Luhman and colleagues announced the detection of a circumstellar disk around OTS 44 based on infrared observations conducted with NASA's Spitzer Space Telescope, specifically using the Infrared Array Camera (IRAC) instrument. These observations revealed excess emission at wavelengths beyond 3 μm in the spectral energy distribution of OTS 44, which spans from 0.8 to 8 μm, indicating the presence of warm dust in a protoplanetary disk. At the time, OTS 44, with an estimated mass of approximately 15 Jupiter masses and a spectral type of M9.5, represented the least massive known object harboring such a disk, extending the phenomenon of disk-bearing brown dwarfs to the planetary-mass regime. The excess infrared flux was modeled as arising from an irradiated viscous accretion disk, with a modeled accretion rate of about 10⁻¹⁰ M⊙ yr⁻¹, suggesting ongoing material infall onto the central object consistent with disk evolution models. This finding highlighted OTS 44's uniqueness compared to higher-mass brown dwarfs (typically >20 M_Jup), which more commonly retain disks; the retention at such low masses implied similar formation mechanisms for planetary-mass objects and stars, challenging prior assumptions about disk stability below the deuterium-burning limit. Follow-up optical spectroscopy provided initial direct evidence of accretion activity through the detection of prominent Hα emission lines. Observations with the Inamori-Magellan Areal Camera and Spectrograph (IMACS) on the Magellan I Baade in January 2005 revealed a broad Hα line, indicative of magnetospheric accretion from the disk onto OTS 44. This emission, with an of approximately -141 Å as later measured, confirmed active accretion and complemented the infrared disk detection, marking OTS 44 as the lowest-mass object with verified accretion signatures.

Physical characteristics

Mass, radius, and age

OTS 44 has an estimated mass of 12–15 Jupiter masses (MJup), positioning it near the boundary between planetary-mass objects and the lowest-mass brown dwarfs. This mass range is derived by placing the object's luminosity and effective temperature on pre-main-sequence evolutionary tracks, such as those developed by Baraffe et al. (1998) and Chabrier et al. (2000). More recent analyses, incorporating revised atmospheric models, suggest a slightly broader mass range of 6–17 MJup. The age of OTS 44 is approximately 2 million years, aligned with the median age of the I star-forming region derived from Hertzsprung-Russell diagram fitting using Baraffe et al. (1998) models for its member stars. This young age supports the object's spectral type of M9.5, which aids in constraining its position on evolutionary tracks.

Spectral properties and atmosphere

OTS 44 is classified as an M9.5 spectral type object based on its optical and near-infrared spectrum, which exhibits strong absorption from metal hydrides and oxides typical of late-type M dwarfs. This classification places it among the coolest known substellar objects at the time of discovery, with features indicating a dominated by cool temperatures. The of OTS 44 has been estimated at approximately 1700 through fitting of BT-Settl atmospheric models to its , accounting for and constraints. Earlier analyses suggested a higher value around 2300 , but more recent modeling favors the lower estimate, consistent with its late spectral type and youth. This cool temperature contributes to its reddish appearance in the near-infrared, as expected for young, low-mass where molecular absorption shapes the emergent spectrum. Near-infrared photometry of OTS 44 in the J, H, and K bands, primarily from observations, reveals a reddened consistent with its M9.5 type and moderate . Atmospheric modeling of OTS 44 employs grids like BT-Settl, which incorporate dust formation and processes relevant to late-M dwarfs on the verge of the L-type transition. These models assume solar metallicity and predict a log g of 3.5, fitting the observed fluxes while highlighting the role of condensate clouds in shaping the cool, opaque .

Location and environment

Position and distance

OTS 44 is positioned at right ascension 11h 10m 09s.32, declination −76° 32′ 17″.8 (J2000 epoch). The distance to OTS 44 is approximately 190 parsecs (620 light-years), determined from the median parallax of spectroscopically confirmed members of the Chamaeleon I star-forming region using Gaia DR2 data. Earlier spectroscopic distance estimates for the region placed OTS 44 at around 160 parsecs, but Gaia measurements have refined this value. Proper motion measurements for OTS 44 align with those of other confirmed young stellar objects in I, supporting its kinematic membership in the cloud. In optical bands, OTS 44 exhibits faint magnitudes of approximately 22 in the I-band, rendering it challenging to observe visually, while it appears brighter in the (J ≈ 16.4, H ≈ 15.4, K ≈ 14.7) owing to its young age and the presence of a circumstellar disk that enhances mid- to far- emission. OTS 44 lies in proximity to the IC 2631 within the I complex.

