What is Protoplanetary disk?
[[File:HL_Tau_protoplanetary_disk.jpg|thumb|right|[[Atacama Large Millimeter Array]] image of [[HL Tauri]]]] A '''protoplanetary disk''' is a rotating [[circumstellar disc]] of [[dense]] [[gas]] and [[dust]] surrounding a young [[star]] that has just formed. Protoplanetary disks have [[Radius|radii]] up to 1000 [[AU]]. Protoplanetary disks have been seen around several young stars in our [[galaxy]].<ref>{{Cite journal|last1=Ricci|first1=L.|last2=Robberto|first2=M.|last3=Soderblom|first3=D. R.|title=Thehubble Space Telescope/Advanced Camera for Surveys Atlas of Protoplanetary Disks in the Great Orion Nebula|date=2008-11-01|url=https://iopscience.iop.org/article/10.1088/0004-6256/136/5/2136|journal=The Astronomical Journal|volume=136|issue=5|pages=2136–2151|doi=10.1088/0004-6256/136/5/2136|bibcode=2008AJ....136.2136R|s2cid=123470043 |issn=0004-6256}}</ref> Protoplanetary disks are thought to be thin structures. They have mass that is much smaller than the young star in the center.<ref>{{Cite journal|last=Armitage|first=Philip J.|date=2011-09-22|title=Dynamics of Protoplanetary Disks|url=http://www.annualreviews.org/doi/10.1146/annurev-astro-081710-102521|journal=Annual Review of Astronomy and Astrophysics|language=en|volume=49|issue=1|pages=195–236|doi=10.1146/annurev-astro-081710-102521|arxiv=1011.1496|bibcode=2011ARA&A..49..195A|s2cid=55900935|issn=0066-4146|access-date=2020-10-22|archive-date=2020-10-28|archive-url=https://web.archive.org/web/20201028014743/https://www.annualreviews.org/doi/10.1146/annurev-astro-081710-102521|url-status=dead}}</ref> ==References== {{Reflist}} {{Physics-stub}} [[Category:Astronomical objects]]