Circumplanetary disk

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PDS 70c
(point-like source on the right side)

A circumplanetary disk (or circumplanetary disc, short CPD) is a torus, pancake or ring-shaped accumulation of matter composed of gas, dust, planetesimals, asteroids or collision fragments in orbit around a planet. They are reservoirs of material out of which moons (or exomoons or subsatellites) may form.[1] Such a disk can manifest itself in various ways.

In August 2018, astronomers reported the probable detection of a circumplanetary disk around

circumstellar.[4]

Candidates around other exoplanets

Possible circumplanetary disks have also been detected around exoplanets, such as

DH Tauri b.[10]

A disk was detected in sub-mm with ALMA around SR 12 c, a planetary-mass companion. SR 12 c might not have formed from the circumstellar disk material of the host star SR 12, so it might not be considered a true circumplanetary disk. PMC disks are relative common around young objects and are easier to study when compared to circumplanetary disks.[11]

Several disks were detected around nearby isolated planetary-mass objects. Disks around such objects within 300 parsecs were found in Rho Ophiuchi Complex,[12] Taurus Complex (e.g. KPNO-Tau 12),[12][13] Lupus I Cloud[14] and the Chamaeleon Complex (e.g. the well studied OTS 44 and Cha 110913−773444[15]). These objects with disks are free-floating and are most of the time called circumstellar disks, despite likely being similar to circumplanetary disks.

2M1207b was suspected to have a circumplanetary disk in the past.[16] New observations from JWST/NIRSpec were able to confirm accretion from an unseen disk by detecting emission from hydrogen and helium. The classification of a circumplanetary disk is however being disputed because 2M1207b (or 2M1207B) might be classified as a binary together with 2M1207A and not an exoplanet. This would make the disk around 2M1207b a circumstellar disk, despite not being around a star, but around a 5-6 MJup planetary-mass object.[17]

PDS 70

Main article: PDS 70

The disk around the planet c of the PDS 70 system is the best evidence for a circumplanetary disk at the time of its discovery. The exoplanet is part of the multiplanetary PDS 70 star system, about 370 light-years (110 parsecs) from Earth.[18]

PDS 70b

In June 2019 astronomers reported the detection of evidence of a circumplanetary disk around

PDS 70b[19] using spectroscopy and accretion signatures. Both types of these signatures had previously been detected for other planetary candidates. A later infrared characterization could not confirm the spectroscopic evidence for the disk around PDS 70b and reports weak evidence that the current data favors a model with a single blackbody component.[20]

PDS 70c

In July 2019 astronomers reported the first-ever detection using the

PDS 70c.[21][22][24]

According to

planet formation ... By comparing our observations to the high-resolution infrared and optical images, we can clearly see that an otherwise enigmatic concentration of tiny dust particles is actually a planet-girding disk of dust, the first such feature ever conclusively observed."[23] Jason Wang from Caltech, lead researcher of another publication, describes, "if a planet appears to sit on top of the disk, which is the case with PDS 70c"[25] then the signal around PDS 70c needs to be spatially separated from the outer ring, not the case in 2019. However, in July 2021 higher resolution, conclusively resolved data were presented.[26]

The planet PDS 70c is detected in H-alpha, which is seen as evidence that it accretes material from the circumplanetary disk at a rate of 10−8±0.4 MJ per year.[27] From ALMA observations it was shown that this disk has a radius smaller than 1.2 astronomical units (AU) or a third of the Hill radius. The dust mass was estimated around 0.007 or 0.031 ME (0.57 to 2.5 Moon masses), depending on the grain size used for the modelling.[26] Later modelling showed that the disk around PDS 70c is optically thick and has an estimated dust mass of 0.07 to 0.7 ME (5.7 to 57 Moon masses). The total (dust+gas) mass of the disk should be higher. The planet's luminosity is the dominant heating mechanism within 0.6 AU of the CPD. Beyond that the photons from the star heat the disk.[28]

See also

References

  1. ^ Parks, Jake (8 November 2021). "Snapshot: ALMA spots moon-forming disk around distant exoplanet - This stellar shot serves as the first unambiguous detection of a circumplanetary disk capable of brewing its own moon". Astronomy. Retrieved 9 November 2021.
  2. doi:10.1051/0004-6361/201732417
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  3. ^ Starr, Michelle. "Astronomers Have Accidentally Taken a Direct Photo of a Possible Baby Exoplanet". Retrieved 10 October 2019.
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  8. doi:10.1093/mnrasl/slad027
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  12. ^
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  13. ISSN 0004-637X
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  14. ISSN 0004-637X
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  15. S2CID 11685964
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  16. S2CID 17326111
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  17. ISSN 0004-637X
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  18. ^ Mandelbaum, Ryan F. (12 July 2019). "Astronomers Think They've Spotted a Moon Forming Around an Exoplanet". Gizmodo. Retrieved 12 July 2019.
  19. S2CID 155100321
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  20. ISSN 0004-6361
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  21. ^
    S2CID 189897829
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  22. ^ a b c Blue, Charles E. (11 July 2019). "'Moon-forming' Circumplanetary Disk Discovered in Distant Star System". National Radio Astronomy Observatory. Retrieved 11 July 2019.
  23. ^ a b Carne, Nick (13 July 2019). "'Moon-forming' disk found in distant star system - Discovery helps confirm theories of planet formation, astronomers say". Cosmos. Archived from the original on 12 July 2019. Retrieved 12 July 2019.
  24. ^ a b Boyd, Jade (11 July 2019). "Moon-forming disk discovered around distant planet". Phys.org. Retrieved 11 July 2019.
  25. ^ Observatory, W. M. Keck. "Astronomers confirm existence of two giant newborn planets in PDS 70 system". phys.org. Retrieved 27 July 2022.
  26. ^
    S2CID 236186222
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  27. ISSN 2397-3366
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  28. ISSN 0004-6361
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External links
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