Association with Chamaeleon I

Chamaeleon I is a nearby dark cloud complex located at a distance of approximately 190 pc from the Sun, consisting of molecular gas and dust that facilitates ongoing low-mass . The region spans several parsecs and has an estimated age of 2–5 million years, placing it among the youngest nearby star-forming environments where pre-main-sequence objects like and planetary-mass objects are actively forming from the collapse of cloud fragments. OTS 44 was identified within this cloud through deep near-infrared imaging surveys targeting potential substellar candidates. Kinematic membership of OTS 44 in I is confirmed by its of 15.2 km/s, which aligns closely with the average value of ~15 km/s observed for stars and other in the region. This velocity match, derived from high-resolution of photospheric and accretion-related lines, supports co-motion with the molecular gas and eliminates the possibility of OTS 44 being a foreground or background interloper. Spectroscopic features indicative of youth, such as low , further corroborate its association with the region's young population. The molecular cloud in Chamaeleon I likely played a key role in OTS 44's formation, providing the dense environment necessary for the leading to such low-mass objects. External photoevaporation effects from ultraviolet radiation by nearby intermediate-mass stars in the cloud may influence the evolution of OTS 44's circumstellar material, potentially truncating its disk and accelerating dispersal, though direct evidence for this process on OTS 44 remains tentative. Compared to other brown dwarfs in Chamaeleon I, such as those with spectral types M6–M8 and masses around 20–50 Jupiter masses, OTS 44 stands out as the least massive confirmed member at ~12 Jupiter masses and is notably isolated as a free-floater without detected companions. This isolation highlights OTS 44's formation as an independent fragment of the cloud, distinct from more clustered or binary systems common among higher-mass brown dwarfs in the same environment.

Circumstellar disk

Structure and mass

The circumstellar disk around OTS 44 was initially detected through mid-infrared excess emission observed by the Spitzer Space Telescope, indicating the presence of warm dust grains, and later confirmed at submillimeter wavelengths by Atacama Large Millimeter/submillimeter Array (ALMA) observations that revealed cold dust emission. The disk is composed primarily of dust and gas, with the dust modeled as a mixture of 62.5% astronomical silicates and 37.5% graphite grains ranging from 0.005 to 0.25 μm in size, well-mixed with gas throughout the structure. Its geometry is highly flared (scale height exponent β > 1.2) and inclined at approximately 58° relative to the line of sight (with a range of 18°–65°), extending from an inner radius of about 0.023 AU (range: 0.01–0.04 AU) to an outer radius of roughly 100 AU. The total disk mass is estimated at 9.1 × 10⁻⁵ M⊙, equivalent to approximately 0.1 M_Jup or 30 M_Earth, which is sufficient to enable the formation of small based on scaling relations observed in more massive stellar disks. The inner edge features a hole or truncation at ~0.023 , potentially arising from accretion onto the central object or magnetospheric interactions that clear material close to OTS 44.

Accretion processes and implications

The accretion of material from the circumstellar disk onto OTS 44 occurs at a rate estimated between 10−1010^{-10} and 10−910^{-9} solar masses per year, primarily derived from measurements of veiling and the luminosity of the Paβ emission line in near-infrared spectra. These rates indicate active disk-object interaction at the regime, with variability observed across spectroscopic epochs, such as 1.7×10−9M⊙1.7 \times 10^{-9} M_\odot yr−1^{-1} on one night and 8.5×10−10M⊙8.5 \times 10^{-10} M_\odot yr−1^{-1} on another. Lower estimates from Hα luminosity yield around 7.6×10−12M⊙7.6 \times 10^{-12} M_\odot yr−1^{-1}, but the higher Paβ values are considered more reliable indicators of magnetospheric processes due to reduced chromospheric contamination. The dominant accretion mechanism for OTS 44 follows the magnetospheric model, where disk material is funneled along lines from the inner disk edge to the surface of the object, analogous to processes in stars but occurring at planetary masses of approximately 12 masses. Broad emission line wings extending to ±200 km/s in Paβ and Hα spectra support this funneling, with potential contributions from magnetospheric winds, extending T Tauri-like accretion signatures down to substellar boundaries. These accretion properties have significant implications for the lifetime and evolution of the disk around OTS 44, as the disk-to-central-object of approximately 10^{-2} suggests a prolonged phase of material processing similar to that in higher-mass young stellar objects. The presence of substantial accretion and a flared disk structure indicates that OTS 44 likely formed through in isolation, akin to mechanisms, rather than alternative pathways like ejection or disk instability. Observations by Joergens et al. in confirmed this significant accretion activity, bridging theoretical frameworks between formation and stellar processes by demonstrating continuity in disk accretion down to ~0.01 solar masses.
Add your contribution
Related Hubs
User Avatar
No comments yet.