TW Hydrae

TW Hydrae

TW Hydrae protoplanetary disc
Observation data
Epoch J2000.0      Equinox ICRS
Constellation Hydra
Right ascension 11h 01m 51.90533s
Declination −34° 42′ 17.0332″
Apparent magnitude (V) 10.92
Characteristics
Evolutionary stage Pre-main-sequence
Spectral type K6Ve
U−B color index −0.33
B−V color index 0.721
Variable type T Tauri
Astrometry
Radial velocity (Rv)+13.40±0.8 km/s
Proper motion (μ) RA: −68.309 mas/yr
Dec.: −13.900 mas/yr
Parallax (π)16.6289±0.0150 mas
Distance196.1 ± 0.2 ly
(60.14 ± 0.05 pc)
Absolute magnitude (MV)7.30
Details
Mass0.80±0.05 M☉
Radius1.16±0.13 R☉
Luminosity (bolometric)0.33±0.08 L☉
Surface gravity (log g)4.2±0.1 cgs
Temperature4050±50 K
Rotation3.606±0.010 d
Rotational velocity (v sin i)3±1 km/s
Age7.5±2.5 Myr
Other designations
TWA 1, TW Hya, CD−34°7151, HIP 53911
Database references
SIMBADdata

TW Hydrae is a T Tauri star approximately 196 light-years away in the constellation of Hydra (the Sea Serpent). TW Hydrae is about 80% of the mass of the Sun, but is only about 5-10 million years old. The star appears to be accreting from a protoplanetary disk of dust and gas, oriented face-on to Earth, which has been resolved in images from the ALMA observatory. TW Hydrae is one of the closest protoplanetary disk hosts, which combined with its face-on orientation makes it one of the best-studied objects to understand planetary formation.

TW Hydrae is accompanied by over 40 other low-mass stars and brown dwarfs with similar ages and spatial motions, comprising the TW Hydrae association or TWA, one of the closest regions of recent "fossil" star-formation to the Sun.

Stellar characteristics

A broadband optical light curve plotted from MOST microsatellite data published by Rucinski et al. (2008)

TW Hydrae is a pre-main-sequence star that is approximately 80% the mass and 116% the radius of the Sun. It has a temperature of 4050 K and is about 7.5 million years old. In comparison, the Sun is about 4.6 billion years old and has a temperature of 5778 K. The star's luminosity is 0.33 times that of the Sun. The stellar classification is K6Ve. The star rotates with a period of 3.6 days.

The star's apparent magnitude, or how bright it appears from Earth's perspective, is 10.92. Therefore, it is too dim to be seen with the naked eye.

Planetary system

Protoplanetary disk

Detection of methanol

In 2016, methanol, one of the building blocks for life, was detected in the star's protoplanetary disk.

Possible planets

The TW Hydrae planetary system
Companion
(in order from star)		 Mass Semimajor axis
(AU)		 Orbital period
(days)		 Eccentricity Inclination
(°)		 Radius
b (unconfirmed) ≥30+9
−7 M🜨		 0.075±0.001 8.339±0.008 — — —
(unconfirmed) — 5.5±0.8 — — — —
(unconfirmed) ~26 M🜨 22 — — — —
(unconfirmed) ~4 M🜨 42 — — — —
(unconfirmed) 6–28 M🜨 80 — — — —
(unconfirmed) ~0.3 MJ 94 — — — —
Protoplanetary disk 1–30? AU — —

Disproven protoplanet (2007)

In December 2007, a team led by Johny Setiawan of the Max Planck Institute for Astronomy in Heidelberg, Germany announced discovery of a planet orbiting TW Hydrae, dubbed "TW Hydrae b" with a minimum mass around 1.2 Jupiter masses, a period of 3.56 days, and an orbital radius of 0.04 astronomical units (inside the inner rim of the protoplanetary disk). Assuming it orbited in the same plane as the outer part of the dust disk (inclination 7±1°), it would have a true mass of 9.8±3.3 Jupiter masses. However, if the inclination was similar to the inner part of the dust disk (4.3±1.0°), the mass would be 16+5
−3 Jupiter masses, making it a brown dwarf. Since the star itself is so young, it was presumed this was the youngest extrasolar planet then discovered, and essentially still in formation.

In 2008 a team of Spanish researchers concluded that the planet does not exist: the radial velocity variations were not consistent when observed at different wavelengths, which would not occur if the origin of the radial velocity variations was caused by an orbiting planet. Instead, the data was better modelled by starspots on TW Hydrae's surface passing in and out of view as the star rotates. "Results support the spot scenario rather than the presence of a hot Jupiter around TW Hya". Similar wavelength-dependent radial velocity variations, also caused by starspots, have been detected on other T Tauri stars.

Other candidates

A 2013 study proposed that a gap in the disk at 80 AU could be formed by a planet with a mass of 6–28 M🜨.

In 2016, astronomers studying the protoplanetary disk of the star with ALMA found evidence that a possible Neptune-like planet was forming in a gap in its disk, at a distance of around 22 AU (somewhat less than the orbital distance of Neptune from the Sun, which is 30 AU). This planet would be an ice giant with an estimated mass around 1.5 times that of Neptune (25.7 M🜨). The study was added to the online journal preprint archive arXiv on May 1, 2016, and published in The Astrophysical Journal in October.

