Editing Betelgeuse (section)

=== Imaging breakthroughs ===
[[File:Betelgeuse pulsating UV (HST).jpg|thumb|right|1998/9 [[ultraviolet|UV]] [[Hubble Space Telescope|HST]] images of Betelgeuse showing asymmetrical pulsations with corresponding [[spectral line]] profiles]]
Astronomers saw some major advances in astronomical imaging technology in the 1970s, beginning with [[Antoine Émile Henry Labeyrie|Antoine Labeyrie]]'s invention of [[speckle interferometry]], a process that significantly reduced the blurring effect caused by [[astronomical seeing]]. It increased the [[optical resolution]] of ground-based [[telescope]]s, allowing for more precise measurements of Betelgeuse's photosphere.<ref name=LABEYRIE1970>
{{cite journal
 | last=Labeyrie |first=A. | author-link=Antoine Émile Henry Labeyrie
 | date=May 1970
 | title=Attainment of diffraction-limited resolution in large telescopes by Fourier analysing speckle patterns in star images
 | journal=[[Astronomy and Astrophysics]]
 | volume=6 | page=85
 | bibcode=1970A&A.....6...85L
}}
</ref><ref name=BONNEAU1973>
{{cite journal
 | last1=Bonneau |first1=D.
 | last2=Labeyrie |first2=A. | author2-link=Antoine Émile Henry Labeyrie
 | year=1973
 | title=Speckle interferometry: Color-dependent limb darkening evidenced on Alpha Orionis and Omicron Ceti
 | journal=[[Astrophysical Journal]]
 | volume= 181 | page=L1
 | bibcode=1973ApJ...181L...1B
 | doi=10.1086/181171
}}
</ref> With improvements in [[infrared telescopy]] atop [[Mount Wilson Observatory|Mount Wilson]], [[McDonald Observatory|Mount Locke]], and [[Mauna Kea Observatories|Mauna Kea]] in Hawaii, astrophysicists began peering into the complex circumstellar shells surrounding the supergiant,<ref name=SUTTON1977>
{{cite journal
 | last1=Sutton |first1=E.C. | last2=Storey |first2=J.W.V.
 | last3=Betz |first3=A.L. | last4=Townes |first4=C.H.
 | last5=Spears |first5=D.L.
 | year=1977
 | title=Spatial heterodyne tnterferometry of VY&nbsp;Canis Majoris, Alpha Orionis, Alpha Scorpii, and R&nbsp;Leonis at 11&nbsp;microns
 | journal=[[Astrophysical Journal Letters]]
 | volume=217 | pages=L97–L100
 | doi=10.1086/182547 | bibcode=1977ApJ...217L..97S
| doi-access=free
 }}
</ref><ref name=BERNAT1975>
{{cite journal
 | last1=Bernat |first1=A.P.
 | last2=Lambert |first2=D.L.
 | date=November 1975
 | title=Observations of the circumstellar gas shells around Betelgeuse and Antares
 | journal=[[Astrophysical Journal]]
 | volume=201 | pages=L153–L156
 | doi=10.1086/181964 | bibcode=1975ApJ...201L.153B
| doi-access=free
 }}
</ref><ref name=DYCK1975>
{{cite journal
 | last1=Dyck |first1=H.M.
 | last2=Simon |first2=T.
 | date=February 1975
 | title=Circumstellar dust shell models for Alpha Orionis
 | journal=[[Astrophysical Journal]]
 | volume=195 | pages=689–693
 | doi=10.1086/153369 | bibcode=1975ApJ...195..689D
}}
</ref> causing them to suspect the presence of huge gas bubbles resulting from convection.<ref name=BOESGAARD1975>
{{cite journal
 | last1=Boesgaard |first1=A.M.
 | last2=Magnan |first2=C.
 | date=June 1975
 | title=The circumstellar shell of alpha Orionis from a study of the Fe&nbsp;II emission lines
 | journal=[[Astrophysical Journal]]
 | volume=198 | issue=1 | pages=369–371, 373–378
 | doi=10.1086/153612 | bibcode=1975ApJ...198..369B
}}
</ref> However, it was not until the late 1980s and early 1990s, when Betelgeuse became a regular target for [[aperture masking interferometry]], that breakthroughs occurred in visible-light and [[Infrared photography|infrared imaging]]. Pioneered by [[John E. Baldwin|J.E.&nbsp;Baldwin]] and colleagues of the [[Cavendish Astrophysics Group]], the new technique employed a small mask with several holes in the telescope pupil plane, converting the [[aperture]] into an ad hoc interferometric array.<ref name=BERNAT2008>
{{cite web
 | last=Bernat |first=David
 | year=2008
 | title=Aperture masking interferometry
 | website=Ask an Astronomer
 | publisher=[[Cornell University]]
 | series=Astronomy department
 | url=http://astro.cornell.edu/~dbernat/apm.html#
 | access-date=15 October 2012
}}
</ref> The technique contributed some of the most accurate measurements of Betelgeuse while revealing bright spots on the star's photosphere.<ref name=BUSCHER>
{{cite journal
 | last1=Buscher |first1=D.F. | last2=Baldwin |first2=J.E.
 | last3=Warner |first3=P.J. | last4=Haniff |first4=C.A.
 | year=1990
 | title=Detection of a bright feature on the surface of Betelgeuse
 | journal=[[Monthly Notices of the Royal Astronomical Society]]
 | volume=245 | page=7
 | bibcode=1990MNRAS.245P...7B
}}
</ref><ref name=WILSON1>
{{cite journal
 | last1=Wilson |first1=R.W.
 | last2=Dhillon |first2=V.S.
 | last3=Haniff |first3=C.A.
