Peter Pan disk
Type of circumstellar disk
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A Peter Pan disk is a circumstellar disk around a star or brown dwarf that appears to have retained enough gas to form a gas giant planet for much longer than the typically assumed gas dispersal timescale of approximately 5 million years. Several examples of such disks have been observed to orbit stars with spectral types of M or later. The presence of gas around these disks has generally been inferred from the total amount of radiation emitted from the disk at infrared wavelengths, and/or spectroscopic signatures of hydrogen accreting onto the star. To fit one specific definition of a Peter Pan disk, the source needs to have an infrared "color" of , an age of >20 Myr and spectroscopic evidence of accretion.[1][2]
In 2016 volunteers of the Disk Detective project, led by Dr. Steven Silverberg of the University of Oklahoma, discovered WISE J080822.18-644357.3 (or J0808). This low-mass star showed signs of youth, for example a strong infrared excess and active accretion of gaseous material. It is part of the 45+11
−7 Myr old Carina young moving group, older than expected for these characteristics of an M-dwarf.[3][4] Other stars and brown dwarfs were discovered to be similar to J0808, with signs of youth while being in an older moving group.[4][2] Together with J0808, these older low-mass accretors in nearby moving groups have been called Peter Pan disks in one scientific paper published in early 2020.[5][2] Since then the term was used by other independent research groups.[6][7][8]
Name
Peter Pan disks are named after the main character Peter Pan in the play and book Peter Pan; or, the Boy Who Wouldn't Grow Up, written by J.M. Barrie in 1904. The Peter Pan disks have a young appearance, while being old in years. In other words: The Peter Pan disks "refuse to grow up", a feature they share with the Lost Boys and titular character in Peter Pan.[2][1]
Characteristics
The known Peter Pan disks have the H-alpha spectroscopic line as a sign of accretion. J0808 shows variations in the Paschen-β and Brackett-γ lines, which is a clear sign of accretion.[1][2] It was also identified as lithium-rich, which is a sign of youth.[4] Two peter pan disks (J0808 and J0632) show variation due to material from the disk blocking the light of the star.[1][9] J0808 and J0501 also showed flares.[1][2] Some of the Peter Pan disks (J0446, J0949, LDS 5606 and J1915) are binaries or suspected binaries.[2][10][11] J0226 is a candidate brown dwarf[2] and Delorme 1 (AB)b is a planetary-mass object in a circumbinary orbit.[7][12][13] A detailed study of J0446B with JWST MIRI detected 9 hydrocarbons, two nitrogen-bearing species, two isotopes of CO2, molecular hydrogen and two noble gases. Neon and molecular hydrogen strongly supports the idea that this disk is a long-lived primordial disk.[14] Delorme 1 (AB)b similarly shows a carbon-rich disk. Additionally an outflow of molecular hydrogen, possibly a disk wind, was detected around the planet.[15]
It was suggested that Peter Pan disks take longer to dissipate due to lower photoevaporation caused by lower far-ultraviolet and X-ray emission coming from the M-dwarf.[2] Modelling has shown that disk can survive for 50 Myrs around stars with a mass less than 0.6 M☉ and in low-radiation environments. At higher masses of 0.6 to 0.8 M☉ the stars form an inner gap before 50 Myr, preventing accretion.[16] Observations with the Chandra X-ray Observatory showed that Peter Pan Disks have a similar X-ray luminosity as field M-dwarfs, with properties similar to weak-lined T Tauri stars. The researchers of this study concluded that the current X-ray luminosity of Peter Pan disk cannot explain their old age. The old age of the disk could be the result of weaker far-ultraviolet flux incident on the disk, due to weaker accretion in the pre-main sequence stage.[17] It was proposed that disks do form with a lifetime distribution, with some disks only existing for a few Myrs and others for dozens of Myrs. This would explain why some >20 Myr old M-dwarfs show accretion due to a disk, but not all M-dwarfs of this age. The research team found an initial disk fraction of 65% for M-dwarfs (M3.7-M6) and the disk lifetime distribution matches a Gaussian or Weibull distribution.[18]
Known Peter Pan disks
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The prototype Peter Pan disk is WISE J080822.18-644357.3.[2] It was discovered by the NASA-led citizen science project Disk Detective.[19]