Another 2016 study detected a candidate companion at 5.5 AU.

A 2018 study proposed two super-Earths of around 4 Earth masses to explain gaps at 24 and 41 AU, and a Saturn-mass planet in a gap at 94 AU.

2024 planetary candidates

In 2024, a study detected radial velocity variations in TW Hydrae with a period of 8.3 days, which may be caused by an orbiting planet, or alternatively by part of the inner accretion disk. Like the 2007 candidate, this was designated planet "b". This object would have a minimum mass of about 30 Earth masses, but if its orbit is aligned with the rotation of the star (which is nearly face-on) its true mass would be 0.55+0.17
−0.13 MJ, about half the mass of Jupiter.

Also in 2024, observations with ALMA showed sulfur monoxide representing an outflow from an embedded protoplanet. The position of the brightest emission coincides with a planet-carved dust gap at 42 au. Previously this gap was suggested to be associated with the formation of a super-Earth, and by modelling the outflow velocity, the researchers estimate a mass of about 4 Earth masses. The mass accretion of this embedded protoplanet is constrained to between 3 ×10−7 and 10−5 MJ/year.

References

  1. 1 2 3 4 5 6 7 Anderson, E.; Francis, Ch. (2012). "XHIP: An extended hipparcos compilation". Astronomy Letters. 38 (5): 331. arXiv:1108.4971. Bibcode:2012AstL...38..331A. doi:10.1134/S1063773712050015. XHIP record for this object at VizieR.
  2. 1 2 3 4 5 Vallenari, A.; et al. (Gaia collaboration) (2023). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy and Astrophysics. 674: A1. arXiv:2208.00211. Bibcode:2023A&A...674A...1G. doi:10.1051/0004-6361/202243940. S2CID 244398875. Gaia DR3 record for this source at VizieR.
  3. ↑ Mermilliod, J.C. (1991), "Homogeneous Means in the UBV System", VizieR On-line Data Catalog, Institut d'Astronomie, Universite de Lausanne, Bibcode:2006yCat.2168....0M.Vizier catalog entry
  4. 1 2 "V* TW Hya". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2014-01-02.
  5. 1 2 3 4 5 6 Donati, J.-F.; Cristofari, P. I.; et al. (June 2024). "SPIRou spectropolarimetry of the T Tauri star TW Hydrae: magnetic fields, accretion, and planets". Monthly Notices of the Royal Astronomical Society. 531 (3): 3256–3278. arXiv:2405.04461. Bibcode:2024MNRAS.531.3256D. doi:10.1093/mnras/stae1227. ISSN 0035-8711.
  6. ↑ Macías, E.; Guerra-Alvarado, O.; et al. (April 2021). "Characterizing the dust content of disk substructures in TW Hydrae". Astronomy & Astrophysics. 648: A33. arXiv:2102.04648. Bibcode:2021A&A...648A..33M. doi:10.1051/0004-6361/202039812. ISSN 0004-6361.
  7. ↑ Gagné, Jonathan; Faherty, Jacqueline K.; et al. (February 2017). "BANYAN. IX. The Initial Mass Function and Planetary-mass Object Space Density of the TW HYA Association". The Astrophysical Journal Supplement Series. 228 (2): 18. arXiv:1612.02881. Bibcode:2017ApJS..228...18G. doi:10.3847/1538-4365/228/2/18. ISSN 0067-0049.
  8. ↑ Rucinski, Slavek M.; Matthews, Jaymie M.; Kuschnig, Rainer; Pojmanski, Grzegorz; Rowe, Jason; Guenther, David B.; Moffat, Anthony F. J.; Sasselov, Dimitar; Walker, Gordon A. H.; Weiss, Werner W. (December 2008). "Photometric variability of the T Tauri star TW Hya on time-scales of hours to years". Monthly Notices of the Royal Astronomical Society. 391 (4): 1913–1924. arXiv:0809.3987. Bibcode:2008MNRAS.391.1913R. doi:10.1111/j.1365-2966.2008.14014.x.
  9. ↑ Fraser Cain (16 September 2008). "How Old is the Sun?". Universe Today. Retrieved 19 February 2011.
  10. ↑ Fraser Cain (15 September 2008). "Temperature of the Sun". Universe Today. Retrieved 19 February 2011.
  11. ↑ "Methanol, a Building Block of Life, Found Around Newborn Star for 1st Time". Space.com. 17 June 2016.
  12. ↑ Astrophysics, Harvard-Smithsonian Center for (2016-06-20). "ALMA Reveals Methanol in the TW Hydrae Protoplanetary Disk". SciTechDaily. Retrieved 2021-08-06.
  13. ↑ "Methanol Detected in Protoplanetary Disc around Young Star TW Hydrae | Astronomy | Sci-News.com". Breaking Science News | Sci-News.com. 15 June 2016. Retrieved 2021-08-06.
