View source for TW Hydrae

{{Short description|T Tauri star in the constellation Hydra}}
{{Starbox begin
| name = TW Hydrae
}}
{{Starbox image
| image = [[File:Inner region of TW Hydrae protoplanetary disc.jpg|250px]]
| caption = Inner region of TW Hydrae protoplanetary disc
| credit = S. Andrews, B. Saxton, ALMA (see description)
}}
{{Starbox observe
| epoch = J2000.0
| constell = [[Hydra (constellation)|Hydra]]
| ra = {{RA|11|01|51.9054}}<ref name="Gaia DR2"/>
| dec = {{DEC|−34|42|17.0316}}<ref name="Gaia DR2"/>>
| appmag_v = {{nowrap|11.27 ± 0.09}}<ref name="SIMBAD"/>
}}
{{Starbox character
| type = [[Pre-main-sequence]]
| class = K6<ref name="SIMBAD"/>
| r-i =
| v-r =
| b-v = 0.67<ref name="SIMBAD"/>
| u-b = -0.33<ref name="Mermilliod1991+2006"/><!--unreliable?-->
| j-h = 0.659<ref name="SIMBAD"/>
| j-k = 0.92<ref name="SIMBAD"/>
| variable = [[T Tauri star|T Tauri]]
}}
{{Starbox astrometry
| radial_v = {{nowrap|13.40 ± 0.8}}<ref name="SIMBAD"/>
| prop_mo_ra = −68.389 ± 0.054<ref name="Gaia DR2"/>
| prop_mo_dec = −14.016 ± 0.059<ref name="Gaia DR2"/>
| parallax = 16.6428
| p_error = 0.0416
| parallax_footnote = <ref name="Gaia DR2"/>
}}
{{Starbox detail
| age_myr = 8<ref name="Rheeetal2007"/>
| metal =
| mass = 0.8<ref name="Chunhua2013"/>
| radius = 1.11<ref name="Rheeetal2007"/>
| gravity=
| rotation =
| luminosity_bolometric=0.28<ref group="note">From <math>\begin{smallmatrix}L=4 \pi R^2 \sigma T_{\rm eff}^4 \end{smallmatrix}</math>, where <math>\begin{smallmatrix}L \end{smallmatrix}</math> is the luminosity, <math>\begin{smallmatrix}R \end{smallmatrix}</math> is the radius, <math>\begin{smallmatrix}T_{\rm eff}\end{smallmatrix}</math> is the effective surface temperature and <math>\begin{smallmatrix}\sigma \end{smallmatrix}</math> is the [[Stefan–Boltzmann constant]].</ref>
| temperature = 4,000<ref name="Rheeetal2007"/>
}}
{{Starbox catalog
| names = {{odlist|name=[[TW Hydrae association|TWA]]&nbsp;1|CD=−34° 7151|HIP=53911|V=TW Hya}}
}}
{{Starbox reference
| Simbad = TW+Hya
}}
{{Starbox end}}
'''TW Hydrae''' is a [[T Tauri star]] approximately 196 [[light-year]]s away<ref name="Gaia DR2"/> in the [[constellation]] of [[Hydra (constellation)|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 [[Atacama Large Millimeter Array|ALMA observatory]]. TW Hydrae is accompanied by about twenty other low-mass stars 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==
[[File:TWHyaLightCurve.png|thumb|left|A broadband optical [[light curve]] plotted from [[MOST (spacecraft)|''MOST'']] [[microsatellite]] data published by Rucinski ''et al.'' (2008)<ref name="Rucinski"/>]]
TW Hydrae is a [[pre-main-sequence star]] that is approximately 80% the mass of and 111% the radius of the [[Sun]]. It has a temperature of 4000 [[Kelvin scale|K]] and is about 8 million years old. In comparison, the Sun is about 4.6 billion years old<ref>{{cite web |url=http://www.universetoday.com/18237/how-old-is-the-sun/ |title=How Old is the Sun? |author=Fraser Cain |date=16 September 2008 |publisher=[[Universe Today]] |access-date=19 February 2011}}</ref> and has a temperature of 5778 K.<ref>{{cite web |url=http://www.universetoday.com/18092/temperature-of-the-sun/ |title=Temperature of the Sun |author=Fraser Cain |date=15 September 2008 |publisher=Universe Today |access-date=19 February 2011}}</ref> The star's luminosity is 28% (0.28x) that of the Sun, equivalent to that of a [[Main sequence|main-sequence]] star of spectral type ~[[Stellar classification|K2]]. However, the spectral class is K6.