Murphy et al. found additional Peter Pan disks in the literature, which were identified as part of the Columba and Tucana-Horologium associations. The Disk Detective Collaboration identified two additional Peter Pan disks in Columba and Carina associations.[2] The paper also mentions that members of NGC 2547 were previously identified to have 22 μm excess and could be similar to Peter Pan disks.[2][20] 2MASS 08093547-4913033, which is one of the M-dwarfs with a debris disk in NGC 2547 was observed with the Spitzer Infrared Spectrograph. In this system the first detection of silicate was made from a debris disk around an M-type star. While the system shows the H-alpha line, it was interpreted to be devoid of gas and non-accreting.[21]
In the following years additional objects were discovered.[7][9][10][11] Some objects do not exactly fit the definition of Peter Pan disks, but are similar enough to be analogs: The object 2MASS J06195260-2903592 was found to be a 31+22
−10 Myr old analog to Peter Pan disks. This object does however not show accretion.[22] The star PDS 111 is interpreted as a higher-mass analog of Peter Pan disks, with an age of 15.9+1.7
−3.7 Myrs, a mass of 1.2±0.1 M☉, active accretion and a directly imaged disk.[23] One team also found old accreting stars in the Large Magellanic Cloud in the Tarantula Nebula.[24] This might be explained with a low metallicity in the LMC, which can lead to more massive disks that are less opaque.[16]
List of Peter Pan disk candidates
Note: Wang et al. 2025[25] lists 14 Peter Pan disks, here only 4 are listed that are older than 20 Myrs. Not included is US 3566 (Gaia DR3 155649614856576), which is a binary of a white dwarf and M-dwarf,[26] which could be a cataclysmic variable. Not included are also 2MASS J04141188+2811535 and 2MASS J04091380+3136325, which could be Taurus members.[25][27]
| Name | Age (Myrs) | Association | spectral type | infrared excess | accretion | Reference |
|---|---|---|---|---|---|---|
| WISE J080822.18-644357.3 | 45+11 −7 |
Carina association | M5 | yes | yes | [3][4] |
| 2MASS J05010082-4337102 | 42+6 −4 |
Columba association | M4.5 | yes | yes | [2][28] |
| 2MASS J02265658-5327032 | 45±4 | Tucana-Horologium association | L0δ | yes | yes | [2][28] |
| WISEA J044634.16-262756.1 | 42+6 −4 |
Columba association (but might be χ1 Fornacis member, which is 34 Myr old) | M6+M6 | yes | likely | [2][29] |
| WISEA J094900.65-713803.1 | 45+11 −7 |
Carina association | M4+M5 | yes | yes both | [2] |
| 2MASS J15460752-6258042 | ~55 | Argus association (but might be Beta Pictoris member) | M5 | yes | yes | [10][29] |
| 2MASS J05082729−2101444 | 30–44 | Columba association (but could be Beta Pictoris member) | M5 | yes | yes | [10] |
| LDS 5606 | 30–44 | Columba association (but could be Beta Pictoris member) | M5+M5 | yes | yes | [30][10] |
| Delorme 1 (AB)b | 30–45 | Tucana-Horologium association | L0 (very low gravity) | yes | yes | [7][12][13][15] |
| 2MASS J06320799-6810419 | ~45 | Carina association | M4.5 | yes | yes | [9] |
| 2MASS J19150079-2847587 | 24±3 | Beta Pictoris moving group | M4.8 (binary candidate) | yes | yes | [11] |
| StHα34 | 24.7+0.9 −0.6 |
Beta Pictoris moving group | M3+M3 | yes | yes | [29][31][32] |
| Gaia DR3 2162887638405193216 | >50 | K9.4 | yes | yes | [25] | |
| CVSO 1241 (Gaia DR3 3223542525253775104) | 25.1 | Orion OB1? (would be 5–10 Myr)[33] | M3.8 | yes | yes | [25] |
| 2MASS J05171175+0702232 (Gaia DR3 3241216624914091136) | 24.7 | Lambda Orionis ring?[34] | M3.2 | yes | yes | [25] |
| Gaia DR3 3319360599927089024 | 29.9 | M3.6 | yes | yes | [25] |
2MASS J0041353-562112 was discarded as it belongs to the Beta Pictoris moving group and does not show excess.[2]
Implications for planet formation around M-stars
There are different models to explain the existence of Peter Pan disks, such as disrupted planetesimals[4] or recent collisions of planetary bodies.[35] One explanation is that Peter Pan disks are long-lived primordial disks.[6] This would follow the trend of lower-mass stars requiring more time to dissipate their disks. Exoplanets around M-stars would have more time to form, significantly affecting the atmospheres on these planets.[1][2]
Peter Pan disks that form multiplanetary systems could force the planets in close-in, resonant orbits. The 7-planet system TRAPPIST-1 could be an end result of such a Peter Pan disk.[9]
A Peter Pan disk could also help to explain the existence of Jovian planets around M-dwarfs, such as TOI-5205b. A longer lifetime for a disk would give more time for a solid core to form, which could initiate runaway core-accretion.[36]