  14. ↑ "NASA Astrobiology". astrobiology.nasa.gov. Retrieved 2021-08-06.
  15. ↑ "First Detection of Methyl Alcohol in a Planet-forming Disk". National Radio Astronomy Observatory. Retrieved 2021-08-06.
  16. ↑ Dockrill, Peter (16 June 2016). "Scientists Just Discovered Methyl Alcohol in a Nearby Planet-Forming Disc". ScienceAlert. Retrieved 2021-08-06.
  17. ↑ Report, Science World (2017-05-29). "Methanol Discovered For The First Time In The Protoplanetary Disk Of Young Star 'TW Hydra'". Science World Report. Retrieved 2021-08-06.
  18. ↑ "A Molecule For Life Has Been Found Inside A Nearby Planetary Nursery". NDTV.com. Retrieved 2021-08-06.
  19. 1 2 Willson, M.; Kraus, S.; et al. (October 2016). "Sparse aperture masking interferometry survey of transitional discs: Search for substellar-mass companions and asymmetries in their parent discs". Astronomy & Astrophysics. 595: A9. arXiv:1608.03629. Bibcode:2016A&A...595A...9W. doi:10.1051/0004-6361/201628859. ISSN 0004-6361.
  20. 1 2 Tsukagoshi, Takashi; Nomura, Hideko; Muto, Takayuki; Kawabe, Ryohei; Ishimoto, Daiki; Kanagawa, Kazuhiro D.; Okuzumi, Satoshi; Ida, Shigeru; Walsh, Catherine; Millar, Tom J. (2016). "A Gap with a Deficit of Large Grains in the protoplanetary disk around TW Hya". The Astrophysical Journal. 829 (2): L35. arXiv:1605.00289. Bibcode:2016ApJ...829L..35T. doi:10.3847/2041-8205/829/2/L35. S2CID 41738556.
  21. 1 2 3 Yoshida, Tomohiro C.; Nomura, Hideko; Law, Charles J.; Teague, Richard; Shibaike, Yuhito; Furuya, Kenji; Tsukagoshi, Takashi (2024-08-01). "Outflow Driven by a Protoplanet Embedded in the TW Hya Disk". The Astrophysical Journal. 971 (1): L15. arXiv:2407.14395. Bibcode:2024ApJ...971L..15Y. doi:10.3847/2041-8213/ad654c. ISSN 0004-637X.
  22. 1 2 Debes, John H.; Jang-Condell, Hannah; et al. (June 2013). "The 0.5-2.22 μm Scattered Light Spectrum of the Disk around TW Hya: Detection of a Partially Filled Disk Gap at 80 AU". The Astrophysical Journal. 771 (1): 45. arXiv:1306.2969. Bibcode:2013ApJ...771...45D. doi:10.1088/0004-637X/771/1/45. ISSN 0004-637X.
  23. 1 2 3 Mentiplay, Daniel; Price, Daniel J; et al. (March 2019). "Super-Earths in the TW Hya disc". Monthly Notices of the Royal Astronomical Society: Letters. 484 (1): L130–L135. arXiv:1811.03636. Bibcode:2019MNRAS.484L.130M. doi:10.1093/mnrasl/sly209. ISSN 1745-3925.
  24. 1 2 Setiawan, J.; Henning, Th.; Launhardt, R.; Müller, A.; Weise, P.; Kürster, M. (3 January 2008). "A young massive planet in a star–disk system". Nature. 451 (7174): 38–41. Bibcode:2008Natur.451...38S. doi:10.1038/nature06426. PMID 18172492. S2CID 4431370.
  25. ↑ McKee, Maggie (2 January 2008). "First planet discovered around a youthful star". NewScientist.com news service. Retrieved 2008-01-02.
  26. 1 2 Pontoppidan, Klaus M.; et al. (2008). "Spectro-astrometric imaging of molecular gas within protoplanetary disk gaps". The Astrophysical Journal. 684 (2): 1323–1329. arXiv:0805.3314. Bibcode:2008ApJ...684.1323P. doi:10.1086/590400. S2CID 15445587.
  27. ↑ "A young extrasolar planet in its cosmic nursery: Astronomers from Heidelberg discover planet in a dusty disk around a newborn star". Max Planck Institute for Astronomy. 2008-01-02. Retrieved 2008-01-03.
  28. ↑ Huelamo, N.; et al. (2008). "TW Hydrae: evidence of stellar spots instead of a Hot Jupiter". Astronomy and Astrophysics. 489 (2): L9–L13. arXiv:0808.2386. Bibcode:2008A&A...489L...9H. doi:10.1051/0004-6361:200810596. S2CID 18775872.
  29. ↑ Prato, L.; et al. (2008). "A Young Planet Search in Visible and IR Light: DN Tau, V836 Tau, and V827 Tau". The Astrophysical Journal. 687 (2): L103–L106. arXiv:0809.3599. Bibcode:2008ApJ...687L.103P. doi:10.1086/593201. S2CID 14888302.
  30. ↑ "Astronomers discover signs of planet being born around a star". Independent.co.uk. 14 September 2016. Archived from the original on 2022-05-26.
  31. ↑ "Shadow on TW Hydrae's disc". www.spacetelescope.org. Retrieved 12 January 2017.

Further reading