The star's [[apparent magnitude]], or how bright it appears from Earth's perspective, is 11.27. It is too dim to be seen with the naked eye.

==Planetary system==
{{OrbitboxPlanet begin
| name = TW Hydrae
| table_ref=<ref name="Tsukagoshi">{{cite journal|arxiv=1605.00289|last1=Tsukagoshi|first1=Takashi|title=A Gap with a Deficit of Large Grains in the protoplanetary disk around TW Hya|last2=Nomura|first2=Hideko|last3=Muto|first3=Takayuki|last4=Kawabe|first4=Ryohei|last5=Ishimoto|first5=Daiki|last6= Kanagawa|first6=Kazuhiro D.|last7=Okuzumi|first7=Satoshi|last8=Ida|first8=Shigeru|last9=Walsh|first9=Catherine|last10= Millar|first10=Tom J.|year=2016|doi=10.3847/2041-8205/829/2/L35|volume=829|journal=The Astrophysical Journal|issue=2|page=L35|bibcode = 2016ApJ...829L..35T |s2cid=41738556 |doi-access=free }}</ref><ref name="Yoshida2024"/>
}}
{{OrbitboxPlanet hypothetical
| exoplanet = [[TW Hydrae b|b]]
| mass_earth = 23.72
| period =
| semimajor = 22
| radius_earth = ~4.25
| inclination =
}}
{{OrbitboxPlanet hypothetical
| exoplanet = c
| mass_earth = 4
| period =
| semimajor = 42
| radius_earth = 
| inclination =
}}
{{OrbitboxPlanet disk
| disk = Protoplanetary disk
| periapsis = 1
| apoapsis = 30?
| inclination =
}}
{{Orbitbox end}}

The star is known to host one likely exoplanet, [[TW Hydrae b]].

===Protoplanetary disk===
====Previously disproven protoplanet====
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 mass]]es, a period of 3.56 days, and an orbital radius of 0.04 [[astronomical unit]]s (inside the inner rim of the protoplanetary disk). Assuming it orbits in the same plane as the outer part of the dust disk ([[inclination]] 7±1°<ref name="setiawan08"/>), it has a true mass of 9.8±3.3 Jupiter masses.<ref name="setiawan08" /><ref name=newscientist/> However, if the inclination is similar to the inner part of the dust disk (4.3±1.0°<ref name="pontoppidan08"/>), the mass would be 16{{±|5|3}} Jupiter masses, making it a [[brown dwarf]].<ref name="pontoppidan08" /> Since the star itself is so young, it was presumed this is the youngest extrasolar planet yet discovered, and essentially still in formation.<ref name=mpia/>

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 [[wavelength]]s, 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 [[starspot]]s 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".<ref name=huelmo/> Similar wavelength-dependent radial velocity variations, also caused by starspots, have been detected on other T Tauri stars.<ref name=prato/>

====New study of more distant planet====
In 2016, [[Atacama Large Millimeter Array|ALMA]] found evidence that a possible Neptune-like planet was forming in its disk, at a distance of around 22 AU.<ref>{{Cite web|url=https://www.independent.co.uk/news/science/giant-planet-born-in-stars-dust-cloud-tw-hydrae-a7307931.html |archive-url=https://ghostarchive.org/archive/20220526/https://www.independent.co.uk/news/science/giant-planet-born-in-stars-dust-cloud-tw-hydrae-a7307931.html |archive-date=2022-05-26 |url-access=subscription |url-status=live|title = Astronomers discover signs of planet being born around a star|website=[[Independent.co.uk]] |date = 14 September 2016}}</ref>