 | year=1997
 | title=The changing face of Betelgeuse
 | journal=[[Monthly Notices of the Royal Astronomical Society]]
 | volume=291 | issue=4 | page=819
 | bibcode=1997MNRAS.291..819W
 | doi=10.1093/mnras/291.4.819 | doi-access=free
 }}
</ref><ref name=BURNS>
{{cite journal
 | last1=Burns | first1=D. | last2=Baldwin | first2=J.E.
 | last3=Boysen | first3=R.C. | last4=Haniff | first4=C.A.
 | last5=Lawson | first5=P.R. | last6=MacKay | first6=C.D.
 | last7=Rogers | first7=J. | last8=Scott | first8=T.R.
 | last9=Warner | first9=P.J.
 | display-authors=6
 | date=September 1997
 | title=The surface structure and limb-darkening profile of Betelgeuse
 | journal=[[Monthly Notices of the Royal Astronomical Society]]
 | volume=290 | issue=1 | pages=L11–L16
 | bibcode=1997MNRAS.290L..11B
 | doi=10.1093/mnras/290.1.l11 | doi-access=free
}}
</ref> These were the first optical and infrared images of a stellar disk other than the [[Sun]], taken first from ground-based interferometers and later from higher-resolution observations of the [[Cambridge Optical Aperture Synthesis Telescope|COAST telescope]]. The "bright patches" or "hotspots" observed with these instruments appeared to corroborate a theory put forth by Schwarzschild decades earlier of massive [[Convection zone|convection]] cells dominating the stellar surface.<ref name=TUTHILL>
{{cite journal
 | last1=Tuthill | first1=P.G.
 | last2=Haniff | first2=C.A.
 | last3=Baldwin | first3=J.E.
 | date=March 1997
 | title=Hotspots on late-type supergiants
 | journal=Monthly Notices of the Royal Astronomical Society
 | volume=285 | issue=3 | pages=529–39
 | bibcode=1997MNRAS.285..529T
 | doi=10.1093/mnras/285.3.529 | doi-access=free
}}
</ref><ref name=SCHWARZSCHILD1975>
{{cite journal
 | last=Schwarzschild | first=M. |author-link=Martin Schwarzschild
 | year=1975
 | title=On the scale of photospheric convection in red giants and supergiants
 | journal=[[Astrophysical Journal]]
 | volume=195 | issue=1 | pages=137–44
 | bibcode=1975ApJ...195..137S | doi=10.1086/153313
| doi-access=free}}
</ref>

In 1995, the [[Hubble Space Telescope]]'s [[Faint Object Camera]] captured an [[Ultraviolet astronomy|ultraviolet image]] with a resolution superior to that obtained by ground-based interferometers—the first conventional-telescope image (or "direct-image" in NASA terminology) of the disk of another star.<ref name=GILLILAND1>
{{cite journal
 | last1=Gilliland | first1=Ronald L.
 | last2=Dupree | first2=Andrea K.
 | date=May 1996
 | title=First image of the surface of a star with the Hubble Space Telescope
 | journal=[[Astrophysical Journal Letters]]
 | volume=463 | issue=1 | pages=L29
 | bibcode=1996ApJ...463L..29G
 | doi=10.1086/310043 | doi-access=free
 | quote=The yellow/red "image" or "photo" of Betelgeuse commonly seen is not a picture of the red supergiant, but a mathematically generated image based on the photograph. The photograph was of much lower resolution: The entire Betelgeuse image fit within a 10×10 pixel area on the [[Hubble Space Telescope]]s [[Faint Object Camera]]. The images were oversampled by a factor of 5 with bicubic spline interpolation, then deconvolved.
}}
</ref>
Because [[ultraviolet]] light is absorbed by the [[Atmosphere of Earth|Earth's atmosphere]], observations at these wavelengths are best performed by [[space telescope]]s.<ref name=cox2000>
{{cite book
 | editor=Cox, A.N.
 | title=Allen's Astrophysical Quantities
 | year=2000
 | publisher=Springer-Verlag
 | location=New York, NY
 | isbn=978-0-387-98746-0
}}
</ref>
This image, like earlier pictures, contained a bright patch indicating a region in the southwestern quadrant {{val|2000|ul=K|fmt=commas}} hotter than the stellar surface.<ref>
{{cite book
 | last1=Petersen | first1=Carolyn Collins
 | last2=Brandt | first2=John C.
 | year=1998 | orig-year=1995
 | title=Hubble Vision: Further adventures with the Hubble Space Telescope | edition=2nd
 | publisher=Cambridge University Press
 | location=Cambridge, UK
 | isbn=978-0-521-59291-8
 | url=https://archive.org/details/hubblevisionfurt0000pete
 | url-access=registration
 | pages=[https://archive.org/details/hubblevisionfurt0000pete/page/91 91–92]
}}
</ref>
Subsequent ultraviolet spectra taken with the [[Goddard High Resolution Spectrograph]] suggested that the hot spot was one of Betelgeuse's poles of rotation. This would give the rotational axis an inclination of about 20° to the direction of Earth, and a [[position angle]] from [[Celestial pole|celestial North]] of about 55°.<ref name=UITENBROEK>
{{cite journal
 | last1=Uitenbroek | first1=Han
 | last2=Dupree | first2=Andrea K.
 | last3=Gilliland | first3=Ronald L.
 | year=1998
 | title=Spatially resolved Hubble Space Telescope spectra of the chromosphere of {{nobr|{{mvar|α}} Orionis}}
 | journal=The Astronomical Journal
 | volume=116 | issue=5 | pages=2501–2512
 | doi=10.1086/300596 | bibcode=1998AJ....116.2501U
 | s2cid=117596395
| doi-access=free
 }}
</ref>