View source for WASP-44b

{{Short description|Extrasolar planet orbiting the sunlike star WASP-44b}}
{{good article}}
{{Infobox planet
| name                     = WASP-44b
<!-- DISCOVERY           -->
| discoverer               = Anderson ''et al.''<ref name="Anderson2012"/>
| discovery_site           = [[La Silla Observatory]]
| discovered               = Published 16 May 2011
| discovery_method         = [[Doppler spectroscopy]]
<!-- DESIGNATIONS        -->
<!-- ORBITAL             --> 
| epoch                    = J2000
| apsis                    = astron
| semimajor                = 0.03473 (± 0.00041)<ref name=EPE /> [[astronomical unit|AU]]
| period                   = {{val|2.423807|0.000003}}<ref name="Moyano2017"/> [[day|d]]
| inclination              = 86.02 {{±|1.11|0.86}}<ref name=EPE />
| star                     = [[WASP-44]]
<!-- PHYS CHARS          --> 
| mean_radius              = 1.002 (± 0.11)<ref name="Mancini2013"/> {{Jupiter radius|link=y}}
| mass                     = 0.889 (± 0.062)<ref name=EPE /> {{Jupiter mass|link=y}}
| density                  = 0.61 {{±|0.23|0.15}}<ref name="Anderson2012"/> [[gram|g]] [[cubic centimetre|cm<sup>−3</sup>]]
| single_temperature       = 1343 (± 64)<ref name="Anderson2012"/>
<!-- ATMOSPHERE          --> 
<!-- NOTES               --> 
}}
'''WASP-44b''' is a closely orbiting [[Jupiter]]-sized planet found in the orbit of the sunlike star [[WASP-44]] by the [[SuperWASP]] program, which searches for [[transit method|transiting]] planets that cross in front of their host stars as seen from Earth.  After follow-up observations using [[radial velocity]], the planet was confirmed. Use of another telescope at the same observatory detected WASP-44 transiting its star. The planet completes an orbit around its star every two and a half days, and orbits at roughly 0.03 AU from its host star. WASP-44b's discovery was reported by the [[Royal Astronomical Society]] in May 2011.

==Discovery==
Using the WASP-South station at the [[South African Astronomical Observatory]], the [[SuperWASP]] project searched the night sky for potential planets that [[transit method|transited]], or crossed in front of, their host stars at a roughly periodic rate. WASP-44 was among the candidates identified as a possible host to a transit event.  WASP-44's reclassification as a potential planetary host came about after WASP-South scanned the [[Cetus (constellation)|Cetus]] constellation between July and November 2009. In combination with later observations using both WASP-South and the SuperWASP-North in the Canary Islands, over 15,755 [[photometry (astronomy)|photometric]] measurements were collected. A later set of observations between August and November 2010 produced a 6,000 point photometric data set, but the light curve was prepared late and was not considered in the discovery paper.<ref name="Anderson2012"/> The star was observed at the same time as stars [[WASP-45]] and [[WASP-46]].<ref name="Anderson2012"/>
[[File:Sw8cams.jpg|200px|left|thumb|The WASP-South cameras in South Africa]]
In 2010, the European team of astronomers used the [[CORALIE spectrograph]] on the 1.2m [[Leonhard Euler Telescope]] at Chile's [[La Silla Observatory]]. The same [[radial velocity]] measurements detected by SuperWASP were detected. The planet WASP-44b was confirmed after analysis of the results ruled out [[spectroscopic binary]] stars, leaving a transiting planet as the most likely cause of the radial velocity variations.<ref name="Anderson2012"/>

The Euler telescope was used to observe WASP-44b as it transited its host star. For 4.2 hours on September 14, 2010, Euler observed WASP-44 in search of a slight dimming in brightness until a more precise light curve could be found. Accounting for all data yet collected, analysis yielded the planet's characteristics.<ref name="Anderson2012"/>

The discovery of WASP-44b, along with those of [[WASP-45b]] and [[WASP-46b]], were reported on May 16, 2011 by the [[Royal Astronomical Society]].<ref name="Anderson2012"/> The scientists who worked on the paper discussed the role of [[orbital eccentricity]], or how elliptical an orbit is, and how poorly constrained it tends to be amongst Hot Jupiters, where a circular orbit is assumed. They used the three newly discovered planets as studies into the creation of a non-eccentric, circular model for a planet's orbit (the most likely solution) or an eccentric, elliptical solution for a planet's orbit (the solution that, according to the discovery team, required less of an assumption).<ref name="Anderson2012"/>