==== Outflow of an embedded protoplanet ====
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 associated with the formation of a [[Super-Earth|super-earth]] and modelling of 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 x10<sup>−7</sup> and 10<sup>−5</sup> {{Jupiter mass|link=true}}/year.<ref name="Yoshida2024"/>

====Detection of methanol====
In 2016, [[methanol]], one of the building blocks for life, was detected in the star's protoplanetary disk.<ref>{{Cite web|url=http://www.space.com/33193-organic-molecule-planet-forming-disk.html|title = Methanol, a Building Block of Life, Found Around Newborn Star for 1st Time| website=[[Space.com]] | date=17 June 2016 }}</ref><ref>{{Cite web|last=Astrophysics|first=Harvard-Smithsonian Center for|date=2016-06-20|title=ALMA Reveals Methanol in the TW Hydrae Protoplanetary Disk|url=https://scitechdaily.com/alma-reveals-methanol-in-the-tw-hydrae-protoplanetary-disk/|access-date=2021-08-06|website=SciTechDaily|language=en-US}}</ref><ref>{{Cite web|title=Methanol Detected in Protoplanetary Disc around Young Star TW Hydrae {{!}} Astronomy {{!}} Sci-News.com|url=http://www.sci-news.com/astronomy/methanol-protoplanetary-disc-tw-hydrae-03952.html|access-date=2021-08-06|website=Breaking Science News {{!}} Sci-News.com|date=15 June 2016 |language=en-US}}</ref><ref>{{Cite web|title=NASA Astrobiology|url=https://astrobiology.nasa.gov/news/methanol-detected-for-first-time-around-young-star/|access-date=2021-08-06|website=astrobiology.nasa.gov|language=en-EN}}</ref><ref>{{Cite web|title=First Detection of Methyl Alcohol in a Planet-forming Disk|url=https://public.nrao.edu/news/2016-methanol-alma/|access-date=2021-08-06|website=National Radio Astronomy Observatory|language=en-US}}</ref><ref>{{Cite web|last=Dockrill|first=Peter|title=Scientists Just Discovered Methyl Alcohol in a Nearby Planet-Forming Disc|url=https://www.sciencealert.com/scientists-just-discovered-methyl-alcohol-in-a-nearby-planet-forming-disc|access-date=2021-08-06|website=ScienceAlert|date=16 June 2016 |language=en-gb}}</ref><ref>{{Cite web|last=Report|first=Science World|date=2017-05-29|title=Methanol Discovered For The First Time In The Protoplanetary Disk Of Young Star 'TW Hydra'|url=https://www.scienceworldreport.com/articles/59704/20170529/methanol-discovered-first-time-protoplanetary-disk-young-star-tw-hydra.htm|access-date=2021-08-06|website=Science World Report|language=en-US}}</ref><ref>{{Cite web|title=A Molecule For Life Has Been Found Inside A Nearby Planetary Nursery|url=https://www.ndtv.com/world-news/a-molecule-for-life-has-been-found-inside-a-nearby-planetary-nursery-1419940|access-date=2021-08-06|website=NDTV.com}}</ref>

==Gallery==
{{Gallery |align=center |width=250
|File:Shadow on TW Hydrae’s disc.jpg|{{center|{{small|Shadow moving counterclockwise around a gas and dust disc.<ref>{{cite web|title=Shadow on TW Hydrae's disc|url=https://www.spacetelescope.org/images/opo1703a/|website=www.spacetelescope.org|access-date=12 January 2017}}</ref>}}}}
|File:Hubble Uncovers Evidence of Farthest Planet Forming From its Star.jpg|{{center|{{small|Simulation based on Hubble observations.}}}}
|File:TW Hydrae protoplanetary disc.jpg|{{center|{{small|TW Hydrae protoplanetary disc.}}}}
|File:Concentric gas and dust discs around the star TW Hydrae (heic2305a).jpg|{{center|{{small|This illustration is based on NASA/ESA Hubble Space Telescope images of a gas and dust discs encircling the young star TW Hydrae.}}}}
|File:Artist’s impression of the disc around the young star TW Hydrae.webm|{{center|{{small|This artist’s impression video shows the protoplanetary disc around TW Hydrae. The organic molecule methyl alcohol (methanol) has been found in this disc.}}}}
}}

