{{Short description|Star in constellation Taurus}} {{distinguish|HL Tau 76}} {{starbox begin | name = HL Tauri }} {{starbox image | image = 225px | caption = Atacama Large Millimeter Array image of HL Tauri<ref name="bbc20141106"/><ref name="NRAO"/> }} {{Starbox observe | epoch = J2000 | constell = Taurus | ra = {{RA|04|31|38.437}}<ref name=SIMBAD /> | dec = {{DEC|+18|13|57.65}}<ref name=SIMBAD /> | appmag_v = <!--Apparent magnitude (Johnson–Cousins V system)--> }} {{Starbox character | type = Pre-main-sequence star | class = Class K9 | appmag_1_passband = V | appmag_1 = 15.1 | v-r = 0.89 | b-v = 0.92 | j-h = 1.45 | j-k = 3.21 | variable = T Tauri }} {{starbox astrometry | prop_mo_ra = {{val|p=+|8.0|6.0}}<ref name=kwon2011 /> | prop_mo_dec = {{val|p=-|21.8|5.8}}<ref name=kwon2011 /> | dist_ly = 450<ref name="bbc20141106"/> | dist_pc = 140 }} {{Starbox reference | Simbad = HL+Tauri }} {{starbox end}}
'''HL Tauri''' (abbreviated '''HL Tau''') is a young T Tauri star<ref name="Weintraub1995"/> in the constellation Taurus, approximately {{convert|450|ly|pc}} from Earth<ref name="bbc20141106"/> in the Taurus Molecular Cloud.<ref name="Stephens2014"/> The luminosity and effective temperature of {{nowrap|HL Tauri}} imply that its age is less than 100,000 years.<ref name="Boss1989"/> At apparent magnitude 15.1,<ref name=SIMBAD/> it is too faint to be seen with the unaided eye. It is surrounded by a protoplanetary disk marked by dark bands visible in submillimeter radiation that may indicate a number of planets in the process of formation.<ref name=NRAO /> It is accompanied by the Herbig–Haro object {{nowrap|HH 150}}, a jet of gas emitted along the rotational axis of the disk that is colliding with nearby interstellar dust and gas.<ref name="esa20141106"/>
==Protoplanetary disk== Indications of a protoplanetary disk were first presented in 1975 with infrared spectral observations in wavelengths between 2 and 4 microns, which were made possible by the recent invention of the indium antimonide photovoltaic detector. Of 29 very young stars examined, only {{nowrap|HL Tauri}} showed a strong absorption feature centered on the expected 3.07 micron absorption of ice particles, which authors attributed to the ν<sub>1</sub>, ν<sub>3</sub>, and 2ν<sub>2</sub> vibrational frequencies of the O–H bond.<ref name="Cohen1975"/> A 1982 survey identified {{nowrap|HL Tauri}} as one of the most highly polarized {{nowrap|T Tauri}} stars known, along with DG Tauri and V536 Aquilae.<ref name="Bastien1982"/>
A gas disk was discovered by interferometric observation of carbon monoxide (CO) emissions in 1986.<ref name="Beckwith1986"/> Based on observation data in 1985 and 1986 from the Millimeter Wave Interferometer of the Owens Valley Radio Observatory, the circumstellar disk was estimated to have a mass between {{solar mass|0.01|link=yes}} and {{solar mass|0.5}}, with a best fit of {{solar mass|0.1}}, and a radius of about 200 AU. The temperature of the gas and grains of the disk are probably of the order of a few tens of kelvins. The gas was found to be bound to and in Keplerian rotation around a star with a mass of about {{solar mass|1}}.<ref name="Sargent1987"/> Bipolar outflow of molecules such as carbon monoxide (CO) and diatomic hydrogen (H<sub>2</sub>) have been observed. The element iron has also been noted in the outflow in its Fe(II) oxidation state, also called Fe<sup>2+</sup> or ''ferrous iron''.<ref name="Takami2011"/>
An image of the protoplanetary disk made at submillimeter wavelengths by the Atacama Large Millimeter/submillimeter Array (ALMA) was made public in 2014, showing a series of concentric bright rings separated by gaps. The disk appeared much more evolved than would have been expected from the age of the system, which suggests that the planetary formation process may be faster than previously thought.<ref name="eso20141106"/> ALMA's Catherine Vlahakis said, "When we first saw this image we were astounded at the spectacular level of detail. HL Tauri is no more than a million years old, yet already its disk appears to be full of forming planets. This one image alone will revolutionize theories of planet formation."<ref name="eso20141106"/>