==Host star==
{{main|WASP-44}}
WASP-44 is a sunlike [[G-type star]] in the Cetus constellation. WASP-44 has a mass of 0.951 [[solar mass]]es and a radius of 0.927 [[solar radius|solar radii]], which means that WASP-44 is 95% the mass of and 92% the size of the Sun. With an [[effective temperature]] of 5410 [[Kelvin scale|K]], WASP-44 is cooler than the Sun, although it is richer in iron, with a measured [[metallicity]] of [Fe/H] = 0.06 (1.15 times the amount of iron found in the Sun). The star is an estimated 900 million years old, although this age is uncertain, as error bars are large.<ref name=EPE /> Based on its spectrum, WASP-44 is not active in its [[chromosphere]] (outer layer). The star was also not found to demonstrate a high rate of rotation.<ref name="Anderson2012"/>

With an [[apparent magnitude]] of 12.9, WASP-44 cannot be seen with the unaided eye from Earth.<ref name=EPE />

==Characteristics==
WASP-44b is a [[Hot Jupiter]]<ref name="Anderson2012"/> with a [[Jupiter mass|mass]] of 0.889 times Jupiter's mass and a radius of 1.002 times [[Jupiter radius|that of Jupiter]].<ref name="Mancini2013"/> Although less massive than Jupiter, the planet is bloated to a greater size because its proximity to its host star heats it, a common effect in such closely orbiting gas giants.<ref name="Anderson2012"/> WASP-44b orbits at a [[semimajor axis|mean distance]] of 0.03473 [[astronomical unit|AU]], which is about 3% of the distance between the Earth and Sun. An orbit is completed every 2.4238039 days (58.171 hours).<ref name=EPE />

WASP-44b has an [[orbital inclination]] of 86.02º, which is almost edge-on as seen from Earth.<ref name=EPE />

==References==
{{reflist|refs=

<ref name="Anderson2012">{{cite journal | title=WASP-44b, WASP-45b and WASP-46b: three short-period, transiting extrasolar planets | last1=Anderson | first1=D. R. | last2=Collier Cameron | first2=A. | last3=Gillon | first3=M. | last4=Hellier | first4=C. | last5=Jehin | first5=E. | last6=Lendl | first6=M. | last7=Maxted | first7=P. F. L. | last8=Queloz | first8=D. | last9=Smalley | first9=B. | last10=Smith | first10=A. M. S. | last11=Triaud | first11=A. H. M. J. | last12=West | first12=R. G. | last13=Pepe | first13=F. | last14=Pollacco | first14=D. | last15=Ségransan | first15=D. | last16=Todd | first16=I. | last17=Udry | first17=S. | display-authors=1 | journal=Monthly Notices of the Royal Astronomical Society | volume=422 | issue=3 | pages=1988–1998 | year=2012 | arxiv=1105.3179 | bibcode=2012MNRAS.422.1988A | doi=10.1111/j.1365-2966.2012.20635.x | doi-access=free | s2cid=34406657 }}</ref>

<ref name=EPE>{{cite encyclopedia |last=r |first=J. |date=2011 |title=Notes for star WASP-44 |url=http://www.exoplanet.eu/star.php?st=WASP-44 |access-date=2011-05-30 |archive-date=2011-06-01 |archive-url=https://web.archive.org/web/20110601191230/http://exoplanet.eu/star.php?st=WASP-44 |encyclopedia=[[Extrasolar Planets Encyclopaedia]] |url-status=dead }}</ref>

<ref name="Mancini2013">{{cite journal | title=Physical properties of the WASP-44 planetary system from simultaneous multi-colour photometry | last1=Mancini | first1=D. R. | last2=Nikolov | first2=N. | last3=Southworth | first3=J. | last4=Chen | first4=G. | last5=Fortney | first5=J. J. | last6=Tregloan-Reed | first6=J. | last7=Ciceri | first7=S. | last8=van Boekel | first8=R. | last9=Henning | first9=Th. | display-authors=1 | journal=Monthly Notices of the Royal Astronomical Society | volume=430 | issue=4 | pages=2932–2942 | year=2013 | arxiv=1301.3005 | bibcode=2013MNRAS.430.2932M | doi=10.1093/mnras/stt095 | doi-access=free }}</ref>

<ref name="Moyano2017">{{cite journal | title=Multi-band characterization of the hot Jupiters: WASP-5b, WASP-44b and WASP-46b | last1=Moyano | first1=M. | last2=Almeida | first2=L. A. | last3=von Essen | first3=C. | last4=Jablonski | first4=F. | last5=Pereira | first5=M. G. | display-authors=1 | journal=Monthly Notices of the Royal Astronomical Society | volume=471 | issue=1 | pages=650–657 | year=2017 | arxiv=1708.05700 | bibcode=2017MNRAS.471..650M | doi=10.1093/mnras/stx1612 | doi-access=free }}</ref>

}}

{{2011 in space}}

[[Category:Hot Jupiters]]
[[Category:Cetus]]
[[Category:Transiting exoplanets]]
[[Category:Exoplanets discovered in 2011]]
[[Category:Exoplanets discovered by WASP]]