==Notes==
{{reflist|group=note}}

==References==
{{reflist|refs=

<ref name="Yoshida2024">{{Cite journal |last1=Yoshida |first1=Tomohiro C. |last2=Nomura |first2=Hideko |last3=Law |first3=Charles J. |last4=Teague |first4=Richard |last5=Shibaike |first5=Yuhito |last6=Furuya |first6=Kenji |last7=Tsukagoshi |first7=Takashi |date=2024-08-01 |title=Outflow Driven by a Protoplanet Embedded in the TW Hya Disk |journal=The Astrophysical Journal |volume=971 |issue=1 |pages=L15 |arxiv=2407.14395 |bibcode=2024ApJ...971L..15Y |doi=10.3847/2041-8213/ad654c |doi-access=free |issn=0004-637X}}</ref>

<ref name="Gaia DR2">{{Cite Gaia DR2|5401795662560500352}}</ref>

<ref name="Rucinski">{{cite journal |last1=Rucinski |first1=Slavek M. |last2=Matthews |first2=Jaymie M. |last3=Kuschnig |first3=Rainer |last4=Pojmanski |first4=Grzegorz |last5=Rowe |first5=Jason |last6=Guenther |first6=David B. |last7=Moffat |first7=Anthony F. J. |last8=Sasselov |first8=Dimitar |last9=Walker |first9=Gordon A. H. |last10=Weiss |first10=Werner W. |title=Photometric variability of the T Tauri star TW Hya on time-scales of hours to years |journal=Monthly Notices of the Royal Astronomical Society |date=December 2008 |volume=391 |issue=4 |pages=1913–1924 |doi=10.1111/j.1365-2966.2008.14014.x |arxiv=0809.3987 |bibcode=2008MNRAS.391.1913R |doi-access=free }}</ref>

<ref name=prato>{{cite journal|author=Prato, L.|display-authors=etal|title=A Young Planet Search in Visible and IR Light: DN Tau, V836 Tau, and V827 Tau|date=2008|journal=[[The Astrophysical Journal]]|volume=687|issue=2|pages=L103–L106|doi=10.1086/593201|bibcode=2008ApJ...687L.103P|arxiv = 0809.3599 |s2cid=14888302}}</ref>

<ref name=huelmo>{{cite journal|author=Huelamo, N.|display-authors=etal|title=TW Hydrae: evidence of stellar spots instead of a Hot Jupiter|journal=[[Astronomy and Astrophysics]]|volume=489|issue=2|pages=L9–L13|date=2008|doi=10.1051/0004-6361:200810596|bibcode=2008A&A...489L...9H|arxiv = 0808.2386 |s2cid=18775872}}</ref>

<ref name=mpia>{{cite web|url=http://www.mpia.de/Public/menu_q2e.php?Aktuelles/PR/2008/PR080103/PR_080103_en.html|title=A young extrasolar planet in its cosmic nursery: Astronomers from Heidelberg discover planet in a dusty disk around a newborn star|date=2008-01-02|publisher=[[Max Planck Institute for Astronomy]]|access-date=2008-01-03}}</ref>

<ref name="pontoppidan08">{{cite journal|title=Spectro-astrometric imaging of molecular gas within protoplanetary disk gaps|author=Pontoppidan, Klaus M.|display-authors=etal|date=2008|journal=[[The Astrophysical Journal]]|volume=684|issue=2|pages=1323–1329|doi=10.1086/590400|bibcode=2008ApJ...684.1323P|arxiv = 0805.3314 |s2cid=15445587}}</ref>

<ref name=newscientist>{{cite news| url=https://www.newscientist.com/article/dn13135-first-planet-discovered-around-a-youthful-star.html | title=First planet discovered around a youthful star| date=2 January 2008| publisher= NewScientist.com news service| first= Maggie| last= McKee| access-date=2008-01-02}}</ref>