Stephens ''et al.'' (2014) suggest that the faster accretion rate might be due to the complex magnetic field of the protoplanetary disk.<ref name="Stephens2014"/>
In 2024, water was found within the protoplanetary disk using the Atacama Large Millimeter Array (ALMA), containing 3.7 Earth oceans worth of water vapour.<ref>{{cite journal|last1=Facchini|first1=Stefano|last2=Testi|first2=Leonardo|last3=Humphreys|first3=Elizabeth|last4=Donckt|first4=Mathieu Vander|last5=Isella|first5=Andrea|last6=Wrzosek|first6=Ramon|last7=Baudry|first7=Alain|last8=Gray|first8=Malcom D.|last9=Richards|first9=Anita M. S.|last10=Vlemmings|first10=Wouter|date=29 February 2024|title=Resolved ALMA observations of water in the inner astronomical units of the HL Tau disk|journal=Nature Astronomy|volume=8 |issue=5 |pages=587–595 |doi=10.1038/s41550-024-02207-w|doi-access=free|pmid=39282476 |pmc=11399093 |arxiv=2403.00647}}</ref><ref>{{cite news|last=de Lazaro|first=Enrico|title=ALMA Detects Water Vapor in Protoplanetary Disk around Young Star|url=https://www.sci.news/astronomy/alma-water-vapor-protoplanetary-disk-young-star-hl-tauri-12727.html|website=Science News|date=29 February 2024|accessdate=29 February 2024}}</ref>
==Gallery== <gallery mode="nolines" widths="180px" heights="180px"> A glowing jet from a young star.tif|A wider view of the region (HL Tauri out of frame at bottom right corner) from the Hubble Space Telescope in visible light shows the Herbig–Haro object {{nowrap|HH 150}}.<ref name="esa20130218"/> Heic1424a.tif|A broader view of the Taurus Molecular Cloud region. {{nowrap|HL Tauri}} is shrouded in the bright blue region at upper center-left. HLTauLightCurve.png|A visual band light curve for HL Tauri, plotted from ''ASAS-SN'' data<ref name="ASAS-SN"/> </gallery>
==References== {{Reflist|30em|refs= <ref name="bbc20141106">{{cite news |url=https://www.bbc.co.uk/news/science-environment-29932609 |title=Planet formation captured in photo |work=BBC News |first=Johnathan |last=Webb |date=6 November 2014 |access-date=6 November 2014}}</ref>
<ref name="NRAO">{{cite press release |url=https://public.nrao.edu/static/pr/planet-formation-alma.html |title=Birth of Planets Revealed in Astonishing Detail in ALMA's 'Best Image Ever' |publisher=National Radio Astronomy Observatory |first=Charles E. |last=Blue |date=6 November 2014 |access-date=6 November 2014 |url-status=dead|archive-url=https://web.archive.org/web/20141106220622/https://public.nrao.edu/static/pr/planet-formation-alma.html |archive-date=6 November 2014 }}</ref>
<ref name="ASAS-SN">{{cite web |url=https://asas-sn.osu.edu/variables/lookup |website=ASAS-SN Variable Stars Database|title=ASAS-SN Variable Stars Database|publisher=ASAS-SN |access-date=6 January 2022}}</ref>
<ref name="SIMBAD">{{cite simbad |title=HL Tauri |access-date=6 November 2014}}</ref>
<ref name="kwon2011">{{cite journal |title=Resolving the Circumstellar Disk of HL Tauri at Millimeter Wavelengths |journal=The Astrophysical Journal |first1=Woojin |last1=Kwon |first2=Leslie W. |last2=Looney |first3=Lee G. |last3=Mundy |volume=741 |issue=1 |at=3 |date=November 2011 |arxiv=1107.5275 |bibcode=2011ApJ...741....3K |doi=10.1088/0004-637X/741/1/3|s2cid=118525138 }}</ref>
<ref name="Weintraub1995">{{cite journal |title=In Search of HL Tauri |journal=The Astrophysical Journal Letters |first1=David A. |last1=Weintraub |first2=Joel H. |last2=Kastner |first3=Barbara A. |last3=Whitney |volume=452 |pages=L141–L145 |date=October 1995 |issue=2 |bibcode=1995ApJ...452L.141W |doi=10.1086/309720|s2cid=122562823 |doi-access= }}</ref>