<ref name="setiawan08">{{cite journal|journal=Nature|volume= 451|pages= 38–41|date=3 January 2008| doi=10.1038/nature06426| title=A young massive planet in a star–disk system
| first1=J.| last1= Setiawan
| first2=Th.| last2= Henning
| first3=R.| last3= Launhardt
| first4=A.| last4= Müller
| first5=P.| last5= Weise
| first6=M.| last6= Kürster
| pmid=18172492 | issue=7174| bibcode=2008Natur.451...38S|s2cid= 4431370}}</ref>

<ref name="SIMBAD">{{cite simbad | title=V* TW Hya | access-date=2014-01-02 }}</ref>

<ref name="Rheeetal2007">{{citation | first1=J.H. | last1=Rhee  | first2=I. | last2=Song | first3=B. | last3=Zuckerman | first4=M. | last4=McElwain |date=May 2007 | title=Characterization of dusty debris disks: the IRAS and Hipparcos catalogs | display-authors=1<!--Expandable--> | journal=The Astrophysical Journal | volume=660 | issue=2 | pages=1556–1571 | bibcode=2007ApJ...660.1556R | doi=10.1086/509912 | postscript=. |arxiv = astro-ph/0609555| s2cid=11879505 }}[http://vizier.u-strasbg.fr/viz-bin/VizieR-5?-ref=VIZ52c4e54377c1&-out.add=.&-source=J/ApJ/660/1556/table2&recno=72 Vizier catalog entry]</ref>

<ref name="Mermilliod1991+2006">{{citation | first=J.C. | last=Mermilliod  | date=1991 | title=Homogeneous Means in the UBV System | journal=VizieR On-line Data Catalog | publisher=Institut d'Astronomie, Universite de Lausanne | publication-date=1991 | bibcode=2006yCat.2168....0M | postscript=. }}[http://vizier.u-strasbg.fr/viz-bin/VizieR-5?-ref=VIZ52c7867946de&-out.add=.&-source=II/168/ubvmeans&recno=76066 Vizier catalog entry]</ref>

<ref name="Chunhua2013">{{cite journal | first1=Qi | last1=Chunhua | first2=Karin I. | last2=Öberg | first3=David J. | last3=Wilner | first4=Paola| last4=D'Alessio |  first5=Edwin | last5=Bergin | first6=Sean M. | last6= Andrews | first7=Geoffrey A. | last7=Blake | first8=Michiel R. | last8=Hogerheijde | first9=Ewine F. | last9=van Dishoeck |date=August 2013 | title=Imaging of the CO Snow Line in a Solar Nebula Analog  | display-authors=1<!--Expandable--> | journal=[[Science (journal)|Science]] | volume=341 | issue=6146 | pages=630–632 | bibcode=2013Sci...341..630Q | doi=10.1126/science.1239560 |arxiv = 1307.7439 | pmid=23868917| s2cid=23271440 }}</ref>
}}

==External links==
{{commons category|TW Hydrae}}
* {{cite web |url=http://www.spacetelescope.org/news/html/heic0501.html |title=Hubble's infrared eyes home in on suspected extrasolar planet |access-date=2008-06-24 |work=[[NASA]] |publisher=[[Hubble Space Telescope]]}}
* {{cite encyclopedia |url=https://exoplanet.eu/catalog/tw_hya_b--448/ |encyclopedia=[[Extrasolar Planets Encyclopaedia]] |title=Notes for star TW Hya and possible planet TW Hya b |access-date=2014-01-06 }}

{{Stars of Hydra}}

{{DEFAULTSORT:TW Hydrae}}
[[Category:Hydra (constellation)]]
[[Category:K-type main-sequence stars]]
[[Category:T Tauri stars]]
[[Category:Circumstellar disks]]
[[Category:TW Hydrae association]]
[[Category:Objects with variable star designations|Hydrae, TW]]
[[Category:Durchmusterung objects]]
[[Category:Hipparcos objects|053911]]
[[Category:Hypothetical planetary systems]]