<ref name="Stephens2014">{{cite journal |title=Spatially resolved magnetic field structure in the disk of a T Tauri star |journal=Nature |first1=Ian W. |last1=Stephens |first2=Leslie W. |last2=Looney |first3=Woojin |last3=Kwon |first4=Manuel |last4=Fernández-López |first5=A. Meredith |last5=Hughes |first6=Lee G. |last6=Mundy |first7=Richard M. |last7=Crutcher |first8=Zhi-Yun |last8=Li |first9=Ramprasad |last9=Rao |display-authors=5 |volume=514 |issue=7524 |pages=597–599 |date=October 2014 |arxiv=1409.2878 |bibcode=2014Natur.514..597S |doi=10.1038/nature13850 |pmid=25337883|s2cid=4396150 }}</ref>
<ref name="Boss1989">{{cite book |chapter-url=https://books.google.com/books?id=DN-v0fQSfPkC&pg=PA45 |chapter=Models of the Formation and Evolution of the Solar Nebula |title=Origin and Evolution of Planetary and Satellite Atmospheres |publisher=The University of Arizona Press |first1=A. P. |last1=Boss |first2=G. E. |last2=Morfill |first3=W. M. |last3=Tscharnuter |editor1-first=S. K. |editor1-last=Atreya |editor2-first=J. B. |editor2-last=Pollack |editor3-first=M. S. |editor3-last=Matthews |page=45 |date=1989 |isbn=978-0-8165-1105-1 |bibcode=1989oeps.book.....A}}</ref>
<ref name="esa20141106">{{cite web |url=http://www.spacetelescope.org/news/heic1424/ |title=Jets, bubbles, and bursts of light in Taurus |publisher=European Space Agency |date=6 November 2014 |access-date=7 November 2014 |id=Photo release Heic1424}}</ref>
<ref name="Cohen1975">{{cite journal |title=Infrared Observations of Young Stars—VI: A 2- to 4-Micron Search for Molecular Features |journal=Monthly Notices of the Royal Astronomical Society |first=Martin |last=Cohen |volume=173 |pages=279–293 |date=November 1975 |issue=2 |bibcode=1975MNRAS.173..279C |doi=10.1093/mnras/173.2.279|doi-access=free }}</ref>
<ref name="Bastien1982">{{cite journal |title=A linear polarization survey of T Tauri stars |journal=Astronomy and Astrophysics Supplement Series |first=Pierre |last=Bastien |volume=48 |pages=153–164 |date=April 1982 |bibcode=1982A&AS...48..153B}}</ref>
<ref name="Beckwith1986">{{cite journal |title=Small-scale structure of the circumstellar gas of HL Tauri and R Monocerotis |journal=The Astrophysical Journal |first1=S. |last1=Beckwith |first2=A. I. |last2=Sargent |first3=N. Z. |last3=Scoville |first4=C. R. |last4=Masson |first5=B. |last5=Zuckerman |first6=T. G. |last6=Phillips |display-authors=5 |volume=309 |pages=755–761 |date=October 1986 |bibcode=1986ApJ...309..755B |doi=10.1086/164645|doi-access=free }}</ref>
<ref name="Sargent1987">{{cite journal |title=Kinematics of the circumstellar gas of HL Tauri and R Monocerotis |journal=The Astrophysical Journal |first1=Anneila I. |last1=Sargent |first2=Steven |last2=Beckwith |volume=323 |pages=294–305 |date=December 1987 |bibcode=1987ApJ...323..294S |doi=10.1086/165827|doi-access= }}</ref>
<ref name="Takami2011">{{cite journal |title=A Micro-Molecular Bipolar Outflow from HL Tauri |journal=The Astrophysical Journal |first1=Michihiro |last1=Takami |first2=Tracy L. |last2=Beck |first3=Tae-Soo |last3=Pyo |first4=Peter |last4=McGregor |first5=Christopher |last5=Davis |volume=670 |issue=1 |pages=L33–L36 |date=November 2011 |arxiv=0710.1148 |bibcode=2007ApJ...670L..33T |doi=10.1086/524138|s2cid=17086864 }}</ref>
<ref name="eso20141106">{{cite news |url=http://www.eso.org/public/news/eso1436/ |title=Revolutionary ALMA Image Reveals Planetary Genesis |publisher=European Southern Observatory |first1=Catherine |last1=Vlahakis |first2=Valeria Foncea |last2=Rubens |first3=Richard |last3=Hook |date=6 November 2014 |access-date=7 November 2014}}</ref>
<ref name="esa20130218">{{cite web |url=http://www.spacetelescope.org/images/potw1307a/|title=A glowing jet from a young star |publisher=European Space Agency |date=18 February 2013 |id=Photo release Potw1307a}}</ref>
}}
==External links== *{{Commons category-inline}}
{{Stars of Taurus}}
Category:K-type pre-main-sequence stars Tauri, HL Category:T Tauri stars Category:Taurus (constellation) Category:Circumstellar disks